# -*- Mode: Python; tab-width: 4 -*-

VERSION_STRING = "$Id: select_trigger.py 37659 2005-08-02 19:20:09Z tim_one $"

import asyncore
import asynchat

import os
import socket
import string
import thread
import errno

if os.name == 'posix':

    class trigger (asyncore.file_dispatcher):
    
        "Wake up a call to select() running in the main thread"
        
        # This is useful in a context where you are using Medusa's I/O
        # subsystem to deliver data, but the data is generated by another
        # thread.  Normally, if Medusa is in the middle of a call to
        # select(), new output data generated by another thread will have
        # to sit until the call to select() either times out or returns.
        # If the trigger is 'pulled' by another thread, it should immediately
        # generate a READ event on the trigger object, which will force the
        # select() invocation to return.
        
        # A common use for this facility: letting Medusa manage I/O for a
        # large number of connections; but routing each request through a
        # thread chosen from a fixed-size thread pool.  When a thread is
        # acquired, a transaction is performed, but output data is
        # accumulated into buffers that will be emptied more efficiently
        # by Medusa. [picture a server that can process database queries
        # rapidly, but doesn't want to tie up threads waiting to send data
        # to low-bandwidth connections]
        
        # The other major feature provided by this class is the ability to
        # move work back into the main thread: if you call pull_trigger()
        # with a thunk argument, when select() wakes up and receives the
        # event it will call your thunk from within that thread.  The main
        # purpose of this is to remove the need to wrap thread locks around
        # Medusa's data structures, which normally do not need them.  [To see
        # why this is true, imagine this scenario: A thread tries to push some
        # new data onto a channel's outgoing data queue at the same time that
        # the main thread is trying to remove some]
        
        def __init__ (self):
            r, w = os.pipe()
            self.trigger = w
            asyncore.file_dispatcher.__init__ (self, r)
            self.lock = thread.allocate_lock()
            self.thunks = []
            
        def __repr__ (self):
            return '<select-trigger (pipe) at %x>' % id(self)
            
        def readable (self):
            return 1
            
        def writable (self):
            return 0
            
        def handle_connect (self):
            pass
            
        def pull_trigger (self, thunk=None):
                # print 'PULL_TRIGGER: ', len(self.thunks)
            if thunk:
                try:
                    self.lock.acquire()
                    self.thunks.append (thunk)
                finally:
                    self.lock.release()
            os.write (self.trigger, 'x')
            
        def handle_read (self):
            self.recv (8192)
            try:
                self.lock.acquire()
                for thunk in self.thunks:
                    try:
                        thunk()
                    except:
                        (file, fun, line), t, v, tbinfo = asyncore.compact_traceback()
                        print 'exception in trigger thunk: (%s:%s %s)' % (t, v, tbinfo)
                self.thunks = []
            finally:
                self.lock.release()
                
else:


    # win32-safe version

    class BindError(Exception):
        pass

    class trigger(asyncore.dispatcher):
    
        def __init__ (self):
            # The __init__ code is taken from ZODB 3.4.1's
            # ZEO/zrpc/trigger.py, to worm around problems in the original
            # Windows __init__ code.

            # Get a pair of connected sockets.  The trigger is the 'w'
            # end of the pair, which is connected to 'r'.  'r' is put
            # in the asyncore socket map.  "pulling the trigger" then
            # means writing something on w, which will wake up r.

            w = socket.socket()
            # Disable buffering -- pulling the trigger sends 1 byte,
            # and we want that sent immediately, to wake up asyncore's
            # select() ASAP.
            w.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)

            count = 0
            while 1:
               count += 1
               # Bind to a local port; for efficiency, let the OS pick
               # a free port for us.
               # Unfortunately, stress tests showed that we may not
               # be able to connect to that port ("Address already in
               # use") despite that the OS picked it.  This appears
               # to be a race bug in the Windows socket implementation.
               # So we loop until a connect() succeeds (almost always
               # on the first try).  See the long thread at
               # http://mail.zope.org/pipermail/zope/2005-July/160433.html
               # for hideous details.
               a = socket.socket()
               a.bind(("127.0.0.1", 0))
               connect_address = a.getsockname()  # assigned (host, port) pair
               a.listen(1)
               try:
                   w.connect(connect_address)
                   break    # success
               except socket.error, detail:
                   if detail[0] != errno.WSAEADDRINUSE:
                       # "Address already in use" is the only error
                       # I've seen on two WinXP Pro SP2 boxes, under
                       # Pythons 2.3.5 and 2.4.1.
                       raise
                   # (10048, 'Address already in use')
                   # assert count <= 2 # never triggered in Tim's tests
                   if count >= 10:  # I've never seen it go above 2
                       a.close()
                       w.close()
                       raise BindError("Cannot bind trigger!")
                   # Close `a` and try again.  Note:  I originally put a short
                   # sleep() here, but it didn't appear to help or hurt.
                   a.close()

