view hgext/fsmonitor/state.py @ 45520:5eee6f4f3d0d

chg: fallback to original hg if stdio fds are missing

If stdio fds are missing (ex. fd 0 is not present), chg might open
fds that take the numbers 0, and attachio would send the wrong fds
to the client, which might cause unwanted behaviors. Avoid that by
detecting the missing fds and falling back to the original hg.

Differential Revision: https://phab.mercurial-scm.org/D9058

# 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.

from __future__ import absolute_import

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(object):
    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 OSError as inst:
            if inst.errno != errno.ENOENT:
                raise
        self._identity = util.filestat(None)

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

    def getlastclock(self):
        return self._lastclock