280 lines
7.3 KiB
C++
280 lines
7.3 KiB
C++
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//
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// MODULE: CRC.CPP
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//
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// PURPOSE: Cache File CRC Calculator Class
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//
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// PROJECT: Generic Troubleshooter DLL for Microsoft AnswerPoint
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//
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// COMPANY: Saltmine Creative, Inc. (206)-284-7511 support@saltmine.com
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//
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// AUTHOR: Richard Meadows
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//
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// ORIGINAL DATE: 8/7/97
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//
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// NOTES:
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// 1.
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//
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// Version Date By Comments
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//--------------------------------------------------------------------
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// V0.2 8/7/97 RM Local Version for Memphis
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// V0.3 04/09/98 JM/OK+ Local Version for NT5
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//
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#include "stdafx.h"
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#include "crc.h"
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#include <stdlib.h>
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#include <memory.h>
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#include "ChmRead.h"
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CCRC::CCRC() : POLYNOMIAL(0x04C11DB7)
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{
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dwCrcTable[0] = 0;
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BuildCrcTable();
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return;
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}
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DWORD CCRC::DscEncode(LPCTSTR szDsc)
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{
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DWORD dwBytesRead;
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DWORD dwCRCValue;
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const int BUF_SIZE = 4096;
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char sznInputFileBuf[BUF_SIZE + 1];
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if (NULL == szDsc)
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{
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CGenException *pErr = new CGenException;
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pErr->m_OsError = 0;
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pErr->m_strError = _T("The dsc file was not specified.");
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throw pErr;
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}
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// Read the source file.
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HANDLE hFile = CreateFile(szDsc,
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GENERIC_READ,
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FILE_SHARE_READ,
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NULL,
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OPEN_EXISTING,
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FILE_FLAG_SEQUENTIAL_SCAN,
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NULL);
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if (INVALID_HANDLE_VALUE == hFile)
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{
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CString strErr;
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CGenException *pErr = new CGenException;
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pErr->m_OsError = GetLastError();
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strErr = GlobFormatMessage(pErr->m_OsError);
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pErr->m_strError.Format(_T("Dsc file, %s was not opened.\nReason: %s"),
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szDsc, (LPCTSTR) strErr);
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throw pErr;
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}
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// Get the crc.
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dwCRCValue = 0xFFFFFFFF;
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do
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{
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if (!ReadFile(hFile, (LPVOID) sznInputFileBuf, BUF_SIZE, &dwBytesRead, NULL))
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{
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CString strErr;
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CGenException *pErr = new CGenException;
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pErr->m_OsError = GetLastError();
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strErr = GlobFormatMessage(pErr->m_OsError);
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pErr->m_strError.Format(_T("The dsc file, %s could not be read.\nReason: %s"),
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szDsc, (LPCTSTR) strErr);
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CloseHandle(hFile);
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throw pErr;
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}
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sznInputFileBuf[dwBytesRead] = NULL;
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dwCRCValue = ComputeCRC(sznInputFileBuf, dwBytesRead, dwCRCValue);
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} while(BUF_SIZE == dwBytesRead);
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CloseHandle(hFile);
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return dwCRCValue;
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}
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void CCRC::AppendCRC(LPCTSTR szCache, DWORD dwCRCValue)
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{
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DWORD dwBytesWritten;
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// Open the cache file.
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HANDLE hDestFile = CreateFile(szCache,
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GENERIC_WRITE,
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0, // No Sharing.
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NULL,
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OPEN_EXISTING,
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FILE_FLAG_WRITE_THROUGH |
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FILE_FLAG_SEQUENTIAL_SCAN,
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NULL);
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if (INVALID_HANDLE_VALUE == hDestFile)
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{
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CString strErr;
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CGenException *pErr = new CGenException;
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pErr->m_OsError = GetLastError();
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strErr = GlobFormatMessage(pErr->m_OsError);
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pErr->m_strError.Format(_T("The cache file, %s could not be opened.\nReason: %s"),
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szCache, (LPCTSTR) strErr);
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throw pErr;
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}
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if (0xFFFFFFFF == SetFilePointer(hDestFile, 0, NULL, FILE_END))
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{
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CString strErr;
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CGenException *pErr = new CGenException;
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pErr->m_OsError = GetLastError();
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strErr = GlobFormatMessage(pErr->m_OsError);
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pErr->m_strError.Format(_T("Seek to end of the cache file, %s failed.\nReason: %s"),
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szCache, (LPCTSTR) strErr);
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CloseHandle(hDestFile);
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throw pErr;
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}
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// Append crc value.
