base32.c

/*
 * Copyright (c) 2006-2009 Bjorn Andersson <flex@kryo.se>, Erik Ekman <yarrick@kryo.se>
 * Mostly rewritten 2009 J.A.Bezemer@opensourcepartners.nl
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

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

//#include "base32.h"

static const char cb32[] = 
	"abcdefghijklmnopqrstuvwxyz234567";
static const char cb32_ucase[] = 
	"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
static unsigned char rev32[256];
static int reverse_init = 0;

int base32_encode(char *buf, size_t *buflen, const void *data, size_t size)
/*
 * Fills *buf with max. *buflen characters, encoding size bytes of *data.
 *
 * NOTE: *buf space should be at least 1 byte _more_ than *buflen
 * to hold the trailing '\0'.
 *
 * return value    : #bytes filled in buf   (excluding \0)
 * sets *buflen to : #bytes encoded from data
 */
{
	unsigned char *udata = (unsigned char *) data;
	int iout = 0;	/* to-be-filled output char */
	int iin = 0;	/* one more than last input byte that can be
			   successfully decoded */

	/* Note: Don't bother to optimize manually. GCC optimizes
	   better(!) when using simplistic array indexing. */

	while (1) {
		if (iout >= *buflen || iin >= size)
			break;
		buf[iout] = cb32[((udata[iin] & 0xf8) >> 3)];
		iout++;

		if (iout >= *buflen || iin >= size) {
			iout--; 	/* previous char is useless */
			break;
		}
		buf[iout] = cb32[((udata[iin] & 0x07) << 2) |
				  ((iin + 1 < size) ?
				   ((udata[iin + 1] & 0xc0) >> 6) : 0)];
		iin++;			/* 0 complete, iin=1 */
		iout++;

		if (iout >= *buflen || iin >= size)
			break;
		buf[iout] = cb32[((udata[iin] & 0x3e) >> 1)];
		iout++;

		if (iout >= *buflen || iin >= size) {
			iout--;		/* previous char is useless */
			break;
		}
		buf[iout] = cb32[((udata[iin] & 0x01) << 4) |
				  ((iin + 1 < size) ?
				   ((udata[iin + 1] & 0xf0) >> 4) : 0)];
		iin++;			/* 1 complete, iin=2 */
		iout++;

		if (iout >= *buflen || iin >= size)
			break;
		buf[iout] = cb32[((udata[iin] & 0x0f) << 1) |
				  ((iin + 1 < size) ?
				   ((udata[iin + 1] & 0x80) >> 7) : 0)];
		iin++;			/* 2 complete, iin=3 */
		iout++;

		if (iout >= *buflen || iin >= size)
			break;
		buf[iout] = cb32[((udata[iin] & 0x7c) >> 2)];
		iout++;

		if (iout >= *buflen || iin >= size) {
			iout--;		/* previous char is useless */
			break;
		}
		buf[iout] = cb32[((udata[iin] & 0x03) << 3) |
				  ((iin + 1 < size) ?
				   ((udata[iin + 1] & 0xe0) >> 5) : 0)];
		iin++;			/* 3 complete, iin=4 */
		iout++;

		if (iout >= *buflen || iin >= size)
			break;
		buf[iout] = cb32[((udata[iin] & 0x1f))];
		iin++;			/* 4 complete, iin=5 */
		iout++;
	}

	buf[iout] = '\0';

	/* store number of bytes from data that was used */
	*buflen = iin;

	return iout;
}