Oddity with Win32API, RegQueryValueEx

ruby-talk
1

Ah, ok. I thought it would just set the size regardless.

Thanks,

Dan

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-----Original Message-----
From: Park Heesob [mailto:phasis68@hotmail.com]
Sent: Monday, May 15, 2006 4:31 AM
To: ruby-talk ML
Subject: Re: Oddity with Win32API, RegQueryValueEx

Hi,

>From: Daniel Berger <djberg96@gmail.com>
>Reply-To: ruby-talk@ruby-lang.org
>To: ruby-talk@ruby-lang.org (ruby-talk ML)
>Subject: Oddity with Win32API, RegQueryValueEx
>Date: Mon, 15 May 2006 18:45:19 +0900
>
>Hi all,
>
>Ruby 1.8.4
>Windows XP
>
>I noticed something curious when using the RegQueryValueEx()
function
>using
>straight C versus a Win32API wrapper. Whenever I call it
via Win32API, it
>always returns ERROR_MORE_DATA (i.e. value 234) on the first
call, not
>matter what I set the buffer size to.
>
>Here's a sample C program that works fine:
>
>#include <windows.h>
>#include <stdio.h>
>
>int main(){
> char* key =
>"SYSTEM\\CurrentControlSet\\Services\\EventLog\\Application\\
SNDSrvc";
> char* val = "EventMessageFile";
> char buf[1024];
> DWORD size;
> int rv;
> HKEY hk;
>
> rv = RegOpenKeyEx(
> HKEY_LOCAL_MACHINE,
> key,
> 0,
> KEY_READ,
> &hk
> );
>
> if(rv == ERROR_SUCCESS){
> rv = RegQueryValueEx(hk, val, NULL, NULL, buf, &size);
> if(rv == ERROR_SUCCESS){
> printf("Success!\n");
> printf("Size: %i\n", size);
> printf("Buf: %s\n", buf);
> RegCloseKey(hk);
> }
> else{
> printf("Failure: %i\n", GetLastError());
> }
> }
>
> return 0;
>}
>
>However, the equivalent Ruby program always returns ERROR_MORE_DATA:
>
>require 'Win32API'
>
>HKEY_LOCAL_MACHINE = 0x80000002
>KEY_READ = 0x20019
>
>RegCloseKey = Win32API.new('advapi32', 'RegCloseKey', 'L', 'L')
>RegOpenKeyEx = Win32API.new('advapi32', 'RegOpenKeyEx',
'LPLLP', 'L')
>RegQueryValueEx = Win32API.new('advapi32',
'RegQueryValueEx', 'LPLPPP',
>'L')
>
>val = 'EventMessageFile'
>key =
>"SYSTEM\\CurrentControlSet\\Services\\EventLog\\Application\\SNDSrvc"
>hk = [0].pack('L')
>
>if RegOpenKeyEx.call(HKEY_LOCAL_MACHINE, key, 0, KEY_READ, hk) == 0
> hk = hk.unpack('L').first
> buf = 0.chr * 1024
> size = 0.chr * 4

should be
      size = [buf.length].pack('L')