/brz/remove-bazaar

# Copyright (C) 2005, 2006, 2007 Canonical Ltd

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

"""Locking using OS file locks or file existence.

Note: This method of locking is generally deprecated in favour of LockDir, but

is used to lock local WorkingTrees, and by some old formats.  It's accessed

through Transport.lock_read(), etc.

This module causes two methods, lock() and unlock() to be defined in

any way that works on the current platform.

It is not specified whether these locks are reentrant (i.e. can be

taken repeatedly by a single process) or whether they exclude

different threads in a single process.  That reentrancy is provided by

LockableFiles.

This defines two classes: ReadLock and WriteLock, which can be

implemented in different ways on different platforms.  Both have an

unlock() method.

"""

import errno

import sys

from bzrlib import (

    errors,

    osutils,

    trace,

    )

class _base_Lock(object):

    def __init__(self):

        self.f = None

        self.filename = None

    def _open(self, filename, filemode):

        self.filename = osutils.realpath(filename)

        try:

            self.f = open(self.filename, filemode)

            return self.f

        except IOError, e:

            if e.errno in (errno.EACCES, errno.EPERM):

                raise errors.ReadOnlyLockError(self.filename, str(e))

            if e.errno != errno.ENOENT:

                raise

            # maybe this is an old branch (before may 2005)

            trace.mutter("trying to create missing lock %r", self.filename)

            self.f = open(self.filename, 'wb+')

            return self.f

    def _clear_f(self):

        """Clear the self.f attribute cleanly."""

        if self.f:

            self.f.close()

            self.f = None

    def __del__(self):

        if self.f:

            from warnings import warn

            warn("lock on %r not released" % self.f)

            self.unlock()

    def unlock(self):

        raise NotImplementedError()

try:

    import fcntl

    have_fcntl = True

except ImportError:

    have_fcntl = False

try:

    import win32con, win32file, pywintypes, winerror, msvcrt

    have_pywin32 = True

except ImportError:

    have_pywin32 = False

try:

    import ctypes, msvcrt

    have_ctypes = True

except ImportError:

    have_ctypes = False

_lock_classes = []

if have_fcntl:

    LOCK_SH = fcntl.LOCK_SH

    LOCK_NB = fcntl.LOCK_NB

    lock_EX = fcntl.LOCK_EX

    class _fcntl_FileLock(_base_Lock):

        def _unlock(self):

            fcntl.lockf(self.f, fcntl.LOCK_UN)

            self._clear_f()

    class _fcntl_WriteLock(_fcntl_FileLock):

        open_locks = {}

        def __init__(self, filename):

            # standard IO errors get exposed directly.

            super(_fcntl_WriteLock, self).__init__()

            self._open(filename, 'rb+')

            if self.filename in self.open_locks:

                self._clear_f()

                raise errors.LockContention(self.filename)

            # reserve a slot for this lock - even if the lockf call fails,

            # at thisi point unlock() will be called, because self.f is set.

            # TODO: make this fully threadsafe, if we decide we care.

            self.open_locks[self.filename] = self.filename

            try:

                # LOCK_NB will cause IOError to be raised if we can't grab a

                # lock right away.

                fcntl.lockf(self.f, fcntl.LOCK_EX | fcntl.LOCK_NB)

            except IOError, e:

                if e.errno in (errno.EAGAIN, errno.EACCES):

                    # We couldn't grab the lock

                    self.unlock()

                # we should be more precise about whats a locking

                # error and whats a random-other error

                raise errors.LockError(e)

        def unlock(self):

            del self.open_locks[self.filename]

            self._unlock()

    class _fcntl_ReadLock(_fcntl_FileLock):

        open_locks = {}

        def __init__(self, filename):

            super(_fcntl_ReadLock, self).__init__()

            self._open(filename, 'rb')

            try:

                # LOCK_NB will cause IOError to be raised if we can't grab a

                # lock right away.

                fcntl.lockf(self.f, fcntl.LOCK_SH | fcntl.LOCK_NB)

            except IOError, e:

                # we should be more precise about whats a locking

                # error and whats a random-other error

                raise errors.LockError(e)

        def unlock(self):

            self._unlock()

