chiark / gitweb /
Base64 encoding and decoding support.
[mLib] / base64.c
CommitLineData
ceba1986 1/* -*-c-*-
2 *
3 * $Id: base64.c,v 1.1 1999/05/17 20:35:00 mdw Exp $
4 *
5 * Base64 encoding and decoding.
6 *
7 * (c) 1997 Straylight/Edgeware
8 */
9
10/*----- Licensing notice --------------------------------------------------*
11 *
12 * This file is part of the mLib utilities library.
13 *
14 * mLib is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU Library General Public License as
16 * published by the Free Software Foundation; either version 2 of the
17 * License, or (at your option) any later version.
18 *
19 * mLib is distributed in the hope that it will be useful,
20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU Library General Public License for more details.
23 *
24 * You should have received a copy of the GNU Library General Public
25 * License along with mLib; if not, write to the Free
26 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
27 * MA 02111-1307, USA.
28 */
29
30/*----- Revision history --------------------------------------------------*
31 *
32 * $Log: base64.c,v $
33 * Revision 1.1 1999/05/17 20:35:00 mdw
34 * Base64 encoding and decoding support.
35 *
36 */
37
38/*----- Header files ------------------------------------------------------*/
39
40#include <stdio.h>
41#include <stdlib.h>
42#include <string.h>
43
44#include "base64.h"
45#include "dstr.h"
46
47/*----- Important tables --------------------------------------------------*/
48
49static const char base64_encodeMap[] = { "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
50 "abcdefghijklmnopqrstuvwxyz"
51 "0123456789+/" };
52
53static const signed char base64_decodeMap[] = {
54 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0x */
55 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 1x */
56 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, /* 2x */
57 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, /* 3x */
58 -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, /* 4x */
59 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, /* 5x */
60 -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36 ,37, 38, 39, 40, /* 6x */
61 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1 /* 7x */
62};
63
64/*----- Main code ---------------------------------------------------------*/
65
66/* --- @base64_encode@ --- *
67 *
68 * Arguments: @base64_ctx *ctx@ = pointer to a context block
69 * @const unsigned char *src@ = pointer to a source buffer
70 * @size_t sz@ = size of the source buffer
71 * @dstr *d@ = pointer to destination string
72 *
73 * Returns: ---
74 *
75 * Use: Encodes a binary string in base64. To flush out the final
76 * few characters (if necessary), pass a null source pointer.
77 */
78
79void base64_encode(base64_ctx *ctx,
80 const unsigned char *src, size_t sz,
81 dstr *d)
82{
83 if (src) {
84 unsigned long acc = ctx->acc;
85 unsigned qsz = ctx->qsz;
86
87 while (sz) {
88 acc = (acc << 8) | *src++;
89 qsz++;
90 sz--;
91 if (qsz == 3) {
92 dstr_putc(d, base64_encodeMap[(acc >> 18) & 0x3f]);
93 dstr_putc(d, base64_encodeMap[(acc >> 12) & 0x3f]);
94 dstr_putc(d, base64_encodeMap[(acc >> 6) & 0x3f]);
95 dstr_putc(d, base64_encodeMap[(acc >> 0) & 0x3f]);
96 ctx->lnlen += 4;
97 if (ctx->maxline && ctx->lnlen >= ctx->maxline) {
98 dstr_puts(d, ctx->indent);
99 ctx->lnlen = 0;
100 }
101 qsz = 0;
102 acc = 0;
103 }
104 }
105
106 ctx->acc = acc;
107 ctx->qsz = qsz;
108 } else {
109 unsigned long acc = ctx->acc;
110 unsigned qsz = ctx->qsz;
111
112 switch (qsz) {
113 case 0:
114 break;
115 case 1:
116 acc <<= 16;
117 dstr_putc(d, base64_encodeMap[(acc >> 18) & 0x3f]);
118 dstr_putc(d, base64_encodeMap[(acc >> 12) & 0x3f]);
119 dstr_putc(d, '=');
120 dstr_putc(d, '=');
121 ctx->lnlen += 4;
122 break;
123 case 2:
124 acc <<= 8;
125 dstr_putc(d, base64_encodeMap[(acc >> 18) & 0x3f]);
126 dstr_putc(d, base64_encodeMap[(acc >> 12) & 0x3f]);
127 dstr_putc(d, base64_encodeMap[(acc >> 6) & 0x3f]);
128 dstr_putc(d, '=');
129 ctx->lnlen += 4;
130 break;
131 }
132 ctx->qsz = 0;
133 ctx->acc = 0;
134 }
135}
136
137/* --- @base64_decode@ --- *
138 *
139 * Arguments: @base64_ctx *ctx@ = pointer to a context block
140 * @const unsigned char *src@ = pointer to a source buffer
141 * @size_t sz@ = size of the source buffer
142 * @dstr *d@ = pointer to destination string
143 *
144 * Returns: ---
145 *
146 * Use: Decodes a binary string in base64. To flush out the final
147 * few characters (if necessary), pass a null source pointer.
