stream.hpp

/*
    SPDX-License-Identifier: MIT
    Copyright © 2023-2024 Amebis
*/
 
#pragma once
 
#include "assert.hpp"
#include "compat.hpp"
#include "endian.hpp"
#include "interval.hpp"
#include "locale.hpp"
#include "math.hpp"
#include "ring.hpp"
#include "socket.hpp"
#include "string.hpp"
#include "unicode.hpp"
#include <stdint.h>
#include <stdlib.h>
#if defined(_WIN32)
#include "windows.h"
#include <asptlb.h>
#include <objidl.h>
#else
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#endif
#include <chrono>
#include <condition_variable>
#include <list>
#include <memory>
#include <set>
#include <string>
#include <thread>
#include <vector>
 
#if defined(__GNUC__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunknown-pragmas"
#endif
 
#if !defined(SET_FILE_OP_TIMES) && defined(RDAT_BELEZI_CAS_DOSTOPA_VER)
#define SET_FILE_OP_TIMES 1
#pragma message("RDAT_BELEZI_CAS_DOSTOPA_VER is deprecated. Use SET_FILE_OP_TIMES instead.")
#elif !defined(SET_FILE_OP_TIMES)
#define SET_FILE_OP_TIMES 0
#endif
#if !defined(CHECK_STREAM_STATE) && defined(RDAT_NE_PREVERJAJ_STANJA_VER)
#define CHECK_STREAM_STATE 0
#pragma message("RDAT_NE_PREVERJAJ_EOF_VER is deprecated. Use CHECK_STREAM_STATE=0 instead.")
#else
#define CHECK_STREAM_STATE 1
#endif
 
namespace stdex
{
    namespace stream
    {
        enum class state_t {
            ok = 0,
            eof,
            fail,
        };
 
        using fsize_t = uint64_t;
        constexpr fsize_t fsize_max = UINT64_MAX;
 
        constexpr size_t iterate_count = 0x10;
        constexpr size_t default_block_size = 0x10000; 
        constexpr utf16_t utf16_bom = u'\ufeff'; 
        constexpr utf32_t utf32_bom = U'\ufeff'; 
        constexpr const char utf8_bom[3] = { '\xef', '\xbb', '\xbf' }; 
 
        class basic
        {
        public:
            basic(_In_ state_t state = state_t::ok) : m_state(state) {}
 
            virtual ~basic() noexcept(false) {}
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                _Unreferenced_(data);
                _Unreferenced_(length);
                m_state = state_t::fail;
                return 0;
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                _Unreferenced_(data);
                _Unreferenced_(length);
                m_state = state_t::fail;
                return 0;
            }
 
            virtual void flush()
            {
                m_state = state_t::ok;
            }
 
            virtual void close()
            {
                m_state = state_t::ok;
            }
 
            virtual void skip(_In_ fsize_t amount)
            {
                if (amount == 1)
                    read_byte();
                else if (amount < iterate_count) {
                    for (size_t i = 0; i < static_cast<size_t>(amount); i++) {
                        read_byte();
                        if (!ok()) _Unlikely_
                            break;
                    }
                }
                else {
                    size_t block = static_cast<size_t>(std::min<fsize_t>(amount, default_block_size));
                    try {
                        std::unique_ptr<uint8_t[]> dummy(new uint8_t[block]);
                        while (amount) {
                            amount -= read_array(dummy.get(), sizeof(uint8_t), static_cast<size_t>(std::min<fsize_t>(amount, block)));
                            if (!ok()) _Unlikely_
                                break;
                        }
                    }
                    catch (const std::bad_alloc&) { m_state = state_t::fail; }
                }
            }
 
            state_t state() const { return m_state; };
 
            bool ok() const { return m_state == state_t::ok; };
 
            virtual std::vector<uint8_t> read_remainder(_In_ size_t max_length = SIZE_MAX)
            {
                std::vector<uint8_t> result;
                size_t offset, length;
                offset = 0;
                length = default_block_size;
                while (offset < max_length) {
                    length = std::min(length, max_length);
                    try { result.resize(length); }
                    catch (const std::bad_alloc&) {
                        m_state = state_t::fail;
                        return result;
                    }
                    auto num_read = read_array(result.data() + offset, sizeof(uint8_t), length - offset);
                    offset += num_read;
                    if (!ok()) _Unlikely_
                        break;
                    length += default_block_size;
                }
                result.resize(offset);
                return result;
            }
 
            uint8_t read_byte()
            {
                uint8_t byte;
                if (read_array(&byte, sizeof(byte), 1) == 1)
                    return byte;
                throw std::system_error(sys_error(), std::system_category(), "failed to read");
            }
 
            void write_byte(_In_ uint8_t byte, _In_ fsize_t amount = 1)
            {
                if (amount == 1)
                    write(&byte, sizeof(uint8_t));
                else if (amount < iterate_count) {
                    for (size_t i = 0; i < static_cast<size_t>(amount); i++) {
                        write(&byte, sizeof(uint8_t));
                        if (!ok()) _Unlikely_
                            break;
                    }
                }
                else {
                    size_t block = static_cast<size_t>(std::min<fsize_t>(amount, default_block_size));
                    try {
                        std::unique_ptr<uint8_t[]> dummy(new uint8_t[block]);
                        memset(dummy.get(), byte, block);
                        while (amount) {
                            amount -= write_array(dummy.get(), sizeof(uint8_t), static_cast<size_t>(std::min<fsize_t>(amount, block)));
                            if (!ok()) _Unlikely_
                                break;
                        }
                    }
                    catch (const std::bad_alloc&) { m_state = state_t::fail; }
                }
            }
 
            template <class T>
            basic& read_data(_Out_ T& data)
            {
                if (!ok()) _Unlikely_ {
                    data = 0;
                    return *this;
                }
                if (read_array(&data, sizeof(T), 1) == 1)
                    (void)LE2HE(&data);
                else {
                    data = 0;
                    if (ok())
                        m_state = state_t::eof;
                }
                return *this;
            }
 
            template <class T>
            basic& write_data(_In_ const T data)
            {
                if (!ok()) _Unlikely_
                    return *this;
#if BYTE_ORDER == BIG_ENDIAN
                T data_le = HE2LE(data);
                write(&data_le, sizeof(T));
#else
                write(&data, sizeof(T));
#endif
                return *this;
            }
 
            template<class T, class TR = std::char_traits<T>, class AX = std::allocator<T>>
            size_t readln(_Inout_ std::basic_string<T, TR, AX>& str)
            {
                str.clear();
                return readln_and_attach(str);
            }
 
            template<class T_from, class T_to, class TR = std::char_traits<T_to>, class AX = std::allocator<T_to>>
            size_t readln(_Inout_ std::basic_string<T_to, TR, AX>& str, _In_ charset_encoder<T_from, T_to>& encoder)
            {
                if (encoder.from_encoding() == encoder.to_encoding())
                    return readln(str);
                std::basic_string<T_from> tmp;
                readln_and_attach(tmp);
                encoder.strcpy(str, tmp);
                return str.size();
            }
 
            template<class T, class TR = std::char_traits<T>, class AX = std::allocator<T>>
            size_t readln_and_attach(_Inout_ std::basic_string<T, TR, AX>& str)
            {
                bool initial = true;
                T chr = static_cast<T>(0), previous = static_cast<T>(0);
                do {
                    read_array(&chr, sizeof(T), 1);
                    if (!initial && !(previous == static_cast<T>('\r') && chr == static_cast<T>('\n')))
                        str += previous;
                    else
                        initial = false;
                    previous = chr;
                } while (ok() && chr != static_cast<T>('\n'));
                return str.size();
            }
 
            template<class T_from, class T_to, class TR = std::char_traits<T_to>, class AX = std::allocator<T_to>>
            size_t readln_and_attach(_Inout_ std::basic_string<T_to, TR, AX>& str, _In_ charset_encoder<T_from, T_to>& encoder)
            {
                if (encoder.from_encoding() == encoder.to_encoding())
                    return readln_and_attach(str);
                std::basic_string<T_from> tmp;
                readln_and_attach(tmp);
                encoder.strcat(str, tmp);
                return str.size();
            }
 
            size_t read_array(_Out_writes_bytes_(size* count) void* array, _In_ size_t size, _In_ size_t count)
            {
                for (size_t to_read = mul(size, count);;) {
                    size_t num_read = read(array, to_read);
                    to_read -= num_read;
                    if (!to_read)
                        return count;
                    if (!ok()) _Unlikely_
                        return count - to_read / size;
                    reinterpret_cast<uint8_t*&>(array) += num_read;
                }
            }
 
            size_t write_array(_In_reads_bytes_opt_(size* count) const void* array, _In_ size_t size, _In_ size_t count)
            {
                return write(array, mul(size, count)) / size;
            }
 
            template <class T_from, class T_to>
            size_t write_array(_In_z_ const T_from* str, _In_ charset_encoder<T_from, T_to>& encoder)
            {
                if (!ok()) _Unlikely_
                    return 0;
                size_t num_chars = stdex::strlen(str);
                if (encoder.from_encoding() == encoder.to_encoding())
                    return write_array(str, sizeof(T_from), num_chars);
                std::basic_string<T_to> tmp(encoder.convert(str, num_chars));
                return write_array(tmp.data(), sizeof(T_to), tmp.size());
            }
 
            template <class T_from, class T_to>
            size_t write_array(_In_reads_or_z_opt_(num_chars) const T_from* str, _In_ size_t num_chars, _In_ charset_encoder<T_from, T_to>& encoder)
            {
                if (!ok()) _Unlikely_
                    return 0;
                num_chars = stdex::strnlen(str, num_chars);
                if (encoder.from_encoding() == encoder.to_encoding())
                    return write_array(str, sizeof(T_from), num_chars);
                std::basic_string<T_to> tmp(encoder.convert(str, num_chars));
                return write_array(tmp.data(), sizeof(T_to), tmp.size());
            }
 
            template<class T_from, class T_to, class TR = std::char_traits<T_from>, class AX = std::allocator<T_from>>
            size_t write_array(_In_ const std::basic_string<T_from, TR, AX>& str, _In_ charset_encoder<T_from, T_to>& encoder)
            {
                if (!ok()) _Unlikely_
                    return 0;
                if (encoder.from_encoding() == encoder.to_encoding())
                    return write_array(str.data(), sizeof(T_from), str.size());
                std::basic_string<T_to> tmp(encoder.convert(str));
                return write_array(tmp.data(), sizeof(T_to), tmp.size());
            }
 
            template<class T, class TR = std::char_traits<T>, class AX = std::allocator<T>>
            basic& read_str(_Out_ std::basic_string<T, TR, AX>& data)
            {
                data.clear();
                if (!ok()) _Unlikely_
                    return *this;
                uint32_t num_chars;
                read_data(num_chars);
                if (!ok()) _Unlikely_
                    return *this;
                data.reserve(num_chars);
                for (;;) {
                    constexpr uint32_t buf_chars = 0x400;
                    T buf[buf_chars];
                    uint32_t num_read = static_cast<uint32_t>(read_array(buf, sizeof(T), std::min<uint32_t>(num_chars, buf_chars)));
                    data.append(buf, num_read);
                    num_chars -= num_read;
                    if (!num_chars || !ok())
                        return *this;
                }
            }
 
            template <class T>
            basic& write_str(_In_z_ const T* data)
            {
                // Stream state will be checked in write_data.
                size_t num_chars = stdex::strlen(data);
                if (num_chars > UINT32_MAX)
                    throw std::invalid_argument("string too long");
                write_data(static_cast<uint32_t>(num_chars));
                if (!ok()) _Unlikely_
                    return *this;
                write_array(data, sizeof(T), num_chars);
                return *this;
            }
 
            template<class T, class TR = std::char_traits<T>, class AX = std::allocator<T>>
            basic& write_str(_In_ const std::basic_string<T, TR, AX>& data)
            {
                // Stream state will be checked in write_data.
                size_t num_chars = data.size();
                if (num_chars > UINT32_MAX)
                    throw std::invalid_argument("string too long");
                write_data(static_cast<uint32_t>(num_chars));
                if (!ok()) _Unlikely_
                    return *this;
                write_array(data.data(), sizeof(T), num_chars);
                return *this;
            }
 
#ifdef _WIN32
            size_t write_sa(_In_ LPSAFEARRAY sa)
            {
                safearray_accessor_with_size<uint8_t> a(sa);
                return write(a.data(), a.size());
            }
#endif
 
            fsize_t write_stream(_Inout_ basic& stream, _In_ fsize_t amount = fsize_max)
            {
                std::unique_ptr<uint8_t[]> data(new uint8_t[static_cast<size_t>(std::min<fsize_t>(amount, default_block_size))]);
                fsize_t num_copied = 0, to_write = amount;
                m_state = state_t::ok;
                while (to_write) {
                    size_t num_read = stream.read(data.get(), static_cast<size_t>(std::min<fsize_t>(default_block_size, to_write)));
                    size_t num_written = write(data.get(), num_read);
                    num_copied += num_written;
                    to_write -= num_written;
                    if (stream.m_state == state_t::eof) {
                        // EOF is not an error.
                        m_state = state_t::ok;
                        break;
                    }
                    m_state = stream.m_state;
                    if (!ok())
                        break;
                }
                return num_copied;
            }
 
            void write_charset(_In_ charset_id charset)
            {
                if (charset == charset_id::utf32)
                    write_data(utf32_bom);
                else if (charset == charset_id::utf16)
                    write_data(utf16_bom);
                else if (charset == charset_id::utf8)
                    write_array(utf8_bom, sizeof(utf8_bom), 1);
            }
 
            size_t write_sprintf(_In_z_ _Printf_format_string_params_(2) const char* format, _In_opt_ locale_t locale, ...)
            {
                va_list params;
                va_start(params, locale);
                size_t num_chars = write_vsprintf(format, locale, params);
                va_end(params);
                return num_chars;
            }
 
            size_t write_sprintf(_In_z_ _Printf_format_string_params_(2) const wchar_t* format, _In_opt_ locale_t locale, ...)
            {
                va_list params;
                va_start(params, locale);
                size_t num_chars = write_vsprintf(format, locale, params);
                va_end(params);
                return num_chars;
            }
 
            size_t write_vsprintf(_In_z_ _Printf_format_string_params_(2) const char* format, _In_opt_ locale_t locale, _In_ va_list params)
            {
                std::string tmp;
                tmp.reserve(default_block_size);
                vappendf(tmp, format, locale, params);
                return write_array(tmp.data(), sizeof(char), tmp.size());
            }
 
            size_t write_vsprintf(_In_z_ _Printf_format_string_params_(2) const wchar_t* format, _In_opt_ locale_t locale, _In_ va_list params)
            {
                std::wstring tmp;
                tmp.reserve(default_block_size);
                vappendf(tmp, format, locale, params);
                return write_array(tmp.data(), sizeof(wchar_t), tmp.size());
            }
 
