mapping.hpp

/*
    SPDX-License-Identifier: MIT
    Copyright © 2023-2024 Amebis
*/
 
#pragma once
 
#include "compat.hpp"
#include <algorithm>
#include <vector>
 
namespace stdex
{
    template <class T>
    struct mapping {
        T from; // index in source string
        T to;   // index in destination string
 
        mapping() : from(0), to(0) {}
 
        mapping(_In_ T x) : from(x), to(x) {}
 
        mapping(_In_ T _from, _In_ T _to) : from(_from), to(_to) {}
 
        bool operator==(const mapping& other) const { return from == other.from && to == other.to; }
 
        bool operator!=(const mapping& other) const { return !operator==(other); }
 
        mapping operator+(_In_ const mapping& other) const
        {
            return mapping(from + other.from, to + other.to);
        }
 
        void invert()
        {
            T tmp = from;
            from = to;
            to = tmp;
        }
    };
 
    template <class T, class AX = std::allocator<mapping<T>>>
    using mapping_vector = std::vector<mapping<T>, AX>;
 
    template <class T, class AX = std::allocator<mapping<T>>>
    T dst2src(_In_ const std::vector<stdex::mapping<T>, AX>& mapping, _In_ T to)
    {
        if (mapping.empty())
            return to;
 
        for (size_t l = 0, r = mapping.size();;) {
            if (l < r) {
                auto m = (l + r) / 2;
                const auto& el = mapping[m];
                if (to < el.to) r = m;
                else if (el.to < to) l = m + 1;
                else return el.from;
            }
            else if (l) {
                const auto& el = mapping[l - 1];
                return el.from + (to - el.to);
            }
            else {
                const auto& el = mapping[0];
                return std::min<T>(to, el.from);
            }
        }
    }
 
    template <class T, class AX = std::allocator<mapping<T>>>
    T dst2src(_In_ const std::vector<stdex::mapping<T>, AX>& mapping, _In_ T to, _Inout_opt_ size_t& m)
    {
        if (mapping.empty())
            return to;
 
        size_t l, r;
        {
            const auto& el = mapping[m];
            if (to < el.to) {
                l = 0;
                r = m;
            }
            else if (el.to < to) {
                if (mapping.size() - 1 <= m || to < mapping[m + 1].to)
                    return el.from + (to - el.to);
                l = m + 1;
                r = mapping.size();
            }
            else
                return el.from;
        }
 
        for (;;) {
            if (l < r) {
                m = (l + r) / 2;
                const auto& el = mapping[m];
                if (to < el.to) r = m;
                else if (el.to < to) l = m + 1;
                else return el.from;
            }
            else if (l) {
                const auto& el = mapping[m = l - 1];
                return el.from + (to - el.to);
            }
            else {
                const auto& el = mapping[m = 0];
                return std::min<T>(to, el.from);
            }
        }
    }
 
    template <class T, class AX = std::allocator<mapping<T>>>
    T src2dst(_In_ const std::vector<stdex::mapping<T>, AX>& mapping, _In_ T from)
    {
        if (mapping.empty())
            return from;
 
        for (size_t l = 0, r = mapping.size();;) {
            if (l < r) {
                auto m = (l + r) / 2;
                const auto& el = mapping[m];
                if (from < el.from) r = m;
                else if (el.from < from) l = m + 1;
                else return el.to;
            }
            else if (l) {
                const auto& el = mapping[l - 1];
                return el.to + (from - el.from);
            }
            else {
                const auto& el = mapping[0];
                return std::min<T>(from, el.to);
            }
        }
    }
 
    template <class T, class AX = std::allocator<mapping<T>>>
    T src2dst(_In_ const std::vector<stdex::mapping<T>, AX>& mapping, _In_ T from, _Inout_opt_ size_t& m)
    {
        if (mapping.empty())
            return from;
 
        size_t l, r;
        {
            const auto& el = mapping[m];
            if (from < el.from) {
                l = 0;
                r = m;
            }
            else if (el.from < from) {
                if (mapping.size() - 1 <= m || from < mapping[m + 1].from)
                    return el.to + (from - el.from);
                l = m + 1;
                r = mapping.size();
            }
            else
                return el.to;
        }
 
        for (;;) {
            if (l < r) {
                m = (l + r) / 2;
                const auto& el = mapping[m];
                if (from < el.from) r = m;
                else if (el.from < from) l = m + 1;
                else return el.to;
            }
            else if (l) {
                const auto& el = mapping[m = l - 1];
                return el.to + (from - el.from);
            }
            else {
                const auto& el = mapping[m = 0];
                return std::min<T>(from, el.to);
            }
        }
    }
}