July 2000/NT Handle-to-Path Conversion/Listing 1
#define STRICT
#include <assert.h>
#include <limits.h>
#include <Tchar.h>
#include "gfnfhnt.h"
#include <WindowsX.h>
#ifdef _MSC_VER
#pragma comment (lib, "MPR")
// VC++ needs MPR.LIB to link WNet... functions
#endif
#define DIM(_array) (sizeof(_array) / sizeof(_array[0]))
#ifdef _UNICODE
#define SUFFIX "W"
#else
#define SUFFIX "A"
#endif
#define BACK_SLASH _T('\\')
BOOL GetFileNameFromHandleNT
(HANDLE hFile, LPTSTR string, INT size)
{
BOOL success = FALSE;
DWORD lasterror;
HINSTANCE hiPSAPI = NULL; // PSAPI.DLL
HINSTANCE hiKERNEL32 = NULL; // KERNEL32.DLL
// Pointer to function getMappedFileName() in PSAPI.DLL
//
typedef DWORD (WINAPI * GetMappedFileName_t)
(HANDLE, LPVOID, LPTSTR, DWORD);
GetMappedFileName_t pfGMFN;
// Pointer to function QueryDosDevice() in KERNEL32.DLL
//
typedef DWORD (WINAPI * QueryDosDevice_t)
(LPCTSTR, LPTSTR, DWORD);
QueryDosDevice_t pfQDD;
HANDLE hFileMap = NULL;
LPVOID pMem = NULL;
TCHAR tName [_MAX_PATH+100] = __TEXT("");
LPTSTR scratch = NULL; // malloc'ed working buffer
DWORD scr_size; // size of scratch in bytes.
HANDLE hNetWalker = INVALID_HANDLE_VALUE;
DWORD FileSizeHi = 0; // 64-bit file size.
DWORD FileSizeLo;
LPCTSTR devname;
int devlength;
SetLastError (0);
do {
// Get the file size.
// I will attempt to memory-map the whole file or 1024
// bytes, whichever is smaller.
//
FileSizeLo = GetFileSize (hFile, & FileSizeHi);
if (0 == FileSizeHi) {
if (0 == FileSizeLo)
break; // Failed: can't mem-map empty file!
if (FileSizeLo > 1024)
FileSizeLo = 1024;
}
else // FileSize > 4Gb
FileSizeLo = 1024;
// Memory-map a portion of the file.
//
hFileMap = CreateFileMapping (
hFile, NULL, PAGE_READONLY, 0, FileSizeLo, NULL);
if (NULL == hFileMap)
break; // Failed: Can't memory-map this handle
pMem = MapViewOfFile (hFileMap, FILE_MAP_READ, 0, 0, 0);
if (NULL == pMem)
break; // Failed: unexpected error
// Call GetMappedFileName() in PSAPI.DLL
// This library is only available on WinNT, not on Win9x.
//
hiPSAPI = LoadLibraryA ("PSAPI.DLL");
if (NULL == hiPSAPI)
break; // Failed: Not on WinNT
pfGMFN = (GetMappedFileName_t) GetProcAddress (
hiPSAPI, "GetMappedFileName" SUFFIX);
if (! pfGMFN)
break; // Failed: unexpected error
if (0 >= (*pfGMFN) (
GetCurrentProcess(), pMem, tName, DIM(tName) ))
break; // Failed: unexpected error
if (__TEXT('\0') == tName[0])
break; // Failed: unexpected error
// Access QueryDosDevice() API in KERNEL32.DLL.
// This function is NOT present on Win95.
//
hiKERNEL32 = LoadLibraryA ("KERNEL32.DLL");
if (NULL == hiKERNEL32)
break; // Failed: unexpected error
pfQDD = (QueryDosDevice_t) GetProcAddress
(hiKERNEL32, "QueryDosDevice" SUFFIX);
if (! pfQDD)
break; // Failed: Win95
// The first call to QueryDosDevice() fetches the
// list of Dos Device names. We must be prepared to
// allocate a larger buffer if necessary.
//
lasterror = S_OK;
for (scr_size = 4096; scr_size < 1000000; scr_size <<= 1) {
scratch = (LPTSTR) malloc (scr_size);
if (! scratch)
break; // out of memory
SetLastError (0);
(*pfQDD) (NULL, scratch, scr_size);
lasterror = GetLastError ();
if (ERROR_INSUFFICIENT_BUFFER != lasterror)
break;
free (scratch);
scratch = NULL;
}
if (! scratch)
break; // Failed: out of memory
if (lasterror)
break; // Failed: unexpected error
// The scratch[] buffer now contains a list of DOS device
// names, seperated by null characters, terminated by a
// double null character, Like this:
// "D:\0DISPLAY1\0E:\0PIPE\0PhysicalDrive0\0PRN\0A:\0AUX\NUL\0\0"
// For each Dos Device Name in the buffer,
// If that is a drive letter (ends in colon),
// call QueryDosDevice() again to get the internal name
// and check for a match.
