Fix array overflow bug in bdiff I ran into a bug while importing a large repository into mercurial. The diff algorithm does not allocate a big enough array of hunks for some test cases. This results in memory corruption, and possibly, as in my case, a seg fault. You should be able to reproduce this problem with any case of more than a few lines that follows this pattern: a b = = 1 1 2 2 3 4 3 5 . 4 . . 5 . . . I.e., "a" has blank lines on every other line that have been removed in "b". In this case, the number of matching hunks is equal to the number of lines in "b". This is more than ((an + bn)/4 + 2). I'm not sure what motivates this formula, but when I changed it to the smaller of an or bn (+ 1), it works. [comment added by mpm]

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# httprangereader.py - just what it says

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#

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# Copyright 2005 Matt Mackall <mpm@selenic.com>

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#

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# This software may be used and distributed according to the terms

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# of the GNU General Public License, incorporated herein by reference.

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import byterange, urllib2

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class httprangereader:

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    def __init__(self, url):

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        self.url = url

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        self.pos = 0

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    def seek(self, pos):

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        self.pos = pos

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    def read(self, bytes=None):

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        opener = urllib2.build_opener(byterange.HTTPRangeHandler())

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        urllib2.install_opener(opener)

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        req = urllib2.Request(self.url)

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        end = ''

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        if bytes: end = self.pos + bytes

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        req.add_header('Range', 'bytes=%d-%s' % (self.pos, end))

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        f = urllib2.urlopen(req)

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        return f.read()