view mercurial/store.py @ 48687:f8f2ecdde4b5

branchmap: skip obsolete revisions while computing heads

It's time to make this part of core Mercurial obsolescence-aware.

Not considering obsolete revisions when computing heads is clearly what
Mercurial should do. But there are a couple of small issues:

- Let's say tip of the repo is obsolete. There are two ways of finding tiprev
  for branchcache (both are in use): looking at input data for update() and
  looking at computed heads after update(). Previously, repo tip would be
  tiprev of the branchcache. With this patch, an obsolete revision can no
  longer be tiprev. And depending on what way we use for finding tiprev (input
  data vs computed heads) we'll get a different result. This is relevant when
  recomputing cache key from cache contents, and may lead to updating cache for
  obsolete revisions multiple times (not from scratch, because it still would
  be considered valid for a subset of revisions in the repo).

- If all commits on a branch are obsolete, the branchcache will include that
  branch, but the list of heads will be empty (that's why there's now `if not
  heads` when recomputing tiprev/tipnode from cache contents). Having an entry
  for every branch is currently required for notify extension (and
  test-notify.t to pass), because notify doesn't handle revsets in its
  subscription config very well and will throw an error if e.g. a branch
  doesn't exist.

- Cloning static HTTP repos may try to stat() a non-existent obsstore file. The
  issue is that we now care about obsolescence during clone, but statichttpvfs
  doesn't implement a stat method, so a regular vfs.stat() is used, and it
  assumes that file is local and calls os.stat().  During a clone, we're trying
  to stat() .hg/store/obsstore, but in static HTTP case we provide a literal
  URL to the obsstore file on the remote as if it were a local file path. On
  windows it actually results in a failure in test-static-http.t.

The first issue is going to be addressed in a series dedicated to making sure
branchcache is properly and timely written on disk (it wasn't perfect even
before this patch, but there aren't enough tests to demonstrate that). The
second issue will be addressed in a future patch for notify extension that will
make it not raise an exception if a branch doesn't exist. And the third one was
partially addressed in the previous patch in this series and will be properly
fixed in a future patch when this series is accepted.

filteredhash() grows a keyword argument to make sure that branchcache is also
invalidated when there are new obsolete revisions in its repo view. This way
the on-disk cache format is unchanged and compatible between versions (although
it will obviously be recomputed when switching versions before/after this patch
and the repo has obsolete revisions).

There's one test that uses plain `hg up` without arguments while updated to a
pruned commit. To make this test pass, simply return current working directory
parent. Later in this series this code will be replaced by what prune command
does: updating to the closest non-obsolete ancestor.

Test changes:

test-branch-change.t: update branch head and cache update message. The head of
default listed in hg heads is changed because revision 2 was rewritten as 7,
and 1 is the closest ancestor on the same branch, so it's the head of default
now.

The cache invalidation message appears now because of the cache hash change,
since we're now accounting for obsolete revisions. Here's some context:

"served.hidden" repo filter means everything is visible (no filtered
revisions), so before this series branch2-served.hidden file would not contain
any cache hash, only revnum and node. Now it also has a hash when there are
obsolete changesets in the repo. The command that the message appears for is
changing branch of 5 and 6, which are now obsolete, so the cache hash changes.

In general, when cache is simply out-of-date, it can be updated using the old
version as a base. But if cache hash differs, then the cache for that
particular repo filter is recomputed (at least with the current
implementation). This is what happens here.

test-obsmarker-template.t: the pull reports 2 heads changed, but after that the
repo correctly sees only 1. The new message could be better, but it's still an
improvement over the previous one where hg pull suggested merging with an
obsolete revision.

test-obsolete.t: we can see these revisions in hg log --hidden, but they
shouldn't be considered heads even with --hidden.

test-rebase-obsolete{,2}.t: there were new heads created previously after
making new orphan changesets, but they weren't detected. Now we are properly
detecting and reporting them.

test-rebase-obsolete4.t: there's only one head now because the other head is
pruned and was falsely reported before.

test-static-http.t: add obsstore to the list of requested files. This file
doesn't exist on the remotes, but clients want it anyway (they get 404). This
is fine, because there are other nonexistent files that clients request, like
.hg/bookmarks or .hg/cache/tags2-served.

