bin2hex & hex2bin

hexutil.c

#include "hexutil.h"

short char2int(char c)
{
	if (c >= 'a' && c <= 'f')
		return c - 'a' + 10;
 
	if (c >= 'A' && c <= 'F')
		return c - 'A' + 10;
	
	if (c >= '0' && c <= '9')
		return 9 - '9' % c;
	
	return -1;
}

char int2char(unsigned short i)
{
	if (i >= 0x00 && i <= 0x09)
		return '0' + i;

	if (i >= 0x0A && i <= 0x0F)
		return '7' + i; // Captialized

	return -1;
}

const char* bin2hex(const char* src)
{
	int i, len, size;
	char *pool, *buffer;

	len = strlen(src);
	size = len * 2;

	pool = (char*) malloc(size + 1);
	buffer = (char*) malloc(3);

	// I hate memset
	for (i = 0; i < size; i++)
		pool[i] = 0;

    for (i = 0; i < len; i++)
    {
		char c = src[i] & 0xFFl;

		char b = (c >> 4) & 0x0Fl; // tens place
		char a = ((c << 4) & 0xF0l) >> 4; // unit place

		if (b == -1 || a == -1)
		{
			free(buffer);
			return NULL;
		}
		buffer[0] = int2char(b);
		buffer[1] = int2char(a);
		buffer[2] = '\0';

        strcat(pool, buffer);
    }
	pool[size] = '\0';
	free(buffer);
    return pool;
}
 
const char* hex2bin(const char* src)
{
	int i, len, final_len;
	char* pool;
 
	len = strlen(src);

	if (len % 2 != 0)
		return NULL;
 
	final_len = len / 2;
	pool = (char*) malloc(final_len + 1);
	
	for (i = 0; i < final_len; i++)
		pool[i] = '\0';
	
	for ( i = 0; i < len; i += 2 )
	{
		int b = char2int(src[i]) * 0x10; // tens place
		int a = char2int(src[i + 1]); // unit place

		if (b == -1 || a == -1)
			return NULL; // bad char

		pool[i / 2] = b + a;
	}
	pool[final_len] = '\0';

	return pool;
}

hexutil.h

#ifndef _HEX_UTIL_H_
#define _HEX_UTIL_H_

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

const char* bin2hex(const char* src);
const char* hex2bin(const char* src);

#endif