ceba1986 |
1 | /* -*-c-*- |
2 | * |
ceba1986 |
3 | * Base64 encoding and decoding. |
4 | * |
5 | * (c) 1997 Straylight/Edgeware |
6 | */ |
7 | |
d4efbcd9 |
8 | /*----- Licensing notice --------------------------------------------------* |
ceba1986 |
9 | * |
10 | * This file is part of the mLib utilities library. |
11 | * |
12 | * mLib is free software; you can redistribute it and/or modify |
13 | * it under the terms of the GNU Library General Public License as |
14 | * published by the Free Software Foundation; either version 2 of the |
15 | * License, or (at your option) any later version. |
d4efbcd9 |
16 | * |
ceba1986 |
17 | * mLib is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
20 | * GNU Library General Public License for more details. |
d4efbcd9 |
21 | * |
ceba1986 |
22 | * You should have received a copy of the GNU Library General Public |
23 | * License along with mLib; if not, write to the Free |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
25 | * MA 02111-1307, USA. |
26 | */ |
27 | |
ceba1986 |
28 | /*----- Header files ------------------------------------------------------*/ |
29 | |
30 | #include <stdio.h> |
31 | #include <stdlib.h> |
32 | #include <string.h> |
33 | |
34 | #include "base64.h" |
35 | #include "dstr.h" |
36 | |
37 | /*----- Important tables --------------------------------------------------*/ |
38 | |
fde30071 |
39 | static const char encodemap[] = { "ABCDEFGHIJKLMNOPQRSTUVWXYZ" |
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40 | "abcdefghijklmnopqrstuvwxyz" |
fde30071 |
41 | "0123456789+/" }; |
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42 | |
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43 | static const signed char decodemap[] = { |
ceba1986 |
44 | -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0x */ |
45 | -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 1x */ |
46 | -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, /* 2x */ |
47 | 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, /* 3x */ |
48 | -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, /* 4x */ |
49 | 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, /* 5x */ |
50 | -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36 ,37, 38, 39, 40, /* 6x */ |
51 | 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1 /* 7x */ |
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52 | }; |
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53 | |
54 | /*----- Main code ---------------------------------------------------------*/ |
55 | |
56 | /* --- @base64_encode@ --- * |
57 | * |
58 | * Arguments: @base64_ctx *ctx@ = pointer to a context block |
c601c4f1 |
59 | * @const void *p@ = pointer to a source buffer |
ceba1986 |
60 | * @size_t sz@ = size of the source buffer |
61 | * @dstr *d@ = pointer to destination string |
62 | * |
63 | * Returns: --- |
64 | * |
65 | * Use: Encodes a binary string in base64. To flush out the final |
66 | * few characters (if necessary), pass a null source pointer. |
67 | */ |
68 | |
69 | void base64_encode(base64_ctx *ctx, |
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70 | const void *p, size_t sz, |
ceba1986 |
71 | dstr *d) |
72 | { |
c601c4f1 |
73 | if (p) { |
ceba1986 |
74 | unsigned long acc = ctx->acc; |
75 | unsigned qsz = ctx->qsz; |
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76 | const unsigned char *src = p; |
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77 | |
78 | while (sz) { |
79 | acc = (acc << 8) | *src++; |
80 | qsz++; |
81 | sz--; |
82 | if (qsz == 3) { |
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83 | DPUTC(d, encodemap[(acc >> 18) & 0x3f]); |
84 | DPUTC(d, encodemap[(acc >> 12) & 0x3f]); |
85 | DPUTC(d, encodemap[(acc >> 6) & 0x3f]); |
86 | DPUTC(d, encodemap[(acc >> 0) & 0x3f]); |
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87 | ctx->lnlen += 4; |
88 | if (ctx->maxline && ctx->lnlen >= ctx->maxline) { |
89 | dstr_puts(d, ctx->indent); |
90 | ctx->lnlen = 0; |
91 | } |
92 | qsz = 0; |
93 | acc = 0; |
94 | } |
95 | } |
96 | |
97 | ctx->acc = acc; |
98 | ctx->qsz = qsz; |
99 | } else { |
100 | unsigned long acc = ctx->acc; |
101 | unsigned qsz = ctx->qsz; |
102 | |
103 | switch (qsz) { |
104 | case 0: |
105 | break; |
106 | case 1: |
107 | acc <<= 16; |
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108 | DPUTC(d, encodemap[(acc >> 18) & 0x3f]); |
109 | DPUTC(d, encodemap[(acc >> 12) & 0x3f]); |
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110 | DPUTC(d, '='); |
111 | DPUTC(d, '='); |
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112 | ctx->lnlen += 4; |
113 | break; |
114 | case 2: |
115 | acc <<= 8; |
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116 | DPUTC(d, encodemap[(acc >> 18) & 0x3f]); |
117 | DPUTC(d, encodemap[(acc >> 12) & 0x3f]); |
118 | DPUTC(d, encodemap[(acc >> 6) & 0x3f]); |
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119 | DPUTC(d, '='); |
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120 | ctx->lnlen += 4; |
121 | break; |
122 | } |
123 | ctx->qsz = 0; |
124 | ctx->acc = 0; |
125 | } |
126 | } |
127 | |
128 | /* --- @base64_decode@ --- * |
129 | * |
130 | * Arguments: @base64_ctx *ctx@ = pointer to a context block |
c601c4f1 |
131 | * @const void *p@ = pointer to a source buffer |
ceba1986 |
