summaryrefslogtreecommitdiff
path: root/cd/src/svg/base64.c
blob: c01b1306ef4d4367fde284ae7b66ff512ca4ee54 (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
230
231
/***********************************************************************
===============
BASE64 Encoding
===============
Available on: http://freecode-freecode.blogspot.com/2008/02/base64c.html
Last access in: November, 10th 2009.
************************************************************************/

#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "base64.h"

/**
 * characters used for Base64 encoding
 */  
const char *BASE64_CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

/**
 * encode three bytes using base64 (RFC 3548)
 *
 * @param triple three bytes that should be encoded
 * @param result buffer of four characters where the result is stored
 */  
void _base64_encode_triple(unsigned char triple[3], char result[4])
{
	int tripleValue, i;
	
	tripleValue = triple[0];
	tripleValue *= 256;
	tripleValue += triple[1];
	tripleValue *= 256;
	tripleValue += triple[2];
	
	for (i=0; i<4; i++)
	{
		result[3-i] = BASE64_CHARS[tripleValue%64];
		tripleValue /= 64;
	}
}

/**
 * encode an array of bytes using Base64 (RFC 3548)
 *
 * @param source the source buffer
 * @param sourcelen the length of the source buffer
 * @param target the target buffer
 * @param targetlen the length of the target buffer
 * @return 1 on success, 0 otherwise
 */  
int base64_encode(unsigned char *source, int sourcelen, char *target, int targetlen)
{
	/* check if the result will fit in the target buffer */
	if ((sourcelen+2)/3*4 > targetlen-1)
		return 0;
	
	/* encode all full triples */
	while (sourcelen >= 3)
	{
		_base64_encode_triple(source, target);
		sourcelen -= 3;
		source += 3;
		target += 4;
	}
	
	/* encode the last one or two characters */
	if (sourcelen > 0)
	{
		unsigned char temp[3];
		memset(temp, 0, sizeof(temp));
		memcpy(temp, source, sourcelen);
		_base64_encode_triple(temp, target);
		target[3] = '=';
		
		if (sourcelen == 1)
			target[2] = '=';
		
		target += 4;
	}
	
	/* terminate the string */
	target[0] = 0;
	
	return 1;
} 

/**
 * determine the value of a base64 encoding character
 *
 * @param base64char the character of which the value is searched
 * @return the value in case of success (0-63), -1 on failure
 */  
int _base64_char_value(char base64char)
{
	if (base64char >= 'A' && base64char <= 'Z')
		return base64char-'A';
	
	if (base64char >= 'a' && base64char <= 'z')
		return base64char-'a'+26;
	
	if (base64char >= '0' && base64char <= '9')
		return base64char-'0'+2*26;
	
	if (base64char == '+')
		return 2*26+10;
	
	if (base64char == '/')
		return 2*26+11;
	
	return -1;
} 

/**
 * decode a 4 char base64 encoded byte triple
 *
 * @param quadruple the 4 characters that should be decoded
 * @param result the decoded data
 * @return lenth of the result (1, 2 or 3), 0 on failure
 */  
int _base64_decode_triple(char quadruple[4], unsigned char *result)
{
	int i, triple_value, bytes_to_decode = 3, only_equals_yet = 1;
	int char_value[4];
	
	for (i=0; i<4; i++)
		char_value[i] = _base64_char_value(quadruple[i]);
	
	/* check if the characters are valid */
	for (i=3; i>=0; i--)
	{
		if (char_value[i]<0)
		{
			if (only_equals_yet && quadruple[i]=='=')
			{
				/* we will ignore this character anyway, make it something
				 * that does not break our calculations */
				 
				char_value[i]=0;
				bytes_to_decode--;
				continue;
			}
			return 0;
		}
		
		/* after we got a real character, no other '=' are allowed anymore */
		only_equals_yet = 0;
	}
	
	/* if we got "====" as input, bytes_to_decode is -1 */
	if (bytes_to_decode < 0)
		bytes_to_decode = 0;
	
	/* make one big value out of the partial values */
	triple_value = char_value[0];
	triple_value *= 64;
	triple_value += char_value[1];
	triple_value *= 64;
	triple_value += char_value[2];
	triple_value *= 64;
	triple_value += char_value[3];
	
	/* break the big value into bytes */
	for (i=bytes_to_decode; i<3; i++)
		triple_value /= 256;
	
	for (i=bytes_to_decode-1; i>=0; i--)
	{
		result[i] = triple_value%256;
		triple_value /= 256;
	}
	
	return bytes_to_decode;
} 

/**
 * decode base64 encoded data
 *
 * @param source the encoded data (zero terminated)
 * @param target pointer to the target buffer
 * @param targetlen length of the target buffer
 * @return length of converted data on success, -1 otherwise
 */  
int base64_decode(char *source, unsigned char *target, int targetlen)
{
	char *src, *tmpptr;
	char quadruple[4], tmpresult[3];
	int i, tmplen = 3;
	int converted = 0;
	
	/* concatenate '===' to the source to handle unpadded base64 data */
	src = (char *)malloc(strlen(source)+5);
	if (src == NULL)
		return -1;
	
	strcpy(src, source);
	strcat(src, "====");
	tmpptr = src;
	
	/* convert as long as we get a full result */
	while (tmplen == 3)
	{
		/* get 4 characters to convert */
		for (i=0; i<4; i++)
		{
			/* skip invalid characters - we won't reach the end */
			while (*tmpptr != '=' && _base64_char_value(*tmpptr)<0)
				tmpptr++;
			
			quadruple[i] = *(tmpptr++);
		}
		
		/* convert the characters */
		tmplen = _base64_decode_triple(quadruple, (unsigned char*)tmpresult);
		
		/* check if the fit in the result buffer */
		if (targetlen < tmplen)
		{
			free(src);
			return -1;
		}
		
		/* put the partial result in the result buffer */
		memcpy(target, tmpresult, tmplen);
		target += tmplen;
		targetlen -= tmplen;
		converted += tmplen;
	}
	
	free(src);
	return converted;
}