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base64-encode.c 4.64 KiB
/* base64-encode.c
*
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2002 Niels Möller
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle library 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 Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02111-1301, USA.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include <assert.h>
#include <stdlib.h>
#include "base64.h"
static const uint8_t encode_table[64] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/";
#define ENCODE(x) (encode_table[0x3F & (x)])
void
base64_encode_raw(uint8_t *dst, unsigned length, const uint8_t *src)
{
const uint8_t *in = src + length;
uint8_t *out = dst + BASE64_ENCODE_RAW_LENGTH(length);
unsigned left_over = length % 3;
if (left_over)
{
in -= left_over;
*--out = '=';
switch(left_over)
{
case 1:
*--out = '=';
*--out = ENCODE(in[0] << 4);
break;
case 2:
*--out = ENCODE( in[1] << 2);
*--out = ENCODE((in[0] << 4) | (in[1] >> 4));
break;
default:
abort();
}
*--out = ENCODE(in[0] >> 2);
}