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.H| Код |
/***************************************************************************/
/* FUNCTION: CRC_File */
/* PURPOSE: Returns CRC32 for file FName */
/* PARAMETERS: FName - File Name */
/* Crc - CRC32 reference */
/* RETURN VALUE: 0 - error CRC32 detection */
/* 1 - CRC32 detected OK */
/***************************************************************************/
int CRC_File(unsigned char *FName,unsigned long &Crc); // Get CRC32 for file
/***************************************************************************/
/* FUNCTION: CRC_FileHandler */
/* PURPOSE: Returns CRC32 for file FName */
/* PARAMETERS: F - File Handler */
/* Crc - CRC32 reference */
/* Start - Start position in file */
/* Len - Data length (0L - all file) */
/* RETURN VALUE: 0 - error CRC32 detection */
/* 1 - CRC32 detected OK */
/***************************************************************************/
int CRC_FileHandler(int F,unsigned long &Crc,long Start,// Get CRC32 FileHand
long Len);
void Gen_crc_table(void); // Generate CRC32 Tbl
unsigned long Update_crc(DWORD ulCrc_accum, // Previous CRC32
BYTE *pchData_blk_ptr, // Block address
DWORD lData_blk_size); // Size of Block
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.CPP
| Код |
/***************************************************************************/
/* PROGRAM: CRC32.cpp */
/* FUNCTIONS: Crc_table, Update_crc, CRC_File */
/* COMMENTS: Unit for calculating of CRC remainder. */
/***************************************************************************/
#include <stdio.h> // Include file
#include <io.h> // section
#define POLYNOMIAL 0x04C11DB7 // Polinom const
static DWORD aulCrc_table[256]; // CRC32 Table
/***************************************************************************/
/* FUNCTION: Gen_crc_table */
/* PURPOSE: Generates a 256 word table containing CRC remainders for */
/* every possible 8-bit byte */
/***************************************************************************/
void Gen_crc_table(void) // Generate CRC32 Tbl
{
register DWORD iI,iJ; // Cycle variables
register DWORD ulCrc_accum; // CRC32 accumulator
for(iI=0;iI < 256;iI++) // For all bytes
{
ulCrc_accum=iI << 24; // Init accumulator
for(iJ=0;iJ < 8;iJ++) // For each bit
{
if (ulCrc_accum & 0x80000000L) // If high bit set
ulCrc_accum=(ulCrc_accum << 1) ^ POLYNOMIAL; // Shift and XOR Poly
else // Else
ulCrc_accum=(ulCrc_accum << 1); // Shift only
}
aulCrc_table[iI]=ulCrc_accum; // Setup table value
}
} // End of initialize
/***************************************************************************/
/* FUNCTION: Update_crc */
/* PURPOSE: Returns the updated value of the CRC after processing each */
/* byte in the adressed block of data */
/* PARAMETERS: ulCrc_accum - present CRC value */
/* pchData_blk_ptr - data for updating CRC */
/* iData_blk_size - data size */
/***************************************************************************/
unsigned long Update_crc(DWORD ulCrc_accum, // Previous CRC32
BYTE *pchData_blk_ptr, // Block address
DWORD lData_blk_size) // Size of Block
{
__asm {
mov esi,pchData_blk_ptr
lea edi,aulCrc_table
mov ecx,lData_blk_size
mov eax,ulCrc_accum
ucrc_loop:
mov dl,[esi]
mov ebx,eax
inc esi
shr ebx,24
shl eax,8
xor edx,ebx
and edx,0xFF
xor eax,[edi+4*edx]
loop ucrc_loop
mov ulCrc_accum,eax;
};
return ulCrc_accum; // Return value
}
//#ifndef WIN32
/***************************************************************************/
/* FUNCTION: CRC_File */
/* PURPOSE: Returns CRC32 for file FName */
/* PARAMETERS: FName - File Name */
/* Crc - CRC32 reference */
/* RETURN VALUE: 0 - error CRC32 detection */
/* 1 - CRC32 detected OK */
/***************************************************************************/
int CRC_File(char *FName,unsigned long &Crc) // Get CRC32 for file
{
FILE *hStream; // File stream
char achBuff1[1000]; // Read buffer
unsigned long ulCrc=0L,ulFileLen; // CRC32 & File len
int iJ; // Return value
unsigned int Siz; // Size to read
unsigned long ulI=0; // Bytes counter
Gen_crc_table(); // Generate CRC Tbl
if((hStream=fopen(FName,"rb")) == NULL) return(0); // If not opened-err
fseek(hStream,0,SEEK_END); // Seek to end
ulFileLen=ftell(hStream); // Get file length
fseek(hStream,0,SEEK_SET); // Return to start
while(ulI < ulFileLen) // For all bytes
{
if((ulI+1000) <= ulFileLen) Siz=1000; // Calculate possible
else Siz=(unsigned int)(ulFileLen-ulI); // block size
if((iJ=fread(achBuff1,1,Siz,hStream)) != (int)Siz) // If read error
{
fclose(hStream); // Close file
return(0); // Return error
}
ulI += iJ; // Update byte cnt
ulCrc=Update_crc(ulCrc,(BYTE*)achBuff1,iJ); // Update CRC32
}
fclose(hStream); // Close file
Crc=ulCrc; // Setup result
return(1); // Return OK
}
/***************************************************************************/
/* FUNCTION: CRC_FileHandler */
/* PURPOSE: Returns CRC32 for file FName */
/* PARAMETERS: F - File Handler */
/* Crc - CRC32 reference */
/* Start - Start position in file */
/* Len - Data length (0L - all file) */
/* RETURN VALUE: 0 - error CRC32 detection */
/* 1 - CRC32 detected OK */
/***************************************************************************/
int CRC_FileHandler(int F,unsigned long &Crc,long Start,// Get CRC32 FileHand
long Len)
{
char achBuff1[1000]; // Read buffer
unsigned long ulCrc=0L,ulFileLen; // CRC32 & File Len
long ulFPos; // File position
int iJ; // Return value
unsigned int Siz; // Size to read
unsigned long ulI=0; // Bytes counter
if((ulFPos=tell(F)) == -1) return(0); // No get position
Gen_crc_table(); // Generate CRC Tbl
if(Len == 0L) ulFileLen=filelength(F)-Start; // Get file length
else ulFileLen=Len; // Or set it from par
if(lseek(F,Start,SEEK_SET) == -1L) return(0); // No seek to start
while(ulI < ulFileLen) // For all bytes
{
if((ulI+1000) <= ulFileLen) Siz=1000; // Calculate possible
else Siz=(unsigned int)(ulFileLen-ulI); // block size
if((iJ=_read(F,achBuff1,Siz)) != (int)Siz) // If read error
{
lseek(F,ulFPos,SEEK_SET); // Return file pos
return(0); // Return error
}
ulI += iJ; // Update byte cnt
ulCrc=Update_crc(ulCrc,(BYTE*)achBuff1,iJ); // Update CRC32
}
lseek(F,ulFPos,SEEK_SET); // Return file pos
Crc=ulCrc; // Setup result
return(1); // Return OK
}
//#endif
/***************************** End of Module ******************************/
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