            basic& operator >>(_Out_ int8_t& data) { return read_data(data); }
            basic& operator <<(_In_ const int8_t data) { return write_data(data); }
            basic& operator >>(_Out_ int16_t& data) { return read_data(data); }
            basic& operator <<(_In_ const int16_t data) { return write_data(data); }
            basic& operator >>(_Out_ int32_t& data) { return read_data(data); }
            basic& operator <<(_In_ const int32_t data) { return write_data(data); }
            basic& operator >>(_Out_ int64_t& data) { return read_data(data); }
            basic& operator <<(_In_ const int64_t data) { return write_data(data); }
            basic& operator >>(_Out_ uint8_t& data) { return read_data(data); }
            basic& operator <<(_In_ const uint8_t data) { return write_data(data); }
            basic& operator >>(_Out_ uint16_t& data) { return read_data(data); }
            basic& operator <<(_In_ const uint16_t data) { return write_data(data); }
            basic& operator >>(_Out_ uint32_t& data) { return read_data(data); }
            basic& operator <<(_In_ const uint32_t data) { return write_data(data); }
            basic& operator >>(_Out_ uint64_t& data) { return read_data(data); }
            basic& operator <<(_In_ const uint64_t data) { return write_data(data); }
            basic& operator >>(_Out_ float& data) { return read_data(data); }
            basic& operator <<(_In_ const float data) { return write_data(data); }
            basic& operator >>(_Out_ double& data) { return read_data(data); }
            basic& operator <<(_In_ const double data) { return write_data(data); }
            basic& operator >>(_Out_ char& data) { return read_data(data); }
            basic& operator <<(_In_ const char data) { return write_data(data); }
#ifdef _NATIVE_WCHAR_T_DEFINED
            basic& operator >>(_Out_ wchar_t& data) { return read_data(data); }
            basic& operator <<(_In_ const wchar_t data) { return write_data(data); }
#endif
            template<class T, class TR = std::char_traits<T>, class AX = std::allocator<T>>
            basic& operator >>(_Out_ std::basic_string<T, TR, AX>& data) { return read_str(data); }
            template <class T>
            basic& operator <<(_In_ const T* data) { return write_str(data); }
            template<class T, class TR = std::char_traits<T>, class AX = std::allocator<T>>
            basic& operator <<(_In_ const std::basic_string<T, TR, AX>& data) { return write_str(data); }
 
            template <class T, class AX = std::allocator<T>>
            basic& operator <<(_In_ const std::vector<T, AX>& data)
            {
                size_t num = data.size();
                if (num > UINT32_MAX) _Unlikely_
                    throw std::invalid_argument("collection too big");
                *this << static_cast<uint32_t>(num);
                for (auto& el : data)
                    *this << el;
                return *this;
            }
 
            template <class T, class AX = std::allocator<T>>
            basic& operator >>(_Out_ std::vector<T, AX>& data)
            {
                data.clear();
                uint32_t num;
                *this >> num;
                if (!ok()) _Unlikely_
                    return *this;
                data.reserve(num);
                for (uint32_t i = 0; i < num; ++i) {
                    T el;
                    *this >> el;
                    if (!ok()) _Unlikely_
                        return *this;
                    data.push_back(std::move(el));
                }
            }
 
            template <class KEY, class PR = std::less<KEY>, class AX = std::allocator<KEY>>
            basic& operator <<(_In_ const std::set<KEY, PR, AX>& data)
            {
                size_t num = data.size();
                if (num > UINT32_MAX) _Unlikely_
                    throw std::invalid_argument("collection too big");
                *this << static_cast<uint32_t>(num);
                for (auto& el : data)
                    *this << el;
                return *this;
            }
 
            template <class KEY, class PR = std::less<KEY>, class AX = std::allocator<KEY>>
            basic& operator >>(_Out_ std::set<KEY, PR, AX>& data)
            {
                data.clear();
                uint32_t num;
                *this >> num;
                if (!ok()) _Unlikely_
                    return *this;
                for (uint32_t i = 0; i < num; ++i) {
                    KEY el;
                    *this >> el;
                    if (!ok()) _Unlikely_
                        return *this;
                    data.insert(std::move(el));
                }
            }
 
            template <class KEY, class PR = std::less<KEY>, class AX = std::allocator<KEY>>
            basic& operator <<(_In_ const std::multiset<KEY, PR, AX>& data)
            {
                size_t num = data.size();
                if (num > UINT32_MAX) _Unlikely_
                    throw std::invalid_argument("collection too big");
                *this << static_cast<uint32_t>(num);
                for (auto& el : data)
                    *this << el;
                return *this;
            }
 
            template <class KEY, class PR = std::less<KEY>, class AX = std::allocator<KEY>>
            basic& operator >>(_Out_ std::multiset<KEY, PR, AX>& data)
            {
                data.clear();
                uint32_t num;
                *this >> num;
                if (!ok()) _Unlikely_
                    return *this;
                for (uint32_t i = 0; i < num; ++i) {
                    KEY el;
                    *this >> el;
                    if (!ok()) _Unlikely_
                        return *this;
                    data.insert(std::move(el));
                }
                return *this;
            }
 
        protected:
            state_t m_state;
        };
 
        using fpos_t = uint64_t;
        constexpr fpos_t fpos_max = UINT64_MAX;
        constexpr fpos_t fpos_min = 0;
 
        using foff_t = int64_t;
        constexpr foff_t foff_max = INT64_MAX;
        constexpr foff_t foff_min = INT64_MIN;
 
        enum class seek_t {
#ifdef _WIN32
            beg = FILE_BEGIN,
            cur = FILE_CURRENT,
            end = FILE_END
#else
            beg = SEEK_SET,
            cur = SEEK_CUR,
            end = SEEK_END
#endif
        };
 
#if _HAS_CXX20
        using clock = std::chrono::file_clock;
#else
        using clock = std::chrono::system_clock;
#endif
        using time_point = std::chrono::time_point<clock>;
 
        class basic_file : virtual public basic
        {
        public:
            virtual std::vector<uint8_t> read_remainder(_In_ size_t max_length = SIZE_MAX)
            {
                size_t length = std::min<size_t>(max_length, static_cast<size_t>(size() - tell()));
                std::vector<uint8_t> result;
                try { result.resize(length); }
                catch (const std::bad_alloc&) {
                    m_state = state_t::fail;
                    return result;
                }
                result.resize(read_array(result.data(), sizeof(uint8_t), length));
                return result;
            }
 
            virtual fpos_t seek(_In_ foff_t offset, _In_ seek_t how = seek_t::beg) = 0;
 
            fpos_t seekbeg(_In_ fpos_t offset)
            {
                return seek(static_cast<foff_t>(offset), seek_t::beg);
            }
 
            fpos_t seekcur(_In_ foff_t offset) { return seek(offset, seek_t::cur); }
 
            fpos_t seekend(_In_ foff_t offset) { return seek(offset, seek_t::end); }
 
            virtual void skip(_In_ fsize_t amount)
            {
                if (amount > foff_max)
                    throw std::invalid_argument("file offset too big");
                seek(static_cast<foff_t>(amount), seek_t::cur);
            }
 
            virtual fpos_t tell() const = 0;
 
            virtual void lock(_In_ fpos_t offset, _In_ fsize_t length)
            {
                _Unreferenced_(offset);
                _Unreferenced_(length);
                throw std::domain_error("not implemented");
            }
 
            virtual void unlock(_In_ fpos_t offset, _In_ fsize_t length)
            {
                _Unreferenced_(offset);
                _Unreferenced_(length);
                throw std::domain_error("not implemented");
            }
 
            virtual fsize_t size() const = 0;
 
            virtual void truncate() = 0;
 
            virtual time_point ctime() const
            {
                return time_point::min();
            }
 
            virtual time_point atime() const
            {
                return time_point::min();
            }
 
            virtual time_point mtime() const
            {
                return time_point::min();
            }
 
            virtual void set_ctime(time_point date)
            {
                _Unreferenced_(date);
                throw std::domain_error("not implemented");
            }
 
            virtual void set_atime(time_point date)
            {
                _Unreferenced_(date);
                throw std::domain_error("not implemented");
            }
 
            virtual void set_mtime(time_point date)
            {
                _Unreferenced_(date);
                throw std::domain_error("not implemented");
            }
 
#ifdef _WIN32
            LPSAFEARRAY read_sa()
            {
                stdex_assert(size() <= SIZE_MAX);
                if (size() > ULONG_MAX)
                    throw std::range_error("data too big");
                ULONG length = static_cast<ULONG>(size());
                std::unique_ptr<SAFEARRAY, SafeArrayDestroy_delete> sa(SafeArrayCreateVector(VT_UI1, 0, length));
                if (!sa) _Unlikely_
                    throw std::runtime_error("SafeArrayCreateVector failed");
                if (seek(0) != 0) _Unlikely_
                    throw std::system_error(sys_error(), std::system_category(), "failed to seek");
                safearray_accessor<void> a(sa.get());
                if (read_array(a.data(), 1, length) != length)
                    throw std::system_error(sys_error(), std::system_category(), "failed to read");
                return sa.release();
            }
#endif
 
            charset_id read_charset(_In_ charset_id default_charset = charset_id::system)
            {
                if (seek(0) != 0) _Unlikely_
                    throw std::system_error(sys_error(), std::system_category(), "failed to seek");
                utf32_t id_utf32;
                read_array(&id_utf32, sizeof(utf32_t), 1);
                if (ok() && id_utf32 == utf32_bom)
                    return charset_id::utf32;
 
                if (seek(0) != 0) _Unlikely_
                    throw std::system_error(sys_error(), std::system_category(), "failed to seek");
                utf16_t id_utf16;
                read_array(&id_utf16, sizeof(utf16_t), 1);
                if (ok() && id_utf16 == utf16_bom)
                    return charset_id::utf16;
 
                if (seek(0) != 0) _Unlikely_
                    throw std::system_error(sys_error(), std::system_category(), "failed to seek");
                char id_utf8[3] = { 0 };
                read_array(id_utf8, sizeof(id_utf8), 1);
                if (ok() && strncmp(id_utf8, _countof(id_utf8), utf8_bom, _countof(utf8_bom)) == 0)
                    return charset_id::utf8;
 
                if (seek(0) != 0) _Unlikely_
                    throw std::system_error(sys_error(), std::system_category(), "failed to seek");
                return default_charset;
            }
        };
 
        class converter : public basic
        {
        protected:
#pragma warning(suppress: 26495) // The delayed init call will finish initializing the class.
            explicit converter() : basic(state_t::fail) {}
 
            void init(_Inout_ basic& source)
            {
                m_source = &source;
                init();
            }
 
            void init()
            {
                m_state = m_source->state();
            }
 
            void done()
            {
                m_source = nullptr;
            }
 
        public:
            converter(_Inout_ basic& source) :
                basic(source.state()),
                m_source(&source)
            {}
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                size_t num_read = m_source->read(data, length);
                m_state = m_source->state();
                return num_read;
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                size_t num_written = m_source->write(data, length);
                m_state = m_source->state();
                return num_written;
            }
 
            virtual void close()
            {
                m_source->close();
                m_state = m_source->state();
            }
 
            virtual void flush()
            {
                m_source->flush();
                m_state = m_source->state();
            }
 
        protected:
            basic* m_source;
        };
 
        class replicator : public basic
        {
        public:
            virtual ~replicator()
            {
                for (auto w = m_workers.begin(), w_end = m_workers.end(); w != w_end; ++w) {
                    auto _w = w->get();
                    {
                        const std::lock_guard<std::mutex> lk(_w->mutex);
                        _w->op = worker::op_t::quit;
                    }
                    _w->cv.notify_one();
                }
                for (auto w = m_workers.begin(), w_end = m_workers.end(); w != w_end; ++w)
                    w->get()->join();
            }
 
            void push_back(_In_ basic* source)
            {
                m_workers.push_back(std::unique_ptr<worker>(new worker(source)));
            }
 
            void remove(basic* source)
            {
                for (auto w = m_workers.begin(), w_end = m_workers.end(); w != w_end; ++w) {
                    auto _w = w->get();
                    if (_w->source == source) {
                        {
                            const std::lock_guard<std::mutex> lk(_w->mutex);
                            _w->op = worker::op_t::quit;
                        }
                        _w->cv.notify_one();
                        _w->join();
                        m_workers.erase(w);
                        return;
                    }
                }
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                for (auto w = m_workers.begin(), w_end = m_workers.end(); w != w_end; ++w) {
                    auto _w = w->get();
                    {
                        const std::lock_guard<std::mutex> lk(_w->mutex);
                        _w->op = worker::op_t::write;
                        _w->data = data;
                        _w->length = length;
                    }
                    _w->cv.notify_one();
                }
                size_t num_written = length;
                m_state = state_t::ok;
                for (auto w = m_workers.begin(), w_end = m_workers.end(); w != w_end; ++w) {
                    auto _w = w->get();
                    std::unique_lock<std::mutex> lk(_w->mutex);
                    _w->cv.wait(lk, [&] {return _w->op == worker::op_t::noop; });
                    if (_w->num_written < num_written)
                        num_written = _w->num_written;
                    if (ok() && !_w->source->ok())
                        m_state = _w->source->state();
                }
                return num_written;
            }
 
            virtual void close()
            {
                foreach_worker(worker::op_t::close);
            }
 
            virtual void flush()
            {
                foreach_worker(worker::op_t::flush);
            }
 
        protected:
            class worker : public std::thread
            {
            public:
                worker(_In_ basic* _source) :
                    source(_source),
                    op(op_t::noop),
                    data(nullptr),
                    length(0),
                    num_written(0)
                {
                    *static_cast<std::thread*>(this) = std::thread([](_Inout_ worker& w) { w.process_op(); }, std::ref(*this));
                }
 
            protected:
                void process_op()
                {
                    for (;;) {
                        std::unique_lock<std::mutex> lk(mutex);
                        cv.wait(lk, [&] {return op != op_t::noop; });
                        switch (op) {
                        case op_t::quit:
                            return;
                        case op_t::write:
                            num_written = source->write(data, length);
                            break;
                        case op_t::close:
                            source->close();
                            break;
                        case op_t::flush:
                            source->flush();
                            break;
                        case op_t::noop:;
                        }
                        op = op_t::noop;
                        lk.unlock();
                        cv.notify_one();
                    }
                }
 
            public:
                basic* source;
                enum class op_t {
                    noop = 0,
                    quit,
                    write,
                    close,
                    flush,
                } op; 
                const void* data; 
                size_t length; 
                size_t num_written; 
                std::mutex mutex;
                std::condition_variable cv;
            };
 
            void foreach_worker(_In_ worker::op_t op)
            {
                for (auto w = m_workers.begin(), w_end = m_workers.end(); w != w_end; ++w) {
                    auto _w = w->get();
                    {
                        const std::lock_guard<std::mutex> lk(_w->mutex);
                        _w->op = op;
                    }
                    _w->cv.notify_one();
                }
                m_state = state_t::ok;
                for (auto w = m_workers.begin(), w_end = m_workers.end(); w != w_end; ++w) {
                    auto _w = w->get();
                    std::unique_lock<std::mutex> lk(_w->mutex);
                    _w->cv.wait(lk, [&] {return _w->op == worker::op_t::noop; });
                    if (ok())
                        m_state = _w->source->state();
                }
            }
 
            std::list<std::unique_ptr<worker>> m_workers;
        };
 
        constexpr size_t default_async_limit = 0x100000; 
 
        template <size_t N_cap = default_async_limit>
        class async_reader : public converter
        {
        public:
            async_reader(_Inout_ basic& source) :
                converter(source),
                m_worker([](_Inout_ async_reader& w) { w.process(); }, std::ref(*this))
            {}
 
            virtual ~async_reader()
            {
                m_ring.quit();
                m_worker.join();
            }
 