Differential Revision: https://phab.mercurial-scm.org/D12097

# store.py - repository store handling for Mercurial
#
# Copyright 2008 Olivia 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 errno
import functools
import os
import re
import stat

from .i18n import _
from .pycompat import getattr
from .node import hex
from . import (
    changelog,
    error,
    manifest,
    policy,
    pycompat,
    util,
    vfs as vfsmod,
)
from .utils import hashutil

parsers = policy.importmod('parsers')
# how much bytes should be read from fncache in one read
# It is done to prevent loading large fncache files into memory
fncache_chunksize = 10 ** 6


def _matchtrackedpath(path, matcher):
    """parses a fncache entry and returns whether the entry is tracking a path
    matched by matcher or not.

    If matcher is None, returns True"""

    if matcher is None:
        return True
    path = decodedir(path)
    if path.startswith(b'data/'):
        return matcher(path[len(b'data/') : -len(b'.i')])
    elif path.startswith(b'meta/'):
        return matcher.visitdir(path[len(b'meta/') : -len(b'/00manifest.i')])

    raise error.ProgrammingError(b"cannot decode path %s" % path)


# This avoids a collision between a file named foo and a dir named
# foo.i or foo.d
def _encodedir(path):
    """
    >>> _encodedir(b'data/foo.i')
    'data/foo.i'
    >>> _encodedir(b'data/foo.i/bla.i')
    'data/foo.i.hg/bla.i'
    >>> _encodedir(b'data/foo.i.hg/bla.i')
    'data/foo.i.hg.hg/bla.i'
    >>> _encodedir(b'data/foo.i\\ndata/foo.i/bla.i\\ndata/foo.i.hg/bla.i\\n')
    'data/foo.i\\ndata/foo.i.hg/bla.i\\ndata/foo.i.hg.hg/bla.i\\n'
    """
    return (
        path.replace(b".hg/", b".hg.hg/")
        .replace(b".i/", b".i.hg/")
        .replace(b".d/", b".d.hg/")
    )


encodedir = getattr(parsers, 'encodedir', _encodedir)


def decodedir(path):
    """
    >>> decodedir(b'data/foo.i')
    'data/foo.i'
    >>> decodedir(b'data/foo.i.hg/bla.i')
    'data/foo.i/bla.i'
    >>> decodedir(b'data/foo.i.hg.hg/bla.i')
    'data/foo.i.hg/bla.i'
    """
    if b".hg/" not in path:
        return path
    return (
        path.replace(b".d.hg/", b".d/")
        .replace(b".i.hg/", b".i/")
        .replace(b".hg.hg/", b".hg/")
    )


def _reserved():
    """characters that are problematic for filesystems

    * ascii escapes (0..31)
    * ascii hi (126..255)
    * windows specials

    these characters will be escaped by encodefunctions
    """
    winreserved = [ord(x) for x in u'\\:*?"<>|']
    for x in range(32):
        yield x
    for x in range(126, 256):
        yield x
    for x in winreserved:
        yield x


def _buildencodefun():
    """
    >>> enc, dec = _buildencodefun()

    >>> enc(b'nothing/special.txt')
    'nothing/special.txt'
    >>> dec(b'nothing/special.txt')
    'nothing/special.txt'

    >>> enc(b'HELLO')
    '_h_e_l_l_o'
    >>> dec(b'_h_e_l_l_o')
    'HELLO'

    >>> enc(b'hello:world?')
    'hello~3aworld~3f'
    >>> dec(b'hello~3aworld~3f')
    'hello:world?'

