Project Update



So far the project is not progressing smoothly however this was anticipated, the root of the issue seems to be, that I am having trouble identifying exactly how the build system is being used and exactly where the assembler code I am interested in is specifically being called so I can reproduce a test case, I have transferred the files over to one of the Linux systems  where it was easier to track down locations I should be paying attention to. I used the first half of the export symbol to grep search all of the files in the project and found several matches. and I think I have party identified how the setup works, I have missed several of the labs that I should have completed by now so its possible that this would be very clear to me by now if I had done so.

So as things stand my current plan of action is to revisit the labs to look for information I may have missed out on, and to prepare for the event that I might not find what I need, I will also in parallel seek out a new project as a fallback option. One that I might be able to use more of my pre existing skills to solve. I will also continue to investigate further by downloading the 7zip source to see how the LZMA SDK was used to help me understand it.




Additional information

The following is some of  code from 7zcrc.c I believe its related to the ambler files and that the assembler file is used at midpoint in the execution of this code but I am unsure exactly how, and I do not yet know enough to build test data to run it, how to pass the data or even how to call the correct function to cause the assembler to run, or even how to incorporate the new assembler file once I write it.



#include "Precomp.h"

#include "7zCrc.h"
#include "CpuArch.h"

#define kCrcPoly 0xEDB88320

#ifdef MY_CPU_LE
  #define CRC_NUM_TABLES 8
#else
  #define CRC_NUM_TABLES 9

  #define CRC_UINT32_SWAP(v) ((v >> 24) | ((v >> 8) & 0xFF00) | ((v << 8) & 0xFF0000) | (v << 24))

  UInt32 MY_FAST_CALL CrcUpdateT1_BeT4(UInt32 v, const void *data, size_t size, const UInt32 *table);
  UInt32 MY_FAST_CALL CrcUpdateT1_BeT8(UInt32 v, const void *data, size_t size, const UInt32 *table);
#endif

#ifndef MY_CPU_BE
  UInt32 MY_FAST_CALL CrcUpdateT4(UInt32 v, const void *data, size_t size, const UInt32 *table);
  UInt32 MY_FAST_CALL CrcUpdateT8(UInt32 v, const void *data, size_t size, const UInt32 *table);
#endif

typedef UInt32 (MY_FAST_CALL *CRC_FUNC)(UInt32 v, const void *data, size_t size, const UInt32 *table);

CRC_FUNC g_CrcUpdateT4;
CRC_FUNC g_CrcUpdateT8;
CRC_FUNC g_CrcUpdate;

UInt32 g_CrcTable[256 * CRC_NUM_TABLES];

UInt32 MY_FAST_CALL CrcUpdate(UInt32 v, const void *data, size_t size)
{
  return g_CrcUpdate(v, data, size, g_CrcTable);
}

UInt32 MY_FAST_CALL CrcCalc(const void *data, size_t size)
{
  return g_CrcUpdate(CRC_INIT_VAL, data, size, g_CrcTable) ^ CRC_INIT_VAL;
}

#define CRC_UPDATE_BYTE_2(crc, b) (table[((crc) ^ (b)) & 0xFF] ^ ((crc) >> 8))

UInt32 MY_FAST_CALL CrcUpdateT1(UInt32 v, const void *data, size_t size, const UInt32 *table)
{
  const Byte *p = (const Byte *)data;
  const Byte *pEnd = p + size;
  for (; p != pEnd; p++)
    v = CRC_UPDATE_BYTE_2(v, *p);
  return v;
}

void MY_FAST_CALL CrcGenerateTable()
{
  UInt32 i;
  for (i = 0; i < 256; i++)
  {
    UInt32 r = i;
    unsigned j;
    for (j = 0; j < 8; j++)
      r = (r >> 1) ^ (kCrcPoly & ((UInt32)0 - (r & 1)));
    g_CrcTable[i] = r;
  }
  for (i = 256; i < 256 * CRC_NUM_TABLES; i++)
  {
    UInt32 r = g_CrcTable[(size_t)i - 256];
    g_CrcTable[i] = g_CrcTable[r & 0xFF] ^ (r >> 8);
  }

  #if CRC_NUM_TABLES < 4
 
  g_CrcUpdate = CrcUpdateT1;
 
  #else

  #ifdef MY_CPU_LE

    g_CrcUpdateT4 = CrcUpdateT4;
    g_CrcUpdate = CrcUpdateT4;

    #if CRC_NUM_TABLES >= 8
      g_CrcUpdateT8 = CrcUpdateT8;
 
      #ifdef MY_CPU_X86_OR_AMD64
      if (!CPU_Is_InOrder())
      #endif
        g_CrcUpdate = CrcUpdateT8;
    #endif

  #else
  {
    #ifndef MY_CPU_BE
    UInt32 k = 0x01020304;
    const Byte *p = (const Byte *)&k;
    if (p[0] == 4 && p[1] == 3)
    {
      g_CrcUpdateT4 = CrcUpdateT4;
      g_CrcUpdate = CrcUpdateT4;
      #if CRC_NUM_TABLES >= 8
      g_CrcUpdateT8 = CrcUpdateT8;
      g_CrcUpdate = CrcUpdateT8;
      #endif
    }
    else if (p[0] != 1 || p[1] != 2)
      g_CrcUpdate = CrcUpdateT1;
    else
    #endif
    {
      for (i = 256 * CRC_NUM_TABLES - 1; i >= 256; i--)
      {
        UInt32 x = g_CrcTable[(size_t)i - 256];
        g_CrcTable[i] = CRC_UINT32_SWAP(x);
      }
      g_CrcUpdateT4 = CrcUpdateT1_BeT4;
      g_CrcUpdate = CrcUpdateT1_BeT4;
      #if CRC_NUM_TABLES >= 8
      g_CrcUpdateT8 = CrcUpdateT1_BeT8;
      g_CrcUpdate = CrcUpdateT1_BeT8;
      #endif
    }
  }
  #endif

  #endif
}










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