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SDL_test_crc32.c (3523B)

      1 /*
      2   Simple DirectMedia Layer
      3   Copyright (C) 1997-2020 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: */