[ python-Bugs-1156259 ] [2.4 regression] seeking in codecs.reader broken

[SourceForge.net]

Bugs item #1156259, was opened at 2005-03-03 23:29
Message generated for change (Comment added) made by lemburg
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1156259&group_id=5470

Category: Extension Modules
Group: Python 2.4
Status: Open
Resolution: None
Priority: 7
Submitted By: Matthias Klose (doko)
Assigned to: Martin v. Löwis (loewis)
Summary: [2.4 regression] seeking in codecs.reader broken

Initial Comment:
[forwarded from
https://bugzilla.ubuntu.com/show_bug.cgi?id=6972 ]

This is a regression; the following script (call as
"scriptname some_textfile")
fails.
It is obvious that the file starts with a number of
random bytes from the
previous run.

Uncommenting the two #XXX lines makes the bug go away.
So does running it with
Python 2.3.5

import sys
import codecs
from random import random

data = codecs.getreader("utf-8")(open(sys.argv[1]))
df = data.read()
for t in range(30):
    #XXX data.seek(0,1)
    #XXX data.read()
    data.seek(0,0)
    dn=""
    for l in data:
        dn += l
        if random() < 0.1: break
    if not df.startswith(dn):
        print "OUCH",t
        print "BAD:", dn[0:100]
        print "GOOD:", df[0:100]
        sys.exit(1)

print "OK",len(df)
sys.exit(0)

----------------------------------------------------------------------

>Comment By: M.-A. Lemburg (lemburg)
Date: 2005-03-04 10:56

Message:
Logged In: YES 
user_id=38388

This is obviously related to the buffer logic that Walter added
to support .readline().

In order to fix the problem, a .seek() method must be
implemented
that resets the buffers whenever called (before asking the
stream
to seek to the specified stream position).

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1156259&group_id=5470