annotate mercurial/vfs.py @ 46149:294d5aca4ff5

copies: iterate over children directly (instead of parents)

Before this change we would gather all parent → child edges and iterate on
all parent, gathering copy information for children and aggregating them from
there.

They are not strict requirement for edges to be processed in that specific
order. We could also simply iterate over all "children" revision and aggregate
data from both parents at the same time. This patch does that.

It make various things simpler:

 * since both parents are processed at the same time, we no longer need to
   cache data for merge (see next changeset for details),

 * we no longer need nested loop to process data,

 * we no longer need to store partial merge data for a rev from distinct loop
   interaction to another when processing merges,

 * we no longer need to build a full parent -> children mapping (we only rely on
   a simpler "parent -> number of children" map (for memory efficiency),

 * the data access pattern is now simpler (from lower revisions to higher
   revisions) and entirely predicable. That predictability open the way to
   prefetching and parallel processing.

So that new iterations order requires simpler code and open the way to
interesting optimisation.

The effect on performance is quite good. In the worse case, we don't see any
significant negative impact. And in the best case, the reduction of roundtrip
to Python provide us with a significant speed. Some example below:

Repo            Case                                  Source-Rev   Dest-Rev      # of revisions  old time    new time      Difference    Factor    time per rev
---------------------------------------------------------------------------------------------------------------------------------------------------------------
mozilla-try     x00000_revs_x00000_added_0_copies     dc8a3ca7010e d16fde900c9c :  34414 revs,   0.962867 s,   0.502584 s,  -0.460283 s, × 0.5220,    14 µs/rev
mozilla-try     x0000_revs_xx000_added_x_copies       156f6e2674f2 4d0f2c178e66 :   8598 revs,   0.110717 s,   0.076323 s,  -0.034394 s, × 0.6894,     8 µs/rev



