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114 lines
2.9 KiB
114 lines
2.9 KiB
/*** crc32.h - 32-bit CRC generator
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*
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* Microsoft Confidential
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* Copyright (C) Microsoft Corporation 1993-1994
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* All Rights Reserved.
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*
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* Author:
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* Mike Sliger
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*
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* History:
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* 10-Aug-1993 bens Copied from IMG2DMF directory.
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*
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* Usage:
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* ULONG crc;
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* //** Compute first block
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* crc = CRC32Compute(pb,cb,CRC32_INITIAL_VALUE);
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* //** Compute remaining blocks
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* crc = CRC32Compute(pb,cb,crc);
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* ...
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* //** When you're done, crc has the CRC.
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*
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* NOTE: See example function getFileChecksum() below that
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* computes the checksum of a file!
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*/
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// ** Must use this as initial value for CRC
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#define CRC32_INITIAL_VALUE 0L
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/*** CRC32Compute - Compute 32-bit
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*
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* Entry:
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* pb - Pointer to buffer to computer CRC on
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* cb - Count of bytes in buffer to CRC
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* crc32 - Result from previous CRC32Compute call (on first call
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* to CRC32Compute, must be CRC32_INITIAL_VALUE!!!!).
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*
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* Exit:
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* Returns updated CRC value.
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*/
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DWORD CRC32Compute(BYTE *pb,unsigned cb,ULONG crc32);
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//** Include nice sample -- don't compile it
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//
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#ifdef HERE_IS_A_SAMPLE
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/*** getFileChecksum - Compute file checksum
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*
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* Entry:
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* pszFile - Filespec
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* pchecksum - Receives 32-bit checksum of file
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* perr - ERROR structure
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*
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* Exit-Success:
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* Returns TRUE, *pchecksum filled in.
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*
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* Exit-Failure:
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* Returns FALSE; perr filled in with error.
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*/
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BOOL getFileChecksum(char *pszFile, ULONG *pchecksum, PERROR perr)
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{
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#define cbCSUM_BUFFER 4096 // File buffer size
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int cb; // Amount of data in read buffer
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ULONG csum=CRC32_INITIAL_VALUE; // Initialize CRC
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char *pb=NULL; // Read buffer
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int hf=-1; // File handle
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int rc;
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BOOL result=FALSE; // Assume failure
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//** Initialize returned checksum (assume failure)
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*pchecksum = csum;
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//** Allocate file buffer
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if (!(pb = MemAlloc(cbCSUM_BUFFER))) {
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ErrSet(perr,pszDIAERR_NO_MEMORY_CRC,"%s",pszFile);
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return FALSE;
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}
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//** Open file
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hf = _open(pszFile,_O_RDONLY | _O_BINARY,&rc);
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if (hf == -1) {
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ErrSet(perr,pszDIAERR_OPEN_FAILED,"%s",pszFile);
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goto Exit;
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}
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//** Compute checksum
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while (_eof(hf) == 0) {
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cb = _read(hf,pb,cbCSUM_BUFFER);
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if (cb == -1) {
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ErrSet(perr,pszDIAERR_READ_FAIL_CRC,"%s",pszFile);
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goto Exit;
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}
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if (cb != 0) {
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csum = CRC32Compute(pb,cb,csum); // Accumulate CRC
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}
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}
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//** Success
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result = TRUE;
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*pchecksum = csum; // Store checksum for caller
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Exit:
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if (hf != -1) {
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_close(hf);
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}
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if (pb != NULL) {
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MemFree(pb);
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}
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return result;
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} /* getFileChecksum() */
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#endif // HERE_IS_A_SAMPLE
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