OPENF.C
/*++
Copyright (c) 1995-1997 Microsoft Corporation
Module Name :
openf.c
Abstract:
This module implements a simple open file handle cache
Project:
ISAPI Extensions Sample DLL
Functions Exported:
Note:
THIS IS NOT ROBUST for REAL WORLD.
I wrote this for testing the ISAPI Async IO processing.
--*/
/************************************************************
* Include Headers
************************************************************/
# include "openf.h"
/************************************************************
* Type definitions and Globals
************************************************************/
//
// internal data structure for maintaining the list of open file handles.
//
typedef struct _OPEN_FILE {
HANDLE hFile;
struct _OPEN_FILE * pNext;
LONG nHits;
LONG nRefs;
CHAR rgchFile[MAX_PATH+1];
} OPEN_FILE, * LPOPEN_FILE;
LPOPEN_FILE g_pOpenFiles = NULL;
CRITICAL_SECTION g_csOpenFiles;
BOOL g_fIsNt = TRUE;
//
// Set up global variables containing the flags for CreateFile
// The flags can be masked for Windows 95 system
//
DWORD g_dwCreateFileShareMode =
(FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE);
DWORD g_dwCreateFileFlags =
(FILE_FLAG_SEQUENTIAL_SCAN | FILE_FLAG_OVERLAPPED);
/************************************************************
* Functions
************************************************************/
DWORD
InitFileHandleCache(VOID)
/*++
This function initializes the file handle cache.
It should be called at the initialization time.
Arguments:
None
Returns:
Win32 error code. NO_ERROR indicates that the call succeeded.
--*/
{
OSVERSIONINFO osInfo;
InitializeCriticalSection( &g_csOpenFiles);
//
// obtain the platform type to find out how to open the file
//
osInfo.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
if ( GetVersionEx( &osInfo ) ) {
g_fIsNt = (osInfo.dwPlatformId == VER_PLATFORM_WIN32_NT);
}
if ( !g_fIsNt) {
//
// Reset the flags appropriately so that Windows 95 will be happy
//
g_dwCreateFileShareMode = (FILE_SHARE_READ | FILE_SHARE_WRITE);
g_dwCreateFileFlags = (FILE_FLAG_SEQUENTIAL_SCAN);
}
return (NO_ERROR);
} // InitFileHandleCache()
DWORD
CleanupFileHandleCache(VOID)
{
LPOPEN_FILE pFileScan;
while ( g_pOpenFiles != NULL) {
pFileScan = g_pOpenFiles;
g_pOpenFiles = g_pOpenFiles->pNext;
if ( pFileScan->hFile != INVALID_HANDLE_VALUE) {
CloseHandle( pFileScan->hFile);
}
LocalFree( pFileScan);
}
DeleteCriticalSection( &g_csOpenFiles);
return (NO_ERROR);
} // CleanupFileHandleCache()
HANDLE
FcOpenFile(IN EXTENSION_CONTROL_BLOCK * pecb, IN LPCSTR pszFile)
/*++
FcOpenFile()
Description:
This function opens the file specified in the 'pszFile'.
If the file name starts with a '/' we use the ECB to map
the given path into a physical file path.
Arguments:
pecb - pointer to the ECB block
pszFile - pointer to file name
Returns:
valid File handle on success
--*/
{
LPOPEN_FILE pFileScan;
HANDLE hFile = INVALID_HANDLE_VALUE;
EnterCriticalSection( &g_csOpenFiles);
for ( pFileScan = g_pOpenFiles;
NULL != pFileScan;
pFileScan = pFileScan->pNext) {
if ( 0 == lstrcmpi( pFileScan->rgchFile, pszFile)) {
//
// there is a file match.
