Obliczenie CRC32

Definicja nagłówka crc32.h:

#ifndef Crc32H
#define Crc32H
#endif
#include
class CCrc32
{
public:
CCrc32();
virtual ~CCrc32();

void Init(void);
void Free(void);

unsigned long int FileCrc32(AnsiString FileName);
AnsiString FileCrc32Hex(AnsiString FileName);
private:
unsigned long int *crc32_tab;
};


Implementacja: crc32.cpp

#pragma hdrstop
#include "Crc32.h"
#include
#include
#define BUFSIZE 8192

#pragma package(smart_init)
CCrc32::CCrc32()
{
}

CCrc32::~CCrc32()
{
Free();
}

void CCrc32::Free(void)
{
delete[] crc32_tab;
}

void CCrc32::Init(void)
{
// Often times the polynomial shown reversed as 0x04C11DB7.
unsigned long int dwPolynomial = 0xEDB88320;

int i = 0, j = 0;

crc32_tab = new unsigned long int[256];
unsigned long int dwCrc;

for(i = 0; i < 256; i++) { dwCrc = i; for(j = 8; j > 0; j--)
{
if(dwCrc & 1)
dwCrc = (dwCrc >> 1) ^ dwPolynomial;
else
dwCrc >>= 1;
}
crc32_tab[i] = dwCrc;
}

}

unsigned long int CCrc32::FileCrc32(AnsiString FileName)
{
FILE *file = NULL;
unsigned char buf[BUFSIZE];
unsigned long int crc32 = 0;
size_t i = 0, n = 0;

if(!(file = fopen(FileName.c_str(), "rb")))
{
return -1;
}

fseek(file, 0, SEEK_SET);

crc32 = 0xffffffff;

while((n = fread(buf, 1, BUFSIZE, file)) > 0)
{
for(i = 0; i < n; i++) crc32 = (crc32 >> 8) ^ crc32_tab[(crc32 & 0xff) ^ buf[i]];
}

crc32 ^= 0xffffffff;

fclose(file);


return crc32;
}

AnsiString CCrc32::FileCrc32Hex(AnsiString FileName)
{
unsigned long int wynik;
AnsiString szHex;
wynik = FileCrc32(FileName);

TVarRec vr[] = { wynik };
szHex = Format("%X",vr,1);
if (szHex.Length()<8) { for (int i = szHex.Length(); i < 8; i++) szHex ="0" +szHex; } szHex ="0x"+szHex; return szHex; }