1 /* Part of publib.
2
3 Copyright (c) 1994-2006 Lars Wirzenius. All rights reserved.
4
5 Redistribution and use in source and binary forms, with or without
6 modification, are permitted provided that the following conditions
7 are met:
8
9 1. Redistributions of source code must retain the above copyright
10 notice, this list of conditions and the following disclaimer.
11
12 2. Redistributions in binary form must reproduce the above
13 copyright notice, this list of conditions and the following
14 disclaimer in the documentation and/or other materials provided
15 with the distribution.
16
17 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
18 OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
21 DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
23 GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
24 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
25 WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
26 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
27 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29 /*
30 * File: base64.c
31 * Purpose: Implementation of MIME's Base64 encoding and decoding.
32 * Author: Lars Wirzenius
33 * Version: $Id: base64.c,v 1.2 2003/11/15 18:24:10 liw Exp $
34 */
35
36 #include <limits.h>
37 #include "publib/base64.h"
38
39 static const unsigned char sixtet_to_base64[] =
40 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
41
42
43 /*
44 * Function: base64_length
45 * Purpose: Compute minimum length of encoded output.
46 */
base64_length(size_t n)47 size_t base64_length(size_t n) {
48 return 4*(n+3)/3 + 1;
49 }
50
51
52 /*
53 * Function: base64_encode
54 * Purpose: Convert octets to base64
55 * Note: Output buffer must be at least base64_length(n) chars.
56 */
base64_encode(char * to,const char * from,size_t n)57 size_t base64_encode(char *to, const char *from, size_t n) {
58 unsigned w;
59 char *to_start;
60 unsigned char *fromp;
61
62 to_start = to;
63
64 fromp = (unsigned char *) from;
65 for (; n >= 3; n -= 3, fromp += 3) {
66 w = (fromp[0] << 16) | (fromp[1] << 8) | fromp[2];
67 *to++ = sixtet_to_base64[(w >> 18) & 0x3f];
68 *to++ = sixtet_to_base64[(w >> 12) & 0x3f];
69 *to++ = sixtet_to_base64[(w >> 6) & 0x3f];
70 *to++ = sixtet_to_base64[w & 0x3f];
71 }
72
73 switch (n) {
74 case 0:
75 /* Nothing to do */
76 break;
77
78 case 1:
79 w = fromp[0];
80 *to++ = sixtet_to_base64[(w >> 2) & 0x3f];
81 *to++ = sixtet_to_base64[(w << 4) & 0x3f];
82 *to++ = '=';
83 *to++ = '=';
84 break;
85
86 case 2:
87 w = (fromp[0] << 8) | fromp[1];
88 *to++ = sixtet_to_base64[(w >> 10) & 0x3f];
89 *to++ = sixtet_to_base64[(w >> 4) & 0x3f];
90 *to++ = sixtet_to_base64[(w << 2) & 0x3f];
91 *to++ = '=';
92 break;
93 }
94
95 return to - to_start;
96 }
97
98
99 /*
100 * Function: base64_decode
101 * Purpose: Convert base64 to octets.
102 * Note: Output buffer must be at least 3*n/4 chars.
103 * The output buffer does not get a '\0' appended.
104 */
base64_decode(char * to,const char * from,size_t len)105 size_t base64_decode(char *to, const char *from, size_t len) {
106 static int base64_to_sixtet[UCHAR_MAX + 1];
107 static int tab_init = 0;
108 int i;
109 unsigned bitbuf;
110 int nbits;
111 unsigned char *fromp;
112 char *to_start;
113
114 if (!tab_init) {
115 tab_init = 1;
116 for (i = 0; i <= UCHAR_MAX + 1; ++i)
117 base64_to_sixtet[i] = -1;
118 for (i = 0; sixtet_to_base64[i] != '\0'; ++i)
119 base64_to_sixtet[sixtet_to_base64[i]] = i;
120 }
121
122 to_start = to;
123
124 bitbuf = 0;
125 nbits = 0;
126 fromp = (unsigned char *) from;
127 for (i = 0; i < len && fromp[i] != '='; ++i) {
128 if (base64_to_sixtet[fromp[i]] != -1) {
129 bitbuf = (bitbuf << 6) | base64_to_sixtet[fromp[i]];
130 nbits += 6;
131 if (nbits >= 8) {
132 *to++ = (bitbuf >> (nbits - 8)) & 0xff;
133 bitbuf >>= 8;
134 nbits -= 8;
135 }
136 }
137 }
138
139 return to - to_start;
140 }
141