1 
2 /*
3  * Copyright 2006 The Android Open Source Project
4  *
5  * Use of this source code is governed by a BSD-style license that can be
6  * found in the LICENSE file.
7  */
8 
9 
10 #include "SkBase64.h"
11 
12 #define DecodePad -2
13 #define EncodePad 64
14 
15 static const char default_encode[] =
16     "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
17     "abcdefghijklmnopqrstuvwxyz"
18     "0123456789+/=";
19 
20 static const signed char decodeData[] = {
21     62, -1, -1, -1, 63,
22     52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, DecodePad, -1, -1,
23     -1,  0,  1,  2,  3,  4,  5,  6, 7,  8,  9, 10, 11, 12, 13, 14,
24     15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
25     -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
26     41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
27 };
28 
SkBase64()29 SkBase64::SkBase64() : fLength((size_t) -1), fData(NULL) {
30 }
31 
32 #if defined _WIN32 && _MSC_VER >= 1300  // disable 'two', etc. may be used without having been initialized
33 #pragma warning ( push )
34 #pragma warning ( disable : 4701 )
35 #endif
36 
decode(const void * srcPtr,size_t size,bool writeDestination)37 SkBase64::Error SkBase64::decode(const void* srcPtr, size_t size, bool writeDestination) {
38     unsigned char* dst = (unsigned char*) fData;
39     const unsigned char* dstStart = (const unsigned char*) fData;
40     const unsigned char* src = (const unsigned char*) srcPtr;
41     bool padTwo = false;
42     bool padThree = false;
43     const unsigned char* end = src + size;
44     while (src < end) {
45         unsigned char bytes[4];
46         int byte = 0;
47         do {
48             unsigned char srcByte = *src++;
49             if (srcByte == 0)
50                 goto goHome;
51             if (srcByte <= ' ')
52                 continue; // treat as white space
53             if (srcByte < '+' || srcByte > 'z')
54                 return kBadCharError;
55             signed char decoded = decodeData[srcByte - '+'];
56             bytes[byte] = decoded;
57             if (decoded < 0) {
58                 if (decoded == DecodePad)
59                     goto handlePad;
60                 return kBadCharError;
61             } else
62                 byte++;
63             if (*src)
64                 continue;
65             if (byte == 0)
66                 goto goHome;
67             if (byte == 4)
68                 break;
69 handlePad:
70             if (byte < 2)
71                 return kPadError;
72             padThree = true;
73             if (byte == 2)
74                 padTwo = true;
75             break;
76         } while (byte < 4);
77         int two = 0;
78         int three = 0;
79         if (writeDestination) {
80             int one = (uint8_t) (bytes[0] << 2);
81             two = bytes[1];
82             one |= two >> 4;
83             two = (uint8_t) (two << 4);
84             three = bytes[2];
85             two |= three >> 2;
86             three = (uint8_t) (three << 6);
87             three |= bytes[3];
88             SkASSERT(one < 256 && two < 256 && three < 256);
89             *dst = (unsigned char) one;
90         }
91         dst++;
92         if (padTwo)
93             break;
94         if (writeDestination)
95             *dst = (unsigned char) two;
96         dst++;
97         if (padThree)
98             break;
99         if (writeDestination)
100             *dst = (unsigned char) three;
101         dst++;
102     }
103 goHome:
104     fLength = dst - dstStart;
105     return kNoError;
106 }
107 
108 #if defined _WIN32 && _MSC_VER >= 1300
109 #pragma warning ( pop )
110 #endif
111 
Encode(const void * srcPtr,size_t length,void * dstPtr,const char * encodeMap)112 size_t SkBase64::Encode(const void* srcPtr, size_t length, void* dstPtr, const char* encodeMap) {
113     const char* encode;
114     if (NULL == encodeMap) {
115         encode = default_encode;
116     } else {
117         encode = encodeMap;
118     }
119     const unsigned char* src = (const unsigned char*) srcPtr;
120     unsigned char* dst = (unsigned char*) dstPtr;
121     if (dst) {
122         size_t remainder = length % 3;
123         const unsigned char* end = &src[length - remainder];
124         while (src < end) {
125             unsigned a = *src++;
126             unsigned b = *src++;
127             unsigned c = *src++;
128             int      d = c & 0x3F;
129             c = (c >> 6 | b << 2) & 0x3F;
130             b = (b >> 4 | a << 4) & 0x3F;
131             a = a >> 2;
132             *dst++ = encode[a];
133             *dst++ = encode[b];
134             *dst++ = encode[c];
135             *dst++ = encode[d];
136         }
137         if (remainder > 0) {
138             int k1 = 0;
139             int k2 = EncodePad;
140             int a = (uint8_t) *src++;
141             if (remainder == 2)
142             {
143                 int b = *src++;
144                 k1 = b >> 4;
145                 k2 = (b << 2) & 0x3F;
146             }
147             *dst++ = encode[a >> 2];
148             *dst++ = encode[(k1 | a << 4) & 0x3F];
149             *dst++ = encode[k2];
150             *dst++ = encode[EncodePad];
151         }
152     }
153     return (length + 2) / 3 * 4;
154 }
155 
decode(const char * src,size_t len)156 SkBase64::Error SkBase64::decode(const char* src, size_t len) {
157     Error err = decode(src, len, false);
158     SkASSERT(err == kNoError);
159     if (err != kNoError)
160         return err;
161     fData = new char[fLength];  // should use sk_malloc/sk_free
162     decode(src, len, true);
163     return kNoError;
164 }
165