Atlas - SDL_test_crc32.c
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1/*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2018 Sam Lantinga <[email protected]>
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
34int 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 */
72int 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
91int 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
109int 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
127int 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
157int 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: */
167
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