    >>> enc(b'the\\x07quick\\xADshot')
    'the~07quick~adshot'
    >>> dec(b'the~07quick~adshot')
    'the\\x07quick\\xadshot'
    """
    e = b'_'
    xchr = pycompat.bytechr
    asciistr = list(map(xchr, range(127)))
    capitals = list(range(ord(b"A"), ord(b"Z") + 1))

    cmap = {x: x for x in asciistr}
    for x in _reserved():
        cmap[xchr(x)] = b"~%02x" % x
    for x in capitals + [ord(e)]:
        cmap[xchr(x)] = e + xchr(x).lower()

    dmap = {}
    for k, v in pycompat.iteritems(cmap):
        dmap[v] = k

    def decode(s):
        i = 0
        while i < len(s):
            for l in pycompat.xrange(1, 4):
                try:
                    yield dmap[s[i : i + l]]
                    i += l
                    break
                except KeyError:
                    pass
            else:
                raise KeyError

    return (
        lambda s: b''.join(
            [cmap[s[c : c + 1]] for c in pycompat.xrange(len(s))]
        ),
        lambda s: b''.join(list(decode(s))),
    )


_encodefname, _decodefname = _buildencodefun()


def encodefilename(s):
    """
    >>> encodefilename(b'foo.i/bar.d/bla.hg/hi:world?/HELLO')
    'foo.i.hg/bar.d.hg/bla.hg.hg/hi~3aworld~3f/_h_e_l_l_o'
    """
    return _encodefname(encodedir(s))


def decodefilename(s):
    """
    >>> decodefilename(b'foo.i.hg/bar.d.hg/bla.hg.hg/hi~3aworld~3f/_h_e_l_l_o')
    'foo.i/bar.d/bla.hg/hi:world?/HELLO'
    """
    return decodedir(_decodefname(s))


def _buildlowerencodefun():
    """
    >>> f = _buildlowerencodefun()
    >>> f(b'nothing/special.txt')
    'nothing/special.txt'
    >>> f(b'HELLO')
    'hello'
    >>> f(b'hello:world?')
    'hello~3aworld~3f'
    >>> f(b'the\\x07quick\\xADshot')
    'the~07quick~adshot'
    """
    xchr = pycompat.bytechr
    cmap = {xchr(x): xchr(x) for x in pycompat.xrange(127)}
    for x in _reserved():
        cmap[xchr(x)] = b"~%02x" % x
    for x in range(ord(b"A"), ord(b"Z") + 1):
        cmap[xchr(x)] = xchr(x).lower()

    def lowerencode(s):
        return b"".join([cmap[c] for c in pycompat.iterbytestr(s)])

    return lowerencode


lowerencode = getattr(parsers, 'lowerencode', None) or _buildlowerencodefun()

# Windows reserved names: con, prn, aux, nul, com1..com9, lpt1..lpt9
_winres3 = (b'aux', b'con', b'prn', b'nul')  # length 3
_winres4 = (b'com', b'lpt')  # length 4 (with trailing 1..9)


def _auxencode(path, dotencode):
    """
    Encodes filenames containing names reserved by Windows or which end in
    period or space. Does not touch other single reserved characters c.
    Specifically, c in '\\:*?"<>|' or ord(c) <= 31 are *not* encoded here.
    Additionally encodes space or period at the beginning, if dotencode is
    True. Parameter path is assumed to be all lowercase.
    A segment only needs encoding if a reserved name appears as a
    basename (e.g. "aux", "aux.foo"). A directory or file named "foo.aux"
    doesn't need encoding.

