Win32::API Help

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

I'm having a problem calling a function so to prove that I have the module figured out (granted I'm a novice PERL gent) I put two functions in the following code. The first one works, the second function call works but the return code is not what I am expecting "0" and I could get a -1 or -2. What I am getting for a return code is 1949630464 which really baffles me.... Thanks for the suggestion BrowserUK, I cleaned up the code, unfortunatly still no luck.

use Win32::API;
use strict;
use warnings "all";

#  MessageBox API - Reference:  http://msdn2.microsoft.com/en-us/libra
+ry/ms712455.aspx
#  int MessageBox(      
#      HWND hWnd,
#      LPCTSTR lpText,
#      LPCTSTR lpCaption,
#      UINT uType
#  );

my $hwndOwner = 0;
my $LpszText = "Message Box Text";
my $LpszTitle = "Message Box Title";
my $uStyle = 0;    #define MB_OKCANCEL                 0x00000001L

my $fnMessageBox = new Win32::API("user32", "MessageBox", 'NPPN', 'I')
+;
my $call1ret = $fnMessageBox->Call($hwndOwner, $LpszText, $LpszTitle, 
+$uStyle);
print "MessageBox Return Code: ".$call1ret."\n";


#  SQLAllocHandle API - Reference:  http://msdn2.microsoft.com/en-us/l
+ibrary/ms712455.aspx
#  SQLRETURN SQLAllocHandle(
#       SQLSMALLINT     HandleType,
#       SQLHANDLE     InputHandle,
#       SQLHANDLE *     OutputHandlePtr);


my $HandleType = 1;
my $InputHandle = 0;
my $OutputHandlePtr = '';
my $fnSQLAllocHandle = new Win32::API("odbc32", "SQLAllocHandle", 'PPP
+', 'I');
my $call2ret = $fnSQLAllocHandle->Call($HandleType, $InputHandle, $Out
+putHandlePtr);
print "?? ".$^E."\n\n";
print "SQLAllocHandle Return Code: ".$call2ret."\n";
[download]