# full comparison between the previous changeset and this one

Repo            Case                                  Source-Rev   Dest-Rev      # of revisions  old time    new time      Difference    Factor    time per rev
---------------------------------------------------------------------------------------------------------------------------------------------------------------
mercurial       x_revs_x_added_0_copies               ad6b123de1c7 39cfcef4f463 :      1 revs,   0.000048 s,   0.000041 s,  -0.000007 s, × 0.8542,    41 µs/rev
mercurial       x_revs_x_added_x_copies               2b1c78674230 0c1d10351869 :      6 revs,   0.000153 s,   0.000102 s,  -0.000051 s, × 0.6667,    17 µs/rev
mercurial       x000_revs_x000_added_x_copies         81f8ff2a9bf2 dd3267698d84 :   1032 revs,   0.004209 s,   0.004254 s,  +0.000045 s, × 1.0107,     4 µs/rev
pypy            x_revs_x_added_0_copies               aed021ee8ae8 099ed31b181b :      9 revs,   0.000203 s,   0.000282 s,  +0.000079 s, × 1.3892,    31 µs/rev
pypy            x_revs_x000_added_0_copies            4aa4e1f8e19a 359343b9ac0e :      1 revs,   0.000059 s,   0.000048 s,  -0.000011 s, × 0.8136,    48 µs/rev
pypy            x_revs_x_added_x_copies               ac52eb7bbbb0 72e022663155 :      7 revs,   0.000194 s,   0.000211 s,  +0.000017 s, × 1.0876,    30 µs/rev
pypy            x_revs_x00_added_x_copies             c3b14617fbd7 ace7255d9a26 :      1 revs,   0.000380 s,   0.000375 s,  -0.000005 s, × 0.9868,   375 µs/rev
pypy            x_revs_x000_added_x000_copies         df6f7a526b60 a83dc6a2d56f :      6 revs,   0.010588 s,   0.010574 s,  -0.000014 s, × 0.9987,  1762 µs/rev
pypy            x000_revs_xx00_added_0_copies         89a76aede314 2f22446ff07e :   4785 revs,   0.048961 s,   0.049974 s,  +0.001013 s, × 1.0207,    10 µs/rev
pypy            x000_revs_x000_added_x_copies         8a3b5bfd266e 2c68e87c3efe :   6780 revs,   0.083612 s,   0.084300 s,  +0.000688 s, × 1.0082,    12 µs/rev
pypy            x000_revs_x000_added_x000_copies      89a76aede314 7b3dda341c84 :   5441 revs,   0.058579 s,   0.060128 s,  +0.001549 s, × 1.0264,    11 µs/rev
pypy            x0000_revs_x_added_0_copies           d1defd0dc478 c9cb1334cc78 :  43645 revs,   0.736783 s,   0.686542 s,  -0.050241 s, × 0.9318,    15 µs/rev
pypy            x0000_revs_xx000_added_0_copies       bf2c629d0071 4ffed77c095c :      2 revs,   0.022050 s,   0.009277 s,  -0.012773 s, × 0.4207,  4638 µs/rev
pypy            x0000_revs_xx000_added_x000_copies    08ea3258278e d9fa043f30c0 :  11316 revs,   0.120800 s,   0.114733 s,  -0.006067 s, × 0.9498,    10 µs/rev
netbeans        x_revs_x_added_0_copies               fb0955ffcbcd a01e9239f9e7 :      2 revs,   0.000140 s,   0.000081 s,  -0.000059 s, × 0.5786,    40 µs/rev
netbeans        x_revs_x000_added_0_copies            6f360122949f 20eb231cc7d0 :      2 revs,   0.000114 s,   0.000107 s,  -0.000007 s, × 0.9386,    53 µs/rev
netbeans        x_revs_x_added_x_copies               1ada3faf6fb6 5a39d12eecf4 :      3 revs,   0.000224 s,   0.000173 s,  -0.000051 s, × 0.7723,    57 µs/rev
netbeans        x_revs_x00_added_x_copies             35be93ba1e2c 9eec5e90c05f :      9 revs,   0.000723 s,   0.000698 s,  -0.000025 s, × 0.9654,    77 µs/rev
netbeans        x000_revs_xx00_added_0_copies         eac3045b4fdd 51d4ae7f1290 :   1421 revs,   0.009665 s,   0.009248 s,  -0.000417 s, × 0.9569,     6 µs/rev
netbeans        x000_revs_x000_added_x_copies         e2063d266acd 6081d72689dc :   1533 revs,   0.014820 s,   0.015446 s,  +0.000626 s, × 1.0422,    10 µs/rev
netbeans        x000_revs_x000_added_x000_copies      ff453e9fee32 411350406ec2 :   5750 revs,   0.076049 s,   0.074373 s,  -0.001676 s, × 0.9780,    12 µs/rev
netbeans        x0000_revs_xx000_added_x000_copies    588c2d1ced70 1aad62e59ddd :  66949 revs,   0.683603 s,   0.639870 s,  -0.043733 s, × 0.9360,     9 µs/rev
mozilla-central x_revs_x_added_0_copies               3697f962bb7b 7015fcdd43a2 :      2 revs,   0.000161 s,   0.000088 s,  -0.000073 s, × 0.5466,    44 µs/rev
mozilla-central x_revs_x000_added_0_copies            dd390860c6c9 40d0c5bed75d :      8 revs,   0.000234 s,   0.000199 s,  -0.000035 s, × 0.8504,    24 µs/rev
mozilla-central x_revs_x_added_x_copies               8d198483ae3b 14207ffc2b2f :      9 revs,   0.000247 s,   0.000171 s,  -0.000076 s, × 0.6923,    19 µs/rev
mozilla-central x_revs_x00_added_x_copies             98cbc58cc6bc 446a150332c3 :      7 revs,   0.000630 s,   0.000592 s,  -0.000038 s, × 0.9397,    84 µs/rev
mozilla-central x_revs_x000_added_x000_copies         3c684b4b8f68 0a5e72d1b479 :      3 revs,   0.003286 s,   0.003151 s,  -0.000135 s, × 0.9589,  1050 µs/rev