#pragma warning(suppress: 6101) // See [1] below
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                for (size_t to_read = length;;) {
                    uint8_t* ptr; size_t num_read;
                    std::tie(ptr, num_read) = m_ring.front();
                    if (!ptr) _Unlikely_ {
                        m_state = to_read < length || !length ? state_t::ok : m_source->state();
                        return length - to_read; // [1] Code analysis misses `length - to_read` bytes were written to data in previous loop iterations.
                    }
                    if (to_read < num_read)
                        num_read = to_read;
                    memcpy(data, ptr, num_read);
                    m_ring.pop(num_read);
                    to_read -= num_read;
                    if (!to_read) {
                        m_state = state_t::ok;
                        return length;
                    }
                    reinterpret_cast<uint8_t*&>(data) += num_read;
                }
            }
 
        protected:
            void process()
            {
                for (;;) {
                    uint8_t* ptr; size_t num_write;
                    std::tie(ptr, num_write) = m_ring.back();
                    if (!ptr) _Unlikely_
                        break;
                    num_write = m_source->read(ptr, num_write);
                    m_ring.push(num_write);
                    if (!m_source->ok()) {
                        m_ring.quit();
                        break;
                    }
                }
            }
 
        protected:
            ring<uint8_t, N_cap> m_ring;
            std::thread m_worker;
        };
 
        template <size_t N_cap = default_async_limit>
        class async_writer : public converter
        {
        public:
            async_writer(_Inout_ basic& source) :
                converter(source),
                m_worker([](_Inout_ async_writer& w) { w.process(); }, std::ref(*this))
            {}
 
            virtual ~async_writer()
            {
                m_ring.quit();
                m_worker.join();
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                for (size_t to_write = length;;) {
                    uint8_t* ptr; size_t num_write;
                    std::tie(ptr, num_write) = m_ring.back();
                    if (!ptr) _Unlikely_ {
                        m_state = state_t::fail;
                        return length - to_write;
                    }
                    if (to_write < num_write)
                        num_write = to_write;
                    memcpy(ptr, data, num_write);
                    m_ring.push(num_write);
                    to_write -= num_write;
                    if (!to_write) {
                        m_state = state_t::ok;
                        return length;
                    }
                    reinterpret_cast<const uint8_t*&>(data) += num_write;
                }
            }
 
            virtual void flush()
            {
                m_ring.sync();
                converter::flush();
            }
 
        protected:
            void process()
            {
                for (;;) {
                    uint8_t* ptr; size_t num_read;
                    std::tie(ptr, num_read) = m_ring.front();
                    if (!ptr)
                        break;
                    num_read = m_source->write(ptr, num_read);
                    m_ring.pop(num_read);
                    if (!m_source->ok()) {
                        m_ring.quit();
                        break;
                    }
                }
            }
 
        protected:
            ring<uint8_t, N_cap> m_ring;
            std::thread m_worker;
        };
 
        constexpr size_t default_buffer_size = 0x400; 
 
        class buffer : public converter
        {
        protected:
            explicit buffer(_In_ size_t read_buffer_size = default_buffer_size, _In_ size_t write_buffer_size = default_buffer_size) :
                converter(),
                m_read_buffer(read_buffer_size),
                m_write_buffer(write_buffer_size)
            {}
 
            void done()
            {
                if (m_source)
                    flush_write();
                converter::done();
            }
 
        public:
            buffer(_Inout_ basic& source, _In_ size_t read_buffer_size = default_buffer_size, _In_ size_t write_buffer_size = default_buffer_size) :
                converter(source),
                m_read_buffer(read_buffer_size),
                m_write_buffer(write_buffer_size)
            {}
 
            virtual ~buffer()
            {
                if (m_source)
                    flush_write();
            }
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                for (size_t to_read = length;;) {
                    size_t buffer_size = m_read_buffer.tail - m_read_buffer.head;
                    if (to_read <= buffer_size) {
                        memcpy(data, m_read_buffer.data + m_read_buffer.head, to_read);
                        m_read_buffer.head += to_read;
                        m_state = state_t::ok;
                        return length;
                    }
                    if (buffer_size) {
                        memcpy(data, m_read_buffer.data + m_read_buffer.head, buffer_size);
                        reinterpret_cast<uint8_t*&>(data) += buffer_size;
                        to_read -= buffer_size;
                    }
                    m_read_buffer.head = 0;
                    if (to_read > m_read_buffer.capacity) {
                        // When needing to read more data than buffer capacity, bypass the buffer.
                        m_read_buffer.tail = 0;
                        to_read -= m_source->read(data, to_read);
                        m_state = to_read < length ? state_t::ok : m_source->state();
                        return length - to_read;
                    }
                    m_read_buffer.tail = m_source->read(m_read_buffer.data, m_read_buffer.capacity);
                    if (m_read_buffer.tail < m_read_buffer.capacity && m_read_buffer.tail < to_read) _Unlikely_ {
                        memcpy(data, m_read_buffer.data, m_read_buffer.tail);
                        m_read_buffer.head = m_read_buffer.tail;
                        to_read -= m_read_buffer.tail;
                        m_state = to_read < length ? state_t::ok : m_source->state();
                        return length - to_read;
                    }
                }
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                if (!length) _Unlikely_ {
                    // Pass null writes (zero-byte length). Null write operations have special meaning with with Windows pipes.
                    flush_write();
                    if (!ok()) _Unlikely_
                        return 0;
                    converter::write(nullptr, 0);
                    return 0;
                }
 
                for (size_t to_write = length;;) {
                    size_t available_buffer = m_write_buffer.capacity - m_write_buffer.tail;
                    if (to_write <= available_buffer) {
                        memcpy(m_write_buffer.data + m_write_buffer.tail, data, to_write);
                        m_write_buffer.tail += to_write;
                        m_state = state_t::ok;
                        return length;
                    }
                    if (available_buffer) {
                        memcpy(m_write_buffer.data + m_write_buffer.tail, data, available_buffer);
                        reinterpret_cast<const uint8_t*&>(data) += available_buffer;
                        to_write -= available_buffer;
                        m_write_buffer.tail += available_buffer;
                    }
                    size_t buffer_size = m_write_buffer.tail - m_write_buffer.head;
                    if (buffer_size) {
                        m_write_buffer.head += converter::write(m_write_buffer.data + m_write_buffer.head, buffer_size);
                        if (m_write_buffer.head == m_write_buffer.tail)
                            m_write_buffer.head = m_write_buffer.tail = 0;
                        else
                            return length - to_write;
                    }
                    if (to_write > m_write_buffer.capacity) {
                        // When needing to write more data than buffer capacity, bypass the buffer.
                        to_write -= converter::write(data, to_write);
                        return length - to_write;
                    }
                }
            }
 
            virtual void flush()
            {
                flush_write();
                if (ok())
                    converter::flush();
            }
 
        protected:
            void flush_write()
            {
                size_t buffer_size = m_write_buffer.tail - m_write_buffer.head;
                if (buffer_size) {
                    m_write_buffer.head += m_source->write(m_write_buffer.data + m_write_buffer.head, buffer_size);
                    if (m_write_buffer.head == m_write_buffer.tail) {
                        m_write_buffer.head = 0;
                        m_write_buffer.tail = 0;
                    }
                    else {
                        m_state = m_source->state();
                        return;
                    }
                }
                m_state = state_t::ok;
            }
 
            struct buffer_t {
                uint8_t* data;
                size_t head, tail, capacity;
 
                buffer_t(_In_ size_t buffer_size) :
                    head(0),
                    tail(0),
                    capacity(buffer_size),
                    data(buffer_size ? new uint8_t[buffer_size] : nullptr)
                {}
 
                ~buffer_t()
                {
                    if (data)
                        delete[] data;
                }
            } m_read_buffer, m_write_buffer;
        };
 
        class limiter : public converter
        {
        public:
            limiter(_Inout_ basic& source, _In_ fsize_t _read_limit = 0, _In_ fsize_t _write_limit = 0) :
                converter(source),
                read_limit(_read_limit),
                write_limit(_write_limit)
            {}
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                size_t num_read;
                if (read_limit == fsize_max)
                    num_read = converter::read(data, length);
                else if (length <= read_limit) {
                    num_read = converter::read(data, length);
                    read_limit -= num_read;
                }
                else if (length && !read_limit) {
                    num_read = 0;
                    m_state = state_t::eof;
                }
                else {
                    num_read = converter::read(data, static_cast<size_t>(read_limit));
                    read_limit -= num_read;
                }
                return num_read;
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                size_t num_written;
                if (write_limit == fsize_max)
                    num_written = converter::write(data, length);
                else if (length <= write_limit) {
                    num_written = converter::write(data, length);
                    write_limit -= num_written;
                }
                else if (length && !write_limit) {
                    num_written = 0;
                    m_state = state_t::fail;
                }
                else {
                    num_written = converter::write(data, static_cast<size_t>(write_limit));
                    write_limit -= num_written;
                }
                return num_written;
            }
 
        public:
            fsize_t
                read_limit, 
                write_limit; 
        };
 
        class window : public limiter
        {
        public:
            window(_Inout_ basic& source, _In_ fpos_t _read_offset = 0, _In_ fsize_t read_limit = fsize_max, _In_ fpos_t _write_offset = 0, _In_ fsize_t write_limit = fsize_max) :
                limiter(source, read_limit, write_limit),
                read_offset(_read_offset),
                write_offset(_write_offset)
            {}
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                if (read_offset) {
                    m_source->skip(read_offset);
                    m_state = m_source->state();
                    if (!ok()) _Unlikely_
                        return 0;
                    read_offset = 0;
                }
                size_t num_read;
                if (read_limit == fsize_max)
                    num_read = converter::read(data, length);
                else if (length <= read_limit) {
                    num_read = converter::read(data, length);
                    read_limit -= num_read;
                }
                else if (length && !read_limit) {
                    num_read = 0;
                    m_source->skip(length);
                    m_state = state_t::eof;
                }
                else {
                    num_read = converter::read(data, static_cast<size_t>(read_limit));
                    read_limit -= num_read;
                }
                return num_read;
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                size_t num_skipped, num_written;
                if (length <= write_offset) {
                    write_offset -= length;
                    m_state = state_t::ok;
                    return length;
                }
                if (write_offset) {
                    reinterpret_cast<const uint8_t*&>(data) += static_cast<size_t>(write_offset);
                    length -= static_cast<size_t>(write_offset);
                    num_skipped = static_cast<size_t>(write_offset);
                    write_offset = 0;
                }
                else
                    num_skipped = 0;
                if (write_limit == fsize_max)
                    num_written = converter::write(data, length);
                else if (length <= write_limit) {
                    num_written = converter::write(data, length);
                    write_limit -= num_written;
                }
                else if (length && !write_limit) {
                    num_skipped += length;
                    num_written = 0;
                    m_state = state_t::ok;
                }
                else {
                    num_skipped += length - static_cast<size_t>(write_limit);
                    num_written = converter::write(data, static_cast<size_t>(write_limit));
                    write_limit -= num_written;
                }
                return num_skipped + num_written;
            }
 
        public:
            fpos_t
                read_offset, 
                write_offset; 
        };
 
        class file_window : public basic_file
        {
        public:
            file_window(_Inout_ basic_file& source, fpos_t offset = 0, fsize_t length = 0) :
                basic(source.state()),
                m_source(source),
                m_offset(source.tell()),
                m_region(offset, offset + length)
            {}
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                if (m_region.contains(m_offset)) {
                    size_t num_read = m_source.read(data, static_cast<size_t>(std::min<fpos_t>(length, m_region.end - m_offset)));
                    m_state = m_source.state();
                    m_offset += num_read;
                    return num_read;
                }
                m_state = length ? state_t::eof : state_t::ok;
                return 0;
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                if (m_region.contains(m_offset)) {
                    size_t num_written = m_source.write(data, static_cast<size_t>(std::min<fpos_t>(length, m_region.end - m_offset)));
                    m_state = m_source.state();
                    m_offset += num_written;
                    return num_written;
                }
                m_state = state_t::fail;
                return 0;
            }
 
            virtual void close()
            {
                m_source.close();
                m_state = m_source.state();
            }
 
            virtual void flush()
            {
                m_source.flush();
                m_state = m_source.state();
            }
 
            virtual fpos_t seek(_In_ foff_t offset, _In_ seek_t how = seek_t::beg)
            {
                m_offset = m_source.seek(offset, how);
                m_state = m_source.state();
                return ok() ? m_offset - m_region.start : fpos_max;
            }
 
            virtual void skip(_In_ fsize_t amount)
            {
                m_source.skip(amount);
                m_state = m_source.state();
            }
 
            virtual fpos_t tell() const
            {
                fpos_t offset = m_source.tell();
                return m_region.contains(offset) ? offset - m_region.start : fpos_max;
            }
 
            virtual void lock(_In_ fpos_t offset, _In_ fsize_t length)
            {
                if (m_region.contains(offset)) {
                    m_source.lock(m_region.start + offset, std::min<fsize_t>(length, m_region.end - offset));
                    m_state = m_source.state();
                }
                else
                    m_state = state_t::fail;
            }
 
            virtual void unlock(_In_ fpos_t offset, _In_ fsize_t length)
            {
                if (m_region.contains(offset)) {
                    m_source.unlock(m_region.start + offset, std::min<fsize_t>(length, m_region.end - offset));
                    m_state = m_source.state();
                }
                else
                    m_state = state_t::fail;
            }
 
            virtual fsize_t size() const
            {
                return m_region.size();
            }
 
            virtual void truncate()
            {
                m_state = state_t::fail;
            }
 
