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/* base16-encode.c
*
* Hex decoding.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2002 Niels Mller
*
* 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., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include "base16.h"
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void
base16_decode_init(struct base16_decode_ctx *ctx)
{
ctx->word = ctx->bits = 0;
}
enum { HEX_INVALID = -1, HEX_SPACE=-2 };
static const signed char
hex_decode_table[0x80] =
{
-1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
};
/* Decodes a single byte. Returns amount of output (0 or 1), or -1 on
* errors. */
int
base16_decode_single(struct base16_decode_ctx *ctx,
uint8_t *dst,
uint8_t src)
{
int digit;
if (src >= 0x80)
return -1;
/* FIXME: This code could use more clever choices of constants. */
digit = hex_decode_table[src];
switch (digit)
{
case -1:
return -1;
case -2:
return 0;
default:
assert(digit >= 0);
assert(digit < 0x10);
if (ctx->bits)
{
*dst = (ctx->word << 4) | digit;
ctx->bits = 0;
return 1;
}
else
{
ctx->word = digit;
ctx->bits = 4;
return 0;
}
}
}
int
base16_decode_update(struct base16_decode_ctx *ctx,
unsigned *dst_length,
uint8_t *dst,
unsigned src_length,
const uint8_t *src)
{
unsigned done;
unsigned i;
assert(*dst_length >= BASE16_DECODE_LENGTH(src_length));
for (i = 0, done = 0; i<src_length; i++)
switch(base16_decode_single(ctx, dst + done, src[i]))
{
case -1:
return 0;
case 1:
done++;
/* Fall through */
case 0:
break;
default:
abort();
}
assert(done <= BASE16_DECODE_LENGTH(src_length));
*dst_length = done;
return 1;
}
int
base16_decode_final(struct base16_decode_ctx *ctx)
{
return ctx->bits == 0;
}