[Python-Dev] Patch to telnetlib.py (original) (raw)

gregory dudek dudek at cim.mcgill.ca
Sat Mar 13 18:24:27 CET 2010

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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."""

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