#include <windows.h>
#include <winioctl.h>
#include <tchar.h>
#include <stdio.h>

   // Prototypes

BOOL EjectVolume (TCHAR cDriveLetter);

HANDLE OpenVolume (TCHAR cDriveLetter);
BOOL LockVolume (HANDLE hVolume);
BOOL DismountVolume (HANDLE hVolume);
BOOL PreventRemovalOfVolume (HANDLE hVolume, BOOL fPrevent);
BOOL AutoEjectVolume (HANDLE hVolume);
BOOL CloseVolume (HANDLE hVolume);

LPTSTR szVolumeFormat = TEXT ("\\\\.\\%c:");
LPTSTR szRootFormat = TEXT ("%c:\\");
LPTSTR szErrorFormat = TEXT ("Error %d: %s\n");

void
ReportError (LPTSTR szMsg)
{
  _tprintf (szErrorFormat, GetLastError (), szMsg);
}

HANDLE
OpenVolume (TCHAR cDriveLetter)
{
  HANDLE hVolume;
  UINT uDriveType;
  TCHAR szVolumeName[8];
  TCHAR szRootName[5];
  DWORD dwAccessFlags;

  sprintf (szRootName, szRootFormat, cDriveLetter);

  uDriveType = GetDriveType (szRootName);
  switch (uDriveType)
    {
    case DRIVE_REMOVABLE:
      dwAccessFlags = GENERIC_READ | GENERIC_WRITE;
      break;
    case DRIVE_CDROM:
      dwAccessFlags = GENERIC_READ;
      break;
    default:
      _tprintf (TEXT ("Cannot eject.  Drive type is incorrect.\n"));
      return INVALID_HANDLE_VALUE;
    }

  sprintf (szVolumeName, szVolumeFormat, cDriveLetter);

  hVolume = CreateFile (szVolumeName,
			dwAccessFlags,
			FILE_SHARE_READ | FILE_SHARE_WRITE,
			NULL, OPEN_EXISTING, 0, NULL);
  if (hVolume == INVALID_HANDLE_VALUE)
    ReportError (TEXT ("CreateFile"));

  return hVolume;
}

BOOL
CloseVolume (HANDLE hVolume)
{
  return CloseHandle (hVolume);
}

#define LOCK_TIMEOUT        10000	// 10 Seconds
#define LOCK_RETRIES        20

BOOL
LockVolume (HANDLE hVolume)
{
  DWORD dwBytesReturned;
  DWORD dwSleepAmount;
  int nTryCount;

  dwSleepAmount = LOCK_TIMEOUT / LOCK_RETRIES;

  // Do this in a loop until a timeout period has expired
  for (nTryCount = 0; nTryCount < LOCK_RETRIES; nTryCount++)
    {
      if (DeviceIoControl (hVolume,
			   FSCTL_LOCK_VOLUME,
			   NULL, 0, NULL, 0, &dwBytesReturned, NULL))
	return TRUE;

      Sleep (dwSleepAmount);
    }

  return FALSE;
}

BOOL
DismountVolume (HANDLE hVolume)
{
  DWORD dwBytesReturned;

  return DeviceIoControl (hVolume,
			  FSCTL_DISMOUNT_VOLUME,
			  NULL, 0, NULL, 0, &dwBytesReturned, NULL);
}

BOOL
PreventRemovalOfVolume (HANDLE hVolume, BOOL fPreventRemoval)
{
  DWORD dwBytesReturned;
  PREVENT_MEDIA_REMOVAL PMRBuffer;

  PMRBuffer.PreventMediaRemoval = fPreventRemoval;

  return DeviceIoControl (hVolume,
			  IOCTL_STORAGE_MEDIA_REMOVAL,
			  &PMRBuffer, sizeof (PREVENT_MEDIA_REMOVAL),
			  NULL, 0, &dwBytesReturned, NULL);
}

AutoEjectVolume (HANDLE hVolume)
{
  DWORD dwBytesReturned;

  return DeviceIoControl (hVolume,
			  IOCTL_STORAGE_EJECT_MEDIA,
			  NULL, 0, NULL, 0, &dwBytesReturned, NULL);
}

BOOL
EjectVolume (TCHAR cDriveLetter)
{
  HANDLE hVolume;

  BOOL fRemoveSafely = FALSE;
  BOOL fAutoEject = FALSE;

  // Open the volume.
  hVolume = OpenVolume (cDriveLetter);
  if (hVolume == INVALID_HANDLE_VALUE)
    return FALSE;

  // Lock and dismount the volume.
  if (LockVolume (hVolume) && DismountVolume (hVolume))
    {
      fRemoveSafely = TRUE;

      // Set prevent removal to false and eject the volume.
      if (PreventRemovalOfVolume (hVolume, FALSE) &&
	  AutoEjectVolume (hVolume))
	fAutoEject = TRUE;
    }

  // Close the volume so other processes can use the drive.
  if (!CloseVolume (hVolume))
    return FALSE;

  if (fAutoEject)
    printf ("Media in Drive %c has been ejected safely.\n", cDriveLetter);
  else
    {
      if (fRemoveSafely)
	printf ("Media in Drive %c can be safely removed.\n", cDriveLetter);
    }

  return TRUE;
}

void
Usage ()
{
  printf ("Usage: Eject <drive letter>\n\n");
  return;
}

void
main (int argc, char *argv[])
{
  if (argc != 2)
    {
      Usage ();
      return;
    }

  if (!EjectVolume (argv[1][0]))
    printf ("Failure ejecting drive %c.\n", argv[1][0]);

  return;
}