view tests/revlog-formatv0.py @ 27475:a2e2a8fa5fd1

revlog: avoid string slice when decompressing u* chunks

Revlog chunks can be stored uncompressed. If the first byte of the
raw data is \0, we store the data as is. Else we prefix it with 'u'.

Before, we performed a string slice to strip out the 'u' prefix.
With this patch, we use a buffer to avoid an extra memory copy and
associated garbage collection overhead.

I was unable to verify any performance impact of this patch. For both
mozilla-central and the hg repos, the number of manifest revisions
with 'u' prefixes is very small - under 1%. So this change likely
isn't called enough to have an impact on manifest reading. However,
the reasoning behind this change is solid, so it should be safe.

#!/usr/bin/env python
# Copyright 2010 Intevation GmbH
# Author(s):
# Thomas Arendsen Hein <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

"""Create a Mercurial repository in revlog format 0

changeset:   0:a1ef0b125355
tag:         tip
user:        user
date:        Thu Jan 01 00:00:00 1970 +0000
files:       empty
description:
empty file
"""

import os, sys

files = [
    ('formatv0/.hg/00changelog.i',
     '000000000000004400000000000000000000000000000000000000'
     '000000000000000000000000000000000000000000000000000000'
     '0000a1ef0b125355d27765928be600cfe85784284ab3'),
    ('formatv0/.hg/00changelog.d',
     '756163613935613961356635353036303562366138343738336237'
     '61623536363738616436356635380a757365720a3020300a656d70'
     '74790a0a656d7074792066696c65'),
    ('formatv0/.hg/00manifest.i',
     '000000000000003000000000000000000000000000000000000000'
     '000000000000000000000000000000000000000000000000000000'
     '0000aca95a9a5f550605b6a84783b7ab56678ad65f58'),
    ('formatv0/.hg/00manifest.d',
     '75656d707479006238306465356431333837353835343163356630'
     '35323635616431343461623966613836643164620a'),
    ('formatv0/.hg/data/empty.i',
     '000000000000000000000000000000000000000000000000000000'
     '000000000000000000000000000000000000000000000000000000'
     '0000b80de5d138758541c5f05265ad144ab9fa86d1db'),
    ('formatv0/.hg/data/empty.d',
     ''),
]

def makedirs(name):
    """recursive directory creation"""
    parent = os.path.dirname(name)
    if parent:
        makedirs(parent)
    os.mkdir(name)

makedirs(os.path.join(*'formatv0/.hg/data'.split('/')))

for name, data in files:
    f = open(name, 'wb')
    f.write(data.decode('hex'))
    f.close()

sys.exit(0)