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/* base85.c - encode and decode base85 strings
Copyright (C) 2010 Free Software Foundation, Inc.
Written by Andreas Gruenbacher <agruen@gnu.org>.
This program 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 3 of the License, or
(at your option) any later version.
This program 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 <http://www.gnu.org/licenses/>. */
#include <sys/types.h>
#include <stdbool.h>
#include "base85.h"
static char const
base85_encode_tab[] = {
/* 0 */ '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
/* 10 */ 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
/* 20 */ 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
/* 30 */ 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
/* 40 */ 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
/* 50 */ 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
/* 60 */ 'y', 'z', '!', '#', '$', '%', '&', '(', ')', '*',
/* 70 */ '+', '-', ';', '<', '=', '>', '?', '@', '^', '_',
/* 80 */ '`', '{', '|', '}', '~',
};
static signed char const
base85_decode_tab[] = {
/* 0 */ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
/* 16 */ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
/* 32 */ -1, 62, -1, 63, 64, 65, 66, -1, 67, 68, 69, 70, -1, 71, -1, -1,
/* 48 */ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, 72, 73, 74, 75, 76,
/* 64 */ 77, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
/* 80 */ 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, -1, -1, -1, 78, 79,
/* 96 */ 80, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50,
/* 112 */ 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 81, 82, 83, 84, -1,
/* 128 */ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
/* 144 */ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
/* 160 */ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
/* 176 */ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
/* 192 */ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
/* 208 */ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
/* 224 */ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
/* 240 */ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
};
static void
base85_encode_data (char *encoded, char const *buffer, unsigned int len)
{
while (len)
{
unsigned int acc = 0;
int a, n;
for (n = 24; n >= 0; n -= 8)
{
a = (unsigned char) *buffer++;
acc |= a << n;
if (--len == 0)
break;
}
for (n = 4; n >= 0; n--)
{
encoded[n] = base85_encode_tab[acc % 85];
acc /= 85;
}
encoded += 5;
}
*encoded = 0;
}
static bool
base85_decode_data (char *buffer, char const *encoded, unsigned int len)
{
while (len)
{
unsigned int acc = 0;
int a, n;
for (n = 4; n > 0; n--)
{
a = base85_decode_tab[(unsigned char) *encoded++];
if (a < 0)
return false;
acc = (acc * 85) + a;
}
a = base85_decode_tab[(unsigned char) *encoded++];
if (a < 0)
return false;
if (acc > 0xffffffff / 85 || 0xffffffff - a < (acc *= 85))
return false;
acc += a;
n = (len > 4) ? 4 : len;
len -= n;
for (; n > 0; n--)
{
acc = (acc << 8) | (acc >> 24);
*buffer++ = acc;
}
}
return true;
}
static int
base85_encode_length (unsigned int len)
{
if (len == 0 || len > 52)
return -1;
if (len <= 26)
return (unsigned char) 'A' + len - 1;
else
return (unsigned char) 'a' + len - 27;
}
static int
base85_decode_length (char c)
{
if (c >= 'A' && c <= 'Z')
return c - 'A' + 1;
else if (c >= 'a' && c <= 'z')
return c - 'a' + 27;
else
return -1;
}
int
base85_encode (char *encoded, char const *buffer, unsigned int len)
{
int c = base85_encode_length (len);
if (c < 0)
return -1;
else
{
*encoded++ = c;
base85_encode_data (encoded, buffer, len);
return 1 + (len + 3) / 4 * 5;
}
}
int
base85_decode (char *buffer, char const *encoded)
{
int len = base85_decode_length (*encoded++);
if (len > 0 && base85_decode_data (buffer, encoded, len))
return len;
else
return -1;
}
#ifdef DEBUG
#include <stdio.h>
#include <string.h>
#define LINE_MAX (2 * 26)
int main (int argc, char *argv[])
{
if (! strcmp (argv[1], "-e"))
{
char buffer[LINE_MAX];
char encoded[BASE85_BUFFER_SIZE(LINE_MAX)];
ssize_t len;
while ((len = fread (buffer, 1, sizeof (buffer), stdin)) > 0)
{
if (base85_encode (encoded, buffer, len) < 0)
return 1;
puts (encoded);
}
}
else if (! strcmp (argv[1], "-d"))
{
char encoded[BASE85_BUFFER_SIZE(LINE_MAX) + 1]; /* + newline */
char buffer[LINE_MAX];
int len;
while (fgets (encoded, sizeof (encoded), stdin))
{
if ((len = base85_decode (buffer, encoded)) < 0)
return 1;
fwrite (buffer, 1, len, stdout);
}
}
return 0;
}
#endif
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