Lib/asyncore.py

# -*- Mode: Python -*-
#   Id: asyncore.py,v 2.51 2000/09/07 22:29:26 rushing Exp
#   Author: Sam Rushing <rushing@nightmare.com>

# ======================================================================
# Copyright 1996 by Sam Rushing
#
#                         All Rights Reserved
#
# Permission to use, copy, modify, and distribute this software and
# its documentation for any purpose and without fee is hereby
# granted, provided that the above copyright notice appear in all
# copies and that both that copyright notice and this permission
# notice appear in supporting documentation, and that the name of Sam
# Rushing not be used in advertising or publicity pertaining to
# distribution of the software without specific, written prior
# permission.
#
# SAM RUSHING DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
# INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
# NO EVENT SHALL SAM RUSHING BE LIABLE FOR ANY SPECIAL, INDIRECT OR
# CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
# OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
# CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
# ======================================================================

"""Basic infrastructure for asynchronous socket service clients and servers.

There are only two ways to have a program on a single processor do "more
than one thing at a time".  Multi-threaded programming is the simplest and
most popular way to do it, but there is another very different technique,
that lets you have nearly all the advantages of multi-threading, without
actually using multiple threads. it's really only practical if your program
is largely I/O bound. If your program is CPU bound, then pre-emptive
scheduled threads are probably what you really need. Network servers are
rarely CPU-bound, however.

If your operating system supports the select() system call in its I/O
library (and nearly all do), then you can use it to juggle multiple
communication channels at once; doing other work while your I/O is taking
place in the "background."  Although this strategy can seem strange and
complex, especially at first, it is in many ways easier to understand and
control than multi-threaded programming. The module documented here solves
many of the difficult problems for you, making the task of building
sophisticated high-performance network servers and clients a snap.
"""

import exceptions
import select
import socket
import sys

import os
from errno import EALREADY, EINPROGRESS, EWOULDBLOCK, ECONNRESET, \
     ENOTCONN, ESHUTDOWN, EINTR, EISCONN

try:
    socket_map
except NameError:
    socket_map = {}

class ExitNow(exceptions.Exception):
    pass

def read(obj):
    try:
        obj.handle_read_event()
    except ExitNow:
        raise
    except:
        obj.handle_error()

def write(obj):
    try:
        obj.handle_write_event()
    except ExitNow:
        raise
    except:
        obj.handle_error()

def readwrite(obj, flags):
    try:
        if flags & select.POLLIN:
            obj.handle_read_event()
        if flags & select.POLLOUT:
            obj.handle_write_event()
    except ExitNow:
        raise
    except:
        obj.handle_error()

def poll (timeout=0.0, map=None):
    if map is None:
        map = socket_map
    if map:
        r = []; w = []; e = []
        for fd, obj in map.iteritems():
            if obj.readable():
                r.append(fd)
            if obj.writable():
                w.append(fd)
        try:
            r, w, e = select.select(r, w, e, timeout)
        except select.error, err:
            if err[0] != EINTR:
                raise

        for fd in r:
            obj = map.get(fd)
            if obj is None:
                continue
            read(obj)

        for fd in w:
            obj = map.get(fd)
            if obj is None:
                continue
            write(obj)

def poll2 (timeout=0.0, map=None):
    import poll
    if map is None:
        map=socket_map
    if timeout is not None:
        # timeout is in milliseconds
        timeout = int(timeout*1000)
    if map:
        l = []
        for fd, obj in map.iteritems():
            flags = 0
            if obj.readable():
                flags = poll.POLLIN
            if obj.writable():
                flags = flags | poll.POLLOUT
            if flags:
                l.append ((fd, flags))
        r = poll.poll (l, timeout)
        for fd, flags in r:
            obj = map.get(fd)
            if obj is None:
                continue
            readwrite(obj, flags)

def poll3 (timeout=0.0, map=None):
    # Use the poll() support added to the select module in Python 2.0
    if map is None:
        map=socket_map
    if timeout is not None:
        # timeout is in milliseconds
        timeout = int(timeout*1000)
    pollster = select.poll()
    if map:
        for fd, obj in map.iteritems():
            flags = 0
            if obj.readable():
                flags = select.POLLIN
            if obj.writable():
                flags = flags | select.POLLOUT
            if flags:
                pollster.register(fd, flags)
        try:
            r = pollster.poll (timeout)
        except select.error, err:
            if err[0] != EINTR:
                raise
            r = []
        for fd, flags in r:
            obj = map.get(fd)
            if obj is None:
                continue
            readwrite(obj, flags)

def loop (timeout=30.0, use_poll=0, map=None):
    if map is None:
        map = socket_map

