mercurial/httprangereader.py
author Matt Mackall <mpm@selenic.com>
Wed, 06 Jul 2005 22:20:12 -0800
changeset 635 85e2209d401c
parent 372 4b0f562c61f4
child 1559 59b3639df0a9
permissions -rw-r--r--
Protocol switch from using generators to stream-like objects. This allows the the pull side to precisely control how much data is read so that another encapsulation layer is not needed. An http client gets a response with a finite size. Because ssh clients need to keep the stream open, we must not read more data than is sent in a response. But due to the streaming nature of the changegroup scheme, only the piece that's parsing the data knows how far it's allowed to read. This means the generator scheme isn't fine-grained enough. Instead we need file-like objects with a read(x) method. This switches everything for push/pull over to using file-like objects rather than generators.
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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()