    >>> s = b'.foo/aux.txt/txt.aux/con/prn/nul/foo.'
    >>> _auxencode(s.split(b'/'), True)
    ['~2efoo', 'au~78.txt', 'txt.aux', 'co~6e', 'pr~6e', 'nu~6c', 'foo~2e']
    >>> s = b'.com1com2/lpt9.lpt4.lpt1/conprn/com0/lpt0/foo.'
    >>> _auxencode(s.split(b'/'), False)
    ['.com1com2', 'lp~749.lpt4.lpt1', 'conprn', 'com0', 'lpt0', 'foo~2e']
    >>> _auxencode([b'foo. '], True)
    ['foo.~20']
    >>> _auxencode([b' .foo'], True)
    ['~20.foo']
    """
    for i, n in enumerate(path):
        if not n:
            continue
        if dotencode and n[0] in b'. ':
            n = b"~%02x" % ord(n[0:1]) + n[1:]
            path[i] = n
        else:
            l = n.find(b'.')
            if l == -1:
                l = len(n)
            if (l == 3 and n[:3] in _winres3) or (
                l == 4
                and n[3:4] <= b'9'
                and n[3:4] >= b'1'
                and n[:3] in _winres4
            ):
                # encode third letter ('aux' -> 'au~78')
                ec = b"~%02x" % ord(n[2:3])
                n = n[0:2] + ec + n[3:]
                path[i] = n
        if n[-1] in b'. ':
            # encode last period or space ('foo...' -> 'foo..~2e')
            path[i] = n[:-1] + b"~%02x" % ord(n[-1:])
    return path


_maxstorepathlen = 120
_dirprefixlen = 8
_maxshortdirslen = 8 * (_dirprefixlen + 1) - 4


def _hashencode(path, dotencode):
    digest = hex(hashutil.sha1(path).digest())
    le = lowerencode(path[5:]).split(b'/')  # skips prefix 'data/' or 'meta/'
    parts = _auxencode(le, dotencode)
    basename = parts[-1]
    _root, ext = os.path.splitext(basename)
    sdirs = []
    sdirslen = 0
    for p in parts[:-1]:
        d = p[:_dirprefixlen]
        if d[-1] in b'. ':
            # Windows can't access dirs ending in period or space
            d = d[:-1] + b'_'
        if sdirslen == 0:
            t = len(d)
        else:
            t = sdirslen + 1 + len(d)
            if t > _maxshortdirslen:
                break
        sdirs.append(d)
        sdirslen = t
    dirs = b'/'.join(sdirs)
    if len(dirs) > 0:
        dirs += b'/'
    res = b'dh/' + dirs + digest + ext
    spaceleft = _maxstorepathlen - len(res)
    if spaceleft > 0:
        filler = basename[:spaceleft]
        res = b'dh/' + dirs + filler + digest + ext
    return res


def _hybridencode(path, dotencode):
    """encodes path with a length limit

    Encodes all paths that begin with 'data/', according to the following.

    Default encoding (reversible):

    Encodes all uppercase letters 'X' as '_x'. All reserved or illegal
    characters are encoded as '~xx', where xx is the two digit hex code
    of the character (see encodefilename).
    Relevant path components consisting of Windows reserved filenames are
    masked by encoding the third character ('aux' -> 'au~78', see _auxencode).

    Hashed encoding (not reversible):

    If the default-encoded path is longer than _maxstorepathlen, a
    non-reversible hybrid hashing of the path is done instead.
    This encoding uses up to _dirprefixlen characters of all directory
    levels of the lowerencoded path, but not more levels than can fit into
    _maxshortdirslen.
    Then follows the filler followed by the sha digest of the full path.
    The filler is the beginning of the basename of the lowerencoded path
    (the basename is everything after the last path separator). The filler
    is as long as possible, filling in characters from the basename until
    the encoded path has _maxstorepathlen characters (or all chars of the
    basename have been taken).
    The extension (e.g. '.i' or '.d') is preserved.