mozilla-central x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :      6 revs,   0.062441 s,   0.061612 s,  -0.000829 s, × 0.9867, 10268 µs/rev
mozilla-central x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   1593 revs,   0.005423 s,   0.005381 s,  -0.000042 s, × 0.9923,     3 µs/rev
mozilla-central x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :     41 revs,   0.005919 s,   0.003742 s,  -0.002177 s, × 0.6322,    91 µs/rev
mozilla-central x000_revs_x000_added_x000_copies      7c97034feb78 4407bd0c6330 :   7839 revs,   0.062597 s,   0.061983 s,  -0.000614 s, × 0.9902,     7 µs/rev
mozilla-central x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :    615 revs,   0.043551 s,   0.019861 s,  -0.023690 s, × 0.4560,    32 µs/rev
mozilla-central x0000_revs_xx000_added_x000_copies    f78c615a656c 96a38b690156 :  30263 revs,   0.192475 s,   0.188101 s,  -0.004374 s, × 0.9773,     6 µs/rev
mozilla-central x00000_revs_x0000_added_x0000_copies  6832ae71433c 4c222a1d9a00 : 153721 revs,   1.955575 s,   1.806696 s,  -0.148879 s, × 0.9239,    11 µs/rev
mozilla-central x00000_revs_x00000_added_x000_copies  76caed42cf7c 1daa622bbe42 : 204976 revs,   2.886501 s,   2.682987 s,  -0.203514 s, × 0.9295,    13 µs/rev
mozilla-try     x_revs_x_added_0_copies               aaf6dde0deb8 9790f499805a :      2 revs,   0.001181 s,   0.000852 s,  -0.000329 s, × 0.7214,   426 µs/rev
mozilla-try     x_revs_x000_added_0_copies            d8d0222927b4 5bb8ce8c7450 :      2 revs,   0.001189 s,   0.000859 s,  -0.000330 s, × 0.7225,   429 µs/rev
mozilla-try     x_revs_x_added_x_copies               092fcca11bdb 936255a0384a :      4 revs,   0.000563 s,   0.000150 s,  -0.000413 s, × 0.2664,    37 µs/rev
mozilla-try     x_revs_x00_added_x_copies             b53d2fadbdb5 017afae788ec :      2 revs,   0.001548 s,   0.001158 s,  -0.000390 s, × 0.7481,   579 µs/rev
mozilla-try     x_revs_x000_added_x000_copies         20408ad61ce5 6f0ee96e21ad :      1 revs,   0.027782 s,   0.027240 s,  -0.000542 s, × 0.9805, 27240 µs/rev
mozilla-try     x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :      6 revs,   0.062781 s,   0.062824 s,  +0.000043 s, × 1.0007, 10470 µs/rev
mozilla-try     x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   1593 revs,   0.005778 s,   0.005463 s,  -0.000315 s, × 0.9455,     3 µs/rev
mozilla-try     x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :     41 revs,   0.006192 s,   0.004238 s,  -0.001954 s, × 0.6844,   103 µs/rev
mozilla-try     x000_revs_x000_added_x000_copies      1346fd0130e4 4c65cbdabc1f :   6657 revs,   0.065391 s,   0.064113 s,  -0.001278 s, × 0.9805,     9 µs/rev
mozilla-try     x0000_revs_x_added_0_copies           63519bfd42ee a36a2a865d92 :  40314 revs,   0.317216 s,   0.294063 s,  -0.023153 s, × 0.9270,     7 µs/rev
mozilla-try     x0000_revs_x_added_x_copies           9fe69ff0762d bcabf2a78927 :  38690 revs,   0.303119 s,   0.281493 s,  -0.021626 s, × 0.9287,     7 µs/rev
mozilla-try     x0000_revs_xx000_added_x_copies       156f6e2674f2 4d0f2c178e66 :   8598 revs,   0.110717 s,   0.076323 s,  -0.034394 s, × 0.6894,     8 µs/rev
mozilla-try     x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :    615 revs,   0.045739 s,   0.020390 s,  -0.025349 s, × 0.4458,    33 µs/rev
mozilla-try     x0000_revs_xx000_added_x000_copies    89294cd501d9 7ccb2fc7ccb5 :  97052 revs,   3.098021 s,   3.023879 s,  -0.074142 s, × 0.9761,    31 µs/rev
mozilla-try     x0000_revs_x0000_added_x0000_copies   e928c65095ed e951f4ad123a :  52031 revs,   0.771480 s,   0.735549 s,  -0.035931 s, × 0.9534,    14 µs/rev
mozilla-try     x00000_revs_x_added_0_copies          6a320851d377 1ebb79acd503 : 363753 revs,  18.813422 s,  18.568900 s,  -0.244522 s, × 0.9870,    51 µs/rev
mozilla-try     x00000_revs_x00000_added_0_copies     dc8a3ca7010e d16fde900c9c :  34414 revs,   0.962867 s,   0.502584 s,  -0.460283 s, × 0.5220,    14 µs/rev
mozilla-try     x00000_revs_x_added_x_copies          5173c4b6f97c 95d83ee7242d : 362229 revs,  18.684923 s,  18.356645 s,  -0.328278 s, × 0.9824,    50 µs/rev
mozilla-try     x00000_revs_x000_added_x_copies       9126823d0e9c ca82787bb23c : 359344 revs,  18.296305 s,  18.250393 s,  -0.045912 s, × 0.9975,    50 µs/rev
mozilla-try     x00000_revs_x0000_added_x0000_copies  8d3fafa80d4b eb884023b810 : 192665 revs,   3.061887 s,   2.792459 s,  -0.269428 s, × 0.9120,    14 µs/rev
mozilla-try     x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 228985 revs, 103.869641 s, 107.697264 s,  +3.827623 s, × 1.0369,   470 µs/rev
mozilla-try     x00000_revs_x00000_added_x000_copies  9b2a99adc05e 8e29777b48e6 : 382065 revs,  64.262957 s,  63.961040 s,  -0.301917 s, × 0.9953,   167 µs/rev

