view mercurial/node.py @ 26306:d157e1f18e3f

revset: speed up existence checks for ordered filtered sets

Previously, calling 'if foo:' on a ordered filtered set would start iterating in
whatever the current direction was and return if a value was available. If the
current direction was ascending, but the set had a fastdesc available, this
meant we did a lot more work than necessary.

If this was applied without my previous max/min fixes, it would improve max()
performance (this was my first attempt at fixing the issue). Since those
previous fixes went in though, this doesn't have a visible benefit in the
benchmarks, but it does seem clearly better than it was before so I think it
should still go in.

# node.py - basic nodeid manipulation for mercurial
#
# Copyright 2005, 2006 Matt Mackall <[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.

from __future__ import absolute_import

import binascii

nullrev = -1
nullid = "\0" * 20

# pseudo identifiers for working directory
# (they are experimental, so don't add too many dependencies on them)
wdirrev = 0x7fffffff
wdirid = "\xff" * 20

# This ugly style has a noticeable effect in manifest parsing
hex = binascii.hexlify
bin = binascii.unhexlify

def short(node):
    return hex(node[:6])