    The string 'data/' at the beginning is replaced with 'dh/', if the hashed
    encoding was used.
    """
    path = encodedir(path)
    ef = _encodefname(path).split(b'/')
    res = b'/'.join(_auxencode(ef, dotencode))
    if len(res) > _maxstorepathlen:
        res = _hashencode(path, dotencode)
    return res


def _pathencode(path):
    de = encodedir(path)
    if len(path) > _maxstorepathlen:
        return _hashencode(de, True)
    ef = _encodefname(de).split(b'/')
    res = b'/'.join(_auxencode(ef, True))
    if len(res) > _maxstorepathlen:
        return _hashencode(de, True)
    return res


_pathencode = getattr(parsers, 'pathencode', _pathencode)


def _plainhybridencode(f):
    return _hybridencode(f, False)


def _calcmode(vfs):
    try:
        # files in .hg/ will be created using this mode
        mode = vfs.stat().st_mode
        # avoid some useless chmods
        if (0o777 & ~util.umask) == (0o777 & mode):
            mode = None
    except OSError:
        mode = None
    return mode


_data = [
    b'bookmarks',
    b'narrowspec',
    b'data',
    b'meta',
    b'00manifest.d',
    b'00manifest.i',
    b'00changelog.d',
    b'00changelog.i',
    b'phaseroots',
    b'obsstore',
    b'requires',
]

REVLOG_FILES_MAIN_EXT = (b'.i', b'i.tmpcensored')
REVLOG_FILES_OTHER_EXT = (
    b'.idx',
    b'.d',
    b'.dat',
    b'.n',
    b'.nd',
    b'.sda',
    b'd.tmpcensored',
)
# files that are "volatile" and might change between listing and streaming
#
# note: the ".nd" file are nodemap data and won't "change" but they might be
# deleted.
REVLOG_FILES_VOLATILE_EXT = (b'.n', b'.nd')

# some exception to the above matching
#
# XXX This is currently not in use because of issue6542
EXCLUDED = re.compile(b'.*undo\.[^/]+\.(nd?|i)$')


def is_revlog(f, kind, st):
    if kind != stat.S_IFREG:
        return None
    return revlog_type(f)


def revlog_type(f):
    # XXX we need to filter `undo.` created by the transaction here, however
    # being naive about it also filter revlog for `undo.*` files, leading to
    # issue6542. So we no longer use EXCLUDED.
    if f.endswith(REVLOG_FILES_MAIN_EXT):
        return FILEFLAGS_REVLOG_MAIN
    elif f.endswith(REVLOG_FILES_OTHER_EXT):
        t = FILETYPE_FILELOG_OTHER
        if f.endswith(REVLOG_FILES_VOLATILE_EXT):
            t |= FILEFLAGS_VOLATILE
        return t
    return None


# the file is part of changelog data
FILEFLAGS_CHANGELOG = 1 << 13
# the file is part of manifest data
FILEFLAGS_MANIFESTLOG = 1 << 12
# the file is part of filelog data
FILEFLAGS_FILELOG = 1 << 11
# file that are not directly part of a revlog
FILEFLAGS_OTHER = 1 << 10

# the main entry point for a revlog
FILEFLAGS_REVLOG_MAIN = 1 << 1
# a secondary file for a revlog
FILEFLAGS_REVLOG_OTHER = 1 << 0

# files that are "volatile" and might change between listing and streaming
FILEFLAGS_VOLATILE = 1 << 20

FILETYPE_CHANGELOG_MAIN = FILEFLAGS_CHANGELOG | FILEFLAGS_REVLOG_MAIN
FILETYPE_CHANGELOG_OTHER = FILEFLAGS_CHANGELOG | FILEFLAGS_REVLOG_OTHER
FILETYPE_MANIFESTLOG_MAIN = FILEFLAGS_MANIFESTLOG | FILEFLAGS_REVLOG_MAIN
FILETYPE_MANIFESTLOG_OTHER = FILEFLAGS_MANIFESTLOG | FILEFLAGS_REVLOG_OTHER
FILETYPE_FILELOG_MAIN = FILEFLAGS_FILELOG | FILEFLAGS_REVLOG_MAIN
FILETYPE_FILELOG_OTHER = FILEFLAGS_FILELOG | FILEFLAGS_REVLOG_OTHER
FILETYPE_OTHER = FILEFLAGS_OTHER


