'''
    Modern recipe for async subprocesses in Linux and Windows. Works in Python 3.3+.
    Written March 28, 2014 by Josiah Carlson
     
    Released into the public domain.
     
    From these two functions you can build buffered reads, writes, timeouts on
    reads or writes, readline, etc.
    '''
     
    import errno
    import os
    import subprocess
    import time
     
    if subprocess.mswindows:
        from _winapi import PeekNamedPipe, ReadFile, WriteFile
        from msvcrt import get_osfhandle
    else:
        import fcntl
        import select
     
    def read(sp, stderr=False):
        """
       Reads all available data from the provided subprocess.
     
       Pass stderr=True if you want to read from stderr.
       """
       
        pipe = sp.stderr if stderr else sp.stdout
        if pipe.closed:
            return b''
     
        flags = fcntl.fcntl(pipe, fcntl.F_GETFL)
        fcntl.fcntl(pipe, fcntl.F_SETFL, flags | os.O_NONBLOCK)
        ret = []
        try:
            while select.select([pipe], [], [], 0)[0]:
                ret.append(pipe.read(4096))
                if not ret[-1]:
                    break
            return b''.join(ret)
        finally:
            if not pipe.closed:
                fcntl.fcntl(pipe, fcntl.F_SETFL, flags)
     
    def write(sp, data):
        """
       Tries to write the data to the provided subprocess.
     
       Returns the number of bytes written.
       """
        if not select.select([], [sp.stdin], [], 0)[1]:
            return 0
     
        try:
            return os.write(sp.stdin.fileno(), data)
        except OSError as why:
            if why[0] == errno.EPIPE:
                return 0
            raise
     
    if subprocess.mswindows:
        def read(sp, stderr=False):
            """
           Reads all available data from the provided subprocess.
           
           Pass stderr=True if you want to read from stderr.
           """
            pipe = sp.stderr if stderr else sp.stdout
            if pipe.closed:
                return b''
     
            try:
                handle = get_osfhandle(pipe.fileno())
                avail = PeekNamedPipe(handle, 0)[0]
                if avail > 0:
                    return ReadFile(handle, avail)[0]
                return b''
            except ValueError:
                return b''
            except (subprocess.pywintypes.error, Exception) as why:
                if why[0] in (109, errno.ESHUTDOWN):
                    return b''
                raise
     
        def write(sp, data):
            """
           Tries to write the data to the provided subprocess.
     
           Returns the number of bytes written.
           """
            try:
                handle = get_osfhandle(sp.stdin.fileno())
                return WriteFile(handle, data)[0]
            except ValueError:
                return 0
            except (subprocess.pywintypes.error, Exception) as why:
                if why[0] in (109, errno.ESHUTDOWN):
                    return 0