Handle from ThreadId, CreateToolhelp32Snapshot, THREADENTRY32

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3 total messages Started by Richard Kavanagh Thu, 11 Oct 2007 11:59

#1224

Author: Richard Kavanagh
Date: Thu, 11 Oct 2007 11:59

37 lines
2099 bytes

One of these days I might understand the Microsoft mind; but not at present.
 I use the following function to obtain ThreadId's of all running processes. 
I then wish to find out their cpu times using GetThreadTimes. However the 
'th32ThreadID' field of the THREADENTRY32 structure is not always the same 
32 bit value as the thread's handle, although it seems to be for the a 
process's main thread. Is there a way to retrieve the handle from this 
structure?
Rivhaed.

// global to function
std::vector<THREADENTRY32> vThread;

bool TProcInfo::GetThreadList()
{
 vThread.clear();
 HANDLE h = ::CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, 0);
 if(h != INVALID_HANDLE_VALUE)
 {
  THREADENTRY32 te;
  te.dwSize = sizeof(te);
  if(::Thread32First(h, &te))
  {
    do
   {
    if(te.dwSize >= FIELD_OFFSET(THREADENTRY32, th32OwnerProcessID) + 
sizeof(te.th32OwnerProcessID))
    {
     vThread.push_back(te);
    }
    te.dwSize = sizeof(te);
   } while(::Thread32Next(h, &te));
  }
  ::CloseHandle(h);
 }
 return h != INVALID_HANDLE_VALUE;
}

Re: Handle from ThreadId, CreateToolhelp32Snapshot, THREADENTRY32

#1226

Author: Remy Lebeau (TeamB)
Date: Thu, 11 Oct 2007 17:34

22 lines
1822 bytes

"Richard Kavanagh" <dd.foldhill[at]googlemail.com> wrote in message
news:470e1044$1@newsgroups.borland.com...

> However the 'th32ThreadID' field of the THREADENTRY32
> structure is not always the same 32 bit value as the thread's handle

It is not supposed to be.  A thread ID is not the same thing as a thread
handle.  The ID is just a unique number that is assigned to identify the
thread.  The handle points to the actual thread object itself.

> Is there a way to retrieve the handle from this structure?

On Windows 2000 and later, you can use OpenThread().  On older versions,
there is no direct way to get a thread handle from a thread ID and vice
versa.  Have a look at the following posting for more information:


http://groups.google.com/group/borland.public.delphi.winapi/msg/ed9350f2ffdd3432


Gambit

Re: Handle from ThreadId, CreateToolhelp32Snapshot, THREADENTRY32

#1227

Author: Richard Kavanagh
Date: Thu, 11 Oct 2007 18:31

13 lines
1559 bytes

> On Windows 2000 and later, you can use OpenThread().  On older versions,
> there is no direct way to get a thread handle from a thread ID and vice
> versa.  Have a look at the following posting for more information:
>
>
> http://groups.google.com/group/borland.public.delphi.winapi/msg/ed9350f2ffdd3432
>
> Gambit

Thank you Remy,
 OpenThread() is just what I need. Pity that the method shown in the link is 
so convoluted.
Richard

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