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1 | /* -*-c-*- |
2 | * |
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3 | * Base32 encoding and decoding. |
4 | * |
5 | * (c) 1997 Straylight/Edgeware |
6 | */ |
7 | |
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8 | /*----- Licensing notice --------------------------------------------------* |
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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. |
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16 | * |
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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. |
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21 | * |
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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 | |
28 | /*----- Header files ------------------------------------------------------*/ |
29 | |
30 | #include <stdio.h> |
31 | #include <stdlib.h> |
32 | #include <string.h> |
33 | |
34 | #include "base32.h" |
35 | #include "dstr.h" |
36 | |
37 | /*----- Important tables --------------------------------------------------*/ |
38 | |
39 | static const char encodemap[] = { "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567" }; |
40 | |
41 | static const signed char decodemap[] = { |
42 | -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0x */ |
43 | -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 1x */ |
44 | -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 2x */ |
45 | -1, -1, 26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1, /* 3x */ |
46 | -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, /* 4x */ |
47 | 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, /* 5x */ |
48 | -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, /* 6x */ |
49 | 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, /* 7x */ |
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50 | }; |
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51 | |
52 | /*----- Main code ---------------------------------------------------------*/ |
53 | |
54 | /* --- @base32_encode@ --- * |
55 | * |
56 | * Arguments: @base32_ctx *ctx@ = pointer to a context block |
57 | * @const void *p@ = pointer to a source buffer |
58 | * @size_t sz@ = size of the source buffer |
59 | * @dstr *d@ = pointer to destination string |
60 | * |
61 | * Returns: --- |
62 | * |
63 | * Use: Encodes a binary string in base32. To flush out the final |
64 | * few characters (if necessary), pass a null source pointer. |
65 | */ |
66 | |
67 | void base32_encode(base32_ctx *ctx, |
68 | const void *p, size_t sz, |
69 | dstr *d) |
70 | { |
71 | if (p) { |
72 | unsigned long accl = ctx->accl, acch = ctx->acch; |
73 | unsigned qsz = ctx->qsz; |
74 | const unsigned char *src = p; |
75 | |
76 | while (sz) { |
77 | acch = (acch << 8) | ((accl >> 24) & 0xff); |
78 | accl = (accl << 8) | *src++; |
79 | qsz++; |
80 | sz--; |
81 | if (qsz == 5) { |
82 | DPUTC(d, encodemap[(acch >> 3) & 0x1f]); |
83 | DPUTC(d, encodemap[((acch << 2) & 0x1c) | ((accl >> 30) & 0x03)]); |
84 | DPUTC(d, encodemap[(accl >> 25) & 0x1f]); |
85 | DPUTC(d, encodemap[(accl >> 20) & 0x1f]); |
86 | DPUTC(d, encodemap[(accl >> 15) & 0x1f]); |
87 | DPUTC(d, encodemap[(accl >> 10) & 0x1f]); |
88 | DPUTC(d, encodemap[(accl >> 5) & 0x1f]); |
89 | DPUTC(d, encodemap[(accl >> 0) & 0x1f]); |
90 | ctx->lnlen += 8; |
91 | if (ctx->maxline && ctx->lnlen >= ctx->maxline) { |
92 | dstr_puts(d, ctx->indent); |
93 | ctx->lnlen = 0; |
94 | } |
95 | qsz = 0; |
96 | accl = acch = 0; |
97 | } |
98 | } |
99 | |
100 | ctx->acch = acch; ctx->accl = accl; |
101 | ctx->qsz = qsz; |
102 | } else { |
103 | unsigned long accl = ctx->accl, acch = ctx->acch; |
104 | unsigned qsz = ctx->qsz; |
105 | |
106 | if (qsz) { |
107 | unsigned pad = 5 - qsz; |
108 | if (pad > 3) { |
109 | acch = accl << (pad * 8 - 32); |
110 | accl = 0; |
111 | } else { |
112 | acch = (acch << (8 * pad)) | ((accl & 0xffffffff) >> (32 - 8 * pad)); |
113 | accl = accl << (8 * pad); |
114 | } |
115 | qsz = 40; |
116 | pad *= 8; |
117 | while (qsz > pad) { |
118 | DPUTC(d, encodemap[(acch >> 3) & 0x1f]); |
119 | acch = (acch << 5) | ((accl >> 27) & 0x1f); |
120 | accl = (accl << 5); |
121 | qsz -= 5; |
122 | } |
123 | while (qsz) { |
124 | DPUTC(d, '='); |
125 | qsz -= 5; |
126 | } |
127 | ctx->lnlen += 8; |
128 | } |
129 | ctx->qsz = 0; |
130 | ctx->acch = ctx->accl = 0; |
131 | } |
132 | } |
133 | |
134 | /* --- @base32_decode@ --- * |
