[Python-Dev] Patch to telnetlib.py

[gregory dudek]

The Telnet module telnetlib.py can be
very slow -- unusably slow -- for large automated data transfers.  There are typically done in raw mode.

The attached patch greatly increased the speed of telnet interactions in raw mode.  I submitted this a couple of year ago, but it was for an older branch of python.

There are 2 key things being done:
 1) concatenations string with string.join instead of '+'  (which is probably a minor issue)
 2) wholesale appending the raw and processed buffers when the IAC character is not found.  The should be examined
     carefully since I am not an expert in the Telnet protocol, but it seems to work very well giving me a 5x speedup.


--- installed/telnetlib.py	2010-02-02 22:57:58.000000000 -0500
+++ telnetlib.py	2010-03-13 12:17:02.000000000 -0500
@@ -30,6 +30,7 @@
 - timeout should be intrinsic to the connection object instead of an
   option on one of the read calls only
 
+Modified by G. Dudek for greater efficiency.
 """
 
 
@@ -420,6 +421,14 @@
         """
         buf = ['', '']
         try:
+            if self.rawq:
+                if not IAC in self.rawq:
+                    # speed hack, no IAC just grab whole queue. --Dudek
+                    buf[self.sb] = "".join((buf[self.sb] , self.rawq))
+                    self.cookedq = "".join((self.cookedq , buf[0] ))
+                    self.sbdataq = "".join((self.sbdataq , buf[1] ))
+                    self.rawq_flush()
+                    return
             while self.rawq:
                 c = self.rawq_getchar()
                 if not self.iacseq:
@@ -428,7 +437,7 @@
                     if c == "\021":
                         continue
                     if c != IAC:
-                        buf[self.sb] = buf[self.sb] + c
+                        buf[self.sb] = "".join((buf[self.sb] , c))
                         continue
                     else:
                         self.iacseq += c
@@ -480,8 +489,14 @@
             self.iacseq = '' # Reset on EOF
             self.sb = 0
             pass
-        self.cookedq = self.cookedq + buf[0]
-        self.sbdataq = self.sbdataq + buf[1]
+        self.cookedq = "".join((self.cookedq , buf[0] ))
+        self.sbdataq = "".join((self.sbdataq , buf[1] ))
+
+
+    def rawq_flush(self):
+        """ Set the queue to empty status """
+        self.rawq = ''
+        self.irawq = 0
 
     def rawq_getchar(self):
         """Get next char from raw queue.
@@ -516,7 +531,7 @@
         buf = self.sock.recv(50)
         self.msg("recv %r", buf)
         self.eof = (not buf)
-        self.rawq = self.rawq + buf
+        self.rawq = "".join((self.rawq,buf))
 
     def sock_avail(self):
         """Test whether data is available on the socket."""