        protected:
            basic_file& m_source;
            fpos_t m_offset;
            interval<fpos_t> m_region;
        };
 
        constexpr size_t default_cache_size = 0x1000; 
 
        class cache : public basic_file
        {
        protected:
#pragma warning(suppress: 26495) // The delayed init call will finish initializing the class.
            explicit cache(_In_ size_t cache_size = default_cache_size) :
                basic(state_t::fail),
                m_cache(cache_size)
            {}
 
            void init(_Inout_ basic_file& source)
            {
                m_source = &source;
                init();
            }
 
            void init()
            {
                m_state = m_source->state();
                m_offset = m_source->tell();
#if SET_FILE_OP_TIMES
                m_atime = m_source->atime();
                m_mtime = m_source->mtime();
#endif
            }
 
            void done()
            {
                if (m_source) {
                    flush_cache();
                    if (!ok()) _Unlikely_
                        throw std::system_error(sys_error(), std::system_category(), "failed to flush cache"); // Data loss occurred
                    m_source->seekbeg(m_offset);
#if SET_FILE_OP_TIMES
                    m_source->set_atime(m_atime);
                    m_source->set_mtime(m_mtime);
#endif
                    m_source = nullptr;
                }
            }
 
        public:
            cache(_Inout_ basic_file& source, _In_ size_t cache_size = default_cache_size) :
                basic(source.state()),
                m_source(&source),
                m_cache(cache_size),
                m_offset(source.tell())
#if SET_FILE_OP_TIMES
                , m_atime(source.atime())
                , m_mtime(source.mtime())
#endif
            {}
 
            virtual ~cache() noexcept(false)
            {
                if (m_source) {
                    flush_cache();
                    if (!ok()) _Unlikely_
                        throw std::system_error(sys_error(), std::system_category(), "failed to flush cache"); // Data loss occurred
                    m_source->seekbeg(m_offset);
#if SET_FILE_OP_TIMES
                    m_source->set_atime(m_atime);
                    m_source->set_mtime(m_mtime);
#endif
                }
            }
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
#if SET_FILE_OP_TIMES
                m_atime = time_point::now();
#endif
                for (size_t to_read = length;;) {
                    if (m_cache.status != cache_t::cache_t::status_t::empty) {
                        if (m_cache.region.contains(m_offset)) {
                            size_t remaining_cache = static_cast<size_t>(m_cache.region.end - m_offset);
                            if (to_read <= remaining_cache) {
                                memcpy(data, m_cache.data + static_cast<size_t>(m_offset - m_cache.region.start), to_read);
                                m_offset += to_read;
                                m_state = state_t::ok;
                                return length;
                            }
                            memcpy(data, m_cache.data + static_cast<size_t>(m_offset - m_cache.region.start), remaining_cache);
                            reinterpret_cast<uint8_t*&>(data) += remaining_cache;
                            to_read -= remaining_cache;
                            m_offset += remaining_cache;
                        }
                        flush_cache();
                        if (!ok()) _Unlikely_ {
                            if (to_read < length)
                                m_state = state_t::ok;
                            return length - to_read;
                        }
                    }
                    {
                        fpos_t end_max = m_offset + to_read;
                        if (m_offset / m_cache.capacity < end_max / m_cache.capacity) {
                            // Read spans multiple cache blocks. Bypass cache to the last block.
                            m_source->seekbeg(m_offset);
                            if (!m_source->ok()) _Unlikely_ {
                                m_state = to_read < length ? state_t::ok : state_t::fail;
                                return length - to_read;
                            }
                            size_t num_read = m_source->read(data, to_read - static_cast<size_t>(end_max % m_cache.capacity));
                            m_offset += num_read;
                            to_read -= num_read;
                            if (!to_read) {
                                m_state = state_t::ok;
                                return length;
                            }
                            reinterpret_cast<uint8_t*&>(data) += num_read;
                            m_state = m_source->state();
                            if (!ok()) {
                                if (to_read < length)
                                    m_state = state_t::ok;
                                return length - to_read;
                            }
                        }
                    }
                    load_cache(m_offset);
                    if (!ok()) _Unlikely_ {
                        m_state = to_read < length ? state_t::ok : state_t::fail;
                        return length - to_read;
                    }
                    if (m_cache.region.end <= m_offset) _Unlikely_ {
                        m_state = to_read < length ? state_t::ok : state_t::eof;
                        return length - to_read;
                    }
                }
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
#if SET_FILE_OP_TIMES
                m_atime = m_mtime = time_point::now();
#endif
                for (size_t to_write = length;;) {
                    if (m_cache.status != cache_t::cache_t::status_t::empty) {
                        fpos_t end_max = m_cache.region.start + m_cache.capacity;
                        if (m_cache.region.start <= m_offset && m_offset < end_max) {
                            size_t remaining_cache = static_cast<size_t>(end_max - m_offset);
                            if (to_write <= remaining_cache) {
                                memcpy(m_cache.data + static_cast<size_t>(m_offset - m_cache.region.start), data, to_write);
                                m_offset += to_write;
                                m_cache.status = cache_t::cache_t::status_t::dirty;
                                m_cache.region.end = std::max(m_cache.region.end, m_offset);
                                m_state = state_t::ok;
                                return length;
                            }
                            memcpy(m_cache.data + static_cast<size_t>(m_offset - m_cache.region.start), data, remaining_cache);
                            reinterpret_cast<const uint8_t*&>(data) += remaining_cache;
                            to_write -= remaining_cache;
                            m_offset += remaining_cache;
                            m_cache.status = cache_t::cache_t::status_t::dirty;
                            m_cache.region.end = end_max;
                        }
                        flush_cache();
                        if (!ok()) _Unlikely_
                            return length - to_write;
                    }
                    {
                        fpos_t end_max = m_offset + to_write;
                        if (m_offset / m_cache.capacity < end_max / m_cache.capacity) {
                            // Write spans multiple cache blocks. Bypass cache to the last block.
                            m_source->seekbeg(m_offset);
                            if (!ok()) _Unlikely_
                                return length - to_write;
                            size_t num_written = m_source->write(data, to_write - static_cast<size_t>(end_max % m_cache.capacity));
                            m_offset += num_written;
                            m_state = m_source->state();
                            to_write -= num_written;
                            if (!to_write || !ok())
                                return length - to_write;
                            reinterpret_cast<const uint8_t*&>(data) += num_written;
                        }
                    }
                    load_cache(m_offset);
                    if (!ok()) _Unlikely_
                        return length - to_write;
                }
            }
 
            virtual void close()
            {
                invalidate_cache();
                if (!ok()) _Unlikely_
                    throw std::system_error(sys_error(), std::system_category(), "failed to flush cache"); // Data loss occurred
                m_source->close();
                m_state = m_source->state();
            }
 
            virtual void flush()
            {
#if SET_FILE_OP_TIMES
                m_atime = m_mtime = time_point::min();
#endif
                flush_cache();
                if (!ok()) _Unlikely_
                    return;
                m_source->flush();
            }
 
            virtual fpos_t seek(_In_ foff_t offset, _In_ seek_t how = seek_t::beg)
            {
                m_state = state_t::ok;
                switch (how) {
                case seek_t::beg:
                    break;
                case seek_t::cur:
                    offset = static_cast<foff_t>(m_offset) + offset;
                    break;
                case seek_t::end: {
                    auto n = size();
                    if (n == fsize_max) _Unlikely_{
                        m_state = state_t::fail;
                        return fpos_max;
                    }
                    offset = static_cast<foff_t>(n) + offset;
                    break;
                }
                default:
                    throw std::invalid_argument("unknown seek origin");
                }
                if (offset < 0) _Unlikely_
                    throw std::invalid_argument("negative file offset");
                return m_offset = static_cast<fpos_t>(offset);
            }
 
            virtual fpos_t tell() const
            {
                return m_offset;
            }
 
            virtual void lock(_In_ fpos_t offset, _In_ fsize_t length)
            {
                m_source->lock(offset, length);
                m_state = m_source->state();
            }
 
            virtual void unlock(_In_ fpos_t offset, _In_ fsize_t length)
            {
                m_source->unlock(offset, length);
                m_state = m_source->state();
            }
 
            virtual fsize_t size() const
            {
                return m_cache.status != cache_t::cache_t::status_t::empty ?
                    std::max(m_source->size(), m_cache.region.end) :
                    m_source->size();
            }
 
            virtual void truncate()
            {
#if SET_FILE_OP_TIMES
                m_atime = m_mtime = time_point::now();
#endif
                m_source->seekbeg(m_offset);
                if (m_cache.region.end <= m_offset) {
                    // Truncation does not affect cache.
                }
                else if (m_cache.region.start <= m_offset) {
                    // Truncation truncates cache.
                    m_cache.region.end = m_offset;
                }
                else {
                    // Truncation invalidates cache.
                    m_cache.status = cache_t::cache_t::status_t::empty;
                }
                m_source->truncate();
                m_state = m_source->state();
            }
 
            virtual time_point ctime() const
            {
                return m_source->ctime();
            }
 
            virtual time_point atime() const
            {
#if SET_FILE_OP_TIMES
                return std::max(m_atime, m_source->atime());
#else
                return m_source->atime();
#endif
            }
 
            virtual time_point mtime() const
            {
#if SET_FILE_OP_TIMES
                return std::max(m_mtime, m_source->mtime());
#else
                return m_source->mtime();
#endif
            }
 
            virtual void set_ctime(time_point date)
            {
                m_source->set_ctime(date);
            }
 
            virtual void set_atime(time_point date)
            {
#if SET_FILE_OP_TIMES
                m_atime = date;
#endif
                m_source->set_atime(date);
            }
 
            virtual void set_mtime(time_point date)
            {
#if SET_FILE_OP_TIMES
                m_mtime = date;
#endif
                m_source->set_mtime(date);
            }
 
        protected:
            void flush_cache()
            {
                if (m_cache.status != cache_t::cache_t::status_t::dirty)
                    m_state = state_t::ok;
                else if (!m_cache.region.empty()) {
                    write_cache();
                    if (ok())
                        m_cache.status = cache_t::cache_t::status_t::loaded;
                }
                else {
                    m_state = state_t::ok;
                    m_cache.status = cache_t::cache_t::status_t::loaded;
                }
            }
 
            void invalidate_cache()
            {
                if (m_cache.status == cache_t::cache_t::status_t::dirty && !m_cache.region.empty()) {
                    write_cache();
                    if (!ok()) _Unlikely_
                        return;
                } else
                    m_state = state_t::ok;
                m_cache.status = cache_t::cache_t::status_t::empty;
            }
 
            void load_cache(_In_ fpos_t start)
            {
                stdex_assert(m_cache.status != cache_t::cache_t::status_t::dirty);
                start -= start % m_cache.capacity; // Align to cache block size.
                m_source->seekbeg(m_cache.region.start = start);
                if (m_source->ok()) {
                    m_cache.region.end = start + m_source->read(m_cache.data, m_cache.capacity);
                    m_cache.status = cache_t::cache_t::status_t::loaded;
                    m_state = state_t::ok; // Regardless the read failure, we still might have cached some data.
                }
                else
                    m_state = state_t::fail;
            }
 
            void write_cache()
            {
                stdex_assert(m_cache.status == cache_t::cache_t::status_t::dirty);
                m_source->seekbeg(m_cache.region.start);
                m_source->write(m_cache.data, static_cast<size_t>(m_cache.region.size()));
                m_state = m_source->state();
            }
 
            basic_file* m_source;
            struct cache_t {
                uint8_t* data;
                size_t capacity;
                enum class status_t {
                    empty = 0,
                    loaded,
                    dirty,
                } status;
                interval<fpos_t> region; 
 
                cache_t(_In_ size_t _capacity) :
                    data(new uint8_t[_capacity]),
                    capacity(_capacity),
                    status(status_t::empty),
                    region(0)
                {}
 
                ~cache_t()
                {
                    delete[] data;
                }
            } m_cache;
            fpos_t m_offset; 
#if SET_FILE_OP_TIMES
            time_point
                m_atime,
                m_mtime;
#endif
        };
 
        class basic_sys : virtual public basic, public sys_object
        {
        public:
            basic_sys(_In_opt_ sys_handle h = invalid_handle, _In_ state_t state = state_t::ok) :
                basic(state),
                sys_object(h)
            {}
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                // Windows Server 2003 and Windows XP:  Pipe write operations across a network are limited in size per write.
                // The amount varies per platform. For x86 platforms it's 63.97 MB. For x64 platforms it's 31.97 MB. For Itanium
                // it's 63.95 MB. For more information regarding pipes, see the Remarks section.
                size_t
#if defined(_WIN64)
                    block_size = 0x1F80000;
#elif defined(_WIN32)
                    block_size = 0x3f00000;
#else
                    block_size = SSIZE_MAX;
#endif
                for (size_t to_read = length;;) {
#ifdef _WIN32
                    // ReadFile() might raise exception (e.g. STATUS_FILE_BAD_FORMAT/0xE0000002).
                    BOOL succeeded;
                    DWORD num_read;
                    __try { succeeded = ReadFile(m_h, data, static_cast<DWORD>(std::min<size_t>(to_read, block_size)), &num_read, nullptr); }
                    __except (EXCEPTION_EXECUTE_HANDLER) { succeeded = FALSE; SetLastError(ERROR_UNHANDLED_EXCEPTION); num_read = 0; }
                    if (!succeeded && GetLastError() == ERROR_NO_SYSTEM_RESOURCES && block_size > default_block_size) _Unlikely_ {
                        // Error "Insufficient system resources exist to complete the requested service." occurs
                        // occasionally, when attempting to read too much data at once (e.g. over \\TSClient).
                        block_size = default_block_size;
                        continue;
                    }
                    if (!succeeded) _Unlikely_
#else
                    auto num_read = ::read(m_h, data, std::min<size_t>(to_read, block_size));
                    if (num_read < 0) _Unlikely_
#endif
                    {
                        m_state = to_read < length ? state_t::ok : state_t::fail;
                        return length - to_read;
                    }
                    if (!num_read) _Unlikely_ {
                        m_state = to_read < length || !length ? state_t::ok : state_t::eof;
                        return length - to_read;
                    }
                    to_read -= static_cast<size_t>(num_read);
                    if (!to_read) {
                        m_state = state_t::ok;
                        return length;
                    }
                    reinterpret_cast<uint8_t*&>(data) += num_read;
                }
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                // Windows Server 2003 and Windows XP:  Pipe write operations across a network are limited in size per write.
                // The amount varies per platform. For x86 platforms it's 63.97 MB. For x64 platforms it's 31.97 MB. For Itanium
                // it's 63.95 MB. For more information regarding pipes, see the Remarks section.
                constexpr size_t
#if defined(_WIN64)
                    block_size = 0x1F80000;
#elif defined(_WIN32)
                    block_size = 0x3f00000;
#else
                    block_size = SSIZE_MAX;
#endif
                for (size_t to_write = length;;) {
#ifdef _WIN32
                    // ReadFile() might raise an exception. Be cautious with WriteFile() too.
                    BOOL succeeded;
                    DWORD num_written;
                    __try { succeeded = WriteFile(m_h, data, static_cast<DWORD>(std::min<size_t>(to_write, block_size)), &num_written, nullptr); }
                    __except (EXCEPTION_EXECUTE_HANDLER) { succeeded = FALSE; SetLastError(ERROR_UNHANDLED_EXCEPTION); num_written = 0; }
                    to_write -= num_written;
                    if (!to_write) {
                        m_state = state_t::ok;
                        return length;
                    }
                    reinterpret_cast<const uint8_t*&>(data) += num_written;
                    if (!succeeded) _Unlikely_ {
                        m_state = state_t::fail;
                        return length - to_write;
                    }
#else
                    auto num_written = ::write(m_h, data, std::min<size_t>(to_write, block_size));
                    if (num_written < 0) _Unlikely_ {
                        m_state = state_t::fail;
                        return length - to_write;
                    }
                    to_write -= static_cast<size_t>(num_written);
                    if (!to_write) {
                        m_state = state_t::ok;
                        return length;
                    }
                    reinterpret_cast<const uint8_t*&>(data) += num_written;
#endif
                }
            }
 