    if use_poll:
        if hasattr (select, 'poll'):
            poll_fun = poll3
        else:
            poll_fun = poll2
    else:
        poll_fun = poll

    while map:
        poll_fun (timeout, map)

class dispatcher:
    debug = 0
    connected = 0
    accepting = 0
    closing = 0
    addr = None

    def __init__ (self, sock=None, map=None):
        if sock:
            self.set_socket (sock, map)
            # I think it should inherit this anyway
            self.socket.setblocking (0)
            self.connected = 1
            # XXX Does the constructor require that the socket passed
            # be connected?
            try:
                self.addr = sock.getpeername()
            except socket.error:
                # The addr isn't crucial
                pass
        else:
            self.socket = None

    def __repr__ (self):
        status = [self.__class__.__module__+"."+self.__class__.__name__]
        if self.accepting and self.addr:
            status.append ('listening')
        elif self.connected:
            status.append ('connected')
        if self.addr is not None:
            try:
                status.append ('%s:%d' % self.addr)
            except TypeError:
                status.append (repr(self.addr))
        return '<%s at %#x>' % (' '.join (status), id (self))

    def add_channel (self, map=None):
        #self.log_info ('adding channel %s' % self)
        if map is None:
            map=socket_map
        map [self._fileno] = self

    def del_channel (self, map=None):
        fd = self._fileno
        if map is None:
            map=socket_map
        if map.has_key (fd):
            #self.log_info ('closing channel %d:%s' % (fd, self))
            del map [fd]

    def create_socket (self, family, type):
        self.family_and_type = family, type
        self.socket = socket.socket (family, type)
        self.socket.setblocking(0)
        self._fileno = self.socket.fileno()
        self.add_channel()

    def set_socket (self, sock, map=None):
        self.socket = sock
##        self.__dict__['socket'] = sock
        self._fileno = sock.fileno()
        self.add_channel (map)

    def set_reuse_addr (self):
        # try to re-use a server port if possible
        try:
            self.socket.setsockopt (
                socket.SOL_SOCKET, socket.SO_REUSEADDR,
                self.socket.getsockopt (socket.SOL_SOCKET,
                                        socket.SO_REUSEADDR) | 1
                )
        except socket.error:
            pass

    # ==================================================
    # predicates for select()
    # these are used as filters for the lists of sockets
    # to pass to select().
    # ==================================================

    def readable (self):
        return True

    if os.name == 'mac':
        # The macintosh will select a listening socket for
        # write if you let it.  What might this mean?
        def writable (self):
            return not self.accepting
    else:
        def writable (self):
            return True

    # ==================================================
    # socket object methods.
    # ==================================================

    def listen (self, num):
        self.accepting = 1
        if os.name == 'nt' and num > 5:
            num = 1
        return self.socket.listen (num)

    def bind (self, addr):
        self.addr = addr
        return self.socket.bind (addr)

    def connect (self, address):
        self.connected = 0
        err = self.socket.connect_ex(address)
        if err in (EINPROGRESS, EALREADY, EWOULDBLOCK):
            return
        if err in (0, EISCONN):
            self.addr = address
            self.connected = 1
            self.handle_connect()
        else:
            raise socket.error, err

    def accept (self):
        # XXX can return either an address pair or None
        try:
            conn, addr = self.socket.accept()
            return conn, addr
        except socket.error, why:
            if why[0] == EWOULDBLOCK:
                pass
            else:
                raise socket.error, why

    def send (self, data):
        try:
            result = self.socket.send (data)
            return result
        except socket.error, why:
            if why[0] == EWOULDBLOCK:
                return 0
            else:
                raise socket.error, why
            return 0

    def recv (self, buffer_size):
        try:
            data = self.socket.recv (buffer_size)
            if not data:
                # a closed connection is indicated by signaling
                # a read condition, and having recv() return 0.
                self.handle_close()
                return ''
            else:
                return data
        except socket.error, why:
            # winsock sometimes throws ENOTCONN
            if why[0] in [ECONNRESET, ENOTCONN, ESHUTDOWN]:
                self.handle_close()
                return ''
            else:
                raise socket.error, why

    def close (self):
        self.del_channel()
        self.socket.close()

    # cheap inheritance, used to pass all other attribute
    # references to the underlying socket object.
    def __getattr__ (self, attr):
        return getattr (self.socket, attr)

    # log and log_info maybe overriden to provide more sophisitcated
    # logging and warning methods. In general, log is for 'hit' logging
    # and 'log_info' is for informational, warning and error logging.

