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Microsoft Windows NT Build 511 (SDK Final Release) 07-24-1993

/******************************************************************************\
*       This is a part of the Microsoft Source Code Samples. 
*       Copyright (C) 1993 Microsoft Corporation.
*       All rights reserved. 
*       This source code is only intended as a supplement to 
*       Microsoft Development Tools and/or WinHelp documentation.
*       See these sources for detailed information regarding the 
*       Microsoft samples programs.
\******************************************************************************/

/****************************************************************************
*
*    PROGRAM: Enumdrv.C
*
*    PURPOSE: Determines all drives in the system, both local and remote,
*             and their file system type
*
****************************************************************************/
#define  STRICT
#include <windows.h>
#include "globals.h"
#include "filer.h"
#include "enumdrv.h"

extern HANDLE           ghHeap;  // Handle to global heap, declared in FILER.C
extern CRITICAL_SECTION gHeapCS; // Global heap critical section var.
extern CRITICAL_SECTION gDrvCS;  // Drive list critical section var.
extern LPDINFO          glpDrives;

/****************************************************************************
*
*    FUNCTION: CheckRM(LPTSTR)
*
*    PURPOSE: Verifies that a removeable media drive contains a disk
*
*    COMMENTS:
*
*        This function is called each time a drive type is determined to be
*        removeable (DRIVE_REMOVEABLE).  An attempt is made to open a
*        file in the root directory of the drive.  If the attempt succeeds,
*        then media is present in the drive and subsequent calls to the
*        drive can be safely made.  If the call fails, then there is no media
*        present in the drive and no attempts should be made to access this
*        drive.  The Error Mode is temporarily set to 1 to allow failures
*        to immediately return to the calling program.  This eliminates
*        unwanted dialog boxes that prompt for disks to be placed in the
*        drive.
*
*    INPUT: szDriveName - removeable media drive name (ex - "a:")
*
*    OUTPUT: Returns TRUE if media present
*                    FALSE if media is not present
*
****************************************************************************/

BOOL CheckRM( LPTSTR lpszDriveName )
{
    TCHAR    szFileName[DIRECTORY_STRING_SIZE];
    DWORD    dwHold;

    SetErrorMode( SEM_FAILCRITICALERRORS );

    lstrcpy( szFileName, lpszDriveName );
    lstrcat( szFileName, TEXT(".") );

    dwHold = GetFileAttributes( szFileName );

    SetErrorMode( 0 );

    //  If no error, media must be in drive.
    if( dwHold != 0xFFFFFFFF ){
        return(TRUE);
    }
    else{
        dwHold = GetLastError();
        if( dwHold != ERROR_NOT_READY )
            ErrorMsg(TEXT("CheckRM: Get Removable Media Info Failure."));

        return(FALSE);
    }

}


/****************************************************************************
*
*    FUNCTION: DWORD EnumDrives(*LPDINFO)
*
*    PURPOSE: Enumerates available drives, and information on them. If the
*               DINFO structure passed in is NULL, it creates a linked list
*               of DINFO structures, reporting information on each available
*               drive.  If DINFO points to an existing structure, the list
*               is updated.
*
*    COMMENTS:
*        The number of available drives is first determined by a call to
*        GetLogicalDrives.  This provides a bit mask of all logical drives.
*
*        For each logical drive, a call is made to GetDriveType to determine
*        the drive type.  If the logical drive is not in the bit mask that
*        was created with the GetLogicalDrives call, then this drive is
*        bypassed.
*
*        GetVolumeInformation is used to determine the file syste for the
*        logical drive. If the drive type is removable, a check must be made
*        to see if the drive contains a disk. If the remote drive contains a
*        disk, then it is safe to proceed with the GetVolumeInformation call.
*
*    INPUT:  LPDINFO dINfo: A pointer to a DRVINFO Structure.
*
*    OUTPUT: Returns the number of DINFO structures in the linked
*            list pointed to by dInfo.  Value is negative if error.
*
\****************************************************************************/

void EnumDrives(LPDINFO *lplpRoot)
{
  DWORD         dwDriveMask;
  DWORD         dwCount;
  LPTSTR        lpszRootPathName=TEXT("?:\\");

  static LPTSTR lpDriveStrings = NULL;
  LPTSTR        lpParse;

  LPDINFO       lpDInfo,                // new node ptr
                lpHold,                 // list walking ptrs
                lpBack,
                lpRoot = *lplpRoot;     // root ptr


  EnterCriticalSection(&gDrvCS);