            virtual void close()
            {
                try {
                    sys_object::close();
                    m_state = state_t::ok;
                }
                catch (...) {
                    m_state = state_t::fail;
                }
            }
 
            virtual void flush()
            {
#ifdef _WIN32
                m_state = FlushFileBuffers(m_h) ? state_t::ok : state_t::fail;
#else
                m_state = fsync(m_h) >= 0 ? state_t::ok : state_t::fail;
#endif
            }
        };
 
        class buffered_sys : public buffer
        {
        public:
            buffered_sys(_In_opt_ sys_handle h = invalid_handle, size_t read_buffer_size = default_buffer_size, size_t write_buffer_size = default_buffer_size) :
                buffer(read_buffer_size, write_buffer_size),
                m_source(h)
            {
                init(m_source);
            }
 
            virtual ~buffered_sys()
            {
                done();
            }
 
        protected:
            basic_sys m_source;
        };
 
        class socket : public basic
        {
        public:
            socket(_In_opt_ socket_t h = stdex::invalid_socket, _In_ state_t state = state_t::ok) :
                basic(state),
                m_h(h)
            {}
 
        private:
            socket(_In_ const socket& other);
            socket& operator =(_In_ const socket& other);
 
        public:
            socket(_Inout_ socket&& other) noexcept : m_h(other.m_h)
            {
                other.m_h = stdex::invalid_socket;
            }
 
            socket& operator =(_Inout_ socket&& other) noexcept
            {
                if (this != std::addressof(other)) {
                    if (m_h != stdex::invalid_socket)
                        closesocket(m_h);
                    m_h = other.m_h;
                    other.m_h = stdex::invalid_socket;
                }
                return *this;
            }
 
            socket(_In_ int af, _In_ int type, _In_ int protocol)
            {
                m_h = ::socket(af, type, protocol);
                if (m_h == stdex::invalid_socket) _Unlikely_
                    m_state = state_t::fail;
            }
 
            virtual ~socket()
            {
                if (m_h != stdex::invalid_socket)
                    closesocket(m_h);
            }
 
            operator bool() const noexcept { return m_h != stdex::invalid_socket; }
 
            socket_t get() const noexcept { return m_h; }
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                constexpr int block_size = 0x10000000;
                for (size_t to_read = length;;) {
                    auto num_read = recv(m_h, reinterpret_cast<char*>(data),
#ifdef _WIN32
                        static_cast<int>(std::min<size_t>(to_read, block_size)),
#else
                        std::min<size_t>(to_read, block_size),
#endif
                        0);
                    if (num_read < 0) _Unlikely_ {
                        m_state = to_read < length ? state_t::ok : state_t::fail;
                        return length - to_read;
                    }
                    if (!num_read) {
                        m_state = to_read < length || !length ? state_t::ok : state_t::eof;
                        return length - to_read;
                    }
                    to_read -= static_cast<size_t>(num_read);
                    if (!to_read) {
                        m_state = state_t::ok;
                        return length;
                    }
                    reinterpret_cast<uint8_t*&>(data) += num_read;
                }
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                constexpr int block_size = 0x10000000;
                for (size_t to_write = length;;) {
                    auto num_written = send(m_h, reinterpret_cast<const char*>(data),
#ifdef _WIN32
                        static_cast<int>(std::min<size_t>(to_write, block_size)),
#else
                        std::min<size_t>(to_write, block_size),
#endif
                        0);
                    if (num_written < 0) _Unlikely_ {
                        m_state = state_t::fail;
                        return length - to_write;
                    }
                    to_write -= static_cast<size_t>(num_written);
                    if (!to_write) {
                        m_state = state_t::ok;
                        return length;
                    }
                    reinterpret_cast<const uint8_t*&>(data) += num_written;
                }
            }
 
            virtual void close()
            {
                if (m_h != stdex::invalid_socket) {
                    closesocket(m_h);
                    m_h = stdex::invalid_socket;
                }
                m_state = state_t::ok;
            }
 
        protected:
            socket_t m_h;
        };
 
#ifdef _WIN32
        class sequential_stream : public basic
        {
        public:
            sequential_stream(_In_ ISequentialStream* source) : m_source(source)
            {
                m_source->AddRef();
            }
 
            virtual ~sequential_stream()
            {
                m_source->Release();
            }
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                for (size_t to_read = length;;) {
                    HRESULT hr;
                    ULONG num_read = 0;
                    __try { hr = m_source->Read(data, (ULONG)std::min<size_t>(to_read, ULONG_MAX), &num_read); }
                    __except (EXCEPTION_EXECUTE_HANDLER) { hr = E_FAIL; }
                    if (FAILED(hr)) _Unlikely_ {
                        m_state = to_read < length ? state_t::ok : state_t::fail;
                        return length - to_read;
                    }
                    to_read -= num_read;
                    if (hr == S_FALSE) _Unlikely_ {
                        m_state = to_read < length || !length ? state_t::ok : state_t::eof;
                        return length - to_read;
                    }
                    if (!to_read) {
                        m_state = state_t::ok;
                        return length;
                    }
                    reinterpret_cast<uint8_t*&>(data) += num_read;
                }
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                for (size_t to_write = length;;) {
                    HRESULT hr;
                    ULONG num_written = 0;
                    __try { hr = m_source->Write(data, static_cast<ULONG>(std::min<size_t>(to_write, ULONG_MAX)), &num_written); }
                    __except (EXCEPTION_EXECUTE_HANDLER) { hr = E_FAIL; }
                    // In absence of documentation whether num_written gets set when FAILED(hr) (i.e. partially successful writes),
                    // assume write failed completely.
                    if (FAILED(hr)) _Unlikely_ {
                        m_state = state_t::fail;
                        return length - to_write;
                    }
                    to_write -= num_written;
                    if (!to_write) {
                        m_state = state_t::ok;
                        return length;
                    }
                    reinterpret_cast<const uint8_t*&>(data) += num_written;
                }
            }
 
        protected:
            ISequentialStream* m_source;
        };
 
        class asp : public basic
        {
        public:
            asp(_In_opt_ IRequest* request, _In_opt_ IResponse* response) :
                m_request(request),
                m_response(response)
            {
                if (m_request)
                    m_request->AddRef();
                if (m_response)
                    m_response->AddRef();
            }
 
            virtual ~asp()
            {
                if (m_request)
                    m_request->Release();
                if (m_response)
                    m_response->Release();
            }
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                if (!m_request) _Unlikely_ {
                    m_state = state_t::fail;
                    return 0;
                }
                for (size_t to_read = length;;) {
                    VARIANT var_amount, var_data;
                    V_VT(&var_amount) = VT_I4;
                    V_I4(&var_amount) = (LONG)std::min<size_t>(to_read, LONG_MAX);
                    V_VT(&var_data) = VT_EMPTY;
                    HRESULT hr = [&]() {
                        __try { return m_request->BinaryRead(&var_amount, &var_data); }
                        __except (EXCEPTION_EXECUTE_HANDLER) { return E_FAIL; }
                    }();
                    if (FAILED(hr)) _Unlikely_ {
                        m_state = to_read < length ? state_t::ok : state_t::fail;
                        return length - to_read;
                    }
                    stdex_assert(V_VT(&var_amount) == VT_I4);
                    stdex_assert(V_VT(&var_data) == (VT_ARRAY | VT_UI1));
                    std::unique_ptr<SAFEARRAY, SafeArrayDestroy_delete> sa(V_ARRAY(&var_data));
                    if (!V_I4(&var_amount)) _Unlikely_ {
                        m_state = to_read < length || !length ? state_t::ok : state_t::eof;
                        return length - to_read;
                    }
                    safearray_accessor<uint8_t> a(sa.get());
                    memcpy(data, a.data(), V_I4(&var_amount));
                    to_read -= V_I4(&var_amount);
                    if (!to_read) {
                        m_state = state_t::ok;
                        return length;
                    }
                    reinterpret_cast<uint8_t*&>(data) += V_I4(&var_amount);
                }
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                if (!m_response) {
                    m_state = state_t::fail;
                    return 0;
                }
                for (size_t to_write = length;;) {
                    UINT num_written = static_cast<UINT>(std::min<size_t>(to_write, UINT_MAX));
                    std::unique_ptr<OLECHAR, SysFreeString_delete> bstr_data(SysAllocStringByteLen(reinterpret_cast<LPCSTR>(data), num_written));
                    VARIANT var_data;
                    V_VT(&var_data) = VT_BSTR;
                    V_BSTR(&var_data) = bstr_data.get();
                    HRESULT hr = [&]() {
                        __try { return m_response->BinaryWrite(var_data); }
                        __except (EXCEPTION_EXECUTE_HANDLER) { return E_FAIL; }
                    }();
                    if (FAILED(hr)) _Unlikely_ {
                        m_state = state_t::fail;
                        return length - to_write;
                    }
                    to_write -= num_written;
                    if (!to_write) {
                        m_state = state_t::ok;
                        return length;
                    }
                    reinterpret_cast<const uint8_t*&>(data) += num_written;
                }
            }
 
            virtual void close()
            {
                if (m_response) {
                    __try { m_response->End(); }
                    __except (EXCEPTION_EXECUTE_HANDLER) {}
                }
                m_state = state_t::ok;
            }
 
            virtual void flush()
            {
                if (m_response) {
                    HRESULT hr;
                    __try { hr = m_response->Flush(); }
                    __except (EXCEPTION_EXECUTE_HANDLER) { hr = E_FAIL; }
                    m_state = SUCCEEDED(hr) ? state_t::ok : state_t::fail;
                }
            }
 
        protected:
            IRequest* m_request;
            IResponse* m_response;
        };
#endif
 
        enum mode_t
        {
            mode_for_reading = 1 << 0,        
            mode_for_writing = 1 << 1,        
            mode_for_chmod = 1 << 2,          
 
            mode_open_existing = 0 << 3,      
            mode_truncate_existing = 1 << 3,  
            mode_preserve_existing = 2 << 3,  
            mode_create_new = 3 << 3,         
            mode_create = 4 << 3,             
            mode_disposition_mask = 7 << 3,   
 
            mode_append = 1 << 6,             
            mode_text = 0,                    
            mode_binary = 1 << 7,             
 
            share_none = 0,                   
            share_reading = 1 << 8,           
            share_writing = 1 << 9,           
            share_deleting = 1 << 10,         
            share_all = share_reading | share_writing | share_deleting, // Allow others all operations on our file
 
            inherit_handle = 1 << 11,         
 
            hint_write_thru = 1 << 12,        
            hint_no_buffering = 1 << 13,      
            hint_random_access = 1 << 14,     
            hint_sequential_access = 1 << 15, 
        };
 
#pragma warning(push)
#pragma warning(disable: 4250)
        class file : virtual public basic_file, virtual public basic_sys
        {
        public:
            file(_In_opt_ sys_handle h = invalid_handle, _In_ state_t state = state_t::ok) : basic_sys(h, state) {}
 
            file(_In_z_ const schar_t* filename, _In_ int mode)
            {
                open(filename, mode);
            }
 
            template <class TR = std::char_traits<schar_t>, class AX = std::allocator<schar_t>>
            file(_In_ const std::basic_string<TR, AX>& filename, _In_ int mode) : file(filename.c_str(), mode) {}
 
            void open(_In_z_ const schar_t* filename, _In_ int mode)
            {
                if (m_h != invalid_handle)
                    close();
 
#ifdef _WIN32
                DWORD dwDesiredAccess = 0;
                if (mode & mode_for_reading) dwDesiredAccess |= GENERIC_READ;
                if (mode & mode_for_writing) dwDesiredAccess |= GENERIC_WRITE;
                if (mode & mode_for_chmod)   dwDesiredAccess |= FILE_WRITE_ATTRIBUTES;
 
                DWORD dwShareMode = 0;
                if (mode & share_reading)  dwShareMode |= FILE_SHARE_READ;
                if (mode & share_writing)  dwShareMode |= FILE_SHARE_WRITE;
                if (mode & share_deleting) dwShareMode |= FILE_SHARE_DELETE;
 
                SECURITY_ATTRIBUTES sa = { sizeof(SECURITY_ATTRIBUTES) };
                sa.bInheritHandle = mode & inherit_handle ? true : false;
 
                DWORD dwCreationDisposition;
                switch (mode & mode_disposition_mask) {
                case mode_open_existing: dwCreationDisposition = OPEN_EXISTING; break;
                case mode_truncate_existing: dwCreationDisposition = TRUNCATE_EXISTING; break;
                case mode_preserve_existing: dwCreationDisposition = OPEN_ALWAYS; break;
                case mode_create_new: dwCreationDisposition = CREATE_NEW; break;
                case mode_create: dwCreationDisposition = CREATE_ALWAYS; break;
                default: throw std::invalid_argument("invalid mode");
                }
 