148 */
149
150void base64_decode(base64_ctx *ctx,
151 const unsigned char *src, size_t sz,
152 dstr *d)
153{
154 if (src) {
155 unsigned long acc = ctx->acc;
156 unsigned qsz = ctx->qsz;
157 int ch;
158
159 while (sz) {
160
161 /* --- Get the next character and convert it --- */
162
163 ch = *src++;
164 if (ch >= 128 || ch < 0)
165 ch = -1;
166 else
167 ch = base64_decodeMap[ch];
168 sz--;
169 if (ch == -1)
170 continue;
171
172 /* --- Bung it in the accumulator --- */
173
174 acc = (acc << 6) | ch;
175 qsz++;
176
177 /* --- Maybe write out a completed triplet --- */
178
179 if (qsz == 4) {
180 dstr_putc(d, (acc >> 16) & 0xff);
181 dstr_putc(d, (acc >> 8) & 0xff);
182 dstr_putc(d, (acc >> 0) & 0xff);
183 acc = 0;
184 qsz = 0;
185 }
186 }
187
188 ctx->acc = acc;
189 ctx->qsz = qsz;
190 } else {
191
192 /* --- Notes about the tail-end bits --- *
193 *
194 * Ending Base64 decoding is messy. The reference I'm using to define
195 * the encoding, RFC1521 section 5.2, is a little hazy on exactly what to
196 * do at the end. It explains that I'm meant to ignore spurious `='
197 * characters, and points out that I'm not guaranteed to see anything
198 * interesting at the end. I'll play safe here, and ignore all `='
199 * characters, relying on my client to work out when to stop feeding me
200 * data. I'll use the queue size to work out how many tail-end bytes
201 * I ought to write.
202 */
203
204 unsigned long acc = ctx->acc;
205 unsigned qsz = ctx->qsz;
206
207 /* --- Now fiddle with everything else --- */
208
209 acc <<= 6 * (4 - qsz);
210 qsz *= 6;
211 while (qsz > 8) {
212 dstr_putc(d, (acc >> 16) & 0xff);
213 acc <<= 8;
214 qsz -= 8;
215 }
216
217 /* --- That seems to be good enough --- */
218
219 ctx->qsz = 0;
220 ctx->acc = 0;
221 }
222}
223
224/* --- @base64_init@ --- *
225 *
226 * Arguments: @base64_ctx *ctx@ = pointer to context block to initialize
227 *
228 * Returns: ---
229 *
230 * Use: Initializes a base64 context properly.
231 */
232
233void base64_init(base64_ctx *ctx)
234{
235 ctx->acc = 0;
236 ctx->qsz = 0;
237 ctx->lnlen = 0;
238 ctx->indent = "\n";
239 ctx->maxline = 72;
240}
241
242/*----- Test driver code --------------------------------------------------*/
243
244#ifdef TEST_RIG
245
246int main(int argc, char *argv[])
247{
248 unsigned char buf[BUFSIZ];
249 dstr d;
250 base64_ctx ctx;
251 void (*proc)(base64_ctx *, const unsigned char *, size_t, dstr *);
252 size_t sz;
253
254 dstr_create(&d);
255 base64_init(&ctx);
256
257 if (argc > 1 && strcmp(argv[1], "-d") == 0)
258 proc = base64_decode;
259 else {
260 proc = base64_encode;
261 putchar('\t');
262 ctx.indent = "\n\t";
263 ctx.maxline = 64;
264 }
265
266 do {
267 sz = fread(buf, 1, sizeof(buf), stdin);
268 if (sz) {
269 proc(&ctx, buf, sz, &d);
270 dstr_write(&d, stdout);
271 dstr_destroy(&d);
272 }
273 } while (sz == sizeof(buf));
274
275 proc(&ctx, 0, 0, &d);
276 dstr_write(&d, stdout);
277
278 if (proc == base64_encode)
279 putchar('\n');
280
281 return (0);
282}
283
284#endif
285
286/*----- That's all, folks -------------------------------------------------*/