class basicstore(object):
    '''base class for local repository stores'''

    def __init__(self, path, vfstype):
        vfs = vfstype(path)
        self.path = vfs.base
        self.createmode = _calcmode(vfs)
        vfs.createmode = self.createmode
        self.rawvfs = vfs
        self.vfs = vfsmod.filtervfs(vfs, encodedir)
        self.opener = self.vfs

    def join(self, f):
        return self.path + b'/' + encodedir(f)

    def _walk(self, relpath, recurse):
        '''yields (revlog_type, unencoded, size)'''
        path = self.path
        if relpath:
            path += b'/' + relpath
        striplen = len(self.path) + 1
        l = []
        if self.rawvfs.isdir(path):
            visit = [path]
            readdir = self.rawvfs.readdir
            while visit:
                p = visit.pop()
                for f, kind, st in readdir(p, stat=True):
                    fp = p + b'/' + f
                    rl_type = is_revlog(f, kind, st)
                    if rl_type is not None:
                        n = util.pconvert(fp[striplen:])
                        l.append((rl_type, decodedir(n), st.st_size))
                    elif kind == stat.S_IFDIR and recurse:
                        visit.append(fp)
        l.sort()
        return l

    def changelog(self, trypending, concurrencychecker=None):
        return changelog.changelog(
            self.vfs,
            trypending=trypending,
            concurrencychecker=concurrencychecker,
        )

    def manifestlog(self, repo, storenarrowmatch):
        rootstore = manifest.manifestrevlog(repo.nodeconstants, self.vfs)
        return manifest.manifestlog(self.vfs, repo, rootstore, storenarrowmatch)

    def datafiles(self, matcher=None, undecodable=None):
        """Like walk, but excluding the changelog and root manifest.

        When [undecodable] is None, revlogs names that can't be
        decoded cause an exception. When it is provided, it should
        be a list and the filenames that can't be decoded are added
        to it instead. This is very rarely needed."""
        files = self._walk(b'data', True) + self._walk(b'meta', True)
        for (t, u, s) in files:
            yield (FILEFLAGS_FILELOG | t, u, s)

    def topfiles(self):
        # yield manifest before changelog
        files = reversed(self._walk(b'', False))
        for (t, u, s) in files:
            if u.startswith(b'00changelog'):
                yield (FILEFLAGS_CHANGELOG | t, u, s)
            elif u.startswith(b'00manifest'):
                yield (FILEFLAGS_MANIFESTLOG | t, u, s)
            else:
                yield (FILETYPE_OTHER | t, u, s)

    def walk(self, matcher=None):
        """return file related to data storage (ie: revlogs)

        yields (file_type, unencoded, size)

        if a matcher is passed, storage files of only those tracked paths
        are passed with matches the matcher
        """
        # yield data files first
        for x in self.datafiles(matcher):
            yield x
        for x in self.topfiles():
            yield x

    def copylist(self):
        return _data

    def write(self, tr):
        pass

    def invalidatecaches(self):
        pass

    def markremoved(self, fn):
        pass

    def __contains__(self, path):
        '''Checks if the store contains path'''
        path = b"/".join((b"data", path))
        # file?
        if self.vfs.exists(path + b".i"):
            return True
        # dir?
        if not path.endswith(b"/"):
            path = path + b"/"
        return self.vfs.exists(path)


class encodedstore(basicstore):
    def __init__(self, path, vfstype):
        vfs = vfstype(path + b'/store')
        self.path = vfs.base
        self.createmode = _calcmode(vfs)
        vfs.createmode = self.createmode
        self.rawvfs = vfs
        self.vfs = vfsmod.filtervfs(vfs, encodefilename)
        self.opener = self.vfs

