FAQ
Hi,

I posted a while ago for some help with my word finder program, which is now
quite a lot faster than I could manage. Thanks to all who helped :)

This time, I've written a basic batch binary usenet poster in Python, but
encoding the data into yEnc format is fairly slow. Is it possible to improve
the routine any, WITHOUT using non-standard libraries? I don't want to have
to rely on something strange ;)

yEncode1 tends to be slightly faster here for me on my K6/2 500:

\$ python2.3 testyenc.py
yEncode1 401563 1.82
yEncode1 401563 1.83
yEncode2 401562 1.83
yEncode2 401562 1.83

Any help would be greatly appreciated :)

Freddie

import struct
import time
from zlib import crc32

def timing(f, n, a):
print f.__name__,
r = range(n)
t1 = time.clock()
for i in r:
#f(a); f(a); f(a); f(a); f(a); f(a); f(a); f(a); f(a); f(a)
f(a)
t2 = time.clock()
print round(t2-t1, 3)

def yEncSetup():
global YENC
YENC = [''] * 256

for I in range(256):
O = (I + 42) % 256
if O in (0, 10, 13, 61):
# Supposed to modulo 256, but err, why bother?
O += 64
YENC[I] = '=%c' % O
else:
YENC[I] = '%c' % O

def yEncode1(data):
global YENC
yenc = YENC

encoded = []
datalen = len(data)
n = 0
while n < datalen:
chunk = data[n:n+256]
n += len(chunk)
encoded.extend([yenc[ord(c)] for c in chunk])
encoded.append('\n')

print len(''.join(encoded)),

def yEncode2(data):
global YENC
yenc = YENC

lines = []
datalen = len(data)
n = 0

bits = divmod(datalen, 256)
format = '256s' * bits
parts = struct.unpack(format, data[:-bits])
for part in parts:
lines.append(''.join([yenc[ord(c)] for c in part]))

lines.append(''.join([yenc[ord(c)] for c in data[-bits:]]))
print len('\n'.join(lines) + '\n'),

yEncSetup()

teststr1 = 'a' * 400000
teststr2 = 'b' * 400000

for meth in (yEncode1, yEncode2):
timing(meth, 1, teststr1)
timing(meth, 1, teststr2)

--
Remove the oinks!

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