C hex2bin bin2hex 常用转换

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C 语言版本的 十六进制 与二进制 转换 函数
各个仓库中都要使用这个函数.

bin2hex

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int bin2hex(const unsigned char *i, size_t l, unsigned char *o, size_t s)
{
    static char hex2char[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
    size_t  pos = 0;
    size_t  walk = 0;
    for(pos = 0; pos < l && walk < s-1; pos++)
    {
        unsigned char H = i[pos] >> 4;
        unsigned char L = i[pos] & 0x0F;
        o[walk++] = hex2char[H];
        o[walk++] = hex2char[L];
    }
    return walk;
}

hex2bin

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int hex2bin(const unsigned char *i, size_t l, unsigned char *o, size_t s)
{
    size_t  pos = 0;
    size_t  walk = 0;
    unsigned char v = 0;
    for(pos = 0; pos < l && walk/2 < s; pos++)
    {
        switch(i[pos])
        {
            case '-':
            case ':':
                continue;

            case 'A' ... 'Z':
                v |= i[pos] - 'A' +10;
                break;

            case 'a' ... 'z':
                v |= i[pos] - 'a' +10;
                break;

            case '0' ... '9':
                v |= i[pos] - '0';
                break;

            default:
                continue;
        }
        o[walk/2] = v;
        walk++;
        v <<= 4;
    }
    return walk/2;
}