doubt in c programming

[deepa.selvaraj]

hi
in the below file in dont know what to pass in const void *data in main.c.can u help
void CrcUpdate(UInt32 *crc, const void *data, size_t size)

/* 7zCrc.c */
 
#include "7zCrc.h"
 
#define kCrcPoly 0xEDB88320
 
UInt32 g_CrcTable[256];
 
void InitCrcTable()
{
  UInt32 i;
  for (i = 0; i < 256; i++)
  {
    UInt32 r = i;
    int j;
    for (j = 0; j < 8; j++)
      if (r & 1) 
        r = (r >> 1) ^ kCrcPoly;
      else     
        r >>= 1;
    g_CrcTable[i] = r;
  }
}
 
void CrcInit(UInt32 *crc) { *crc = 0xFFFFFFFF; }
UInt32 CrcGetDigest(UInt32 *crc) { return *crc ^ 0xFFFFFFFF; } 
 
void CrcUpdateByte(UInt32 *crc, Byte b)
{
  *crc = g_CrcTable[((Byte)(*crc)) ^ b] ^ (*crc >> 8);
}
 
void CrcUpdateUInt16(UInt32 *crc, UInt16 v)
{
  CrcUpdateByte(crc, (Byte)v);
  CrcUpdateByte(crc, (Byte)(v >> 8));
}
 
void CrcUpdateUInt32(UInt32 *crc, UInt32 v)
{
  int i;
  for (i = 0; i < 4; i++)
    CrcUpdateByte(crc, (Byte)(v >> (8 * i)));
}
 
void CrcUpdateUInt64(UInt32 *crc, UInt64 v)
{
  int i;
  for (i = 0; i < 8; i++)
  {
    CrcUpdateByte(crc, (Byte)(v));
    v >>= 8;
  }
}
 
void CrcUpdate(UInt32 *crc, const void *data, size_t size)
{
  UInt32 v = *crc;
  const Byte *p = (const Byte *)data;
  for (; size > 0 ; size--, p++)
    v = g_CrcTable[((Byte)(v)) ^ *p] ^ (v >> 8);
  *crc = v;
}
 
UInt32 CrcCalculateDigest(const void *data, size_t size)
{
  UInt32 crc;
  CrcInit(&crc);
  CrcUpdate(&crc, data, size);
  return CrcGetDigest(&crc);
}
 
int CrcVerifyDigest(UInt32 digest, const void *data, size_t size)
{
  return (CrcCalculateDigest(data, size) == digest);
}

/* 7zCrc.c */

#include "7zCrc.h"

#define kCrcPoly 0xEDB88320

UInt32 g_CrcTable[256];

void InitCrcTable()
{
  UInt32 i;
  for (i = 0; i < 256; i++)
  {
    UInt32 r = i;
    int j;
    for (j = 0; j < 8; j++)
      if (r & 1) 
        r = (r >> 1) ^ kCrcPoly;
      else     
        r >>= 1;
    g_CrcTable[i] = r;
  }
}

void CrcInit(UInt32 *crc) { *crc = 0xFFFFFFFF; }
UInt32 CrcGetDigest(UInt32 *crc) { return *crc ^ 0xFFFFFFFF; } 

void CrcUpdateByte(UInt32 *crc, Byte b)
{
  *crc = g_CrcTable[((Byte)(*crc)) ^ b] ^ (*crc >> 8);
}

void CrcUpdateUInt16(UInt32 *crc, UInt16 v)
{
  CrcUpdateByte(crc, (Byte)v);
  CrcUpdateByte(crc, (Byte)(v >> 8));
}

void CrcUpdateUInt32(UInt32 *crc, UInt32 v)
{
  int i;
  for (i = 0; i < 4; i++)
    CrcUpdateByte(crc, (Byte)(v >> (8 * i)));
}

void CrcUpdateUInt64(UInt32 *crc, UInt64 v)
{
  int i;
  for (i = 0; i < 8; i++)
  {
    CrcUpdateByte(crc, (Byte)(v));
    v >>= 8;
  }
}

void CrcUpdate(UInt32 *crc, const void *data, size_t size)
{
  UInt32 v = *crc;
  const Byte *p = (const Byte *)data;
  for (; size > 0 ; size--, p++)
    v = g_CrcTable[((Byte)(v)) ^ *p] ^ (v >> 8);
  *crc = v;
}

UInt32 CrcCalculateDigest(const void *data, size_t size)
{
  UInt32 crc;
  CrcInit(&crc);
  CrcUpdate(&crc, data, size);
  return CrcGetDigest(&crc);
}

int CrcVerifyDigest(UInt32 digest, const void *data, size_t size)
{
  return (CrcCalculateDigest(data, size) == digest);
}

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[wysota]

But what is the problem? Are you aware what the above functions do? If so, you should have no problem in determining what to pass as an argument to each function. The "data" pointer should probably a pointer to a buffer containing the data to update the checksum with.