list Windows drive Letters (compile on Linux)
lazarus / 66-Unix

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bjlockie1 · 2020-11-19 21:39

I am writing a file manager type app on Linux that also needs to run
on Windows.
It is ok on Linux but I don't account for drive letters on Windows.
Is there a way to list available drive letters (instead of hard coding
A: to Z:)?

I am using ChDir, is that going to change the drive?

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Leledumbo · 2020-11-19 21:45

Guess you have to ifdef since drive letters is a Windows only concept.
Windows API has GetLogicalDrives function that you can call, it will
return a single LongWord / DWord value whose bits indicate whether the
corresponding drive letter is assigned or not, i.e. bit 0 = drive A,
bit 1 = drive B and so on.

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Bart · 2020-11-19 21:47

Maybe take a look at TShellTreeView and see how the root node is
populated?

Bart

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Aidex · 2020-11-19 21:57

And if it is of interest what type each drive is, I recommend
Windows.GetDriveType()

https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-
getdrivetypea

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Remy Lebeau · 2020-11-20 17:08

Quote from: Leledumbo on November 19, 2020, 10:45:58 pmWindows API has
GetLogicalDrives function that you can call, it will return a single
LongWord / DWord value whose bits indicate whether the corresponding
drive letter is assigned or not

The API also has a GetLogicalDriveStrings() function, which returns
each assigned drive letter in a '<letter>:\' string format, which can
be passed as-is to any API that takes a drive root as input, including
GetDriveType().

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Bart · 2020-11-20 17:22

From one of my units:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
DiskInDrive(Drive: Char): Boolean;var  ErrorMode: word;begin  { maak
er een hoofdletter van }  Drive := UpCase(Drive);  if not (Drive in
['A'..'Z']) then    raise EConvertError.Create('Geen geldige
stationsaanduiding: '+Drive+':');  { schakel kritieke fouten uit } 
ErrorMode := SetErrorMode(SEM_FailCriticalErrors);  try    { drive 1 =
a, 2 = b, 3 = c, etc. }    if DiskSize(Ord(Drive) - Ord('A') + 1) = -1
then      Result := False    else      Result := True;  finally    {
restore old error mode }    SetErrorMode(ErrorMode); 
end;end; function GetAvailableDrives(DiskMustBeInDrive: Boolean =
False): TSysCharSet;var  D, Mask: DWORD;  C: Char;begin  Result :=
[];  D := GetLogicalDrives;  for C := 'A' to 'Z' do  begin    Mask :=
(1 shl (Ord(C) - Ord('A')));    if (Mask and D) = Mask then    begin 
   if (not DiskMustBeInDrive) or DiskInDrive(C) then     
Include(Result, C);    end;  end;end; 
And from a unit that imlements a DriveCombobox:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i type  
TDriveType = (dtUnknown, dtNoRootDir, dtRemovable, dtFixed, dtRemote,
dtCdrom, dtRamDisk);  TDriveTypes = set of TDriveType; function
GetDriveType(ADrive: Char): TDriveType;var  WinDriveType: UINT;begin 
WinDriveType := Windows.GetDriveType(PChar(LowerCase(ADrive+':\'))); 
case WinDriveType of    DRIVE_UNKNOWN: Result := dtUnknown;   
DRIVE_NO_ROOT_DIR: Result := dtNoRootDir;    DRIVE_REMOVABLE: Result
:= dtRemovable;    DRIVE_FIXED: Result := dtFixed;    DRIVE_REMOTE:
Result := dtRemote;    DRIVE_CDROM: Result := dtCdrom;   
DRIVE_RAMDISK: Result := dtRamDisk;    else Result := dtUnknown;  end;
//caseend;//refreshs the drive list//FMountedDrivesOnly: if True then
disk must be in drive//DriveTypes: a set of drivetypes you want in the
list, so you can e.g. filter for only removable drives procedure
TFSICustomDriveComboBox.RefreshDriveList;var  C: Char;  ADriveType:
TDriveType;begin  if (csDesigning in ComponentState) then    Exit; 
Items.Clear;  for C in GetAvailableDrives(FMountedDrivesOnly) do 
begin    ADriveType := GetDriveType(C);    if ADriveType in DriveTypes
then      Items.Add(C + ':\');  end;  if
FSelectFirstDriveOnRefreshDriveList and (not DroppedDown) and
(Items.Count > -1) then    ItemIndex := 0;end; 
Bart

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Sieben · 2020-11-20 17:48

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i ... and
(Items.Count > -1)
?

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Bart · 2020-11-20 18:19

Quote from: Sieben on November 20, 2020, 06:48:24 pmCode: Pascal
 [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i ... and
(Items.Count > -1)
?

