I need to control the priorities of various longrunning jobs - some of which kick off threads with nonstandard priority settings which cause some to hog the cpu, others to get none - this Perl utility is intended to keep them running at uniform settings.
I have been given the source of a C program that adjusts thread priority. The relevant code :- 
    HANDLE         hProcessSnap = NULL; 
    BOOL           bRet      = FALSE; 
    THREADENTRY32  te32      = {0}; 
     
    //  Take a snapshot of all processes in the system. 

    hProcessSnap = CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, 0); 

    if (hProcessSnap == INVALID_HANDLE_VALUE) 
        return (FALSE); 
     
    //  Fill in the size of the structure before using it. 
    te32.dwSize = sizeof(THREADENTRY32); 

    // Get first process information
    Thread32First(hProcessSnap, &te32)

    // get the thread priority
    HANDLE hThread;
    hThread = OpenThread(THREAD_SET_INFORMATION|THREAD_QUERY_INFORMATI
+ON, FALSE, te32.th32ThreadID); 

    // set new priority class
    if (SetThreadPriority(hThread, threadPriority) != TRUE)
    {
        cerr << "SetThreadPriority() ";
        printError();
    }
    CloseHandle(hThread);

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I can't see why the last parameter to CreateToolhelp32Snapshot is 0, as that means current process Id, in this case Perl - I would have thought this should be PID of the process whose thread I want to change. ??
I converted the above to Perl calls to Win32::API as follows :- 
$pid = 952;
# 952 is a running job pid
use threads;
use threads::shared;
use Win32::API;
Win32::API->Import( 'Kernel32', q[ DWORD GetLastError( ) ] );
Win32::API->Import( 'Kernel32', 
     q[ HANDLE  CreateToolhelp32Snapshot( DWORD dwFlags,  DWORD th32Pr
+ocessID ) ] );
$hProcessSnap = CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, $pid);    
+  
print "hProcessSnap = $hProcessSnap \n";

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580 output, presumably an open handle to the snapshot 
Win32::API->Import( 'Kernel32', 
     q[ BOOL Thread32First(  HANDLE hSnapshot, THREADENTRY32 lpte)] );
$retcode = GetLastError();
print "import threadfirst error was $retcode \n";

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WARNING Unknown parameter type THREADENTRY32 ??
0 output, import OK ??
The following is my attempt to define the C THREADENTRY32 structure - not to sure about this. 
# typedef for THREADENTRY32
typedef Win32::API::Struct AA => qw{
   DWORD dwSize;
  DWORD cntUsage;
  DWORD th32ThreadID;
  DWORD th32OwnerProcessID;
  LONG tpBasePri;
  LONG tpDeltaPri;
  DWORD dwFlags;  
  };
my $Point = Win32::API::Struct->new( AA );
$Point->{dwSize} = 24;
##$size=Win32::API::Struct->sizeof(AA);
##always returns 0. ??

Thread32First($hProcessSnap, LPAA);
$retcode = GetLastError();
print "threadfirst error was $retcode \n";

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error code 24 is output, indicating incorrect command length.
Acording to the Win32::API::Struct Pod, LPAA is a pointer to AA generated automatically by Win32::API::Struct, but I don't think it's getting a correct address. Any Perl way to get the address of AA to pass to Thread32First ?
The rest of the Perl code will be :- 
Win32::API->Import( 'Kernel32', q[HANDLE OpenThread( DWORD dwDesiredAc
+cess, BOOL bInheritHandle, DWORD dwThreadId) ] );

$hThread = OpenThread(THREAD_SET_INFORMATION|THREAD_QUERY_INFORMATION,
                     FALSE, $point->{th32ThreadID});

Win32::API->Import( 'Kernel32', q[ BOOL SetThreadPriority( HANDLE hThr
+ead, int nPriority ) ] );

SetThreadPriority( hThread, $threadpriority );

[download]
But I'm stuck at Thread32First

In reply to Re^10: how to change process & thread priority on Win32 ? by rbutcher
in thread how to change process & thread priority on Win32 ? by rbutcher

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