release/src/router/nettle/base16-decode.c

   1 /* base16-encode.c
   2  *
   3  * Hex decoding.
   4  */
   5
   6 /* nettle, low-level cryptographics library
   7  *
   8  * Copyright (C) 2002 Niels Möller
   9  *
  10  * The nettle library is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU Lesser General Public License as published by
  12  * the Free Software Foundation; either version 2.1 of the License, or (at your
  13  * option) any later version.
  14  *
  15  * The nettle library is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  17  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  18  * License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public License
  21  * along with the nettle library; see the file COPYING.LIB.  If not, write to
  22  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  23  * MA 02111-1301, USA.
  24  */
  25
  26 #if HAVE_CONFIG_H
  27 # include "config.h"
  28 #endif
  29
  30 #include <assert.h>
  31 #include <stdlib.h>
  32
  33 #include "base16.h"
  34
  35 void
  36 base16_decode_init(struct base16_decode_ctx *ctx)
  37 {
  38   ctx->word = ctx->bits = 0;
  39 }
  40
  41 enum { HEX_INVALID = -1, HEX_SPACE=-2 };
  42
  43 static const signed char
  44 hex_decode_table[0x80] =
  45   {
  46     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
  47     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  48     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  49      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
  50     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  51     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  52     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  53     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  54   };
  55
  56 /* Decodes a single byte. Returns amount of output (0 or 1), or -1 on
  57  * errors. */
  58 int
  59 base16_decode_single(struct base16_decode_ctx *ctx,
  60                      uint8_t *dst,
  61                      uint8_t src)
  62 {
  63   int digit;
  64
  65   if (src >= 0x80)
  66     return -1;
  67
  68   digit = hex_decode_table[src];
  69   switch (digit)
  70     {
  71     case -1:
  72       return -1;
  73     case -2:
  74       return 0;
  75     default:
  76       assert(digit >= 0);
  77       assert(digit < 0x10);
  78
  79       if (ctx->bits)
  80         {
  81           *dst = (ctx->word << 4) | digit;
  82           ctx->bits = 0;
  83           return 1;
  84         }
  85       else
  86         {
  87           ctx->word = digit;
  88           ctx->bits = 4;
  89           return 0;
  90         }
  91     }
  92 }
  93
  94 int
  95 base16_decode_update(struct base16_decode_ctx *ctx,
  96                      unsigned *dst_length,
  97                      uint8_t *dst,
  98                      unsigned src_length,
  99                      const uint8_t *src)
 100 {
 101   unsigned done;
 102   unsigned i;
 103
 104   assert(*dst_length >= BASE16_DECODE_LENGTH(src_length));
 105
 106   for (i = 0, done = 0; i<src_length; i++)
 107     switch(base16_decode_single(ctx, dst + done, src[i]))
 108       {
 109       case -1:
 110         return 0;
 111       case 1:
 112         done++;
 113         /* Fall through */
 114       case 0:
 115         break;
 116       default:
 117         abort();
 118       }
 119
 120   assert(done <= BASE16_DECODE_LENGTH(src_length));
 121
 122   *dst_length = done;
 123   return 1;
 124 }
 125
 126 int
 127 base16_decode_final(struct base16_decode_ctx *ctx)
 128 {
 129   return ctx->bits == 0;
 130 }