    # note: topfiles would also need a decode phase. It is just that in
    # practice we do not have any file outside of `data/` that needs encoding.
    # However that might change so we should probably add a test and encoding
    # decoding for it too. see issue6548

    def datafiles(self, matcher=None, undecodable=None):
        for t, f1, size in super(encodedstore, self).datafiles():
            try:
                f2 = decodefilename(f1)
            except KeyError:
                if undecodable is None:
                    msg = _(b'undecodable revlog name %s') % f1
                    raise error.StorageError(msg)
                else:
                    undecodable.append(f1)
                    continue
            if not _matchtrackedpath(f2, matcher):
                continue
            yield t, f2, size

    def join(self, f):
        return self.path + b'/' + encodefilename(f)

    def copylist(self):
        return [b'requires', b'00changelog.i'] + [b'store/' + f for f in _data]


class fncache(object):
    # the filename used to be partially encoded
    # hence the encodedir/decodedir dance
    def __init__(self, vfs):
        self.vfs = vfs
        self.entries = None
        self._dirty = False
        # set of new additions to fncache
        self.addls = set()

    def ensureloaded(self, warn=None):
        """read the fncache file if not already read.

        If the file on disk is corrupted, raise. If warn is provided,
        warn and keep going instead."""
        if self.entries is None:
            self._load(warn)

    def _load(self, warn=None):
        '''fill the entries from the fncache file'''
        self._dirty = False
        try:
            fp = self.vfs(b'fncache', mode=b'rb')
        except IOError:
            # skip nonexistent file
            self.entries = set()
            return

        self.entries = set()
        chunk = b''
        for c in iter(functools.partial(fp.read, fncache_chunksize), b''):
            chunk += c
            try:
                p = chunk.rindex(b'\n')
                self.entries.update(decodedir(chunk[: p + 1]).splitlines())
                chunk = chunk[p + 1 :]
            except ValueError:
                # substring '\n' not found, maybe the entry is bigger than the
                # chunksize, so let's keep iterating
                pass

        if chunk:
            msg = _(b"fncache does not ends with a newline")
            if warn:
                warn(msg + b'\n')
            else:
                raise error.Abort(
                    msg,
                    hint=_(
                        b"use 'hg debugrebuildfncache' to "
                        b"rebuild the fncache"
                    ),
                )
        self._checkentries(fp, warn)
        fp.close()

    def _checkentries(self, fp, warn):
        """make sure there is no empty string in entries"""
        if b'' in self.entries:
            fp.seek(0)
            for n, line in enumerate(util.iterfile(fp)):
                if not line.rstrip(b'\n'):
                    t = _(b'invalid entry in fncache, line %d') % (n + 1)
                    if warn:
                        warn(t + b'\n')
                    else:
                        raise error.Abort(t)

    def write(self, tr):
        if self._dirty:
            assert self.entries is not None
            self.entries = self.entries | self.addls
            self.addls = set()
            tr.addbackup(b'fncache')
            fp = self.vfs(b'fncache', mode=b'wb', atomictemp=True)
            if self.entries:
                fp.write(encodedir(b'\n'.join(self.entries) + b'\n'))
            fp.close()
            self._dirty = False
        if self.addls:
            # if we have just new entries, let's append them to the fncache
            tr.addbackup(b'fncache')
            fp = self.vfs(b'fncache', mode=b'ab', atomictemp=True)
            if self.addls:
                fp.write(encodedir(b'\n'.join(self.addls) + b'\n'))
            fp.close()
            self.entries = None
            self.addls = set()

    def add(self, fn):
        if self.entries is None:
            self._load()
        if fn not in self.entries:
            self.addls.add(fn)

    def remove(self, fn):
        if self.entries is None:
            self._load()
        if fn in self.addls:
            self.addls.remove(fn)
            return
        try:
            self.entries.remove(fn)
            self._dirty = True
        except KeyError:
            pass

