view hgext/fsmonitor/state.py @ 49680:40e24d82b513

delta-find: make sure we only use newer full snapshot as candidate

The current code does not needs to protect against this, as there are no older
snapshot in the current cache. However as we are getting ready to reuse this
cache from one revision to another, we need the code to protect itself about
what's coming.

# state.py - fsmonitor persistent state
#
# Copyright 2013-2016 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.


import errno
import os
import socket
import struct

from mercurial.i18n import _
from mercurial import (
    encoding,
    pathutil,
    util,
)

_version = 4
_versionformat = b">I"


class state:
    def __init__(self, repo):
        self._vfs = repo.vfs
        self._ui = repo.ui
        self._rootdir = pathutil.normasprefix(repo.root)
        self._lastclock = None
        self._identity = util.filestat(None)

        self.mode = self._ui.config(b'fsmonitor', b'mode')
        self.walk_on_invalidate = self._ui.configbool(
            b'fsmonitor', b'walk_on_invalidate'
        )
        self.timeout = float(self._ui.config(b'fsmonitor', b'timeout'))

    def get(self):
        try:
            file = self._vfs(b'fsmonitor.state', b'rb')
        except IOError as inst:
            self._identity = util.filestat(None)
            if inst.errno != errno.ENOENT:
                raise
            return None, None, None

        self._identity = util.filestat.fromfp(file)

        versionbytes = file.read(4)
        if len(versionbytes) < 4:
            self._ui.log(
                b'fsmonitor',
                b'fsmonitor: state file only has %d bytes, '
                b'nuking state\n' % len(versionbytes),
            )
            self.invalidate()
            return None, None, None
        try:
            diskversion = struct.unpack(_versionformat, versionbytes)[0]
            if diskversion != _version:
                # different version, nuke state and start over
                self._ui.log(
                    b'fsmonitor',
                    b'fsmonitor: version switch from %d to '
                    b'%d, nuking state\n' % (diskversion, _version),
                )
                self.invalidate()
                return None, None, None

            state = file.read().split(b'\0')
            # state = hostname\0clock\0ignorehash\0 + list of files, each
            # followed by a \0
            if len(state) < 3:
                self._ui.log(
                    b'fsmonitor',
                    b'fsmonitor: state file truncated (expected '
                    b'3 chunks, found %d), nuking state\n',
                    len(state),
                )
                self.invalidate()
                return None, None, None
            diskhostname = state[0]
            hostname = encoding.strtolocal(socket.gethostname())
            if diskhostname != hostname:
                # file got moved to a different host
                self._ui.log(
                    b'fsmonitor',
                    b'fsmonitor: stored hostname "%s" '
                    b'different from current "%s", nuking state\n'
                    % (diskhostname, hostname),
                )
                self.invalidate()
                return None, None, None

            clock = state[1]
            ignorehash = state[2]
            # discard the value after the last \0
            notefiles = state[3:-1]

        finally:
            file.close()

        return clock, ignorehash, notefiles

    def set(self, clock, ignorehash, notefiles):
        if clock is None:
            self.invalidate()
            return

        # Read the identity from the file on disk rather than from the open file
        # pointer below, because the latter is actually a brand new file.
        identity = util.filestat.frompath(self._vfs.join(b'fsmonitor.state'))
        if identity != self._identity:
            self._ui.debug(
                b'skip updating fsmonitor.state: identity mismatch\n'
            )
            return

        try:
            file = self._vfs(
                b'fsmonitor.state', b'wb', atomictemp=True, checkambig=True
            )
        except (IOError, OSError):
            self._ui.warn(_(b"warning: unable to write out fsmonitor state\n"))
            return

        with file:
            file.write(struct.pack(_versionformat, _version))
            file.write(encoding.strtolocal(socket.gethostname()) + b'\0')
            file.write(clock + b'\0')
            file.write(ignorehash + b'\0')
            if notefiles:
                file.write(b'\0'.join(notefiles))
                file.write(b'\0')

    def invalidate(self):
        try:
            os.unlink(os.path.join(self._rootdir, b'.hg', b'fsmonitor.state'))
        except FileNotFoundError:
            pass
        self._identity = util.filestat(None)

    def setlastclock(self, clock):
        self._lastclock = clock

    def getlastclock(self):
        return self._lastclock