Basic implementation of a multiplex protocol - client side only.

Currently the 'server' is just a pipe to run 'hd' (hexdump) for looking at
the client-side results.  Lame, but true.

ssnet.py

@@ -1,6 +1,17 @@
-import socket, errno, select
+import struct, socket, errno, select
 from helpers import *
 
+HDR_LEN = 8
+
+CMD_EXIT = 0x4200
+CMD_PING = 0x4201
+CMD_PONG = 0x4202
+CMD_CONNECT = 0x4203
+CMD_CLOSE = 0x4204
+CMD_EOF = 0x4205
+CMD_DATA = 0x4206
+
+
 def _nb_clean(func, *args):
     try:
         return func(*args)
@@ -34,29 +45,33 @@ class SockWrapper:
             log('%r: done writing\n' % self)
             self.shut_write = True
             self.sock.shutdown(socket.SHUT_WR)
+
+    def uwrite(self, buf):
+        self.sock.setblocking(False)
+        return _nb_clean(self.sock.send, buf)
         
     def write(self, buf):
         assert(buf)
-        self.sock.setblocking(False)
-        return _nb_clean(self.sock.send, buf)
+        return self.uwrite(buf)
 
-    def fill(self):
+    def uread(self):
         if self.shut_read:
             return
         self.sock.setblocking(False)
-        rb = _nb_clean(self.sock.recv, 65536)
+        return _nb_clean(self.sock.recv, 65536)
+
+    def fill(self):
+        if self.buf:
+            return
+        rb = self.uread()
         if rb:
             self.buf.append(rb)
         if rb == '':  # empty string means EOF; None means temporarily empty
             self.noread()
 
-    def maybe_fill(self):
-        if not self.buf:
-            self.fill()
-
     def copy_to(self, outwrap):
         if self.buf and self.buf[0]:
-            wrote = outwrap.sock.send(self.buf[0])
+            wrote = outwrap.write(self.buf[0])
             self.buf[0] = self.buf[0][wrote:]
         while self.buf and not self.buf[0]:
             self.buf.pop(0)
@@ -102,8 +117,8 @@ class Proxy(Handler):
             r.add(self.wrap2.sock)
 
     def callback(self):
-        self.wrap1.maybe_fill()
-        self.wrap2.maybe_fill()
+        self.wrap1.fill()
+        self.wrap2.fill()
         self.wrap1.copy_to(self.wrap2)
         self.wrap2.copy_to(self.wrap1)
         if (self.wrap1.shut_read and self.wrap2.shut_read and
@@ -111,3 +126,125 @@ class Proxy(Handler):
             self.ok = False
 
 
+class Mux(Handler):
+    def __init__(self, sock):
+        Handler.__init__(self, [sock])
+        self.sock = sock
+        self.channels = {}
+        self.chani = 0
+        self.want = 0
+        self.inbuf = ''
+        self.outbuf = []
+        self.send(0, CMD_PING, 'chicken')
+
+    def next_channel(self):
+        # channel 0 is special, so we never allocate it
+        for timeout in xrange(1024):
+            self.chani += 1
+            if self.chani > 65535:
+                self.chani = 1
+            if not self.channels.get(self.chani):
+                return self.chani
+            
+    def send(self, channel, cmd, data):
+        data = str(data)
+        assert(len(data) <= 65535)
+        p = struct.pack('!ccHHH', 'S', 'S', channel, cmd, len(data)) + data
+        self.outbuf.append(p)
+        log('Mux: send queue is %d/%d\n' 
+            % (len(self.outbuf), sum(len(b) for b in self.outbuf)))
+
+    def got_packet(self, channel, cmd, data):
+        log('--got-packet--\n')
+        if cmd == CMD_PING:
+            self.mux.send(0, CMD_PONG, data)
+        elif cmd == CMD_EXIT:
+            self.ok = False
+        else:
+            c = self.channels[channel]
+            c.got_packet(cmd, data)
+
+    def flush(self):
+        self.sock.setblocking(False)
+        if self.outbuf and self.outbuf[0]:
+            wrote = _nb_clean(self.sock.send, self.outbuf[0])
+            if wrote:
+                self.outbuf[0] = self.outbuf[0][wrote:]
+        while self.outbuf and not self.outbuf[0]:
+            self.outbuf.pop()
+
+    def fill(self):
+        self.sock.setblocking(False)
+        b = _nb_clean(self.sock.recv, 32768)
+        if b == '': # EOF
+            ok = False
+        if b:
+            self.inbuf += b
+
+    def handle(self):
+        log('inbuf is: %r\n' % self.inbuf)
+        if len(self.inbuf) >= (self.want or HDR_LEN):
+            (s1,s2,channel,cmd,datalen) = struct.unpack('!ccHHH',
+                                                        self.inbuf[:HDR_LEN])
+            assert(s1 == 'S')
+            assert(s2 == 'S')
+            self.want = datalen + HDR_LEN
+        if self.want and len(self.inbuf) >= self.want:
+            data = self.inbuf[HDR_LEN:self.want]
+            self.inbuf = self.inbuf[self.want:]
+            self.got_packet(channel, cmd, data)
+        else:
+            self.fill()
+
+    def pre_select(self, r, w, x):
+        if self.inbuf < (self.want or HDR_LEN):
+            r.add(self.sock)
+        if self.outbuf:
+            w.add(self.sock)
+
+    def callback(self):
+        (r,w,x) = select.select([self.sock], [self.sock], [], 0)
+        if self.sock in r:
+            self.handle()
+        if self.outbuf and self.sock in w:
+            self.flush()
+
+
+class MuxWrapper(SockWrapper):
+    def __init__(self, mux, channel):
+        SockWrapper.__init__(self, mux.sock)
+        self.mux = mux
+        self.channel = channel
+        self.mux.channels[channel] = self
+        log('Created MuxWrapper on channel %d\n' % channel)
+
+    def noread(self):
+        if not self.shut_read:
+            self.shut_read = True
+
+    def nowrite(self):
+        if not self.shut_write:
+            self.shut_write = True
+            self.mux.send(self.channel, CMD_EOF, '')
+
+    def uwrite(self, buf):
+        self.mux.send(self.channel, CMD_DATA, buf)
+        return len(buf)
+
+    def uread(self):
+        if self.shut_read:
+            return '' # EOF
+        else:
+            return None  # no data available right now
+
+    def got_packet(self, cmd, data):
+        if cmd == CMD_CLOSE:
+            self.noread()
+            self.nowrite()
+        elif cmd == CMD_EOF:
+            self.noread()
+        elif cmd == CMD_DATA:
+            self.buf.append(data)
+        else:
+            raise Exception('unknown command %d (%d bytes)' 
+                            % (cmd, len(data)))