SDL  2.0
SDL_test_crc32.c
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1 /*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2018 Sam Lantinga <slouken@libsdl.org>
4 
5  This software is provided 'as-is', without any express or implied
6  warranty. In no event will the authors be held liable for any damages
7  arising from the use of this software.
8 
9  Permission is granted to anyone to use this software for any purpose,
10  including commercial applications, and to alter it and redistribute it
11  freely, subject to the following restrictions:
12 
13  1. The origin of this software must not be misrepresented; you must not
14  claim that you wrote the original software. If you use this software
15  in a product, an acknowledgment in the product documentation would be
16  appreciated but is not required.
17  2. Altered source versions must be plainly marked as such, and must not be
18  misrepresented as being the original software.
19  3. This notice may not be removed or altered from any source distribution.
20 */
21 
22 /*
23 
24  Used by the test execution component.
25  Original source code contributed by A. Schiffler for GSOC project.
26 
27 */
28 
29 #include "SDL_config.h"
30 
31 #include "SDL_test.h"
32 
33 
34 int SDLTest_Crc32Init(SDLTest_Crc32Context *crcContext)
35 {
36  int i,j;
37  CrcUint32 c;
38 
39  /* Sanity check context pointer */
40  if (crcContext==NULL) {
41  return -1;
42  }
43 
44  /*
45  * Build auxiliary table for parallel byte-at-a-time CRC-32
46  */
47 #ifdef ORIGINAL_METHOD
48  for (i = 0; i < 256; ++i) {
49  for (c = i << 24, j = 8; j > 0; --j) {
50  c = c & 0x80000000 ? (c << 1) ^ CRC32_POLY : (c << 1);
51  }
52  crcContext->crc32_table[i] = c;
53  }
54 #else
55  for (i=0; i<256; i++) {
56  c = i;
57  for (j=8; j>0; j--) {
58  if (c & 1) {
59  c = (c >> 1) ^ CRC32_POLY;
60  } else {
61  c >>= 1;
62  }
63  }
64  crcContext->crc32_table[i] = c;
65  }
66 #endif
67 
68  return 0;
69 }
70 
71 /* Complete CRC32 calculation on a memory block */
72 int SDLTest_Crc32Calc(SDLTest_Crc32Context * crcContext, CrcUint8 *inBuf, CrcUint32 inLen, CrcUint32 *crc32)
73 {
74  if (SDLTest_Crc32CalcStart(crcContext,crc32)) {
75  return -1;
76  }
77 
78  if (SDLTest_Crc32CalcBuffer(crcContext, inBuf, inLen, crc32)) {
79  return -1;
80  }
81 
82  if (SDLTest_Crc32CalcEnd(crcContext, crc32)) {
83  return -1;
84  }
85 
86  return 0;
87 }
88 
89 /* Start crc calculation */
90 
91 int SDLTest_Crc32CalcStart(SDLTest_Crc32Context * crcContext, CrcUint32 *crc32)
92 {
93  /* Sanity check pointers */
94  if (crcContext==NULL) {
95  *crc32=0;
96  return -1;
97  }
98 
99  /*
100  * Preload shift register, per CRC-32 spec
101  */
102  *crc32 = 0xffffffff;
103 
104  return 0;
105 }
106 
107 /* Finish crc calculation */
108 
109 int SDLTest_Crc32CalcEnd(SDLTest_Crc32Context * crcContext, CrcUint32 *crc32)
110 {
111  /* Sanity check pointers */
112  if (crcContext==NULL) {
113  *crc32=0;
114  return -1;
115  }
116 
117  /*
118  * Return complement, per CRC-32 spec
119  */
120  *crc32 = (~(*crc32));
121 
122  return 0;
123 }
124 
125 /* Include memory block in crc */
126 
127 int SDLTest_Crc32CalcBuffer(SDLTest_Crc32Context * crcContext, CrcUint8 *inBuf, CrcUint32 inLen, CrcUint32 *crc32)
128 {
129  CrcUint8 *p;
130  register CrcUint32 crc;
131 
132  if (crcContext==NULL) {
133  *crc32=0;
134  return -1;
135  }
136 
137  if (inBuf==NULL) {
138  return -1;
139  }
140 
141  /*
142  * Calculate CRC from data
143  */
144  crc = *crc32;
145  for (p = inBuf; inLen > 0; ++p, --inLen) {
146 #ifdef ORIGINAL_METHOD
147  crc = (crc << 8) ^ crcContext->crc32_table[(crc >> 24) ^ *p];
148 #else
149  crc = ((crc >> 8) & 0x00FFFFFF) ^ crcContext->crc32_table[ (crc ^ *p) & 0xFF ];
150 #endif
151  }
152  *crc32 = crc;
153 
154  return 0;
155 }
156 
157 int SDLTest_Crc32Done(SDLTest_Crc32Context * crcContext)
158 {
159  if (crcContext==NULL) {
160  return -1;
161  }
162 
163  return 0;
164 }
165 
166 /* vi: set ts=4 sw=4 expandtab: */