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base32.c
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base32.c
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/*
* $Id: base32.c 15781 2008-09-02 16:30:18Z rmanfredi $
*
* Copyright (c) 2006, Christian Biere
*
*----------------------------------------------------------------------
* This file is part of gtk-gnutella.
*
* gtk-gnutella is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* gtk-gnutella is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with gtk-gnutella; if not, write to the Free Software
* Foundation, Inc.:
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*----------------------------------------------------------------------
*/
/**
* @ingroup lib
* @file
*
* Base32 encoding/decoding.
*
* @author Christian Biere
* @date 2006
*/
/*
* Copyright (c) 2006 Christian Biere <christianbiere@gmx.de>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the authors nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <string.h>
#include <unistd.h>
#include <stdint.h>
#include <ctype.h>
#include "base32.h"
/*
* See RFC 3548 for details about Base 32 encoding:
* http://www.faqs.org/rfcs/rfc3548.html
*/
/* Shiren DS encoding */
static const char base32_alphabet[32] = {
'0', '1', '2', '3', '4', '5', '6', '7',
'8', '9', 'B', 'C', 'D', 'F', 'G', 'H',
'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R',
'S', 'T', 'V', 'W', 'X', 'Y', 'Z', '!'
};
/**
* Encode in base32 `len' bytes of `data' into the buffer `dst'.
*
* @param dst destination buffer
* @param size length of destination
* @param data start of data to encode
* @param len amount of bytes to encode
*
* @return the amount of bytes generated into the destination.
*/
int
base32_encode(char *dst, size_t size, const void *data, size_t len)
{
size_t i = 0;
const uint8_t *p = data;
const char *end = &dst[size];
char *q = dst;
do {
size_t j, k;
uint8_t x[5];
char s[8];
switch (len - i) {
case 4:
k = 7;
break;
case 3:
k = 5;
break;
case 2:
k = 3;
break;
case 1:
k = 2;
break;
default:
k = 8;
}
for (j = 0; j < 5; j++)
x[j] = i < len ? p[i++] : 0;
/*
+-------+-----------+--------+
| target| source | source |
| byte | bits | byte |
+-------+-----------+--------+
| 0 | 7 6 5 4 3 | 0 |
| 1 | 2 1 0 7 6 | 0-1 |
| 2 | 5 4 3 2 1 | 1 |
| 3 | 0 7 6 5 4 | 1-2 |
| 4 | 3 2 1 0 7 | 2-3 |
| 5 | 6 5 4 3 2 | 3 |
| 6 | 1 0 7 6 5 | 3-4 |
| 7 | 4 3 2 1 0 | 4 |
+-------+-----------+--------+
*/
/****** Shiren changes the order around
s[0] = (x[0] >> 3);
s[1] = ((x[0] & 0x07) << 2) | (x[1] >> 6);
s[2] = (x[1] >> 1) & 0x1f;
s[3] = ((x[1] & 0x01) << 4) | (x[2] >> 4);
s[4] = ((x[2] & 0x0f) << 1) | (x[3] >> 7);
s[5] = (x[3] >> 2) & 0x1f;
s[6] = ((x[3] & 0x03) << 3) | (x[4] >> 5);
s[7] = x[4] & 0x1f;
********/
s[0] = (x[0] & 0x1F);
s[1] = ((x[0] & 0xE0) >> 5) | ((x[1] & 0x03) << 3);
s[2] = (x[1] & 0x7C) >> 2;
s[3] = ((x[1] & 0x80) >> 7) | ((x[2] & 0x0F) << 1);
s[4] = ((x[2] & 0xF0) >> 4) | ((x[3] & 0x01) << 4);
s[5] = ((x[3] & 0x3E) >> 1);
s[6] = ((x[3] & 0xC0) >> 6) | ((x[4] & 0x07) << 2);
s[7] = (x[4] & 0xF8) >> 3;
for (j = 0; j < k && q != end; j++) {
*q++ = base32_alphabet[(uint8_t) s[j]];
}
if (end == q) {
break;
}
} while (i < len);
return q - dst;
}
static char base32_map[(unsigned char) -1];
/**
* Decode a base32 encoding of `len' bytes of `data' into the buffer `dst'.
*
* @param dst destination buffer
* @param size length of destination
* @param data start of data to decode
* @param len amount of encoded data to decode
*
* @return the amount of bytes decoded into the destination.
*/
int
base32_decode(char *dst, size_t size, const void *data, size_t len)
{
const char *end = &dst[size];
const unsigned char *p = data;
char s[8];
char *q = dst;
int pad = 0;
size_t i, si;
if (0 == base32_map[0]) {
for (i = 0; i < G_N_ELEMENTS(base32_map); i++) {
const char *x;
x = memchr(base32_alphabet, toupper(i),
sizeof base32_alphabet);
base32_map[i] = x ? (x - base32_alphabet) : (unsigned char) -1;
}
}
memset(&s[0], 0, sizeof s);
si = 0;
i = 0;
while (i < len) {
unsigned char c;
c = p[i++];
if ('=' == c) {
pad++;
c = 0;
} else {
c = base32_map[c];
if ((unsigned char) -1 == c) {
return -1;
}
}
s[si++] = c;
if (G_N_ELEMENTS(s) == si || pad > 0 || i == len) {
char b[5];
size_t bi;
memset(&s[si], 0, G_N_ELEMENTS(s) - si);
si = 0;
/***** Shiren reverses this, starts at the LSB first
b[0] =
((s[0] << 3) & 0xf8) |
((s[1] >> 2) & 0x07);
b[1] =
((s[1] & 0x03) << 6) |
((s[2] & 0x1f) << 1) |
((s[3] >> 4) & 1);
b[2] =
((s[3] & 0x0f) << 4) |
((s[4] >> 1) & 0x0f);
b[3] =
((s[4] & 1) << 7) |
((s[5] & 0x1f) << 2) |
((s[6] >> 3) & 0x03);
b[4] =
((s[6] & 0x07) << 5) |
(s[7] & 0x1f);
******/
b[0] =
(s[0] & 0x1F) |
((s[1] & 0x07) << 5);
b[1] =
((s[1] & 0x18) >> 3) |
((s[2] & 0x1F) << 2) |
((s[3] & 0x01) << 7);
b[2] =
((s[3] & 0x1E) >> 1) |
((s[4] & 0x0F) << 4);
b[3] =
((s[4] & 0x10) >> 4) |
((s[5] & 0x1F) << 1) |
((s[6] & 0x03) << 6);
b[4] =
((s[6] & 0x1C) >> 2) |
((s[7] & 0x1F) << 3);
for (bi = 0; bi < G_N_ELEMENTS(b) && q != end; bi++) {
*q++ = b[bi];
}
}
if (end == q) {
break;
}
}
return q - dst;
}
/* vi: set ai et ts=4 sw=4 cindent: */