base64.c

#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <event.h>
#include "base64.h"

static const char base64_chars[] =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static unsigned char base64_map(const char **strp)
{
	const char *str = *strp;
	const char *ptr;

	while (*(str = *strp) && *str != '=') {
		*strp = str + 1;
		ptr = strchr(base64_chars, *str);
		if (ptr)
			return ptr - base64_chars;
	}

	return 0;
}

/*
 * Returns actual size of decoded buffer.
 */
size_t base64_decode(const char *str, unsigned char *buf, size_t size)
{
	unsigned int n;
	size_t i, j, actual = 0;

	for (i = 0; *str && *str != '='; ) {
		n =  base64_map(&str) << 18;
		n += base64_map(&str) << 12;
		n += base64_map(&str) << 6;
		n += base64_map(&str);

		if (i < size)
			buf[i++] = (n >> 16) & 255;
		if (i < size)
			buf[i++] = (n >> 8) & 255;
		if (i < size)
			buf[i++] = n & 255;

		actual += 3;
	}

	/* account for padding */
	for (j = 0; j < 3 && str[j] == '='; j ++)
		actual --;

	return actual;
}

int base64_encode_evbuf(struct evbuffer *evbuf, const unsigned char *s,
		size_t length)
{               
	unsigned int n;
	char string[4]; 
	size_t i;
	int ret = 0;

	for (i = 0; i < length;) { 
		n = s[i++] << 16;
		n += (i < length) ? s[i++] << 8 : 0; 
		n += (i < length) ? s[i++] : 0;

		string[0] = base64_chars[(n >> 18) & 63];
		string[1] = base64_chars[(n >> 12) & 63];
		string[2] = base64_chars[(n >> 6) & 63];
		string[3] = base64_chars[n & 63]; 

		ret = evbuffer_add(evbuf, string, 4);
		if (ret)
			return ret;
	}

	/* padd to make length a multiple of 3 */
	for (i = 0; length % 3 != 0; i ++, length ++)
		string[i] = '=';
	if (i)
		ret = evbuffer_add(evbuf, string, i);

	return ret;
}