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

Guido van Rossum guido at python.org
Sat Mar 13 19:22:59 CET 2010

On Sat, Mar 13, 2010 at 9:24 AM, gregory dudek <dudek at cim.mcgill.ca> wrote:

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.

For which Python version is your new patch?

There are 2 key things being done:  1) concatenations string with string.join instead of '+'  (which is probably a minor issue)

This looks like superstition in the patch below -- there is no reason why "".join((a, b)) should be any faster than a+b. (The join trick is important when joining many strings, but for two it doesn't make a difference, both strings have to be copied at least once no matter what you try.)

 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.

This makes sense and is likely the reason your patch is faster.

You should really submit this to the bug tracker at bugs.python.org.

--- 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.

You're gonna need to submit a Python contributor agreement (http://www.python.org/psf/contrib/contrib-form/) if/when your patch gets accepted. Welcome to the club!

 """

@@ -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.rawqflush() +                    return while self.rawq: c = self.rawqgetchar() 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 rawqflush(self): +        """ Set the queue to empty status """ +        self.rawq = '' +        self.irawq = 0 def rawqgetchar(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 sockavail(self): """Test whether data is available on the socket."""

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-- --Guido van Rossum (python.org/~guido)

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