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/* zb32.c - z-base-32 functions
* Copyright (C) 2014 Werner Koch
*
* This file is part of GnuPG.
*
* This file is free software; you can redistribute it and/or modify
* it under the terms of either
*
* - the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* or
*
* - 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.
*
* or both in parallel, as here.
*
* This file 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 this program; if not, see <https://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include "util.h"
#include "zb32.h"
/* Zooko's base32 variant. See RFC-6189 and
http://philzimmermann.com/docs/human-oriented-base-32-encoding.txt
Caller must xfree the returned string. Returns NULL and sets ERRNO
on error. To avoid integer overflow DATALEN is limited to 2^16
bytes. Note, that DATABITS is measured in bits!. */
char *
zb32_encode (const void *data, unsigned int databits)
{
static char const zb32asc[32] = {'y','b','n','d','r','f','g','8',
'e','j','k','m','c','p','q','x',
'o','t','1','u','w','i','s','z',
'a','3','4','5','h','7','6','9' };
const unsigned char *s;
char *output, *d;
size_t datalen;
datalen = (databits + 7) / 8;
if (datalen > (1 << 16))
{
errno = EINVAL;
return NULL;
}
d = output = xtrymalloc (8 * (datalen / 5)
+ 2 * (datalen % 5)
- ((datalen%5)>2)
+ 1);
if (!output)
return NULL;
/* I use straightforward code. The compiler should be able to do a
better job on optimization than me and it is easier to read. */
for (s = data; datalen >= 5; s += 5, datalen -= 5)
{
*d++ = zb32asc[((s[0] ) >> 3) ];
*d++ = zb32asc[((s[0] & 7) << 2) | (s[1] >> 6) ];
*d++ = zb32asc[((s[1] & 63) >> 1) ];
*d++ = zb32asc[((s[1] & 1) << 4) | (s[2] >> 4) ];
*d++ = zb32asc[((s[2] & 15) << 1) | (s[3] >> 7) ];
*d++ = zb32asc[((s[3] & 127) >> 2) ];
*d++ = zb32asc[((s[3] & 3) << 3) | (s[4] >> 5) ];
*d++ = zb32asc[((s[4] & 31) ) ];
}
switch (datalen)
{
case 4:
*d++ = zb32asc[((s[0] ) >> 3) ];
*d++ = zb32asc[((s[0] & 7) << 2) | (s[1] >> 6) ];
*d++ = zb32asc[((s[1] & 63) >> 1) ];
*d++ = zb32asc[((s[1] & 1) << 4) | (s[2] >> 4) ];
*d++ = zb32asc[((s[2] & 15) << 1) | (s[3] >> 7) ];
*d++ = zb32asc[((s[3] & 127) >> 2) ];
*d++ = zb32asc[((s[3] & 3) << 3) ];
break;
case 3:
*d++ = zb32asc[((s[0] ) >> 3) ];
*d++ = zb32asc[((s[0] & 7) << 2) | (s[1] >> 6) ];
*d++ = zb32asc[((s[1] & 63) >> 1) ];
*d++ = zb32asc[((s[1] & 1) << 4) | (s[2] >> 4) ];
*d++ = zb32asc[((s[2] & 15) << 1) ];
break;
case 2:
*d++ = zb32asc[((s[0] ) >> 3) ];
*d++ = zb32asc[((s[0] & 7) << 2) | (s[1] >> 6) ];
*d++ = zb32asc[((s[1] & 63) >> 1) ];
*d++ = zb32asc[((s[1] & 1) << 4) ];
break;
case 1:
*d++ = zb32asc[((s[0] ) >> 3) ];
*d++ = zb32asc[((s[0] & 7) << 2) ];
break;
default:
break;
}
*d = 0;
/* Need to strip some bytes if not a multiple of 40. */
output[(databits + 5 - 1) / 5] = 0;
return output;
}

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