hex.h

/*
    SPDX-License-Identifier: MIT
    Copyright © 2016-2022 Amebis
*/
 
#pragma once
 
#include <string>
#include <vector>
 
 
namespace stdex
{
    class hex_enc
    {
    public:
        hex_enc() noexcept
        {
        }
 
 
        template<class _Elem, class _Traits, class _Ax>
        void encode(_Inout_ std::basic_string<_Elem, _Traits, _Ax> &out, _In_bytecount_(size) const void *data, _In_ size_t size)
        {
            assert(data || !size);
 
            // Preallocate output
            out.reserve(out.size() + enc_size(size));
 
            // Convert data character by character.
            for (size_t i = 0; i < size; i++) {
                unsigned char
                    x   = reinterpret_cast<const unsigned char*>(data)[i],
                    x_h = ((x & 0xf0) >> 4),
                    x_l = ((x & 0x0f)     );
 
                out += x_h < 10 ? '0' + x_h : 'A' - 10 + x_h;
                out += x_l < 10 ? '0' + x_l : 'A' - 10 + x_l;
            }
        }
 
 
        size_t enc_size(size_t size) const noexcept
        {
            return size*2;
        }
    };
 
 
    class hex_dec
    {
    public:
        hex_dec() noexcept :
            buf(0),
            num(0)
        {
        }
 
 
        template<class _Ty, class _Ax, class _Tchr>
        void decode(_Inout_ std::vector<_Ty, _Ax> &out, _Out_ bool &is_last, _In_z_count_(size) const _Tchr *data, _In_ size_t size)
        {
            is_last = false;
 
            // Trim data size to first terminator.
            for (size_t k = 0; k < size; k++)
                if (!data[k]) { size = k; break; }
 
            // Preallocate output
            out.reserve(out.size() + dec_size(size));
 
            for (size_t i = 0;; i++) {
                if (num >= 2) {
                    // Buffer full.
                    out.push_back(buf);
                    num = 0;
                    is_last = true;
                } else
                    is_last = false;
 
                if (i >= size)
                    break;
 
                int x = data[i];
                if ('0' <= x && x <= '9') {
                    buf = ((buf & 0xf) << 4) | (unsigned char)(x - '0');
                    num++;
                } else if ('A' <= x && x <= 'F') {
                    buf = ((buf & 0xf) << 4) | (unsigned char)(x - ('A' - 10));
                    num++;
                } else if ('a' <= x && x <= 'f') {
                    buf = ((buf & 0xf) << 4) | (unsigned char)(x - ('a' - 10));
                    num++;
                }
            }
        }
 
 
        void clear() noexcept
        {
            num = 0;
        }
 
 
        size_t dec_size(size_t size) const noexcept
        {
            return (size + 1)/2;
        }
 
 
    protected:
        unsigned char buf;  
        size_t num;         
    };
}