  //
  // Free old drive strings;
  // With a buffer size of 0, the first call returns the size of buffer needed.
  //
  if(lpDriveStrings != NULL){
    EnterCriticalSection(&gHeapCS);
    HeapFree( ghHeap, 0, lpDriveStrings);
    LeaveCriticalSection(&gHeapCS);
  }

  dwCount=GetLogicalDriveStrings( 0, lpDriveStrings);
  if( !dwCount ){
    LeaveCriticalSection(&gDrvCS);
    ErrorMsg(TEXT("EnumDrives: Get Drive Strings error"));
    ExitThread((DWORD)-1);
  }

  EnterCriticalSection(&gHeapCS);
  // allocate memory, +1 for trailing NULL
  lpDriveStrings = (LPTSTR)HeapAlloc( ghHeap, 0, (dwCount + 1) * sizeof(TCHAR) );
  LeaveCriticalSection(&gHeapCS);

  if( lpDriveStrings == NULL){
      LeaveCriticalSection(&gDrvCS);
      ErrorMsg(TEXT("EnumDrives: Allocation error"));
      ExitThread((DWORD)-2);
  }

  if(dwCount < GetLogicalDriveStrings( dwCount, lpDriveStrings) ){
      LeaveCriticalSection(&gDrvCS);
      ErrorMsg(TEXT("EnumDrives: Drive String size Changed!"));
      ExitThread((DWORD)-3);
  }
  lpParse = lpDriveStrings;

  dwDriveMask=GetLogicalDrives();

  //
  // walk list, inserting, deleting, & updating nodes as necessary
  //
  dwCount = 0;
  lpHold = lpBack = lpRoot;

  for (*lpszRootPathName=TEXT('a');*lpszRootPathName<=TEXT('z');(*lpszRootPathName)++){
    if (dwDriveMask & 1){   // drive exists. Insert or update.

      dwCount++;

      //
      // if lpHold (the list walking ptr) is NULL, or the drive that exists
      //  does not already have a node in the list, allocate a node.
      //
      if( !lpHold || lpHold->DriveLetter > *lpszRootPathName ){
        //
        // Allocating memory for DRVINFO node
        //
        EnterCriticalSection(&gHeapCS);
        lpDInfo = (LPDINFO) HeapAlloc( ghHeap, 0, (DWORD)sizeof(DRVINFO) );
        LeaveCriticalSection(&gHeapCS);
        if( lpDInfo == NULL){
          LeaveCriticalSection(&gDrvCS);
          ErrorMsg(TEXT("EnumDrives: DRVINFO Allocation error"));
          ExitThread((DWORD)-4);
        }

        //
        // insert new node into list
        //
        if( lpHold == lpRoot ){
          lpDInfo->next = lpRoot;
          lpRoot = lpDInfo;
        }
        else{
          lpDInfo->next = lpBack->next;
          lpBack->next = lpDInfo;
        }

        lpBack = lpDInfo;
        lpHold = lpDInfo->next;

        lpDInfo->DriveLetter = *lpszRootPathName;
      }
      else{
        if( lpBack != lpHold )
          lpBack = lpBack->next;
        lpHold = lpHold->next;
      }

      lpBack->DriveType = GetDriveType(lpszRootPathName);
      if( lpBack->DriveType == DRIVE_REMOVABLE ||
          lpBack->DriveType == DRIVE_CDROM )
        if( CheckRM(lpszRootPathName ) )
          if( !GetVolumeInformation(lpszRootPathName,NULL,0,NULL,NULL,NULL,
                                   (LPTSTR)lpBack->FileSystem,
                                   (DWORD)FILE_SYSTEM_STRING_SIZE) )
            lstrcpy(lpBack->FileSystem, TEXT("UNKNOWN"));
          else;
        else      // no removable media
          lstrcpy(lpBack->FileSystem, TEXT("UNKNOWN"));
      else        // not removable
        if( !GetVolumeInformation(lpszRootPathName,NULL,0,NULL,NULL,NULL,
                                  (LPTSTR)lpBack->FileSystem,
                                  (DWORD)FILE_SYSTEM_STRING_SIZE) )
          lstrcpy(lpBack->FileSystem, TEXT("UNKNOWN"));
        else;

      lpBack->DriveName = lpParse;
      lpParse += lstrlen(lpParse)+1;
    }
    else{               // drive does not exist.
      if( lpHold )      //   if node exists, delete it.
        if( lpHold->DriveLetter == *lpszRootPathName ){
          if( lpHold == lpRoot )
            lpRoot = lpBack = lpHold->next;
          else
            lpBack->next = lpHold->next;

          EnterCriticalSection(&gHeapCS);
          HeapFree(ghHeap, 0, (LPVOID)lpHold);
          LeaveCriticalSection(&gHeapCS);

          lpHold = lpBack->next;
        }
    }
    dwDriveMask >>= 1;

  } // end for

  *lplpRoot = lpRoot;

  LeaveCriticalSection(&gDrvCS);

  ExitThread(dwCount);
}

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