                DWORD dwFlagsAndAttributes = FILE_ATTRIBUTE_NORMAL;
                if (mode & hint_write_thru)        dwFlagsAndAttributes |= FILE_FLAG_WRITE_THROUGH;
                if (mode & hint_no_buffering)      dwFlagsAndAttributes |= FILE_FLAG_NO_BUFFERING;
                if (mode & hint_random_access)     dwFlagsAndAttributes |= FILE_FLAG_RANDOM_ACCESS;
                if (mode & hint_sequential_access) dwFlagsAndAttributes |= FILE_FLAG_SEQUENTIAL_SCAN;
 
                m_h = CreateFile(filename, dwDesiredAccess, dwShareMode, &sa, dwCreationDisposition, dwFlagsAndAttributes, NULL);
#else
                int flags = 0;
                switch (mode & (mode_for_reading | mode_for_writing)) {
                case mode_for_reading: flags |= O_RDONLY; break;
                case mode_for_writing: flags |= O_WRONLY; break;
                case mode_for_reading | mode_for_writing: flags |= O_RDWR; break;
                }
                switch (mode & mode_disposition_mask) {
                case mode_open_existing: break;
                case mode_truncate_existing: flags |= O_TRUNC; break;
                case mode_preserve_existing: flags |= O_CREAT; break;
                case mode_create_new: flags |= O_CREAT | O_EXCL; break;
                case mode_create: flags |= O_CREAT | O_TRUNC; break;
                default: throw std::invalid_argument("invalid mode");
                }
                if (mode & hint_write_thru) flags |= O_DSYNC;
#ifndef __APPLE__
                if (mode & hint_no_buffering) flags |= O_RSYNC;
#endif
 
                m_h = ::open(filename, flags, DEFFILEMODE);
#endif
                if (m_h != invalid_handle) {
                    m_state = state_t::ok;
                    if (mode & mode_append)
                        seek(0, seek_t::end);
                }
                else
                    m_state = state_t::fail;
            }
 
            template <class TR = std::char_traits<schar_t>, class AX = std::allocator<schar_t>>
            void open(_In_ const std::basic_string<TR, AX>& filename, _In_ int mode)
            {
                open(filename.c_str(), mode);
            }
 
            virtual fpos_t seek(_In_ foff_t offset, _In_ seek_t how = seek_t::beg)
            {
#ifdef _WIN32
                LARGE_INTEGER li;
                li.QuadPart = offset;
                li.LowPart = SetFilePointer(m_h, li.LowPart, &li.HighPart, static_cast<DWORD>(how));
                if (li.LowPart != 0xFFFFFFFF || GetLastError() == NO_ERROR) {
                    m_state = state_t::ok;
                    return li.QuadPart;
                }
#else
                off64_t result = lseek64(m_h, offset, static_cast<int>(how));
                if (result >= 0) {
                    m_state = state_t::ok;
                    return static_cast<fpos_t>(result);
                }
#endif
                m_state = state_t::fail;
                return fpos_max;
            }
 
            virtual fpos_t tell() const
            {
                if (m_h != invalid_handle) {
#ifdef _WIN32
                    LARGE_INTEGER li;
                    li.QuadPart = 0;
                    li.LowPart = SetFilePointer(m_h, 0, &li.HighPart, FILE_CURRENT);
                    if (li.LowPart != 0xFFFFFFFF || GetLastError() == NO_ERROR)
                        return li.QuadPart;
#else
                    off64_t result = lseek64(m_h, 0, SEEK_CUR);
                    if (result >= 0)
                        return static_cast<fpos_t>(result);
#endif
                }
                return fpos_max;
            }
 
            virtual void lock(_In_ fpos_t offset, _In_ fsize_t length)
            {
#ifdef _WIN32
                LARGE_INTEGER liOffset;
                LARGE_INTEGER liSize;
                liOffset.QuadPart = offset;
                liSize.QuadPart = length;
                if (LockFile(m_h, liOffset.LowPart, liOffset.HighPart, liSize.LowPart, liSize.HighPart)) {
                    m_state = state_t::ok;
                    return;
                }
#else
                off64_t orig = lseek64(m_h, 0, SEEK_CUR);
                if (orig >= 0) {
                    if (offset > std::numeric_limits<off64_t>::max())
                        throw std::invalid_argument("file offset too big");
                    if (length > std::numeric_limits<off64_t>::max())
                        throw std::invalid_argument("file section length too big");
                    m_state = lseek64(m_h, static_cast<off64_t>(offset), SEEK_SET) >= 0 && lockf64(m_h, F_LOCK, static_cast<off64_t>(length)) >= 0 ? state_t::ok : state_t::fail;
                    lseek64(m_h, orig, SEEK_SET);
                    m_state = state_t::ok;
                    return;
                }
#endif
                m_state = state_t::fail;
            }
 
            virtual void unlock(_In_ fpos_t offset, _In_ fsize_t length)
            {
#ifdef _WIN32
                LARGE_INTEGER liOffset;
                LARGE_INTEGER liSize;
                liOffset.QuadPart = offset;
                liSize.QuadPart = length;
                if (UnlockFile(m_h, liOffset.LowPart, liOffset.HighPart, liSize.LowPart, liSize.HighPart)) {
                    m_state = state_t::ok;
                    return;
                }
#else
                off64_t orig = lseek64(m_h, 0, SEEK_CUR);
                if (orig >= 0) {
                    if (offset > std::numeric_limits<off64_t>::max())
                        throw std::invalid_argument("file offset too big");
                    if (length > std::numeric_limits<off64_t>::max())
                        throw std::invalid_argument("file section length too big");
                    if (lseek64(m_h, static_cast<off64_t>(offset), SEEK_SET) >= 0 && lockf64(m_h, F_ULOCK, static_cast<off64_t>(length)) >= 0) {
                        lseek64(m_h, orig, SEEK_SET);
                        m_state = state_t::ok;
                        return;
                    }
                    lseek64(m_h, orig, SEEK_SET);
                }
#endif
                m_state = state_t::fail;
            }
 
            virtual fsize_t size() const
            {
#ifdef _WIN32
                LARGE_INTEGER li;
                li.LowPart = GetFileSize(m_h, (LPDWORD)&li.HighPart);
                if (li.LowPart == 0xFFFFFFFF && GetLastError() != NO_ERROR)
                    li.QuadPart = -1;
                return li.QuadPart;
#else
                off64_t orig = lseek64(m_h, 0, SEEK_CUR);
                if (orig >= 0) {
                    off64_t length = lseek64(m_h, 0, SEEK_END);
                    lseek64(m_h, orig, SEEK_SET);
                    if (length >= 0)
                        return static_cast<fsize_t>(length);
                }
                return fsize_max;
#endif
            }
 
            virtual void truncate()
            {
#ifdef _WIN32
                if (SetEndOfFile(m_h)) {
                    m_state = state_t::ok;
                    return;
                }
#else
                off64_t length = lseek64(m_h, 0, SEEK_CUR);
                if (length >= 0 && ftruncate64(m_h, length) >= 0) {
                    m_state = state_t::ok;
                    return;
                }
#endif
                m_state = state_t::fail;
            }
 
#ifdef _WIN32
            static time_point ft2tp(_In_ const FILETIME& ft)
            {
#if _HAS_CXX20
                uint64_t t = (static_cast<int64_t>(ft.dwHighDateTime) << 32) | ft.dwLowDateTime;
#else
                uint64_t t = ((static_cast<int64_t>(ft.dwHighDateTime) << 32) | ft.dwLowDateTime) - 116444736000000000ll;
#endif
                return time_point(time_point::duration(t));
            }
 
            static void tp2ft(_In_ time_point tp, _Out_ FILETIME& ft)
            {
#if _HAS_CXX20
                uint64_t t = tp.time_since_epoch().count();
#else
                uint64_t t = tp.time_since_epoch().count() + 116444736000000000ll;
#endif
                ft.dwHighDateTime = static_cast<DWORD>((t >> 32) & 0xffffffff);
                ft.dwLowDateTime = static_cast<DWORD>(t & 0xffffffff);
            }
#endif
 
            virtual time_point ctime() const
            {
#ifdef _WIN32
                FILETIME ft;
                if (GetFileTime(m_h, &ft, nullptr, nullptr))
                    return ft2tp(ft);
#endif
                return time_point::min();
            }
 
            virtual time_point atime() const
            {
#ifdef _WIN32
                FILETIME ft;
                if (GetFileTime(m_h, nullptr, &ft, nullptr))
                    return ft2tp(ft);
#else
                struct stat buf;
                if (fstat(m_h, &buf) >= 0)
                    return clock::from_time_t(buf.st_atime);
#endif
                return time_point::min();
            }
 
            virtual time_point mtime() const
            {
#ifdef _WIN32
                FILETIME ft;
                if (GetFileTime(m_h, nullptr, nullptr, &ft))
                    return ft2tp(ft);
#else
                struct stat buf;
                if (fstat(m_h, &buf) >= 0)
                    return clock::from_time_t(buf.st_mtime);
#endif
                return time_point::min();
            }
 
            virtual void set_ctime(time_point date)
            {
                stdex_assert(m_h != invalid_handle);
#ifdef _WIN32
                FILETIME ft;
                tp2ft(date, ft);
                if (SetFileTime(m_h, &ft, nullptr, nullptr))
                    return;
                throw std::system_error(GetLastError(), std::system_category(), "SetFileTime failed");
#else
                _Unreferenced_(date);
                throw std::runtime_error("not supported");
#endif
            }
 
            virtual void set_atime(time_point date)
            {
                stdex_assert(m_h != invalid_handle);
#ifdef _WIN32
                FILETIME ft;
                tp2ft(date, ft);
                if (SetFileTime(m_h, nullptr, &ft, nullptr))
                    return;
                throw std::system_error(GetLastError(), std::system_category(), "SetFileTime failed");
#else
                struct timespec ts[2] = {
                    { date.time_since_epoch().count(), 0 },
                    { 0, UTIME_OMIT },
                };
                if (futimens(m_h, ts) >= 0)
                    return;
                throw std::system_error(errno, std::system_category(), "futimens failed");
#endif
            }
 
            virtual void set_mtime(time_point date)
            {
#ifdef _WIN32
                FILETIME ft;
                tp2ft(date, ft);
                if (SetFileTime(m_h, nullptr, nullptr, &ft))
                    return;
                throw std::system_error(GetLastError(), std::system_category(), "SetFileTime failed");
#else
                struct timespec ts[2] = {
                    { 0, UTIME_OMIT },
                    { date.time_since_epoch().count(), 0 },
                };
                if (futimens(m_h, ts) >= 0)
                    return;
                throw std::system_error(errno, std::system_category(), "futimens failed");
#endif
            }
 
            static bool exists(_In_z_ const stdex::schar_t* filename)
            {
#ifdef _WIN32
                return GetFileAttributes(filename) != INVALID_FILE_ATTRIBUTES;
#else
                struct stat s;
                return stat(filename, &s) == 0;
#endif
            }
 
            template <class TR = std::char_traits<schar_t>, class AX = std::allocator<schar_t>>
            static bool exists(_In_ const std::basic_string<TR, AX>& filename)
            {
                return exists(filename.c_str());
            }
 
            static bool readonly(_In_z_ const stdex::schar_t* filename)
            {
#ifdef _WIN32
                DWORD dwAttr = GetFileAttributes(filename);
                return dwAttr != INVALID_FILE_ATTRIBUTES && (dwAttr & FILE_ATTRIBUTE_READONLY) != 0;
#else
                struct stat s;
                return stat(filename, &s) == 0 && (s.st_mode & (S_IWUSR|S_IWGRP|S_IWOTH)) == 0;
#endif
            }
 
            template <class TR = std::char_traits<schar_t>, class AX = std::allocator<schar_t>>
            static bool readonly(_In_ const std::basic_string<TR, AX>& filename)
            {
                return readonly(filename.c_str());
            }
        };
#pragma warning(pop)
 
        class cached_file : public cache
        {
        public:
            cached_file(_In_opt_ sys_handle h = invalid_handle, _In_ state_t state = state_t::ok, _In_ size_t cache_size = default_cache_size) :
                cache(cache_size),
                m_source(h, state)
            {
                init(m_source);
            }
 
            cached_file(_In_z_ const schar_t* filename, _In_ int mode, _In_ size_t cache_size = default_cache_size) :
                cache(cache_size),
                m_source(filename, mode & mode_for_writing ? mode | mode_for_reading : mode)
            {
                init(m_source);
            }
 
            template <class TR = std::char_traits<schar_t>, class AX = std::allocator<schar_t>>
            cached_file(_In_ const std::basic_string<TR, AX>& filename, _In_ int mode, _In_ size_t cache_size = default_cache_size) : cached_file(filename.c_str(), mode, cache_size) {}
 
            virtual ~cached_file()
            {
                done();
            }
 
            void open(_In_z_ const schar_t* filename, _In_ int mode)
            {
                invalidate_cache();
                if (!ok()) _Unlikely_{
                    m_state = state_t::fail;
                    return;
                }
                m_source.open(filename, mode & mode_for_writing ? mode | mode_for_reading : mode);
                if (m_source.ok()) {
                    init();
                    return;
                }
                m_state = state_t::fail;
            }
 
            template <class TR = std::char_traits<schar_t>, class AX = std::allocator<schar_t>>
            void open(_In_ const std::basic_string<TR, AX>& filename, _In_ int mode)
            {
                open(filename.c_str(), mode);
            }
 
            operator bool() const noexcept { return m_source; }
 
        protected:
            file m_source;
        };
 
        class memory_file : public basic_file
        {
        public:
            memory_file(_In_ state_t state = state_t::ok) :
                basic(state),
                m_data(nullptr),
                m_offset(0),
                m_size(0),
                m_reserved(0),
                m_manage(true)
            {
#if SET_FILE_OP_TIMES
                m_ctime = m_atime = m_mtime = time_point::now();
#endif
            }
 
            memory_file(_In_ size_t size, _In_ state_t state = state_t::ok) :
                basic(state),
                m_data(reinterpret_cast<uint8_t*>(malloc(size))),
                m_offset(0),
                m_size(0),
                m_reserved(size),
                m_manage(true)
            {
                if (!m_data) {
                    m_state = state_t::fail;
                    throw std::bad_alloc();
                }
#if SET_FILE_OP_TIMES
                m_ctime = m_atime = m_mtime = time_point::now();
#endif
            }
 
            memory_file(_Inout_ void* data, _In_ size_t size, _In_ size_t reserved, _In_ bool manage = false, _In_ state_t state = state_t::ok) :
                basic(state),
                m_data(reinterpret_cast<uint8_t*>(data)),
                m_offset(0),
                m_size(size),
                m_reserved(reserved),
                m_manage(manage)
            {
                stdex_assert(data || !size);
                stdex_assert(reserved >= size);
#if SET_FILE_OP_TIMES
                m_ctime = m_atime = m_mtime = time_point::now();
#endif
            }
 
            memory_file(_Inout_ void* data, _In_ size_t size, _In_ bool manage = false, _In_ state_t state = state_t::ok) :
                memory_file(data, size, size, manage, state)
            {}
 
            memory_file(_In_z_ const schar_t* filename, _In_ int mode) : memory_file()
            {
                load(filename, mode);
            }
 