Comment on Win32::API Help Download Code

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Re: Win32::API Help by BrowserUk (Patriarch) on Sep 27, 2007 at 23:24 UTC
If you used strict and warning, and fixed your code to avoid the first bunch of errors, then you'll get this set of errors: c:\test>junk syntax error at c:\test\junk.pl line 34, near "$OutputHandlePtr;" Bareword "null" not allowed while "strict subs" in use at c:\test\junk +.pl line 13. Bareword "N" not allowed while "strict subs" in use at c:\test\junk.pl + line 18. Bareword "P" not allowed while "strict subs" in use at c:\test\junk.pl + line 18. Bareword "P" not allowed while "strict subs" in use at c:\test\junk.pl + line 18. Bareword "N" not allowed while "strict subs" in use at c:\test\junk.pl + line 18. Bareword "I" not allowed while "strict subs" in use at c:\test\junk.pl + line 18. Bareword "null" not allowed while "strict subs" in use at c:\test\junk +.pl line 32. Bareword "N" not allowed while "strict subs" in use at c:\test\junk.pl + line 33. Bareword "N" not allowed while "strict subs" in use at c:\test\junk.pl + line 33. Bareword "P" not allowed while "strict subs" in use at c:\test\junk.pl + line 33. Bareword "N" not allowed while "strict subs" in use at c:\test\junk.pl + line 33. Execution of c:\test\junk.pl aborted due to compilation errors. [download] And if you pay particular attention to the two 'Bareword "null"' messages, then you might get somewhere. Also, it is often, but not always useful, to print `$^E` in a string context if the api call fails. Update: If you are using AS perl, then take a look at the html pod for the package Win32, wher eyou will find that MessageBox() is available without using Win32::API. `Win32::MsgBox(MESSAGE [, FLAGS [, TITLE]])` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l] [select]
Re: Win32::API Help by almut (Canon) on Sep 27, 2007 at 21:27 UTC
Just guessing... but have you tried specifying "I" (int) instead of "N" (long) as the return value type (4th parameter)? (The API docs don't explicitly say what type/size SQLRETURN is (at least it's not immediately evident to me), so I'd just try likely candidates...)	[reply]
Re: Win32::API Help by syphilis (Archbishop) on Sep 27, 2007 at 23:58 UTC
What I am getting for a return code is 1949630464 sql.h defines the 4 possible return values (SQL_SUCCESS, SQL_SUCCESS_WITH_INFO, SQL_INVALID_HANDLE, and SQL_ERROR) to 0, 1, -2, and -1 (respectively). Cheers, Rob	[reply]
Re: Win32::API Help by Anonymous Monk on Sep 28, 2007 at 00:22 UTC
Why aren't you using Win32::ODBC?	[reply]
Re: Win32::API Help by FFSparky (Acolyte) on Sep 28, 2007 at 02:22 UTC
Thanks for the suggestion BrowserUK, I cleaned up the code and need to use strict more often, unfortunately still no luck in figuring this out. My guess is it's something with the parms as I wrote a quick C (and I'm a novice C person as well, but COBOL on the other hand ;^)... ) program to make sure I was passing the correct values for the parms in perl. And to answer Anonymous Monk, the example I am playing with is more for me in gaining knowledge in working with windows API's and I just happened to pick this particular function.	[reply]
Re^2: Win32::API Help by syphilis (Archbishop) on Sep 28, 2007 at 10:40 UTC
the example I am playing with is more for me in gaining knowledge in working with windows API's You're probably better off getting hold of a compiler (say, the freely available MinGW port of gcc) and using it and Inline::C to access the Windows API's. It's fairly trivial with Inline::C. The following script outputs 0: `use warnings; use strict; use Inline C => <<'EOC'; #include <sql.h> int foo() { SQLHENV henv = SQL_NULL_HENV; return SQLAllocHandle(1, 0, &henv); } EOC print foo();` [download] Admittedly that doesn't do anything useful, but at least it returns a sane value and is nowhere near as obtuse as Win32::API. I must confess that I've spent quite some time trying to get the Win32::API version to return a sane value ... and have failed miserably. Usually, when I can get the Inline::C rendition working, I can then get the Win32::API rendition to work correctly ... sadly, not tonight :-) I assume it's because I haven't found the correct way to deal with the 3rd argument, but I really don't know. Update: Nope ... looks like apl and Corion have picked up the scent, however. Update 2:Yep ... I just checked and the SQLRETURN type is a short ... and apparently Win32::API simply fills the other 2 bytes with garbage. Cheers, Rob	[reply] [d/l]
Re^3: Win32::API Help by FFSparky (Acolyte) on Sep 28, 2007 at 14:45 UTC
Thank you all for sharing your wisdom, I have gained knowledge :^) I believe syphilis is correct in Win32::API does not deal well with short data types. So I took the suggestion and played around with InLine and now have another option for calling APIs: `use warnings; use strict; print "InLineC.pl Started:\n\n Now to Execute some C code:\n\n"; print " fnTest Returned: ".fnTest()."\n"; print "\n Back from the C Code\n\nInLineC.pl Finished.\n"; use Inline C => <<'END_C'; #include <sql.h> int fnTest() { SQLHENV env; SQLRETURN ret; ret = SQLAllocHandle(1, 0, &env); return ret; } END_C` [download]	[reply] [d/l]
Re: Win32::API Help by apl (Monsignor) on Sep 28, 2007 at 09:54 UTC
Your return value (1949630464 decimal) is 74350000 hex. Are you certain you don't need to only look at the low 16 bits? If so, you got a successful return. I'm just tossing out an idea; I'm not familiar with the module you're using.	[reply]
Re^2: Win32::API Help by Corion (Patriarch) on Sep 28, 2007 at 10:00 UTC
Exactly. Googling for SQLAllocHandle 1949630464 has as one of the few hits this page, where somebody tackled the same problem with Common Lisp (it seems). If one encounters a magic number, it's always good to Google for that.	[reply]