Differential Revision: https://phab.mercurial-scm.org/D9422

# vfs.py - Mercurial 'vfs' classes
#
#  Copyright 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 contextlib
import errno
import os
import shutil
import stat
import threading

from .i18n import _
from .pycompat import (
    delattr,
    getattr,
    setattr,
)
from . import (
    encoding,
    error,
    pathutil,
    pycompat,
    util,
)


def _avoidambig(path, oldstat):
    """Avoid file stat ambiguity forcibly

    This function causes copying ``path`` file, if it is owned by
    another (see issue5418 and issue5584 for detail).
    """

    def checkandavoid():
        newstat = util.filestat.frompath(path)
        # return whether file stat ambiguity is (already) avoided
        return not newstat.isambig(oldstat) or newstat.avoidambig(path, oldstat)

    if not checkandavoid():
        # simply copy to change owner of path to get privilege to
        # advance mtime (see issue5418)
        util.rename(util.mktempcopy(path), path)
        checkandavoid()


class abstractvfs(object):
    """Abstract base class; cannot be instantiated"""

    def __init__(self, *args, **kwargs):
        '''Prevent instantiation; don't call this from subclasses.'''
        raise NotImplementedError('attempted instantiating ' + str(type(self)))

    def __call__(self, path, mode=b'rb', **kwargs):
        raise NotImplementedError

    def _auditpath(self, path, mode):
        raise NotImplementedError

    def join(self, path, *insidef):
        raise NotImplementedError

    def tryread(self, path):
        '''gracefully return an empty string for missing files'''
        try:
            return self.read(path)
        except IOError as inst:
            if inst.errno != errno.ENOENT:
                raise
        return b""

    def tryreadlines(self, path, mode=b'rb'):
        '''gracefully return an empty array for missing files'''
        try:
            return self.readlines(path, mode=mode)
        except IOError as inst:
            if inst.errno != errno.ENOENT:
                raise
        return []

    @util.propertycache
    def open(self):
        """Open ``path`` file, which is relative to vfs root.

        Newly created directories are marked as "not to be indexed by
        the content indexing service", if ``notindexed`` is specified
        for "write" mode access.
        """
        return self.__call__

    def read(self, path):
        with self(path, b'rb') as fp:
            return fp.read()

    def readlines(self, path, mode=b'rb'):
        with self(path, mode=mode) as fp:
            return fp.readlines()

    def write(self, path, data, backgroundclose=False, **kwargs):
        with self(path, b'wb', backgroundclose=backgroundclose, **kwargs) as fp:
            return fp.write(data)

    def writelines(self, path, data, mode=b'wb', notindexed=False):
        with self(path, mode=mode, notindexed=notindexed) as fp:
            return fp.writelines(data)

    def append(self, path, data):
        with self(path, b'ab') as fp:
            return fp.write(data)

    def basename(self, path):
        """return base element of a path (as os.path.basename would do)

        This exists to allow handling of strange encoding if needed."""
        return os.path.basename(path)

    def chmod(self, path, mode):
        return os.chmod(self.join(path), mode)

    def dirname(self, path):
        """return dirname element of a path (as os.path.dirname would do)

        This exists to allow handling of strange encoding if needed."""
        return os.path.dirname(path)

    def exists(self, path=None):
        return os.path.exists(self.join(path))

    def fstat(self, fp):
        return util.fstat(fp)

    def isdir(self, path=None):
        return os.path.isdir(self.join(path))

    def isfile(self, path=None):
        return os.path.isfile(self.join(path))

    def islink(self, path=None):
        return os.path.islink(self.join(path))

    def isfileorlink(self, path=None):
        """return whether path is a regular file or a symlink

