summaryrefslogtreecommitdiff
path: root/base64-encode.c
blob: 6fc5e6ba1d256bdec9237b4e35ce25d008a2dd4d (plain)
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
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
/* 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., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, 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);
    }
  
  while (in > src)
    {
      in -= 3;
      *--out = ENCODE( in[2]);
      *--out = ENCODE((in[1] << 2) | (in[2] >> 6));
      *--out = ENCODE((in[0] << 4) | (in[1] >> 4));
      *--out = ENCODE( in[0] >> 2);      
    }
  assert(in == src);
  assert(out == dst);
}

#if 0
unsigned 
base64_encode(uint8_t *dst,
	      unsigned src_length,
	      const uint8_t *src)
{
  unsigned dst_length = BASE64_ENCODE_RAW_LENGTH(src_length);
  unsigned n = src_length / 3;
  unsigned left_over  = src_length % 3;
  unsigned done = 0;
  
  if (left_over)
    {
      const uint8_t *in = src + n * 3;
      uint8_t *out = dst + dst_length;

      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);

      done = 4;
    }
  base64_encode_raw(n, dst, src);
  done += n * 4;

  assert(done == dst_length);

  return done;
}
#endif

void
base64_encode_group(uint8_t *dst, uint32_t group)
{
  *dst++ = ENCODE(group >> 18);
  *dst++ = ENCODE(group >> 12);
  *dst++ = ENCODE(group >> 6);
  *dst++ = ENCODE(group);
}

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

/* Encodes a single byte. */
unsigned
base64_encode_single(struct base64_encode_ctx *ctx,
		     uint8_t *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(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). */
unsigned
base64_encode_update(struct base64_encode_ctx *ctx,
		     uint8_t *dst,
		     unsigned length,
		     const uint8_t *src)
{
  unsigned done = 0;
  unsigned left = length;
  unsigned left_over;
  unsigned 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));
      
      base64_encode_raw(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 */
unsigned
base64_encode_final(struct base64_encode_ctx *ctx,
		    uint8_t *dst)
{
  unsigned done = 0;
  unsigned bits = ctx->bits;
  
  if (bits)
    {
      dst[done++] = ENCODE(ctx->word << (6 - ctx->bits));
      for (; bits < 6; bits += 2)
	dst[done++] = '=';

      ctx->bits = 0;
    }

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