#  Copyright (c) 2007, Monju System Architects
#
#  Released under the Monju-Public copyright license:
#
#  Permission is hereby granted, free of charge, to any person or entity
#  obtaining a copy of this software and associated documentation files
#  (the "Software"), to deal in the Software without restriction,
#  including without limitation the rights to use, copy, modify, merge,
#  publish, distribute, sublicense, and/or sell copies and modifications
#  of the Software, and to permit persons to whom the Software is
#  furnished to do so, subject to the following conditions:
#
#  The above copyright notice and this permission notice shall be
#  included in all copies or substantial portions of published, sold, or
#  ownership-transferred versions of the Software. The notices are not
#  required for binary-only releases or binary-only derivatives of the
#  Software, or documentation provided with binary-only releases and
#  binary-only derivatives.
#
#  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
#  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
#  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
#  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
#  CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
#  TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
#  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.




import sys
import errno



_IS_WINDOWS = sys.platform.lower().startswith("win")



if _IS_WINDOWS:
	import msvcrt
	import win32pipe
	import win32file

else:
	import fcntl
	import os
	import select




#  readNonBlocking()
#
#  This function is useful for reading the pipes returned by starting a process,
#  so as to not block waiting on child processes to output data.
def readNonBlocking(pipe, maximumAmount=4000):
	""" Returns None when the pipe is closed.  Otherwise, returns the data read."""

	#  HANDLE WINDOWS...
	if _IS_WINDOWS:

		try:
			osfHandle = msvcrt.get_osfhandle(pipe.fileno())
			(ignore, amountAvailable, ignore) = win32pipe.PeekNamedPipe(osfHandle, 0)
			if amountAvailable == 0:
				if pipe.closed:
					return None
				return ""
			if maximumAmount > amountAvailable:
				maximumAmount = amountAvailable
			errrCode, data = win32file.ReadFile(osfHandle, maximumAmount, None)
			return data
		except ValueError:
			pipe.close()
			return None
		except Exception, exception:
			if exception[0] in (109, errno.ESHUTDOWN):
				pipe.close()
				return None
			raise

	#  HANDLE NON-WINDOWS.
	else:

		#  MAKE SURE WE ARE NON BLOCKING.
		try:
			flags = fcntl.fcntl(pipe, fcntl.F_GETFL)
		except ValueError, exception:
			if "closed" in str(exception):
				return None
		try:
			if not pipe.closed:
				fcntl.fcntl(pipe, fcntl.F_SETFL, flags | os.O_NONBLOCK)

			#  IF NOTHING IS READY, RETURN EMPTY STRING.
			if len(select.select([pipe], [], [], 0)[0]) == 0:
				return ""

			#  DO THE READ.
			data = pipe.read(maximumAmount)
			if len(data) == 0:
				return pipe.close()
			return data

		#  RETURN THE PIPE TO THE PREVIOUS FLAG STATE.
		finally:
			if not pipe.closed:
				fcntl.fcntl(pipe, fcntl.F_SETFL, flags)