yEnc implementation in Python, bit slow

Freddie oinkfreddie at oinkshlick.oinknet
Tue Aug 5 06:23:57 CEST 2003


Oren Tirosh <oren-py-l at hishome.net> wrote in
news:mailman.1060033689.18067.python-list at python.org: 

> Suggestions:
> 
> For the (x+42)%256 build a translation table and use str.translate.
> To encode characters as escape sequences use str.replace or re.sub.
> 
>     Oren

Aahh. I couldn't work out how to use translate() at 4am this morning, but I 
worked it out now :) This version is a whoooole lot faster, and actually 
meets the yEnc line splitting spec. Bonus!

$ python2.3 testyenc.py
yEncode1 407682 1.98
yEncode2 407707 0.18

I'm not sure how to use re.sub to escape the characters, I assume it would 
also be 4 seperate replaces? Also, it needs a slightly more random input 
string than 'a' * 400000, so here we go.


test = []
for i in xrange(256):
	test.append(chr(i))
teststr = ''.join(test*1562)


def yEncode2(data):
	trans = ''
	for i in range(256):
		trans += chr((i+42)%256)
	
	translated = data.translate(trans)
	
	# escape =, NUL, LF, CR
	for i in (61, 0, 10, 13):
		j = '=%c' % (i + 64)
		translated = translated.replace(chr(i), j)
	
	
	encoded = []
	n = 0
	for i in range(0, len(translated), 256):
		chunk = translated[n+i:n+i+256]
		if chunk[-1] == '=':
			chunk += translated[n+i+256+1]
			n += 1
		encoded.append(chunk)
		encoded.append('\n')
	
	result = ''.join(encoded)
	
	print len(result),
	return result

-- 
-----------------------------------------------------------
Remove the oinks!




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