[Patches] [ python-Patches-895445 ] hmac.HMAC.copy() speedup

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Patches item #895445, was opened at 2004-02-12 00:28
Message generated for change (Comment added) made by tim_one
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Category: Library (Lib)
Group: Python 2.3
>Status: Closed
>Resolution: Accepted
Priority: 5
Submitted By: Trevor Perrin (trevp)
Assigned to: Nobody/Anonymous (nobody)
Summary: hmac.HMAC.copy() speedup

Initial Comment:

Hi,

I'm using python 2.3.2, on WinXP.  This is my first 
submitted patch, let me know if I'm doing anything 
wrong..

The current hmac.HMAC.copy() constructs a new 
instance first, then overwrites it.  The hmac._strxor() 
function called in the constructor is slow.  

HMAC is used in protocols like TLS & IPSEC where you 
want to MAC each packet or record sent, so you'd want 
to construct an HMAC object once, then copy() it for 
each record.  I'm writing a TLS implementation, and the 
patch here gives me ~30% increase in throughput.

Trevor






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>Comment By: Tim Peters (tim_one)
Date: 2004-03-20 15:24

Message:
Logged In: YES 
user_id=31435

It's a decent idea -- thanks!  The mechanics of the patch 
were fine.  It's not good to use None as a secret backdoor 
argument, since passing a computed None by mistake is a 
common program flaw, and getting back an insane HMAC 
object then is a poor outcome.  So the patch I checked in 
uses a different gimmick (a unique module-private object -- 
such a thing cannot be passed by mistake).

Lib/hmac.py; new revision: 1.8

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