damus/damus-c/hex.c

/* CC0 license (public domain) - see LICENSE file for details */
#include "hex.h"
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>

static bool char_to_hex(unsigned char *val, char c)
{
    if (c >= '0' && c <= '9') {
        *val = c - '0';
        return true;
    }
     if (c >= 'a' && c <= 'f') {
        *val = c - 'a' + 10;
        return true;
    }
     if (c >= 'A' && c <= 'F') {
        *val = c - 'A' + 10;
        return true;
    }
    return false;
}

bool hex_decode(const char *str, size_t slen, void *buf, size_t bufsize)
{
    unsigned char v1, v2;
    unsigned char *p = buf;

    while (slen > 1) {
        if (!char_to_hex(&v1, str[0]) || !char_to_hex(&v2, str[1]))
            return false;
        if (!bufsize)
            return false;
        *(p++) = (v1 << 4) | v2;
        str += 2;
        slen -= 2;
        bufsize--;
    }
    return slen == 0 && bufsize == 0;
}

static char hexchar(unsigned int val)
{
    if (val < 10)
        return '0' + val;
    if (val < 16)
        return 'a' + val - 10;
    abort();
}

bool hex_encode(const void *buf, size_t bufsize, char *dest, size_t destsize)
{
    size_t i;

    if (destsize < hex_str_size(bufsize))
        return false;

    for (i = 0; i < bufsize; i++) {
        unsigned int c = ((const unsigned char *)buf)[i];
        *(dest++) = hexchar(c >> 4);
        *(dest++) = hexchar(c & 0xF);
    }
    *dest = '\0';

    return true;
}