    def log (self, message):
        sys.stderr.write ('log: %s\n' % str(message))

    def log_info (self, message, type='info'):
        if __debug__ or type != 'info':
            print '%s: %s' % (type, message)

    def handle_read_event (self):
        if self.accepting:
            # for an accepting socket, getting a read implies
            # that we are connected
            if not self.connected:
                self.connected = 1
            self.handle_accept()
        elif not self.connected:
            self.handle_connect()
            self.connected = 1
            self.handle_read()
        else:
            self.handle_read()

    def handle_write_event (self):
        # getting a write implies that we are connected
        if not self.connected:
            self.handle_connect()
            self.connected = 1
        self.handle_write()

    def handle_expt_event (self):
        self.handle_expt()

    def handle_error (self):
        nil, t, v, tbinfo = compact_traceback()

        # sometimes a user repr method will crash.
        try:
            self_repr = repr (self)
        except:
            self_repr = '<__repr__ (self) failed for object at %0x>' % id(self)

        self.log_info (
            'uncaptured python exception, closing channel %s (%s:%s %s)' % (
                self_repr,
                t,
                v,
                tbinfo
                ),
            'error'
            )
        self.close()

    def handle_expt (self):
        self.log_info ('unhandled exception', 'warning')

    def handle_read (self):
        self.log_info ('unhandled read event', 'warning')

    def handle_write (self):
        self.log_info ('unhandled write event', 'warning')

    def handle_connect (self):
        self.log_info ('unhandled connect event', 'warning')

    def handle_accept (self):
        self.log_info ('unhandled accept event', 'warning')

    def handle_close (self):
        self.log_info ('unhandled close event', 'warning')
        self.close()

# ---------------------------------------------------------------------------
# adds simple buffered output capability, useful for simple clients.
# [for more sophisticated usage use asynchat.async_chat]
# ---------------------------------------------------------------------------

class dispatcher_with_send (dispatcher):
    def __init__ (self, sock=None):
        dispatcher.__init__ (self, sock)
        self.out_buffer = ''

    def initiate_send (self):
        num_sent = 0
        num_sent = dispatcher.send (self, self.out_buffer[:512])
        self.out_buffer = self.out_buffer[num_sent:]

    def handle_write (self):
        self.initiate_send()

    def writable (self):
        return (not self.connected) or len(self.out_buffer)

    def send (self, data):
        if self.debug:
            self.log_info ('sending %s' % repr(data))
        self.out_buffer = self.out_buffer + data
        self.initiate_send()

# ---------------------------------------------------------------------------
# used for debugging.
# ---------------------------------------------------------------------------

def compact_traceback ():
    t,v,tb = sys.exc_info()
    tbinfo = []
    while 1:
        tbinfo.append ((
            tb.tb_frame.f_code.co_filename,
            tb.tb_frame.f_code.co_name,
            str(tb.tb_lineno)
            ))
        tb = tb.tb_next
        if not tb:
            break

    # just to be safe
    del tb

    file, function, line = tbinfo[-1]
    info = '[' + '] ['.join(map(lambda x: '|'.join(x), tbinfo)) + ']'
    return (file, function, line), t, v, info

def close_all (map=None):
    if map is None:
        map=socket_map
    for x in map.values():
        x.socket.close()
    map.clear()

# Asynchronous File I/O:
#
# After a little research (reading man pages on various unixen, and
# digging through the linux kernel), I've determined that select()
# isn't meant for doing doing asynchronous file i/o.
# Heartening, though - reading linux/mm/filemap.c shows that linux
# supports asynchronous read-ahead.  So _MOST_ of the time, the data
# will be sitting in memory for us already when we go to read it.
#
# What other OS's (besides NT) support async file i/o?  [VMS?]
#
# Regardless, this is useful for pipes, and stdin/stdout...

if os.name == 'posix':
    import fcntl

    class file_wrapper:
        # here we override just enough to make a file
        # look like a socket for the purposes of asyncore.
        def __init__ (self, fd):
            self.fd = fd

        def recv (self, *args):
            return os.read(self.fd, *args)

        def send (self, *args):
            return os.write(self.fd, *args)

        read = recv
        write = send

        def close (self):
            return os.close (self.fd)

        def fileno (self):
            return self.fd

    class file_dispatcher (dispatcher):
        def __init__ (self, fd):
            dispatcher.__init__ (self)
            self.connected = 1
            # set it to non-blocking mode
            flags = fcntl.fcntl (fd, fcntl.F_GETFL, 0)
            flags = flags | os.O_NONBLOCK
            fcntl.fcntl (fd, fcntl.F_SETFL, flags)
            self.set_file (fd)

        def set_file (self, fd):
            self._fileno = fd
            self.socket = file_wrapper (fd)
            self.add_channel()