            template <class TR = std::char_traits<schar_t>, class AX = std::allocator<schar_t>>
            memory_file(_In_ const std::basic_string<TR, AX>& filename, _In_ int mode) : memory_file(filename.c_str(), mode) {}
 
            memory_file(_In_ const memory_file& other) :
                basic_file(other),
                m_data(reinterpret_cast<uint8_t*>(malloc(other.m_size))),
                m_offset(other.m_offset),
                m_size(other.m_size),
                m_reserved(other.m_size),
                m_manage(true)
#if SET_FILE_OP_TIMES
                , m_ctime(other.m_ctime)
                , m_atime(other.m_atime)
                , m_mtime(other.m_mtime)
#endif
            {
                if (!m_data) {
                    m_state = state_t::fail;
                    throw std::bad_alloc();
                }
                memcpy(m_data, other.m_data, other.m_size);
            }
 
            memory_file& operator=(_In_ const memory_file& other)
            {
                if (this != std::addressof(other)) {
                    *static_cast<basic_file*>(this) = other;
                    if (m_manage && m_data)
                        free(m_data);
                    m_data = reinterpret_cast<uint8_t*>(malloc(other.m_size));
                    if (!m_data) {
                        m_state = state_t::fail;
                        throw std::bad_alloc();
                    }
                    memcpy(m_data, other.m_data, other.m_size);
                    m_offset = other.m_offset;
                    m_size = other.m_size;
                    m_reserved = other.m_size;
                    m_manage = true;
#if SET_FILE_OP_TIMES
                    m_ctime = other.m_ctime;
                    m_atime = other.m_atime;
                    m_mtime = other.m_mtime;
#endif
                }
                return *this;
            }
 
            memory_file(_Inout_ memory_file&& other) noexcept :
                basic_file(std::move(other)),
                m_data(other.m_data),
                m_offset(other.m_offset),
                m_size(other.m_size),
                m_reserved(other.m_reserved),
                m_manage(other.m_manage)
#if SET_FILE_OP_TIMES
                , m_ctime(other.m_ctime)
                , m_atime(other.m_atime)
                , m_mtime(other.m_mtime)
#endif
            {
                other.m_state = state_t::ok;
                other.m_data = nullptr;
                other.m_offset = 0;
                other.m_size = 0;
                other.m_reserved = 0;
                other.m_manage = true;
#if SET_FILE_OP_TIMES
                other.m_ctime = other.m_atime = other.m_mtime = time_point::now();
#endif
            }
 
            memory_file& operator=(_Inout_ memory_file&& other) noexcept
            {
                if (this != std::addressof(other)) {
                    *static_cast<basic_file*>(this) = std::move(other);
                    if (m_manage && m_data)
                        free(m_data);
                    m_data = other.m_data;
                    other.m_data = nullptr;
                    m_offset = other.m_offset;
                    other.m_offset = 0;
                    m_size = other.m_size;
                    other.m_size = 0;
                    m_reserved = other.m_reserved;
                    other.m_reserved = 0;
                    m_manage = other.m_manage;
                    other.m_manage = true;
#if SET_FILE_OP_TIMES
                    m_ctime = other.m_ctime;
                    m_atime = other.m_atime;
                    m_mtime = other.m_mtime;
                    other.m_ctime = other.m_atime = other.m_mtime = time_point::now();
#endif
                }
                return *this;
            }
 
            virtual ~memory_file()
            {
                if (m_manage && m_data)
                    free(m_data);
            }
 
            void reserve(_In_ size_t required, _In_ bool tight = false) noexcept
            {
                if (required <= m_reserved && (!tight || required >= m_reserved)) {
                    m_state = state_t::ok;
                    return;
                }
                if (!m_manage) {
                    m_state = state_t::fail;
                    return;
                }
                size_t reserved = tight ? required : ((required + required / 4 + (default_block_size - 1)) / default_block_size) * default_block_size;
                auto data = reinterpret_cast<uint8_t*>(realloc(m_data, reserved));
                if (!data && reserved) _Unlikely_ {
                    m_state = state_t::fail;
                    return;
                }
                m_data = data;
                if (reserved < m_size)
                    m_size = reserved;
                m_reserved = reserved;
                m_state = state_t::ok;
            }
 
            void load(_In_z_ const schar_t* filename, _In_ int mode)
            {
                file f(filename, (mode & ~hint_random_access) | mode_for_reading | hint_sequential_access);
                if (!f.ok()) {
                    m_state = state_t::fail;
                    return;
                }
                fsize_t size = f.size();
                if (size > SIZE_MAX) {
                    m_state = state_t::fail;
                    return;
                }
                reserve(static_cast<size_t>(size), true);
                if (!ok()) _Unlikely_ {
                    return;
                }
                m_offset = m_size = 0;
                write_stream(f);
                if (ok())
                    m_offset = 0;
#if SET_FILE_OP_TIMES
                m_ctime = f.ctime();
                m_atime = f.atime();
                m_mtime = f.mtime();
#endif
            }
 
            template <class TR = std::char_traits<schar_t>, class AX = std::allocator<schar_t>>
            void load(_In_ const std::basic_string<TR, AX>& filename, _In_ int mode)
            {
                load(filename.c_str(), mode);
            }
 
            void save(_In_z_ const schar_t* filename, _In_ int mode)
            {
                file f(filename, (mode & ~hint_random_access) | mode_for_writing | hint_sequential_access);
                if (!f.ok()) {
                    m_state = state_t::fail;
                    return;
                }
                f.write(m_data, m_size);
                if (!f.ok()) {
                    m_state = state_t::fail;
                    return;
                }
                f.truncate();
#if SET_FILE_OP_TIMES
                f.set_ctime(m_ctime);
                f.set_atime(m_atime);
                f.set_mtime(m_mtime);
#endif
            }
 
            template <class TR = std::char_traits<schar_t>, class AX = std::allocator<schar_t>>
            void save(_In_ const std::basic_string<TR, AX>& filename, _In_ int mode)
            {
                save(filename.c_str(), mode);
            }
 
            const void* data() const { return m_data; }
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
#if SET_FILE_OP_TIMES
                m_atime = time_point::now();
#endif
                size_t available = m_size - m_offset;
                if (length <= available) {
                    memcpy(data, &m_data[m_offset], length);
                    m_offset += length;
                    m_state = state_t::ok;
                    return length;
                }
                if (length && !available) {
                    m_state = state_t::eof;
                    return 0;
                }
                memcpy(data, &m_data[m_offset], available);
                m_offset += available;
                m_state = state_t::ok;
                return available;
            }
 
            template <class T>
            memory_file& read_data(_Out_ T& data)
            {
#if SET_FILE_OP_TIMES
                m_atime = time_point::now();
#endif
                if (CHECK_STREAM_STATE && !ok()) _Unlikely_ {
                    data = 0;
                    return *this;
                }
                size_t end_offset = m_offset + sizeof(T);
                if (end_offset <= m_size) {
                    data = LE2HE(*reinterpret_cast<T*>(&m_data[m_offset]));
                    m_offset = end_offset;
#if !CHECK_STREAM_STATE
                    m_state = state_t::ok;
#endif
                }
                else {
                    data = 0;
                    m_offset = m_size;
                    m_state = state_t::eof;
                }
                return *this;
            }
 
            template<class T, class TR = std::char_traits<T>, class AX = std::allocator<T>>
            memory_file& read_str(_Inout_ std::basic_string<T, TR, AX>&data)
            {
#if SET_FILE_OP_TIMES
                m_atime = time_point::now();
#endif
                if (CHECK_STREAM_STATE && !ok()) _Unlikely_ {
                    data.clear();
                    return *this;
                }
                size_t end_offset = m_offset + sizeof(uint32_t);
                if (end_offset <= m_size) {
                    uint32_t num_chars = LE2HE(*reinterpret_cast<uint32_t*>(&m_data[m_offset]));
                    m_offset = end_offset;
                    end_offset = stdex::add(m_offset, stdex::mul(num_chars, sizeof(T)));
                    T* start = reinterpret_cast<T*>(&m_data[m_offset]);
                    if (end_offset <= m_size) {
                        data.assign(start, start + num_chars);
                        m_offset = end_offset;
#if !CHECK_STREAM_STATE
                        m_state = state_t::ok;
#endif
                        return *this;
                    }
                    if (end_offset <= m_size)
                        data.assign(start, reinterpret_cast<T*>(&m_data[m_size]));
                }
                m_offset = m_size;
                m_state = state_t::eof;
                return *this;
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
#if SET_FILE_OP_TIMES
                m_atime = m_mtime = time_point::now();
#endif
                size_t end_offset = m_offset + length;
                if (end_offset > m_reserved) {
                    reserve(end_offset);
                    if (!ok()) _Unlikely_
                        return 0;
                }
                memcpy(&m_data[m_offset], data, length);
                m_offset = end_offset;
                if (m_offset > m_size)
                    m_size = m_offset;
                m_state = state_t::ok;
                return length;
            }
 
            void write_byte(_In_ uint8_t byte, _In_ size_t amount = 1)
            {
#if SET_FILE_OP_TIMES
                m_atime = m_mtime = time_point::now();
#endif
                size_t end_offset = m_offset + amount;
                if (end_offset > m_reserved) {
                    reserve(end_offset);
                    if (!ok()) _Unlikely_
                        return;
                }
                memset(&m_data[m_offset], byte, amount);
                m_offset = end_offset;
                if (m_offset > m_size)
                    m_size = m_offset;
                m_state = state_t::ok;
            }
 
            template <class T>
            memory_file& write_data(const T data)
            {
#if SET_FILE_OP_TIMES
                m_atime = m_mtime = time_point::now();
#endif
                if (CHECK_STREAM_STATE && !ok()) _Unlikely_
                    return *this;
                size_t end_offset = m_offset + sizeof(T);
                if (end_offset > m_reserved) {
                    reserve(end_offset);
                    if (!ok()) _Unlikely_
                        return *this;
                }
                (*reinterpret_cast<T*>(&m_data[m_offset])) = HE2LE(data);
                m_offset = end_offset;
                if (m_offset > m_size)
                    m_size = m_offset;
#if !CHECK_STREAM_STATE
                m_state = state_t::ok;
#endif
                return *this;
            }
 
            template <class T>
            memory_file& write_str(_In_z_ const T * data)
            {
#if SET_FILE_OP_TIMES
                m_atime = m_mtime = time_point::now();
#endif
                if (CHECK_STREAM_STATE && !ok()) _Unlikely_
                    return *this;
                size_t num_chars = stdex::strlen(data);
                if (num_chars > UINT32_MAX)
                    throw std::invalid_argument("string too long");
                size_t size_chars = num_chars * sizeof(T);
                size_t size = sizeof(uint32_t) + size_chars;
                size_t end_offset = m_offset + size;
                if (end_offset > m_reserved) {
                    reserve(end_offset);
                    if (!ok()) _Unlikely_
                        return *this;
                }
                auto p = &m_data[m_offset];
                *reinterpret_cast<uint32_t*>(p) = HE2LE((uint32_t)num_chars);
                memcpy(p + sizeof(uint32_t), data, size_chars);
                m_offset = end_offset;
                if (m_offset > m_size)
                    m_size = m_offset;
#if !CHECK_STREAM_STATE
                m_state = state_t::ok;
#endif
                return *this;
            }
 
            template<class T, class TR = std::char_traits<T>, class AX = std::allocator<T>>
            memory_file& write_str(_In_ const std::basic_string<T, TR, AX>& data)
            {
#if SET_FILE_OP_TIMES
                m_atime = m_mtime = time_point::now();
#endif
                if (CHECK_STREAM_STATE && !ok()) _Unlikely_
                    return *this;
                size_t num_chars = data.size();
                if (num_chars > UINT32_MAX)
                    throw std::invalid_argument("string too long");
                size_t size_chars = num_chars * sizeof(T);
                size_t size = sizeof(uint32_t) + size_chars;
                size_t end_offset = m_offset + size;
                if (end_offset > m_reserved) {
                    reserve(end_offset);
                    if (!ok()) _Unlikely_
                        return *this;
                }
                auto p = &m_data[m_offset];
                *reinterpret_cast<uint32_t*>(p) = HE2LE((uint32_t)num_chars);
                memcpy(p + sizeof(uint32_t), data.data(), size_chars);
                m_offset = end_offset;
                if (m_offset > m_size)
                    m_size = m_offset;
#if !CHECK_STREAM_STATE
                m_state = state_t::ok;
#endif
                return *this;
            }
 
            size_t write_stream(_Inout_ basic & stream, _In_ size_t amount = SIZE_MAX)
            {
#if SET_FILE_OP_TIMES
                m_atime = m_mtime = time_point::now();
#endif
                size_t num_read, dst_offset = m_offset, dst_size = m_offset;
                size_t num_copied = 0, to_write = amount;
                m_state = state_t::ok;
                if (amount != SIZE_MAX) {
                    dst_size = stdex::add(dst_size, amount);
                    reserve(dst_size);
                    if (!ok()) _Unlikely_
                        return 0;
                    while (to_write) {
                        num_read = stream.read(&m_data[dst_offset], to_write);
                        /*dst_size =*/ dst_offset += num_read;
                        num_copied += num_read;
                        to_write -= num_read;
                        if (!stream.ok()) {
                            if (stream.state() != state_t::eof)
                                m_state = state_t::fail;
                            break;
                        }
                    };
                }
                else {
                    size_t block_size;
                    while (to_write) {
                        block_size = std::min(to_write, default_block_size);
                        dst_size = stdex::add(dst_size, block_size);
                        reserve(dst_size);
                        if (!ok()) _Unlikely_
                            break;
                        num_read = stream.read(&m_data[dst_offset], block_size);
                        dst_size = dst_offset += num_read;
                        num_copied += num_read;
                        to_write -= num_read;
                        if (!stream.ok()) {
                            if (stream.state() != state_t::eof)
                                m_state = state_t::fail;
                            break;
                        }
                    };
                }
                m_offset = dst_offset;
                if (m_offset > m_size)
                    m_size = m_offset;
                return num_copied;
            }
 
            virtual void close()
            {
                if (m_manage && m_data)
                    free(m_data);
                m_data = nullptr;
                m_manage = true;
                m_offset = 0;
                m_size = m_reserved = 0;
#if SET_FILE_OP_TIMES
                m_ctime = m_atime = m_mtime = time_point::min();
#endif
                m_state = state_t::ok;
            }
 
            virtual fpos_t seek(_In_ foff_t offset, _In_ seek_t how = seek_t::beg)
            {
                switch (how) {
                case seek_t::beg: break;
                case seek_t::cur: offset = static_cast<foff_t>(m_offset) + offset; break;
                case seek_t::end: offset = static_cast<foff_t>(m_size) + offset; break;
                default: throw std::invalid_argument("unknown seek origin");
                }
                if (offset < 0) _Unlikely_
                    throw std::invalid_argument("negative file offset");
                if (static_cast<fpos_t>(offset) > SIZE_MAX) _Unlikely_
                    throw std::invalid_argument("file offset too big");
                m_state = state_t::ok;
                return m_offset = static_cast<size_t>(offset);
            }
 
            virtual fpos_t tell() const
            {
                return m_offset;
            }
 
            virtual fsize_t size() const
            {
                return m_size;
            }
 
            virtual void truncate()
            {
#if SET_FILE_OP_TIMES
                m_atime = m_mtime = time_point::now();
#endif
                m_size = m_offset;
                reserve(m_offset);
            }
 