//
for (devname = scratch;
(0 < (devlength = _tcslen (devname)));
devname += devlength+1) {
_TCHAR objectname [_MAX_PATH];
int objlength;
if (2 != devlength)
continue;
if (_T(':') != devname[devlength-1])
continue;
objlength = (*pfQDD) (
devname, objectname, DIM(objectname));
if (0 >= objlength)
continue; // this shouldn't happen
// *** UNDOCUMENTED BEHAVIOR:
// For mapped network drives,
// QueryDosDevice ("X:") on NT4 will typically return
// "\Device\LanmanRedirector\X:\Server\SERVICE"
// and on Win2K (RC2) will typically return
// "\Device\LanmanRedirector\;X:0\Server\SERVICE"
// I need to edit out the extra drive letter, etc.
//
do {
LPTSTR ptmp1, ptmp2;
ptmp2 = _tcsstr (objectname, devname);
if (!ptmp2)
break;
*ptmp2 = 0;
ptmp1 = _tcsrchr (objectname, BACK_SLASH);
*ptmp2 = devname[0];
if (NULL == ptmp1)
break;
ptmp2 = _tcschr (ptmp2+devlength, BACK_SLASH);
if (NULL == ptmp2)
break;
_tcscpy (ptmp1, ptmp2);
} while (0);
// Test for a match
//
objlength = _tcslen (objectname);
if (0 != _tcsnicmp (objectname, tName, objlength))
continue;
if ((BACK_SLASH != tName[objlength])
&& (BACK_SLASH != objectname[objlength-1]) )
continue;
// We have a match; Make the substitution
//
assert (objlength >= devlength);
_tcscpy (tName, devname);
_tcscat (tName, tName+objlength);
success = TRUE;
break;
} // for
if (success)
break;
// If the file is not on a local or mapped drive,
// it could have been opened by UNC.
// (Or a new redirector may have broken the code above.)
// Enumerate the current network connections.
//
if (NO_ERROR != WNetOpenEnum (RESOURCE_CONNECTED,
RESOURCETYPE_ANY, 0, NULL, &hNetWalker ))
break;
{
DWORD bytes_needed = scr_size;
NETRESOURCE* pnr = NULL;
int count = 0;
DWORD code;
LPTSTR remote, ptmp;
int length, match;
int best_match = INT_MAX;
for (; ; --count, (pnr = (NULL!=pnr) ? pnr+1 : pnr) ) {
// If the buffer is empty, fill it up again
//
if (count <= 0) {
// Allocate or reallocate a memory buffer,
// if necessary.
//
if ((NULL != scratch)
&& (scr_size >= bytes_needed))
// ok, I've already got enough memory
bytes_needed = scr_size;
else {
if (scratch)
free (scratch);
scratch = (LPTSTR) malloc (bytes_needed);
if (! scratch)
break; // Failed: out of memory
scr_size = bytes_needed;
}
count = -1;
code = WNetEnumResource (hNetWalker,
(DWORD *) &count, scratch, &bytes_needed);
if (NO_ERROR == code)
pnr = (NETRESOURCE *) scratch;
else if (ERROR_MORE_DATA == code) {
// Buffer isn't big enough;
// allocate a bigger one.
//
bytes_needed *= 2;
continue;
}
else
break; // ERROR_NO_MORE_ITEMS
}
// The NETRESOURCE::lpRemoteName should point
// to the UNC name for the service:
// \\Server\Service
// See if the kernel object name contains
// ...\Server\Service\...
//
remote = pnr->lpRemoteName;
if ((remote == NULL) // impossible?
|| (remote[0] != BACK_SLASH)
|| (remote[1] != BACK_SLASH) )
continue;
ptmp = _tcsstr (tName+1, remote+1);
if (! ptmp)
continue;
length = _tcslen (remote+1);
// At this point ptmp points to the
// substring "\Server\Service\...\file.ext".
// Discard spurious matches.
// First, \server\foobar != \server\foo
//
if ((remote[length] != BACK_SLASH)
&& (ptmp[length] != BACK_SLASH) )
continue;
// Test if the match identifies a valid,
// existing file.
//
{ DWORD attributes;
_TCHAR save = ptmp[-1];
ptmp[-1] = BACK_SLASH;
attributes = GetFileAttributes (ptmp-1);
ptmp[-1] = save;
if ((DWORD) -1 == attributes)
continue;
}
// If multiple matches identify valid files,
// (highly unlikely!) take the match
// closest to the root
//
match = ptmp - tName;
if (best_match > match)
best_match = match;
} // for
if (best_match < INT_MAX) {
assert ((0 < best_match)
&& (best_match < (int) _tcslen (tName)));
_tcscpy (tName+1, tName+best_match);
success = TRUE;
}
}
} while (0);
// Clean up your mess: release all resources.
// (This code is executed whether I succeed or fail.)
//
if (INVALID_HANDLE_VALUE != hNetWalker)
WNetCloseEnum (hNetWalker);
if (NULL != pMem)
UnmapViewOfFile (pMem);
if (NULL != hFileMap)
CloseHandle (hFileMap);
if (NULL != hiPSAPI)
FreeLibrary (hiPSAPI);
if (NULL != hiKERNEL32)
FreeLibrary (hiKERNEL32);
if (scratch)
free (scratch);
// Return the results
//
_tcsncpy (string, tName, size-1);
string[size-1] = 0;
return (BOOL) success;
} // end of GetFileNameFromHandleNT ()
//End of File