//
break;
}
} // for
if ( NULL == pFileScan) {
//
// File was not found. Create a new file handle
//
CHAR rgchFileName[ MAX_PATH]; // local copy
LPCSTR pszInputPath = pszFile;
lstrcpyn( rgchFileName, pszFile, MAX_PATH);
if ( *pszFile == '/') {
DWORD cbSize = sizeof(rgchFileName);
BOOL fRet;
// reset the file pointer, so subsequent use will fail
pszFile = NULL;
//
// Using the ECB map the Virtual path to the Physical path
//
fRet = pecb->ServerSupportFunction( pecb->ConnID,
HSE_REQ_MAP_URL_TO_PATH,
rgchFileName,
&cbSize, NULL);
if (fRet) {
// we got the mapping. Use it.
pszFile = rgchFileName;
}
}
if ( NULL != pszFile) {
pFileScan = LocalAlloc( LPTR, sizeof( *pFileScan));
if ( NULL != pFileScan) {
SECURITY_ATTRIBUTES sa;
sa.nLength = sizeof(sa);
sa.lpSecurityDescriptor = NULL;
sa.bInheritHandle = FALSE;
pFileScan->hFile =
CreateFile( pszFile,
GENERIC_READ,
g_dwCreateFileShareMode,
&sa,
OPEN_EXISTING,
g_dwCreateFileFlags,
NULL );
if ( INVALID_HANDLE_VALUE == pFileScan->hFile) {
LocalFree( pFileScan);
pFileScan = NULL;
} else {
// insert this into the list at the top
lstrcpyn( pFileScan->rgchFile, pszInputPath, MAX_PATH);
pFileScan->pNext = g_pOpenFiles;
g_pOpenFiles = pFileScan;
pFileScan->nRefs = 1;
pFileScan->nHits = 0;
}
}
}
}
if ( NULL != pFileScan) {
hFile = pFileScan->hFile;
pFileScan->nHits++;
pFileScan->nRefs++;
}
LeaveCriticalSection( &g_csOpenFiles);
return (hFile);
} // FcOpenFile()
DWORD
FcCloseFile(IN HANDLE hFile)
{
LPOPEN_FILE pFileScan;
DWORD dwError = NO_ERROR;
EnterCriticalSection( &g_csOpenFiles);
//
// Look for the handle and decrement the ref count.
//
for ( pFileScan = g_pOpenFiles;
NULL != pFileScan;
pFileScan = pFileScan->pNext) {
if ( hFile == pFileScan->hFile) {
//
// there is a file match.
//
pFileScan->nRefs--;
//
// BUGBUG: There is no freeing of the file when Ref hits '0' :(
//
break;
}
} // for
if ( NULL == pFileScan) {
//
// file handle not found
//
dwError = ( ERROR_INVALID_HANDLE);
}
LeaveCriticalSection( &g_csOpenFiles);
return ( dwError);
} // FcCloseFile()
BOOL
FcReadFromFile(
IN HANDLE hFile,
OUT CHAR * pchBuffer,
IN DWORD dwBufferSize,
OUT LPDWORD pcbRead,
IN OUT LPOVERLAPPED pov
)
/*++
Description:
Reads contents of file [hFile] from the specified offset in the overlapped
structure. The contents are read into the buffer supplied.
Arguments:
hFile - handle for the File from which to read data
pchBuffer - pointer to the buffer into which the data is to be read
dwBufferSize - DWORD containing the max size of the buffer supplied
pcbRead - number of bytes read from the file
pov - pointer to an overlapped structure that contains the
offset from where to read the contents. The
overlapped structure also is used for Overlapped
IO in NT.
Notes:
This function automatically handles both Windows 95 and NT
Returns:
TRUE on success and FALSE if there is a failure.
Use GetLastError() to get the last error code on failure.
--*/
{
BOOL fRet = TRUE;
*pcbRead = 0;
if ( !g_fIsNt ) {
//
// Windows95 does not support Overlapped IO.
// So we shall thunk it out and use Synchronous IO
//
fRet = (
SetFilePointer( hFile,
pov->Offset,
NULL,
FILE_BEGIN) &&
ReadFile( hFile,
pchBuffer,
dwBufferSize,
pcbRead,
NULL
)
);
} else {
ResetEvent( pov->hEvent);
fRet = TRUE;
// read data from file
if (!ReadFile(hFile,
pchBuffer,
dwBufferSize,
pcbRead,
pov
)) {
DWORD err = GetLastError();
if ( (err != ERROR_IO_PENDING) ||
!GetOverlappedResult( hFile, pov, pcbRead, TRUE) ) {
fRet = FALSE;
}
}
}
if ( fRet ) {
pov->Offset += *pcbRead;
}
return ( fRet );
} // FcReadFromFile()
/************************ End of File ***********************/