#if SET_FILE_OP_TIMES
            virtual time_point ctime() const
            {
                return m_ctime;
            }
 
            virtual time_point atime() const
            {
                return m_atime;
            }
 
            virtual time_point mtime() const
            {
                return m_mtime;
            }
 
            virtual void set_ctime(time_point date)
            {
                m_ctime = date;
            }
 
            virtual void set_atime(time_point date)
            {
                m_atime = date;
            }
 
            virtual void set_mtime(time_point date)
            {
                m_mtime = date;
            }
#endif
 
        protected:
            template <class T>
            void set(_In_ fpos_t offset, _In_ const T data)
            {
#if SET_FILE_OP_TIMES
                m_atime = m_mtime = time_point::now();
#endif
                stdex_assert(offset + sizeof(T) < m_size);
                (*reinterpret_cast<T*>(&m_data[offset])) = HE2LE(data);
            }
 
        public:
            void set(_In_ fpos_t offset, _In_ const int8_t data) { set<int8_t>(offset, data); }
            void set(_In_ fpos_t offset, _In_ const int16_t data) { set<int16_t>(offset, data); }
            void set(_In_ fpos_t offset, _In_ const int32_t data) { set<int32_t>(offset, data); }
            void set(_In_ fpos_t offset, _In_ const int64_t data) { set<int64_t>(offset, data); }
            void set(_In_ fpos_t offset, _In_ const uint8_t data) { set<uint8_t>(offset, data); }
            void set(_In_ fpos_t offset, _In_ const uint16_t data) { set<uint16_t>(offset, data); }
            void set(_In_ fpos_t offset, _In_ const uint32_t data) { set<uint32_t>(offset, data); }
            void set(_In_ fpos_t offset, _In_ const uint64_t data) { set<uint64_t>(offset, data); }
            void set(_In_ fpos_t offset, _In_ const float data) { set<float>(offset, data); }
            void set(_In_ fpos_t offset, _In_ const double data) { set<double>(offset, data); }
            void set(_In_ fpos_t offset, _In_ const char data) { set<char>(offset, data); }
#ifdef _NATIVE_WCHAR_T_DEFINED
            void set(_In_ fpos_t offset, _In_ const wchar_t data) { set<wchar_t>(offset, data); }
#endif
 
        protected:
            template <class T>
            void get(_In_ fpos_t offset, _Out_ T & data)
            {
                stdex_assert(offset + sizeof(T) < m_size);
                data = LE2HE(*(T*)(&m_data[offset]));
#if SET_FILE_OP_TIMES
                m_atime = time_point::now();
#endif
            }
 
        public:
            void get(_In_ fpos_t offset, _Out_ int8_t & data) { get<int8_t>(offset, data); }
            void get(_In_ fpos_t offset, _Out_ int16_t & data) { get<int16_t>(offset, data); }
            void get(_In_ fpos_t offset, _Out_ int32_t & data) { get<int32_t>(offset, data); }
            void get(_In_ fpos_t offset, _Out_ int64_t & data) { get<int64_t>(offset, data); }
            void get(_In_ fpos_t offset, _Out_ uint8_t & data) { get<uint8_t>(offset, data); }
            void get(_In_ fpos_t offset, _Out_ uint16_t & data) { get<uint16_t>(offset, data); }
            void get(_In_ fpos_t offset, _Out_ uint32_t & data) { get<uint32_t>(offset, data); }
            void get(_In_ fpos_t offset, _Out_ uint64_t & data) { get<uint64_t>(offset, data); }
            void get(_In_ fpos_t offset, _Out_ float& data) { get<float>(offset, data); }
            void get(_In_ fpos_t offset, _Out_ double& data) { get<double>(offset, data); }
            void get(_In_ fpos_t offset, _Out_ char& data) { get<char>(offset, data); }
#ifdef _NATIVE_WCHAR_T_DEFINED
            void get(_In_ fpos_t offset, _Out_ wchar_t& data) { get<wchar_t>(offset, data); }
#endif
 
            memory_file& operator <<(_In_ const int8_t data) { return write_data(data); }
            memory_file& operator >>(_Out_ int8_t & data) { return read_data(data); }
            memory_file& operator <<(_In_ const int16_t data) { return write_data(data); }
            memory_file& operator >>(_Out_ int16_t & data) { return read_data(data); }
            memory_file& operator <<(_In_ const int32_t data) { return write_data(data); }
            memory_file& operator >>(_Out_ int32_t & data) { return read_data(data); }
            memory_file& operator <<(_In_ const int64_t data) { return write_data(data); }
            memory_file& operator >>(_Out_ int64_t & data) { return read_data(data); }
            memory_file& operator <<(_In_ const uint8_t data) { return write_data(data); }
            memory_file& operator >>(_Out_ uint8_t & data) { return read_data(data); }
            memory_file& operator <<(_In_ const uint16_t data) { return write_data(data); }
            memory_file& operator >>(_Out_ uint16_t & data) { return read_data(data); }
            memory_file& operator <<(_In_ const uint32_t data) { return write_data(data); }
            memory_file& operator >>(_Out_ uint32_t & data) { return read_data(data); }
            memory_file& operator <<(_In_ const uint64_t data) { return write_data(data); }
            memory_file& operator >>(_Out_ uint64_t & data) { return read_data(data); }
            memory_file& operator <<(_In_ const float data) { return write_data(data); }
            memory_file& operator >>(_Out_ float& data) { return read_data(data); }
            memory_file& operator <<(_In_ const double data) { return write_data(data); }
            memory_file& operator >>(_Out_ double& data) { return read_data(data); }
            memory_file& operator <<(_In_ const char data) { return write_data(data); }
            memory_file& operator >>(_Out_ char& data) { return read_data(data); }
#ifdef _NATIVE_WCHAR_T_DEFINED
            memory_file& operator <<(_In_ const wchar_t data) { return write_data(data); }
            memory_file& operator >>(_Out_ wchar_t& data) { return read_data(data); }
#endif
            template<class T, class TR = std::char_traits<T>, class AX = std::allocator<T>>
            memory_file& operator >>(_Out_ std::basic_string<T, TR, AX>&data) { return read_str(data); }
            template <class T>
            memory_file& operator <<(_In_ const T * data) { return write_str(data); }
            template<class T, class TR = std::char_traits<T>, class AX = std::allocator<T>>
            memory_file& operator <<(_In_ const std::basic_string<T, TR, AX>& data) { return write_str(data); }
 
        protected:
            uint8_t* m_data; 
            bool m_manage; 
            size_t m_offset; 
            size_t m_size; 
            size_t m_reserved; 
#if SET_FILE_OP_TIMES
            time_point
                m_ctime,
                m_atime,
                m_mtime;
#endif
        };
 
        class fifo : public basic {
        public:
            fifo() :
                m_offset(0),
                m_size(0),
                m_head(nullptr),
                m_tail(nullptr)
            {}
 
            virtual ~fifo()
            {
                while (m_head) {
                    auto p = m_head;
                    m_head = p->next;
                    delete p;
                }
            }
 
#pragma warning(suppress: 6101) // See [2] below
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                for (size_t to_read = length;;) {
                    if (!m_head) _Unlikely_ {
                        m_state = to_read < length || !length ? state_t::ok : state_t::eof;
                        return length - to_read; // [2] Code analysis misses `length - to_read` bytes were written to data in previous loop iterations.
                    }
                    size_t remaining = m_head->size - m_offset;
                    if (remaining > to_read) {
                        memcpy(data, m_head->data + m_offset, to_read);
                        m_offset += to_read;
                        m_size -= to_read;
                        m_state = state_t::ok;
                        return length;
                    }
                    memcpy(data, m_head->data + m_offset, remaining);
                    m_offset = 0;
                    m_size -= remaining;
                    reinterpret_cast<uint8_t*&>(data) += remaining;
                    to_read -= remaining;
                    auto p = m_head;
                    m_head = p->next;
                    delete p;
                }
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                try {
                    std::unique_ptr<node_t> n(reinterpret_cast<node_t*>(new uint8_t[sizeof(node_t) + length]));
                    n->next = nullptr;
                    n->size = length;
                    memcpy(n->data, data, length);
                    m_size += length;
                    if (m_head)
                        m_tail = m_tail->next = n.release();
                    else
                        m_head = m_tail = n.release();
                    m_state = state_t::ok;
                    return length;
                }
                catch (const std::bad_alloc&) {
                    m_state = state_t::fail;
                    return 0;
                }
            }
 
            virtual void close()
            {
                m_size = m_offset = 0;
                while (m_head) {
                    auto p = m_head;
                    m_head = p->next;
                    delete p;
                }
                m_state = state_t::ok;
            }
 
            size_t size() const { return m_size; };
 
        protected:
            size_t m_offset, m_size;
            struct node_t {
                node_t* next;
                size_t size;
#pragma warning(suppress:4200)
                uint8_t data[0];
            } *m_head, * m_tail;
        };
 
        class diag_file : public basic_file {
        public:
            diag_file(_In_count_(num_files) basic_file* const* files, _In_ size_t num_files) :
                basic(num_files ? files[0]->state() : state_t::fail),
                m_files(files, files + num_files)
            {}
 
            virtual _Success_(return != 0 || length == 0) size_t read(
                _Out_writes_bytes_to_opt_(length, return) void* data, _In_ size_t length)
            {
                stdex_assert(data || !length);
                if (m_files.empty()) {
                    m_state = state_t::fail;
                    return 0;
                }
                size_t result = m_files[0]->read(data, length);
                stdex_assert(result <= length);
                m_state = m_files[0]->state();
                if (length > m_tmp.size())
                    m_tmp.resize(length);
                for (size_t i = 1, n = m_files.size(); i < n; ++i) {
                    if (m_files[i]->read(m_tmp.data(), length) != result ||
                        memcmp(m_tmp.data(), data, result))
                        throw std::runtime_error("read mismatch");
                    if (m_files[i]->state() != m_state)
                        throw std::runtime_error("state mismatch");
                }
                return result;
            }
 
            virtual _Success_(return != 0) size_t write(
                _In_reads_bytes_opt_(length) const void* data, _In_ size_t length)
            {
                if (m_files.empty()) {
                    m_state = state_t::fail;
                    return 0;
                }
                size_t result = m_files[0]->write(data, length);
                m_state = m_files[0]->state();
                for (size_t i = 1, n = m_files.size(); i < n; ++i) {
                    if (m_files[i]->write(data, length) != result)
                        throw std::runtime_error("write mismatch");
                    if (m_files[i]->state() != m_state)
                        throw std::runtime_error("state mismatch");
                }
                return result;
            }
 
            virtual void flush()
            {
                if (m_files.empty()) {
                    m_state = state_t::ok;
                    return;
                }
                m_files[0]->flush();
                m_state = m_files[0]->state();
                for (size_t i = 1, n = m_files.size(); i < n; ++i) {
                    m_files[i]->flush();
                    if (m_files[i]->state() != m_state)
                        throw std::runtime_error("state mismatch");
                }
            }
 
            virtual void close()
            {
                if (m_files.empty()) {
                    m_state = state_t::ok;
                    return;
                }
                m_files[0]->close();
                m_state = m_files[0]->state();
                for (size_t i = 1, n = m_files.size(); i < n; ++i) {
                    m_files[i]->close();
                    if (m_files[i]->state() != m_state)
                        throw std::runtime_error("state mismatch");
                }
                m_tmp.clear();
                m_tmp.shrink_to_fit();
            }
 
            virtual fpos_t seek(_In_ foff_t offset, _In_ seek_t how = seek_t::beg)
            {
                if (m_files.empty()) {
                    m_state = state_t::fail;
                    return fpos_max;
                }
                fpos_t result = m_files[0]->seek(offset, how);
                m_state = m_files[0]->state();
                for (size_t i = 1, n = m_files.size(); i < n; ++i) {
                    if (m_files[i]->seek(offset, how) != result)
                        throw std::runtime_error("seek mismatch");
                    if (m_files[i]->state() != m_state)
                        throw std::runtime_error("state mismatch");
                }
                return result;
            }
 
            virtual fpos_t tell() const
            {
                if (m_files.empty())
                    return fpos_max;
                fpos_t result = m_files[0]->tell();
                for (size_t i = 1, n = m_files.size(); i < n; ++i) {
                    if (m_files[i]->tell() != result)
                        throw std::runtime_error("tell mismatch");
                }
                return result;
            }
 
            virtual void lock(_In_ fpos_t offset, _In_ fsize_t length)
            {
                if (m_files.empty())
                    m_state = state_t::fail;
                m_files[0]->lock(offset, length);
                m_state = m_files[0]->state();
                for (size_t i = 1, n = m_files.size(); i < n; ++i) {
                    m_files[i]->lock(offset, length);
                    if (m_files[i]->state() != m_state)
                        throw std::runtime_error("state mismatch");
                }
            }
 
            virtual void unlock(_In_ fpos_t offset, _In_ fsize_t length)
            {
                if (m_files.empty())
                    m_state = state_t::fail;
                m_files[0]->unlock(offset, length);
                m_state = m_files[0]->state();
                for (size_t i = 1, n = m_files.size(); i < n; ++i) {
                    m_files[i]->unlock(offset, length);
                    if (m_files[i]->state() != m_state)
                        throw std::runtime_error("state mismatch");
                }
            }
 
            virtual fsize_t size() const
            {
                if (m_files.empty())
                    return fsize_max;
                fsize_t result = m_files[0]->size();
                for (size_t i = 1, n = m_files.size(); i < n; ++i) {
                    if (m_files[i]->size() != result)
                        throw std::runtime_error("size mismatch");
                }
                return result;
            }
 
            virtual void truncate()
            {
                if (m_files.empty())
                    m_state = state_t::fail;
                m_files[0]->truncate();
                m_state = m_files[0]->state();
                for (size_t i = 1, n = m_files.size(); i < n; ++i) {
                    m_files[i]->truncate();
                    if (m_files[i]->state() != m_state)
                        throw std::runtime_error("state mismatch");
                }
            }
 
        protected:
            std::vector<basic_file*> m_files;
            std::vector<uint8_t> m_tmp;
        };
    }
}
 
#if defined(__GNUC__)
#pragma GCC diagnostic pop
#endif