Method: Process.get_affinity

Defined in:
lib/win32/process.rb

.get_affinity(int = Process.pid) ⇒ Object

Returns the process and system affinity mask for the given pid, or the current process if no pid is provided. The return value is a two element array, with the first containing the process affinity mask, and the second containing the system affinity mask. Both are decimal values.

A process affinity mask is a bit vector indicating the processors that a process is allowed to run on. A system affinity mask is a bit vector in which each bit represents the processors that are configured into a system.

Example:

# System has 4 processors, current process is allowed to run on all.
Process.get_affinity # => [[15], [15]], where '15' is 1 + 2 + 4 + 8

# System has 4 processors, current process only allowed on 1 and 4.
Process.get_affinity # => [[9], [15]]

If you want to convert a decimal bit vector into an array of 0’s and 1’s indicating the flag value of each processor, you can use something like this approach:

mask = Process.get_affinity.first
(0..mask).to_a.map{ |n| mask[n] }



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# File 'lib/win32/process.rb', line 51

def get_affinity(int = Process.pid)
  pmask = FFI::MemoryPointer.new(:ulong)
  smask = FFI::MemoryPointer.new(:ulong)

  if int == Process.pid
    unless GetProcessAffinityMask(GetCurrentProcess(), pmask, smask)
      raise SystemCallError, FFI.errno, "GetProcessAffinityMask"
    end
  else
    begin
      handle = OpenProcess(PROCESS_QUERY_INFORMATION, 0 , int)

      if handle == 0
        raise SystemCallError, FFI.errno, "OpenProcess"
      end

      unless GetProcessAffinityMask(handle, pmask, smask)
        raise SystemCallError, FFI.errno, "GetProcessAffinityMask"
      end
    ensure
      CloseHandle(handle)
    end
  end

  [pmask.read_ulong, smask.read_ulong]
end