File: base64-encode.c

package info (click to toggle)
nettle 3.5.1+really3.4.1-1
  • links: PTS, VCS
  • area: main
  • in suites: sid
  • size: 8,012 kB
  • sloc: ansic: 51,527; asm: 12,157; sh: 3,632; makefile: 846; cpp: 71; awk: 7
file content (200 lines) | stat: -rw-r--r-- 4,495 bytes parent folder | download | duplicates (3)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
/* base64-encode.c

   Copyright (C) 2002 Niels Möller

   This file is part of GNU Nettle.

   GNU Nettle 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.

   GNU Nettle 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 copies of the GNU General Public License and
   the GNU Lesser General Public License along with this program.  If
   not, see http://www.gnu.org/licenses/.
*/

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include <assert.h>
#include <stdlib.h>

#include "base64.h"

#define ENCODE(alphabet,x) ((alphabet)[0x3F & (x)])

static void
encode_raw(const char *alphabet,
	   char *dst, size_t length, const uint8_t *src)
{
  const uint8_t *in = src + length;
  char *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(alphabet, (in[0] << 4));
	  break;
	  
	case 2:
	  *--out = ENCODE(alphabet, (in[1] << 2));
	  *--out = ENCODE(alphabet, ((in[0] << 4) | (in[1] >> 4)));
	  break;

	default:
	  abort();
	}
      *--out = ENCODE(alphabet, (in[0] >> 2));
    }
  
  while (in > src)
    {
      in -= 3;
      *--out = ENCODE(alphabet, (in[2]));
      *--out = ENCODE(alphabet, ((in[1] << 2) | (in[2] >> 6)));
      *--out = ENCODE(alphabet, ((in[0] << 4) | (in[1] >> 4)));
      *--out = ENCODE(alphabet, (in[0] >> 2));
    }
  assert(in == src);
  assert(out == dst);
}

static const char base64_encode_table[64] =
  "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
  "abcdefghijklmnopqrstuvwxyz"
  "0123456789+/";

void
base64_encode_raw(char *dst, size_t length, const uint8_t *src)
{
  encode_raw(base64_encode_table, dst, length, src);
}

void
base64_encode_group(char *dst, uint32_t group)
{
  *dst++ = ENCODE(base64_encode_table, (group >> 18));
  *dst++ = ENCODE(base64_encode_table, (group >> 12));
  *dst++ = ENCODE(base64_encode_table, (group >> 6));
  *dst++ = ENCODE(base64_encode_table, group);
}

void
base64_encode_init(struct base64_encode_ctx *ctx)
{
  ctx->word = ctx->bits = 0;
  ctx->alphabet = base64_encode_table;
}

/* Encodes a single byte. */
size_t
base64_encode_single(struct base64_encode_ctx *ctx,
		     char *dst,
		     uint8_t src)
{
  unsigned done = 0;
  unsigned word = ctx->word << 8 | src;
  unsigned bits = ctx->bits + 8;
  
  while (bits >= 6)
    {
      bits -= 6;
      dst[done++] = ENCODE(ctx->alphabet, (word >> bits));
    }

  ctx->bits = bits;
  ctx->word = word;

  assert(done <= 2);
  
  return done;
}

/* Returns the number of output characters. DST should point to an
 * area of size at least BASE64_ENCODE_LENGTH(length). */
size_t
base64_encode_update(struct base64_encode_ctx *ctx,
		     char *dst,
		     size_t length,
		     const uint8_t *src)
{
  size_t done = 0;
  size_t left = length;
  unsigned left_over;
  size_t bulk;
  
  while (ctx->bits && left)
    {
      left--;
      done += base64_encode_single(ctx, dst + done, *src++);
    }
  
  left_over = left % 3;
  bulk = left - left_over;
  
  if (bulk)
    {
      assert(!(bulk % 3));
      
      encode_raw(ctx->alphabet, dst + done, bulk, src);
      done += BASE64_ENCODE_RAW_LENGTH(bulk);
      src += bulk;
      left = left_over;
    }

  while (left)
    {
      left--;
      done += base64_encode_single(ctx, dst + done, *src++);
    }

  assert(done <= BASE64_ENCODE_LENGTH(length));

  return done;
}

/* DST should point to an area of size at least
 * BASE64_ENCODE_FINAL_SIZE */
size_t
base64_encode_final(struct base64_encode_ctx *ctx,
		    char *dst)
{
  unsigned done = 0;
  unsigned bits = ctx->bits;
  
  if (bits)
    {
      dst[done++] = ENCODE(ctx->alphabet, (ctx->word << (6 - ctx->bits)));
      for (; bits < 6; bits += 2)
	dst[done++] = '=';

      ctx->bits = 0;
    }

  assert(done <= BASE64_ENCODE_FINAL_LENGTH);
  return done;
}