        Unlike isfile, this doesn't follow symlinks."""
        try:
            st = self.lstat(path)
        except OSError:
            return False
        mode = st.st_mode
        return stat.S_ISREG(mode) or stat.S_ISLNK(mode)

    def reljoin(self, *paths):
        """join various elements of a path together (as os.path.join would do)

        The vfs base is not injected so that path stay relative. This exists
        to allow handling of strange encoding if needed."""
        return os.path.join(*paths)

    def split(self, path):
        """split top-most element of a path (as os.path.split would do)

        This exists to allow handling of strange encoding if needed."""
        return os.path.split(path)

    def lexists(self, path=None):
        return os.path.lexists(self.join(path))

    def lstat(self, path=None):
        return os.lstat(self.join(path))

    def listdir(self, path=None):
        return os.listdir(self.join(path))

    def makedir(self, path=None, notindexed=True):
        return util.makedir(self.join(path), notindexed)

    def makedirs(self, path=None, mode=None):
        return util.makedirs(self.join(path), mode)

    def makelock(self, info, path):
        return util.makelock(info, self.join(path))

    def mkdir(self, path=None):
        return os.mkdir(self.join(path))

    def mkstemp(self, suffix=b'', prefix=b'tmp', dir=None):
        fd, name = pycompat.mkstemp(
            suffix=suffix, prefix=prefix, dir=self.join(dir)
        )
        dname, fname = util.split(name)
        if dir:
            return fd, os.path.join(dir, fname)
        else:
            return fd, fname

    def readdir(self, path=None, stat=None, skip=None):
        return util.listdir(self.join(path), stat, skip)

    def readlock(self, path):
        return util.readlock(self.join(path))

    def rename(self, src, dst, checkambig=False):
        """Rename from src to dst

        checkambig argument is used with util.filestat, and is useful
        only if destination file is guarded by any lock
        (e.g. repo.lock or repo.wlock).

        To avoid file stat ambiguity forcibly, checkambig=True involves
        copying ``src`` file, if it is owned by another. Therefore, use
        checkambig=True only in limited cases (see also issue5418 and
        issue5584 for detail).
        """
        self._auditpath(dst, b'w')
        srcpath = self.join(src)
        dstpath = self.join(dst)
        oldstat = checkambig and util.filestat.frompath(dstpath)
        if oldstat and oldstat.stat:
            ret = util.rename(srcpath, dstpath)
            _avoidambig(dstpath, oldstat)
            return ret
        return util.rename(srcpath, dstpath)

    def readlink(self, path):
        return util.readlink(self.join(path))

    def removedirs(self, path=None):
        """Remove a leaf directory and all empty intermediate ones"""
        return util.removedirs(self.join(path))

    def rmdir(self, path=None):
        """Remove an empty directory."""
        return os.rmdir(self.join(path))

    def rmtree(self, path=None, ignore_errors=False, forcibly=False):
        """Remove a directory tree recursively

        If ``forcibly``, this tries to remove READ-ONLY files, too.
        """
        if forcibly:

            def onerror(function, path, excinfo):
                if function is not os.remove:
                    raise
                # read-only files cannot be unlinked under Windows
                s = os.stat(path)
                if (s.st_mode & stat.S_IWRITE) != 0:
                    raise
                os.chmod(path, stat.S_IMODE(s.st_mode) | stat.S_IWRITE)
                os.remove(path)

        else:
            onerror = None
        return shutil.rmtree(
            self.join(path), ignore_errors=ignore_errors, onerror=onerror
        )

    def setflags(self, path, l, x):
        return util.setflags(self.join(path), l, x)

    def stat(self, path=None):
        return os.stat(self.join(path))

    def unlink(self, path=None):
        return util.unlink(self.join(path))

    def tryunlink(self, path=None):
        """Attempt to remove a file, ignoring missing file errors."""
        util.tryunlink(self.join(path))

    def unlinkpath(self, path=None, ignoremissing=False, rmdir=True):
        return util.unlinkpath(
            self.join(path), ignoremissing=ignoremissing, rmdir=rmdir
        )

    def utime(self, path=None, t=None):
        return os.utime(self.join(path), t)

    def walk(self, path=None, onerror=None):
        """Yield (dirpath, dirs, files) tuple for each directories under path

        ``dirpath`` is relative one from the root of this vfs. This
        uses ``os.sep`` as path separator, even you specify POSIX
        style ``path``.