Oops, must be > 0 of course.
Must have been confused with ItemIndex. Count of course can never be <
0.

Thanks.
Fixed in trunk.

Files reside here:
https://svn.code.sf.net/p/flyingsheep/code/trunk/MijnLib
Units fsiwinutils and fsiwincontrols.

Bart

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Sieben · 2020-11-20 19:06

Thanks for sharing. And Flying Sheep is one of my absolute favourites
as well...

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Remy Lebeau · 2020-11-20 20:17

Quote from: Bart on November 20, 2020, 06:22:35 pmCode: Pascal
 [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i ErrorMode
:= SetErrorMode(SEM_FailCriticalErrors);
Just to point out that SetErrorMode() is global to the whole process
and changing its mode introduces a race condition in multi-threaded
code.  You really should be using SetThreadErrorMode() instead.

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bjlockie1 · 2020-11-20 21:15

Quote from: Leledumbo on November 19, 2020, 10:45:58 pmGuess you have
to ifdef since drive letters is a Windows only concept. Windows API
has GetLogicalDrives function that you can call, it will return a
single LongWord / DWord value whose bits indicate whether the
corresponding drive letter is assigned or not, i.e. bit 0 = drive A,
bit 1 = drive B and so on.

Thanks.
I have it compiling but it can't ChDir to drive D:\
C:\ and Z:\ work fine.

I'm going to post in the Windows forum.
I could wrap it in a try but I don't think drive D: should be listed.

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lucamar · 2020-11-20 23:33

Quote from: bjlockie1 on November 20, 2020, 10:15:44 pmI have it
compiling but it can't ChDir to drive D:\
C:\ and Z:\ work fine.
That might be normal if drive D: is a CD-ROM but there is no CD in it,
or a card-reader without card (or an unmounted card), or similar.

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winni · 2020-11-20 23:39

Quote from: lucamar on November 21, 2020, 12:33:23 amQuote from:
bjlockie1 on November 20, 2020, 10:15:44 pmI have it compiling but it
can't ChDir to drive D:\
C:\ and Z:\ work fine.
That might be normal if drive D: is a CD-ROM but there is no CD in it,
or a card-reader without card (or an unmounted card), or similar.

Or D: is a Linux partition
Or D: is a not formatted partition
Or on D:  the filesystem is broken - Windows gives up very quick
Or D: is an external drive and you pulled the plug
Or or or ...

Winni

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lucamar · 2020-11-20 23:57

Quote from: winni on November 21, 2020, 12:39:25 amOr D: is a Linux
partition
Or D: is a not formatted partition
...
Or D: is an external drive and you pulled the plug

In none of those cases (except maybe the "broken FS" one) do my
Windows machines ever bother to assign a letter.

The general case I was thinking about is a removable-media drive which
gets a letter assigned but fails if no media is loaded, like a CD/DVD
drive or a card-reader; in that case and unless you have auto-run set
on Windows frequently doesn't bother to ascertain whether there is any
media at all until you try to access it (which caused me endless
headaches with a 7-slot flash card reader: one never knew which letter
Window assigned to each slot so I had to try all 7 until one deigned
to respond  ).

But I left Windows (except punctually 2K, XP, 7 and 10) on Vista times
so I might be missing something

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winni · 2020-11-21 01:03

Quote from: lucamar on November 21, 2020, 12:57:42 am
In none of those cases (except maybe the "broken FS" one) do my
Windows machines ever bother to assign a letter.


Hey,hey, hey - you lucky boy!

* Win7 asked me often, if it should format my Linux Partition !!!
Somewhere in the Win-Jungle I disabled the partition.
Too long ago, don't know, where it was exactly.
* If you just pull the plug of an external drive and you don't inform
the OS to "eject" it, you got a valid  drive letter - until you try
the first time to read or write from/to that drive.
* If a network drive (Samba) does not react, but it was alive at boot
times, Win is really insistent. It retries in an endless loop to
reconnect. It shows a drive letter and the hourglass but not the
directory. Until the end of all days. Or a reboot.

And so on.

Winni

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lucamar · 2020-11-21 04:28

Well, I don't know about the Samba one but neither of the other
situations have ever happened to me: Win 7 leaves non-win partitions
alone (as it should!) and if you just disconnect a device (say, a USB
disk) it sometimes, as do Win10, complains about your lack of manners
but is otherwise notified and frees up the volume letter.

I'm not much on Windows (and less each year, thank the gods) but some
of my customers do and I've never heard about such problems. But then,
again, that's not very representative: most of us as well as our
customers are on Linux or other *nixen ... or on very ancient systems,
but that's another story