posix: give checkexec a fast path; keep the check files and test read only
Before, Mercurial would create a new temporary file every time, stat it, change
its exec mode, stat it again, and delete it. Most of this dance was done to
handle the rare and not-so-essential case of VFAT mounts on unix. The cost of
that was paid by the much more common and important case of using normal file
systems.
Instead, try to create and preserve .hg/cache/checkisexec and
.hg/cache/checknoexec with and without exec flag set. If the files exist and
have correct exec flags set, we can conclude that that file system supports the
exec flag. Best case, the whole exec check can thus be done with two stat
calls. Worst case, we delete the wrong files and check as usual. That will be
because temporary loss of exec bit or on file systems without support for the
exec bit. In that case we check as we did before, with the additional overhead
of one extra stat call.
It is possible that this different test algorithm in some cases on odd file
systems will give different behaviour. Again, I think it will be rare and
special cases and I think it is worth the risk.
test-clone.t happens to show the situation where checkisexec is left behind
from the old style check, while checknoexec only will be created next time a
exec check will be performed.
# peer.py - repository base classes for mercurial
#
# Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
# Copyright 2006 Vadim Gelfer <vadim.gelfer@gmail.com>
#
# 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
from .i18n import _
from . import (
error,
util,
)
# abstract batching support
class future(object):
'''placeholder for a value to be set later'''
def set(self, value):
if util.safehasattr(self, 'value'):
raise error.RepoError("future is already set")
self.value = value
class batcher(object):
'''base class for batches of commands submittable in a single request
All methods invoked on instances of this class are simply queued and
return a a future for the result. Once you call submit(), all the queued
calls are performed and the results set in their respective futures.
'''
def __init__(self):
self.calls = []
def __getattr__(self, name):
def call(*args, **opts):
resref = future()
self.calls.append((name, args, opts, resref,))
return resref
return call
def submit(self):
raise NotImplementedError()
class iterbatcher(batcher):
def submit(self):
raise NotImplementedError()
def results(self):
raise NotImplementedError()
class localbatch(batcher):
'''performs the queued calls directly'''
def __init__(self, local):
batcher.__init__(self)
self.local = local
def submit(self):
for name, args, opts, resref in self.calls:
resref.set(getattr(self.local, name)(*args, **opts))
class localiterbatcher(iterbatcher):
def __init__(self, local):
super(iterbatcher, self).__init__()
self.local = local
def submit(self):
# submit for a local iter batcher is a noop
pass
def results(self):
for name, args, opts, resref in self.calls:
yield getattr(self.local, name)(*args, **opts)
def batchable(f):
'''annotation for batchable methods
Such methods must implement a coroutine as follows:
@batchable
def sample(self, one, two=None):
# Handle locally computable results first:
if not one:
yield "a local result", None
# Build list of encoded arguments suitable for your wire protocol:
encargs = [('one', encode(one),), ('two', encode(two),)]
# Create future for injection of encoded result:
encresref = future()
# Return encoded arguments and future:
yield encargs, encresref
# Assuming the future to be filled with the result from the batched
# request now. Decode it:
yield decode(encresref.value)
The decorator returns a function which wraps this coroutine as a plain
method, but adds the original method as an attribute called "batchable",
which is used by remotebatch to split the call into separate encoding and
decoding phases.
'''
def plain(*args, **opts):
batchable = f(*args, **opts)
encargsorres, encresref = next(batchable)
if not encresref:
return encargsorres # a local result in this case
self = args[0]
encresref.set(self._submitone(f.func_name, encargsorres))
return next(batchable)
setattr(plain, 'batchable', f)
return plain
class peerrepository(object):
def batch(self):
return localbatch(self)
def iterbatch(self):
"""Batch requests but allow iterating over the results.
This is to allow interleaving responses with things like
progress updates for clients.
"""
return localiterbatcher(self)
def capable(self, name):
'''tell whether repo supports named capability.
return False if not supported.
if boolean capability, return True.
if string capability, return string.'''
caps = self._capabilities()
if name in caps:
return True
name_eq = name + '='
for cap in caps:
if cap.startswith(name_eq):
return cap[len(name_eq):]
return False
def requirecap(self, name, purpose):
'''raise an exception if the given capability is not present'''
if not self.capable(name):
raise error.CapabilityError(
_('cannot %s; remote repository does not '
'support the %r capability') % (purpose, name))
def local(self):
'''return peer as a localrepo, or None'''
return None
def peer(self):
return self
def canpush(self):
return True
def close(self):
pass