            r, addr = a.accept()  # r becomes asyncore's (self.)socket
            a.close()
            self.trigger = w
            asyncore.dispatcher.__init__ (self, r)

            self.lock = thread.allocate_lock()
            self.thunks = []
            self._trigger_connected = 0
            
        def __repr__(self):
            return '<select-trigger (loopback) at %x>' % id(self)
            
        def readable(self):
            return 1
            
        def writable(self):
            return 0
            
        def handle_connect(self):
            pass
            
        def pull_trigger(self, thunk=None):
            if thunk:
                try:
                    self.lock.acquire()
                    self.thunks.append (thunk)
                finally:
                    self.lock.release()
            self.trigger.send ('x')
            
        def handle_read(self):
            self.recv(8192)
            try:
                self.lock.acquire()
                for thunk in self.thunks:
                    try:
                        thunk()
                    except:
                        (file, fun, line), t, v, tbinfo = asyncore.compact_traceback()
                        print 'exception in trigger thunk: (%s:%s %s)' % (t, v, tbinfo)
                self.thunks = []
            finally:
                self.lock.release()
                
                
the_trigger = None

class trigger_file:

    "A 'triggered' file object"
    
    buffer_size = 4096
    
    def __init__ (self, parent):
        global the_trigger
        if the_trigger is None:
            the_trigger = trigger()
        self.parent = parent
        self.buffer = ''
        
    def write (self, data):
        self.buffer = self.buffer + data
        if len(self.buffer) > self.buffer_size:
            d, self.buffer = self.buffer, ''
            the_trigger.pull_trigger (
                    lambda d=d,p=self.parent: p.push (d)
                    )
            
    def writeline (self, line):
        self.write (line+'\r\n')
        
    def writelines (self, lines):
        self.write (
                string.joinfields (
                        lines,
                        '\r\n'
                        ) + '\r\n'
                )
        
    def flush (self):
        if self.buffer:
            d, self.buffer = self.buffer, ''
            the_trigger.pull_trigger (
                    lambda p=self.parent,d=d: p.push (d)
                    )
            
    def softspace (self, *args):
        pass
        
    def close (self):
            # in a derived class, you may want to call trigger_close() instead.
        self.flush()
        self.parent = None
        
    def trigger_close (self):
        d, self.buffer = self.buffer, ''
        p, self.parent = self.parent, None
        the_trigger.pull_trigger (
                lambda p=p,d=d: (p.push(d), p.close_when_done())
                )
        
if __name__ == '__main__':

    import time
    
    def thread_function (output_file, i, n):
        print 'entering thread_function'
        while n:
            time.sleep (5)
            output_file.write ('%2d.%2d %s\r\n' % (i, n, output_file))
            output_file.flush()
            n = n - 1
        output_file.close()
        print 'exiting thread_function'
        
    class thread_parent (asynchat.async_chat):
    
        def __init__ (self, conn, addr):
            self.addr = addr
            asynchat.async_chat.__init__ (self, conn)
            self.set_terminator ('\r\n')
            self.buffer = ''
            self.count = 0
            
        def collect_incoming_data (self, data):
            self.buffer = self.buffer + data
            
        def found_terminator (self):
            data, self.buffer = self.buffer, ''
            if not data:
                asyncore.close_all()
                print "done"
                return
            n = string.atoi (string.split (data)[0])
            tf = trigger_file (self)
            self.count = self.count + 1
            thread.start_new_thread (thread_function, (tf, self.count, n))
            
    class thread_server (asyncore.dispatcher):
    
        def __init__ (self, family=socket.AF_INET, address=('', 9003)):
            asyncore.dispatcher.__init__ (self)
            self.create_socket (family, socket.SOCK_STREAM)
            self.set_reuse_addr()
            self.bind (address)
            self.listen (5)
            
        def handle_accept (self):
            conn, addr = self.accept()
            tp = thread_parent (conn, addr)
            
    thread_server()
    #asyncore.loop(1.0, use_poll=1)
    try:
        asyncore.loop ()
    except:
        asyncore.close_all()