    def __contains__(self, fn):
        if fn in self.addls:
            return True
        if self.entries is None:
            self._load()
        return fn in self.entries

    def __iter__(self):
        if self.entries is None:
            self._load()
        return iter(self.entries | self.addls)


class _fncachevfs(vfsmod.proxyvfs):
    def __init__(self, vfs, fnc, encode):
        vfsmod.proxyvfs.__init__(self, vfs)
        self.fncache = fnc
        self.encode = encode

    def __call__(self, path, mode=b'r', *args, **kw):
        encoded = self.encode(path)
        if mode not in (b'r', b'rb') and (
            path.startswith(b'data/') or path.startswith(b'meta/')
        ):
            # do not trigger a fncache load when adding a file that already is
            # known to exist.
            notload = self.fncache.entries is None and self.vfs.exists(encoded)
            if notload and b'r+' in mode and not self.vfs.stat(encoded).st_size:
                # when appending to an existing file, if the file has size zero,
                # it should be considered as missing. Such zero-size files are
                # the result of truncation when a transaction is aborted.
                notload = False
            if not notload:
                self.fncache.add(path)
        return self.vfs(encoded, mode, *args, **kw)

    def join(self, path):
        if path:
            return self.vfs.join(self.encode(path))
        else:
            return self.vfs.join(path)

    def register_file(self, path):
        """generic hook point to lets fncache steer its stew"""
        if path.startswith(b'data/') or path.startswith(b'meta/'):
            self.fncache.add(path)


class fncachestore(basicstore):
    def __init__(self, path, vfstype, dotencode):
        if dotencode:
            encode = _pathencode
        else:
            encode = _plainhybridencode
        self.encode = encode
        vfs = vfstype(path + b'/store')
        self.path = vfs.base
        self.pathsep = self.path + b'/'
        self.createmode = _calcmode(vfs)
        vfs.createmode = self.createmode
        self.rawvfs = vfs
        fnc = fncache(vfs)
        self.fncache = fnc
        self.vfs = _fncachevfs(vfs, fnc, encode)
        self.opener = self.vfs

    def join(self, f):
        return self.pathsep + self.encode(f)

    def getsize(self, path):
        return self.rawvfs.stat(path).st_size

    def datafiles(self, matcher=None, undecodable=None):
        for f in sorted(self.fncache):
            if not _matchtrackedpath(f, matcher):
                continue
            ef = self.encode(f)
            try:
                t = revlog_type(f)
                assert t is not None, f
                t |= FILEFLAGS_FILELOG
                yield t, f, self.getsize(ef)
            except OSError as err:
                if err.errno != errno.ENOENT:
                    raise

    def copylist(self):
        d = (
            b'bookmarks',
            b'narrowspec',
            b'data',
            b'meta',
            b'dh',
            b'fncache',
            b'phaseroots',
            b'obsstore',
            b'00manifest.d',
            b'00manifest.i',
            b'00changelog.d',
            b'00changelog.i',
            b'requires',
        )
        return [b'requires', b'00changelog.i'] + [b'store/' + f for f in d]

    def write(self, tr):
        self.fncache.write(tr)

    def invalidatecaches(self):
        self.fncache.entries = None
        self.fncache.addls = set()

    def markremoved(self, fn):
        self.fncache.remove(fn)

    def _exists(self, f):
        ef = self.encode(f)
        try:
            self.getsize(ef)
            return True
        except OSError as err:
            if err.errno != errno.ENOENT:
                raise
            # nonexistent entry
            return False

    def __contains__(self, path):
        '''Checks if the store contains path'''
        path = b"/".join((b"data", path))
        # check for files (exact match)
        e = path + b'.i'
        if e in self.fncache and self._exists(e):
            return True
        # now check for directories (prefix match)
        if not path.endswith(b'/'):
            path += b'/'
        for e in self.fncache:
            if e.startswith(path) and self._exists(e):
                return True
        return False