Problems with Win32::API module

leek has asked for the wisdom of the Perl Monks concerning the following question:

I've seen this question elsewhere and I have been all over Google trying to find a solution but I cannot find one anywhere. Here is the code:

#!/usr/bin/perl

use Win32::API;

my $ZP4StartSession = new Win32::API("ZP4", "ZP4StartSession", [N], P)
+ || die Win32::FormatMessage(Win32::GetLastError);

my $LLHandle = $ZP4StartSession->Call($LLHandle) || die Win32::FormatM
+essage(Win32::GetLastError);
[download]

The Call() function causes my command line to lock up. Any help on why this is happening and/or a solution is greatly appreciated. Thanks, Chris

Comment on Problems with Win32::API module Download Code

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Re: Problems with Win32::API module by shigetsu (Hermit) on Apr 30, 2007 at 20:31 UTC
My guess is that `$LLHandle` is first 'introduced' within your code by the call of `Call($LLHandle)` and thus is undefined. The use of strictures, i.e. `#!/usr/bin/perl use strict; use warnings;` [download] would have caught that though. Unless `$LLHandle` is exported per default by Win32::API, which I don't know. But I saw no mention of `$LLHandle` in Win32::API's documentation. Perhaps you accidentally forgot to include some relevant code?	[reply] [d/l] [select]
Re^2: Problems with Win32::API module by Anonymous Monk on May 01, 2007 at 12:48 UTC
Here is the corrected code.. my fault: `#!/usr/bin/perl use Win32::API; my $lpBuffer = "\0" x 64; my $ZP4StartSession = new Win32::API("ZP4", "ZP4StartSession", [N], P) + \|\| die Win32::FormatMessage(Win32::GetLastError); my $LLHandle = $ZP4StartSession->Call($lpBuffer) \|\| die Win32::FormatM +essage(Win32::GetLastError);` [download]	[reply] [d/l]
Re^3: Problems with Win32::API module (addr) by tye (Sage) on May 01, 2007 at 16:17 UTC
The "N" in "`[N]`" causes $lpBuffer to be interpretted as a number. `"\0" x 64` as a number is just 0. Although you tell us nothing about ZP4StartSession(), it appears clear that what you want to pass to it is a pointer to the buffer you allocated in $lpBuffer. Win32::API doesn't support this type of argument very well / easily. It only supports pointers to '\0'-terminated strings. However, it might work to use `[P]` instead. That depends on implementation details of Win32::API that I am not certain of. If that doesn't work, then you should probably do: `my $lpBuffer= "\0" x 64; my $bufAddr= unpack "L", pack "p", $lpBuffer; #... ... $ZP4StartSession->Call( $bufAddr ) ...` [download] - tye	[reply] [d/l] [select]