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if (!WriteFile(hDestFile, (LPVOID) &dwCRCValue, 4, &dwBytesWritten, NULL))
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{
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CString strErr;
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CGenException *pErr = new CGenException;
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pErr->m_OsError = GetLastError();
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strErr = GlobFormatMessage(pErr->m_OsError);
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pErr->m_strError.Format(_T("The crc value was not appened to cache file %s.\nReason: %s"),
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szCache, (LPCTSTR) strErr);
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CloseHandle(hDestFile);
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throw pErr;
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}
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CloseHandle(hDestFile);
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if (4 != dwBytesWritten)
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{
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CString strErr;
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CGenException *pErr = new CGenException;
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pErr->m_OsError = GetLastError();
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strErr = GlobFormatMessage(pErr->m_OsError);
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pErr->m_strError.Format(_T("%d bytes of the crc were not appended to the cache file %s.Reason: %s"),
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4 - dwBytesWritten, szCache, (LPCTSTR) strErr);
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throw pErr;
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}
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return;
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}
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bool CCRC::Decode(LPCTSTR szDsc, LPCTSTR szCache, const CString& strCacheFileWithinCHM)
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{
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DWORD dwDecodeFileCrc;
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DWORD dwComputedCrc;
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DWORD dwBytesRead;
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DWORD dwLen;
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char sznDecodeBytes[5] = {0};
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bool bRet = true;
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bool bUseCHM = strCacheFileWithinCHM.GetLength() != 0;
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if (NULL == szDsc)
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{
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CGenException *pErr = new CGenException;
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pErr->m_OsError = 0;
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pErr->m_strError = _T("The source file was not specified.");
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throw pErr;
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}
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if (NULL == szCache)
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{
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CGenException *pErr = new CGenException;
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pErr->m_OsError = 0;
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pErr->m_strError = _T("The destination file was not specified.");
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throw pErr;
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}
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if (bUseCHM)
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{
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void* buf =NULL;
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if (S_OK != ::ReadChmFile(szCache, strCacheFileWithinCHM, &buf, &dwBytesRead))
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{
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CGenException *pErr = new CGenException;
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pErr->m_OsError = 0;
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pErr->m_strError = _T("Can not read cache from the CHM file.");
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throw pErr;
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}
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if (dwBytesRead < 5)
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return false;
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memcpy(sznDecodeBytes, (char*)buf + dwBytesRead - 4, 4);
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}
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else
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{
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// Read the source file.
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HANDLE hDecodeFile = CreateFile(szCache,
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GENERIC_READ,
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FILE_SHARE_READ,
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NULL,
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OPEN_EXISTING,
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FILE_FLAG_SEQUENTIAL_SCAN,
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NULL);
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if (INVALID_HANDLE_VALUE == hDecodeFile)
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{ // Should continue as if the check sums did not match.
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return false;
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}
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// Return false if the file is shorter than 1 byte + crc length.
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dwLen = GetFileSize(hDecodeFile, NULL);
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if (0xFFFFFFFF == dwLen)
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{
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CGenException *pExc = new CGenException;
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pExc->m_OsError = GetLastError();
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pExc->m_strOsMsg = GlobFormatMessage(pExc->m_OsError);
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pExc->m_strError.Format(
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_T("Could not get the size of cache file %s.\nReason: %s"),
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szCache, (LPCTSTR) pExc->m_strOsMsg);
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CloseHandle(hDecodeFile);
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throw pExc;
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}
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if (dwLen < 5)
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{
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CloseHandle(hDecodeFile);
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return false;
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}
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// Seek to end and backup 4 bytes.
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if (0xFFFFFFFF == SetFilePointer(hDecodeFile, -4, NULL, FILE_END))
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{
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CString strErr;
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CGenException *pErr = new CGenException;
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pErr->m_OsError = GetLastError();
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strErr = GlobFormatMessage(pErr->m_OsError);
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pErr->m_strError.Format(_T("Seek to end of the cache file, %s failed.\nReason: %s"),
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szCache, (LPCTSTR) strErr);
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CloseHandle(hDecodeFile);
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throw pErr;
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}
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if (!ReadFile(hDecodeFile, (LPVOID) sznDecodeBytes, 4, &dwBytesRead, NULL))
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{
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CString strErr;
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CGenException *pErr = new CGenException;
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pErr->m_OsError = GetLastError();
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strErr = GlobFormatMessage(pErr->m_OsError);
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pErr->m_strError.Format(_T("The cache file, %s could not be read.\nReason: %s"),
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szDsc, (LPCTSTR) strErr);
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CloseHandle(hDecodeFile);
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throw pErr;
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}
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if (4 != dwBytesRead)
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{
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CString strErr;
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CGenException *pErr = new CGenException;
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pErr->m_OsError = GetLastError();
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strErr = GlobFormatMessage(pErr->m_OsError);
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pErr->m_strError.Format(_T("%d bytes of the cache file were not read.\nReason: %s"),
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4 - dwBytesRead, szDsc, (LPCTSTR) strErr);
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CloseHandle(hDecodeFile);
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throw pErr;
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}
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CloseHandle(hDecodeFile);
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}
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// Read the crc.
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sznDecodeBytes[4] = NULL;
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DWORD byte;
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byte = (BYTE) sznDecodeBytes[0];
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dwDecodeFileCrc = byte;
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byte = (BYTE) sznDecodeBytes[1];
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byte <<= 8;
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dwDecodeFileCrc |= byte;
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byte = (BYTE) sznDecodeBytes[2];
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byte <<= 16;
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dwDecodeFileCrc |= byte;
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byte = (BYTE) sznDecodeBytes[3];
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byte <<= 24;
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dwDecodeFileCrc |= byte;
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// Get the crc value.
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dwComputedCrc = DscEncode(szDsc);
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if (dwComputedCrc != dwDecodeFileCrc)
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bRet = false;
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return bRet;
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}
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