135 | * |
136 | * Arguments: @base32_ctx *ctx@ = pointer to a context block |
137 | * @const void *p@ = pointer to a source buffer |
138 | * @size_t sz@ = size of the source buffer |
139 | * @dstr *d@ = pointer to destination string |
140 | * |
141 | * Returns: --- |
142 | * |
143 | * Use: Decodes a binary string in base32. To flush out the final |
144 | * few characters (if necessary), pass a null source pointer. |
145 | */ |
146 | |
147 | void base32_decode(base32_ctx *ctx, |
148 | const void *p, size_t sz, |
149 | dstr *d) |
150 | { |
151 | if (p) { |
152 | unsigned long accl = ctx->accl, acch = ctx->acch; |
153 | unsigned qsz = ctx->qsz; |
154 | const char *src = p; |
155 | int ch; |
156 | |
157 | while (sz) { |
158 | |
159 | /* --- Get the next character and convert it --- */ |
160 | |
161 | ch = *src++; |
162 | if (ch >= 128 || ch < 0) |
163 | ch = -1; |
164 | else |
165 | ch = decodemap[ch]; |
166 | sz--; |
167 | if (ch == -1) |
168 | continue; |
169 | |
170 | /* --- Bung it in the accumulator --- */ |
171 | |
172 | acch = (acch << 5) | ((accl >> 27) & 0x1f); |
173 | accl = (accl << 5) | ch; |
174 | qsz++; |
175 | |
176 | /* --- Maybe write out a completed triplet --- */ |
177 | |
178 | if (qsz == 8) { |
179 | DPUTC(d, (acch >> 0) & 0xff); |
180 | DPUTC(d, (accl >> 24) & 0xff); |
181 | DPUTC(d, (accl >> 16) & 0xff); |
182 | DPUTC(d, (accl >> 8) & 0xff); |
183 | DPUTC(d, (accl >> 0) & 0xff); |
184 | acch = accl = 0; |
185 | qsz = 0; |
186 | } |
187 | } |
188 | |
189 | ctx->acch = acch; ctx->accl = accl; |
190 | ctx->qsz = qsz; |
191 | } else { |
192 | |
193 | /* --- Notes about the tail-end bits --- * |
194 | * |
195 | * I'll use the queue size to work out how many tail-end bytes I ought to |
196 | * write. This isn't strictly right, but it's easier. |
197 | */ |
198 | |
199 | unsigned long acch = ctx->acch, accl = ctx->accl; |
200 | unsigned qsz = ctx->qsz; |
201 | |
202 | /* --- Now fiddle with everything else --- * |
203 | * |
204 | * There's a bodge here for invalid encodings which have a funny number |
205 | * of quintets in the final group. I'm not sure this is really worth |
206 | * having, but it might save some unexpected behaviour. (Not that you |
207 | * won't still get unexpected behaviour if the stream is completely |
208 | * empty, of course.) |
209 | */ |
210 | |
211 | if (qsz) { |
212 | unsigned pad = 8 - qsz; |
213 | if (pad > 6) { |
214 | acch = accl << (5 * pad - 32); |
215 | accl = 0; |
216 | } else { |
217 | acch = (acch << (5 * pad)) | ((accl & 0xffffffff) >> (32 - 5 * pad)); |
218 | accl = accl << (5 * pad); |
219 | } |
220 | |
221 | qsz *= 5; |
222 | while (qsz >= 8) { |
223 | DPUTC(d, acch & 0xff); |
224 | acch = accl >> 24; |
225 | accl <<= 8; |
226 | qsz -= 8; |
227 | } |
228 | } |
229 | |
230 | /* --- That seems to be good enough --- */ |
231 | |
232 | ctx->qsz = 0; |
233 | ctx->acch = ctx->accl = 0; |
234 | } |
235 | } |
236 | |
237 | /* --- @base32_init@ --- * |
238 | * |
239 | * Arguments: @base32_ctx *ctx@ = pointer to context block to initialize |
240 | * |
241 | * Returns: --- |
242 | * |
243 | * Use: Initializes a base32 context properly. |
244 | */ |
245 | |
246 | void base32_init(base32_ctx *ctx) |
247 | { |
248 | ctx->accl = ctx->acch = 0; |
249 | ctx->qsz = 0; |
250 | ctx->lnlen = 0; |
251 | ctx->indent = "\n"; |
252 | ctx->maxline = 72; |
253 | } |
254 | |
255 | /*----- Test driver code --------------------------------------------------*/ |
256 | |
257 | #ifdef TEST_RIG |
258 | |
259 | int main(int argc, char *argv[]) |
260 | { |
261 | unsigned char buf[BUFSIZ]; |
262 | dstr d = DSTR_INIT; |
263 | base32_ctx ctx; |
264 | void (*proc)(base32_ctx *, const void *, size_t, dstr *); |
265 | size_t sz; |
266 | |
267 | base32_init(&ctx); |
268 | |
269 | if (argc > 1 && strcmp(argv[1], "-d") == 0) |
270 | proc = base32_decode; |
271 | else { |
272 | proc = base32_encode; |
273 | putchar('\t'); |
274 | ctx.indent = "\n\t"; |
275 | ctx.maxline = 32; |
276 | } |
277 | |
278 | do { |
279 | sz = fread(buf, 1, sizeof(buf), stdin); |
280 | if (sz) { |
281 | proc(&ctx, buf, sz, &d); |
282 | dstr_write(&d, stdout); |
283 | dstr_destroy(&d); |
284 | } |
285 | } while (sz == sizeof(buf)); |
286 | |
287 | proc(&ctx, 0, 0, &d); |
288 | dstr_write(&d, stdout); |
289 | |
290 | if (proc == base32_encode) |
291 | putchar('\n'); |
292 | |
293 | return (0); |
294 | } |
295 | |
296 | #endif |
297 | |
298 | /*----- That's all, folks -------------------------------------------------*/ |