        "The root of this vfs" is represented as empty ``dirpath``.
        """
        root = os.path.normpath(self.join(None))
        # when dirpath == root, dirpath[prefixlen:] becomes empty
        # because len(dirpath) < prefixlen.
        prefixlen = len(pathutil.normasprefix(root))
        for dirpath, dirs, files in os.walk(self.join(path), onerror=onerror):
            yield (dirpath[prefixlen:], dirs, files)

    @contextlib.contextmanager
    def backgroundclosing(self, ui, expectedcount=-1):
        """Allow files to be closed asynchronously.

        When this context manager is active, ``backgroundclose`` can be passed
        to ``__call__``/``open`` to result in the file possibly being closed
        asynchronously, on a background thread.
        """
        # Sharing backgroundfilecloser between threads is complex and using
        # multiple instances puts us at risk of running out of file descriptors
        # only allow to use backgroundfilecloser when in main thread.
        if not isinstance(
            threading.currentThread(),
            threading._MainThread,  # pytype: disable=module-attr
        ):
            yield
            return
        vfs = getattr(self, 'vfs', self)
        if getattr(vfs, '_backgroundfilecloser', None):
            raise error.Abort(
                _(b'can only have 1 active background file closer')
            )

        with backgroundfilecloser(ui, expectedcount=expectedcount) as bfc:
            try:
                vfs._backgroundfilecloser = (
                    bfc  # pytype: disable=attribute-error
                )
                yield bfc
            finally:
                vfs._backgroundfilecloser = (
                    None  # pytype: disable=attribute-error
                )


class vfs(abstractvfs):
    """Operate files relative to a base directory

    This class is used to hide the details of COW semantics and
    remote file access from higher level code.

    'cacheaudited' should be enabled only if (a) vfs object is short-lived, or
    (b) the base directory is managed by hg and considered sort-of append-only.
    See pathutil.pathauditor() for details.
    """

    def __init__(
        self,
        base,
        audit=True,
        cacheaudited=False,
        expandpath=False,
        realpath=False,
    ):
        if expandpath:
            base = util.expandpath(base)
        if realpath:
            base = os.path.realpath(base)
        self.base = base
        self._audit = audit
        if audit:
            self.audit = pathutil.pathauditor(self.base, cached=cacheaudited)
        else:
            self.audit = lambda path, mode=None: True
        self.createmode = None
        self._trustnlink = None
        self.options = {}

    @util.propertycache
    def _cansymlink(self):
        return util.checklink(self.base)

    @util.propertycache
    def _chmod(self):
        return util.checkexec(self.base)

    def _fixfilemode(self, name):
        if self.createmode is None or not self._chmod:
            return
        os.chmod(name, self.createmode & 0o666)

    def _auditpath(self, path, mode):
        if self._audit:
            if os.path.isabs(path) and path.startswith(self.base):
                path = os.path.relpath(path, self.base)
            r = util.checkosfilename(path)
            if r:
                raise error.Abort(b"%s: %r" % (r, path))
            self.audit(path, mode=mode)

    def __call__(
        self,
        path,
        mode=b"r",
        atomictemp=False,
        notindexed=False,
        backgroundclose=False,
        checkambig=False,
        auditpath=True,
        makeparentdirs=True,
    ):
        """Open ``path`` file, which is relative to vfs root.

        By default, parent directories are created as needed. Newly created
        directories are marked as "not to be indexed by the content indexing
        service", if ``notindexed`` is specified for "write" mode access.
        Set ``makeparentdirs=False`` to not create directories implicitly.

        If ``backgroundclose`` is passed, the file may be closed asynchronously.
        It can only be used if the ``self.backgroundclosing()`` context manager
        is active. This should only be specified if the following criteria hold:

        1. There is a potential for writing thousands of files. Unless you
           are writing thousands of files, the performance benefits of
           asynchronously closing files is not realized.
        2. Files are opened exactly once for the ``backgroundclosing``
           active duration and are therefore free of race conditions between
           closing a file on a background thread and reopening it. (If the
           file were opened multiple times, there could be unflushed data
           because the original file handle hasn't been flushed/closed yet.)

        ``checkambig`` argument is passed to atomictempfile (valid
        only for writing), and is useful only if target file is
        guarded by any lock (e.g. repo.lock or repo.wlock).