132 | * @size_t sz@ = size of the source buffer |
133 | * @dstr *d@ = pointer to destination string |
134 | * |
135 | * Returns: --- |
136 | * |
137 | * Use: Decodes a binary string in base64. To flush out the final |
138 | * few characters (if necessary), pass a null source pointer. |
139 | */ |
140 | |
141 | void base64_decode(base64_ctx *ctx, |
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142 | const void *p, size_t sz, |
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143 | dstr *d) |
144 | { |
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145 | if (p) { |
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146 | unsigned long acc = ctx->acc; |
147 | unsigned qsz = ctx->qsz; |
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148 | const char *src = p; |
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149 | int ch; |
150 | |
151 | while (sz) { |
152 | |
153 | /* --- Get the next character and convert it --- */ |
154 | |
155 | ch = *src++; |
156 | if (ch >= 128 || ch < 0) |
157 | ch = -1; |
158 | else |
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159 | ch = decodemap[ch]; |
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160 | sz--; |
161 | if (ch == -1) |
162 | continue; |
163 | |
164 | /* --- Bung it in the accumulator --- */ |
165 | |
166 | acc = (acc << 6) | ch; |
167 | qsz++; |
168 | |
169 | /* --- Maybe write out a completed triplet --- */ |
170 | |
171 | if (qsz == 4) { |
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172 | DPUTC(d, (acc >> 16) & 0xff); |
173 | DPUTC(d, (acc >> 8) & 0xff); |
174 | DPUTC(d, (acc >> 0) & 0xff); |
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175 | acc = 0; |
176 | qsz = 0; |
177 | } |
178 | } |
179 | |
180 | ctx->acc = acc; |
181 | ctx->qsz = qsz; |
182 | } else { |
183 | |
184 | /* --- Notes about the tail-end bits --- * |
185 | * |
186 | * Ending Base64 decoding is messy. The reference I'm using to define |
187 | * the encoding, RFC1521 section 5.2, is a little hazy on exactly what to |
188 | * do at the end. It explains that I'm meant to ignore spurious `=' |
189 | * characters, and points out that I'm not guaranteed to see anything |
190 | * interesting at the end. I'll play safe here, and ignore all `=' |
191 | * characters, relying on my client to work out when to stop feeding me |
192 | * data. I'll use the queue size to work out how many tail-end bytes |
193 | * I ought to write. |
194 | */ |
195 | |
196 | unsigned long acc = ctx->acc; |
197 | unsigned qsz = ctx->qsz; |
198 | |
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199 | /* --- Now fiddle with everything else --- * |
200 | * |
201 | * There's a bodge here for invalid encodings which have only one hextet |
202 | * in the final group. I'm not sure this is really worth having, but it |
203 | * might save some unexpected behaviour. (Not that you won't still get |
204 | * unexpected behaviour if the stream is completely empty, of course.) |
205 | */ |
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206 | |
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207 | if (qsz) { |
208 | acc <<= 6 * (4 - qsz); |
209 | qsz *= 6; |
210 | if (qsz < 8) |
211 | qsz = 8; |
212 | while (qsz >= 8) { |
213 | DPUTC(d, (acc >> 16) & 0xff); |
214 | acc <<= 8; |
215 | qsz -= 8; |
216 | } |
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217 | } |
218 | |
219 | /* --- That seems to be good enough --- */ |
220 | |
221 | ctx->qsz = 0; |
222 | ctx->acc = 0; |
223 | } |
224 | } |
225 | |
226 | /* --- @base64_init@ --- * |
227 | * |
228 | * Arguments: @base64_ctx *ctx@ = pointer to context block to initialize |
229 | * |
230 | * Returns: --- |
231 | * |
232 | * Use: Initializes a base64 context properly. |
233 | */ |
234 | |
235 | void base64_init(base64_ctx *ctx) |
236 | { |
237 | ctx->acc = 0; |
238 | ctx->qsz = 0; |
239 | ctx->lnlen = 0; |
240 | ctx->indent = "\n"; |
241 | ctx->maxline = 72; |
242 | } |
243 | |
244 | /*----- Test driver code --------------------------------------------------*/ |
245 | |
246 | #ifdef TEST_RIG |
247 | |
248 | int main(int argc, char *argv[]) |
249 | { |
250 | unsigned char buf[BUFSIZ]; |
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251 | dstr d = DSTR_INIT; |
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252 | base64_ctx ctx; |
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253 | void (*proc)(base64_ctx *, const void *, size_t, dstr *); |
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254 | size_t sz; |
255 | |
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256 | base64_init(&ctx); |
257 | |
258 | if (argc > 1 && strcmp(argv[1], "-d") == 0) |
259 | proc = base64_decode; |
260 | else { |
261 | proc = base64_encode; |
262 | putchar('\t'); |
263 | ctx.indent = "\n\t"; |
264 | ctx.maxline = 64; |
265 | } |
266 | |
267 | do { |
268 | sz = fread(buf, 1, sizeof(buf), stdin); |
269 | if (sz) { |
270 | proc(&ctx, buf, sz, &d); |
271 | dstr_write(&d, stdout); |
272 | dstr_destroy(&d); |
273 | } |
274 | } while (sz == sizeof(buf)); |
275 | |
276 | proc(&ctx, 0, 0, &d); |
277 | dstr_write(&d, stdout); |
278 | |
279 | if (proc == base64_encode) |
280 | putchar('\n'); |
281 | |
282 | return (0); |
283 | } |
284 | |
285 | #endif |
286 | |
287 | /*----- That's all, folks -------------------------------------------------*/ |