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# proto - Proto interface. {{{
#
# Copyright (C) 2008 Nicolas Schodet
#
# APBTeam:
#        Web: http://apbteam.org/
#      Email: team AT apbteam DOT org
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
#
# }}}
"""Proto interface module."""
import binascii, struct, select

START = 0
BANG = 1
CMD = 2
ARG = 3

class Proto:

    def __init__ (self, file, date, timeout, log = None):
        """Initialise and set file (serial port, pty, socket...), date
        function and timeout value.

        - file: open file connected to the slave device.
        - date: when called, should return the current time.
        - timeout: time after which retransmission is done.
        - log: if defined, will be called with a log string.

        """
        self.file = file
        self.date = date
        self.last_send = None
        self.timeout = timeout
        self.send_queue = [ ]
        self.state = START
        self.log = log
        self.handlers = { }

    def send (self, *frame):
        """Queue a frame to send."""
        if not self.send_queue:
            self.last_send = None
        self.send_queue.append (Frame (*frame))

    def read (self):
        """Read from file and receive frames."""
        for f in self.recv ():
            if self.log:
                self.log ('recv %s' % f)
            if self.send_queue and f == self.send_queue[0]:
                del self.send_queue[0]
                if self.send_queue:
                    self.send_head ()
            else:
                self.dispatch (f)

    def sync (self):
        """Send frames, return True if all is sent."""
        if self.send_queue and (self.last_send is None
                or self.last_send + self.timeout < self.date ()):
            self.send_head ()
        return not self.send_queue

    def wait (self, cond = None):
        """Wait forever or until cond () is True."""
        while not (self.sync () and cond is not None and cond ()):
            fds = select.select ((self,), (), (), self.timeout)[0]
            for i in fds:
                assert i is self
                i.read ()

    def register (self, command, fmt, handler):
        """Register a handler for the specified command and format.  The
        handler will receive decoded arguments."""
        key = (command, struct.calcsize ('!' + fmt))
        assert key not in self.handlers
        self.handlers[key] = (handler, fmt)

    def fileno (self):
        """Return file descriptor, for use with select."""
        return self.file.fileno ()

    def send_head (self):
        """Send first frame from the send queue."""
        if self.log:
            self.log ('send %s' % self.send_queue[0])
        self.file.write (self.send_queue[0].data ())
        self.last_send = self.date ()

    def recv (self):
        """Receive a frame, used as a generator."""
        for c in self.file.read (1):
            if c == '!':
                self.state = BANG
            else:
                if self.state == START:
                    pass
                elif self.state == BANG:
                    if c.isalpha ():
                        self.recv_command = c
                        self.recv_args = ''
                        self.state = CMD
                    else:
                        self.recv_error ()
                elif self.state == CMD:
                    if c == '\r' or c == '\n':
                        f = Frame (self.recv_command)
                        f.args = binascii.unhexlify (self.recv_args)
                        yield f
                    elif (c >= '0' and c <= '9') or (c >= 'a' and c <= 'f'):
                        self.recv_args += c
                        self.state = ARG
                    else:
                        self.recv_error ()
                else:
                    assert self.state == ARG
                    if (c >= '0' and c <= '9') or (c >= 'a' and c <= 'f'):
                        self.recv_args += c
                        self.state = CMD
                    else:
                        self.recv_error ()

    def recv_error (self):
        """Handle reception errors."""
        self.state = START
        if self.log:
            self.log ('error')
        # Resend now.
        if self.send_queue:
            self.send_head ()

    def dispatch (self, frame):
        """Pass a received frame to the correct handler."""
        key = (frame.command, len (frame.args))
        if key in self.handlers:
            h = self.handlers[key]
            h[0] (*(frame.decode (h[1])))

    def flush (self):
        """Drop any pending frames."""
        self.send_queue = [ ]

class Frame:

    def __init__ (self, command = None, fmt = '', *args):
        """Initiliase a frame.  If command is given, the frame is constructed
        using a struct.pack like fmt string."""
        if command:
            assert len (command) == 1 and command.isalpha ()
            self.command = command
            self.args = struct.pack ('!' + fmt, *args)
        else:
            self.command = None
            self.args = ''
    
    def data (self):
        """Get a frame representation ready to send."""
        return '!' + self.command + binascii.hexlify (self.args) + '\r'

    def decode (self, fmt):
        """Decode using a struct.unpack like fmt string."""
        return struct.unpack ('!' + fmt, self.args)

    def __eq__ (self, other):
        """Compare for equality."""
        return self.command == other.command and self.args == other.args

    def __str__ (self):
        """Convert to string."""
        return '!' + self.command + binascii.hexlify (self.args)