        To avoid file stat ambiguity forcibly, checkambig=True involves
        copying ``path`` file opened in "append" mode (e.g. for
        truncation), if it is owned by another. Therefore, use
        combination of append mode and checkambig=True only in limited
        cases (see also issue5418 and issue5584 for detail).
        """
        if auditpath:
            self._auditpath(path, mode)
        f = self.join(path)

        if b"b" not in mode:
            mode += b"b"  # for that other OS

        nlink = -1
        if mode not in (b'r', b'rb'):
            dirname, basename = util.split(f)
            # If basename is empty, then the path is malformed because it points
            # to a directory. Let the posixfile() call below raise IOError.
            if basename:
                if atomictemp:
                    if makeparentdirs:
                        util.makedirs(dirname, self.createmode, notindexed)
                    return util.atomictempfile(
                        f, mode, self.createmode, checkambig=checkambig
                    )
                try:
                    if b'w' in mode:
                        util.unlink(f)
                        nlink = 0
                    else:
                        # nlinks() may behave differently for files on Windows
                        # shares if the file is open.
                        with util.posixfile(f):
                            nlink = util.nlinks(f)
                            if nlink < 1:
                                nlink = 2  # force mktempcopy (issue1922)
                except (OSError, IOError) as e:
                    if e.errno != errno.ENOENT:
                        raise
                    nlink = 0
                    if makeparentdirs:
                        util.makedirs(dirname, self.createmode, notindexed)
                if nlink > 0:
                    if self._trustnlink is None:
                        self._trustnlink = nlink > 1 or util.checknlink(f)
                    if nlink > 1 or not self._trustnlink:
                        util.rename(util.mktempcopy(f), f)
        fp = util.posixfile(f, mode)
        if nlink == 0:
            self._fixfilemode(f)

        if checkambig:
            if mode in (b'r', b'rb'):
                raise error.Abort(
                    _(
                        b'implementation error: mode %s is not'
                        b' valid for checkambig=True'
                    )
                    % mode
                )
            fp = checkambigatclosing(fp)

        if backgroundclose and isinstance(
            threading.currentThread(),
            threading._MainThread,  # pytype: disable=module-attr
        ):
            if (
                not self._backgroundfilecloser  # pytype: disable=attribute-error
            ):
                raise error.Abort(
                    _(
                        b'backgroundclose can only be used when a '
                        b'backgroundclosing context manager is active'
                    )
                )

            fp = delayclosedfile(
                fp,
                self._backgroundfilecloser,  # pytype: disable=attribute-error
            )

        return fp

    def symlink(self, src, dst):
        self.audit(dst)
        linkname = self.join(dst)
        util.tryunlink(linkname)

        util.makedirs(os.path.dirname(linkname), self.createmode)

        if self._cansymlink:
            try:
                os.symlink(src, linkname)
            except OSError as err:
                raise OSError(
                    err.errno,
                    _(b'could not symlink to %r: %s')
                    % (src, encoding.strtolocal(err.strerror)),
                    linkname,
                )
        else:
            self.write(dst, src)

    def join(self, path, *insidef):
        if path:
            return os.path.join(self.base, path, *insidef)
        else:
            return self.base


opener = vfs


class proxyvfs(abstractvfs):
    def __init__(self, vfs):
        self.vfs = vfs

    def _auditpath(self, path, mode):
        return self.vfs._auditpath(path, mode)

    @property
    def options(self):
        return self.vfs.options

    @options.setter
    def options(self, value):
        self.vfs.options = value


class filtervfs(proxyvfs, abstractvfs):
    '''Wrapper vfs for filtering filenames with a function.'''

    def __init__(self, vfs, filter):
        proxyvfs.__init__(self, vfs)
        self._filter = filter

    def __call__(self, path, *args, **kwargs):
        return self.vfs(self._filter(path), *args, **kwargs)

    def join(self, path, *insidef):
        if path:
            return self.vfs.join(self._filter(self.vfs.reljoin(path, *insidef)))
        else:
            return self.vfs.join(path)


filteropener = filtervfs


class readonlyvfs(proxyvfs):
    '''Wrapper vfs preventing any writing.'''

    def __init__(self, vfs):
        proxyvfs.__init__(self, vfs)

    def __call__(self, path, mode=b'r', *args, **kw):
        if mode not in (b'r', b'rb'):
            raise error.Abort(_(b'this vfs is read only'))
        return self.vfs(path, mode, *args, **kw)

    def join(self, path, *insidef):
        return self.vfs.join(path, *insidef)


class closewrapbase(object):
    """Base class of wrapper, which hooks closing

    Do not instantiate outside of the vfs layer.
    """

    def __init__(self, fh):
        object.__setattr__(self, '_origfh', fh)

    def __getattr__(self, attr):
        return getattr(self._origfh, attr)

    def __setattr__(self, attr, value):
        return setattr(self._origfh, attr, value)

    def __delattr__(self, attr):
        return delattr(self._origfh, attr)

    def __enter__(self):
        self._origfh.__enter__()
        return self

    def __exit__(self, exc_type, exc_value, exc_tb):
        raise NotImplementedError('attempted instantiating ' + str(type(self)))

    def close(self):
        raise NotImplementedError('attempted instantiating ' + str(type(self)))


class delayclosedfile(closewrapbase):
    """Proxy for a file object whose close is delayed.

