src/test/SDL_test_crc32.c
author Sam Lantinga <slouken@libsdl.org>
Wed, 04 Jun 2014 10:56:56 -0700
changeset 8820 0e935d5b193a
parent 8149 681eb46b8ac4
child 9619 b94b6d0bff0f
permissions -rw-r--r--
Added annotations to help code analysis tools

CR: Bruce Dawson
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2014 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 
    73 int SDLTest_Crc32Calc(SDLTest_Crc32Context * crcContext, CrcUint8 *inBuf, CrcUint32 inLen, CrcUint32 *crc32)
    74 {
    75   if (SDLTest_Crc32CalcStart(crcContext,crc32)) {
    76    return -1;
    77   }
    78 
    79   if (SDLTest_Crc32CalcBuffer(crcContext, inBuf, inLen, crc32)) {
    80    return -1;
    81   }
    82 
    83   if (SDLTest_Crc32CalcEnd(crcContext, crc32)) {
    84    return -1;
    85   }
    86 
    87   return 0;
    88 }
    89 
    90 /* Start crc calculation */
    91 
    92 int SDLTest_Crc32CalcStart(SDLTest_Crc32Context * crcContext, CrcUint32 *crc32)
    93 {
    94   /* Sanity check pointers */
    95   if (crcContext==NULL) {
    96    *crc32=0;
    97    return -1;
    98   }
    99 
   100   /*
   101    * Preload shift register, per CRC-32 spec
   102    */
   103   *crc32 = 0xffffffff;
   104 
   105   return 0;
   106 }
   107 
   108 /* Finish crc calculation */
   109 
   110 int SDLTest_Crc32CalcEnd(SDLTest_Crc32Context * crcContext, CrcUint32 *crc32)
   111 {
   112   /* Sanity check pointers */
   113   if (crcContext==NULL) {
   114    *crc32=0;
   115    return -1;
   116   }
   117 
   118   /*
   119    * Return complement, per CRC-32 spec
   120    */
   121   *crc32 = (~(*crc32));
   122 
   123   return 0;
   124 }
   125 
   126 /* Include memory block in crc */
   127 
   128 int SDLTest_Crc32CalcBuffer(SDLTest_Crc32Context * crcContext, CrcUint8 *inBuf, CrcUint32 inLen, CrcUint32 *crc32)
   129 {
   130   CrcUint8    *p;
   131   register CrcUint32    crc;
   132 
   133   if (crcContext==NULL) {
   134    *crc32=0;
   135    return -1;
   136   }
   137 
   138   if (inBuf==NULL) {
   139    return -1;
   140   }
   141 
   142   /*
   143    * Calculate CRC from data
   144    */
   145   crc = *crc32;
   146   for (p = inBuf; inLen > 0; ++p, --inLen) {
   147 #ifdef ORIGINAL_METHOD
   148     crc = (crc << 8) ^ crcContext->crc32_table[(crc >> 24) ^ *p];
   149 #else
   150     crc = ((crc >> 8) & 0x00FFFFFF) ^ crcContext->crc32_table[ (crc ^ *p) & 0xFF ];
   151 #endif
   152   }
   153   *crc32 = crc;
   154 
   155   return 0;
   156 }
   157 
   158 int SDLTest_Crc32Done(SDLTest_Crc32Context * crcContext)
   159 {
   160   if (crcContext==NULL) {
   161      return -1;
   162   }
   163 
   164   return 0;
   165 }