    Do not instantiate outside of the vfs layer.
    """

    def __init__(self, fh, closer):
        super(delayclosedfile, self).__init__(fh)
        object.__setattr__(self, '_closer', closer)

    def __exit__(self, exc_type, exc_value, exc_tb):
        self._closer.close(self._origfh)

    def close(self):
        self._closer.close(self._origfh)


class backgroundfilecloser(object):
    """Coordinates background closing of file handles on multiple threads."""

    def __init__(self, ui, expectedcount=-1):
        self._running = False
        self._entered = False
        self._threads = []
        self._threadexception = None

        # Only Windows/NTFS has slow file closing. So only enable by default
        # on that platform. But allow to be enabled elsewhere for testing.
        defaultenabled = pycompat.iswindows
        enabled = ui.configbool(b'worker', b'backgroundclose', defaultenabled)

        if not enabled:
            return

        # There is overhead to starting and stopping the background threads.
        # Don't do background processing unless the file count is large enough
        # to justify it.
        minfilecount = ui.configint(b'worker', b'backgroundcloseminfilecount')
        # FUTURE dynamically start background threads after minfilecount closes.
        # (We don't currently have any callers that don't know their file count)
        if expectedcount > 0 and expectedcount < minfilecount:
            return

        maxqueue = ui.configint(b'worker', b'backgroundclosemaxqueue')
        threadcount = ui.configint(b'worker', b'backgroundclosethreadcount')

        ui.debug(
            b'starting %d threads for background file closing\n' % threadcount
        )

        self._queue = pycompat.queue.Queue(maxsize=maxqueue)
        self._running = True

        for i in range(threadcount):
            t = threading.Thread(target=self._worker, name='backgroundcloser')
            self._threads.append(t)
            t.start()

    def __enter__(self):
        self._entered = True
        return self

    def __exit__(self, exc_type, exc_value, exc_tb):
        self._running = False

        # Wait for threads to finish closing so open files don't linger for
        # longer than lifetime of context manager.
        for t in self._threads:
            t.join()

    def _worker(self):
        """Main routine for worker thread."""
        while True:
            try:
                fh = self._queue.get(block=True, timeout=0.100)
                # Need to catch or the thread will terminate and
                # we could orphan file descriptors.
                try:
                    fh.close()
                except Exception as e:
                    # Stash so can re-raise from main thread later.
                    self._threadexception = e
            except pycompat.queue.Empty:
                if not self._running:
                    break

    def close(self, fh):
        """Schedule a file for closing."""
        if not self._entered:
            raise error.Abort(
                _(b'can only call close() when context manager active')
            )

        # If a background thread encountered an exception, raise now so we fail
        # fast. Otherwise we may potentially go on for minutes until the error
        # is acted on.
        if self._threadexception:
            e = self._threadexception
            self._threadexception = None
            raise e

        # If we're not actively running, close synchronously.
        if not self._running:
            fh.close()
            return

        self._queue.put(fh, block=True, timeout=None)


class checkambigatclosing(closewrapbase):
    """Proxy for a file object, to avoid ambiguity of file stat

    See also util.filestat for detail about "ambiguity of file stat".

    This proxy is useful only if the target file is guarded by any
    lock (e.g. repo.lock or repo.wlock)

    Do not instantiate outside of the vfs layer.
    """

    def __init__(self, fh):
        super(checkambigatclosing, self).__init__(fh)
        object.__setattr__(self, '_oldstat', util.filestat.frompath(fh.name))

    def _checkambig(self):
        oldstat = self._oldstat
        if oldstat.stat:
            _avoidambig(self._origfh.name, oldstat)

    def __exit__(self, exc_type, exc_value, exc_tb):
        self._origfh.__exit__(exc_type, exc_value, exc_tb)
        self._checkambig()

    def close(self):
        self._origfh.close()
        self._checkambig()