    _lock_classes.append(('fcntl', _fcntl_WriteLock, _fcntl_ReadLock))

if have_pywin32 and sys.platform == 'win32':

    LOCK_SH = 0 # the default

    LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK

    LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY

    class _w32c_FileLock(_base_Lock):

        def _lock(self, filename, openmode, lockmode):

            self._open(filename, openmode)

            self.hfile = msvcrt.get_osfhandle(self.f.fileno())

            overlapped = pywintypes.OVERLAPPED()

            try:

                win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000,

                                     overlapped)

            except pywintypes.error, e:

                self._clear_f()

                if e.args[0] in (winerror.ERROR_LOCK_VIOLATION,):

                    raise errors.LockContention(filename)

                ## import pdb; pdb.set_trace()

                raise

            except Exception, e:

                self._clear_f()

                raise errors.LockError(e)

        def unlock(self):

            overlapped = pywintypes.OVERLAPPED()

            try:

                win32file.UnlockFileEx(self.hfile, 0, 0x7fff0000, overlapped)

                self._clear_f()

            except Exception, e:

                raise errors.LockError(e)

    class _w32c_ReadLock(_w32c_FileLock):

        def __init__(self, filename):

            super(_w32c_ReadLock, self).__init__()

            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)

    class _w32c_WriteLock(_w32c_FileLock):

        def __init__(self, filename):

            super(_w32c_WriteLock, self).__init__()

            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)

    _lock_classes.append(('pywin32', _w32c_WriteLock, _w32c_ReadLock))

if have_ctypes and sys.platform == 'win32':

    # These constants were copied from the win32con.py module.

    LOCKFILE_FAIL_IMMEDIATELY = 1

    LOCKFILE_EXCLUSIVE_LOCK = 2

    # Constant taken from winerror.py module

    ERROR_LOCK_VIOLATION = 33

    LOCK_SH = 0

    LOCK_EX = LOCKFILE_EXCLUSIVE_LOCK

    LOCK_NB = LOCKFILE_FAIL_IMMEDIATELY

    _LockFileEx = ctypes.windll.kernel32.LockFileEx

    _UnlockFileEx = ctypes.windll.kernel32.UnlockFileEx

    _GetLastError = ctypes.windll.kernel32.GetLastError

    ### Define the OVERLAPPED structure.

    #   http://msdn2.microsoft.com/en-us/library/ms684342.aspx

    # typedef struct _OVERLAPPED {

    #   ULONG_PTR Internal;

    #   ULONG_PTR InternalHigh;

    #   union {

    #     struct {

    #       DWORD Offset;

    #       DWORD OffsetHigh;

    #     };

    #     PVOID Pointer;

    #   };

    #   HANDLE hEvent;

    # } OVERLAPPED,

    class _inner_struct(ctypes.Structure):

        _fields_ = [('Offset', ctypes.c_uint), # DWORD

                    ('OffsetHigh', ctypes.c_uint), # DWORD

                   ]

    class _inner_union(ctypes.Union):

        _fields_  = [('anon_struct', _inner_struct), # struct

                     ('Pointer', ctypes.c_void_p), # PVOID

                    ]

    class OVERLAPPED(ctypes.Structure):

        _fields_ = [('Internal', ctypes.c_void_p), # ULONG_PTR

                    ('InternalHigh', ctypes.c_void_p), # ULONG_PTR

                    ('_inner_union', _inner_union),

                    ('hEvent', ctypes.c_void_p), # HANDLE

                   ]

    class _ctypes_FileLock(_base_Lock):

        def _lock(self, filename, openmode, lockmode):

            self._open(filename, openmode)

            self.hfile = msvcrt.get_osfhandle(self.f.fileno())

            overlapped = OVERLAPPED()

            p_overlapped = ctypes.pointer(overlapped)

            result = _LockFileEx(self.hfile, # HANDLE hFile

                                 lockmode,   # DWORD dwFlags

                                 0,          # DWORD dwReserved

                                 0x7fffffff, # DWORD nNumberOfBytesToLockLow

                                 0x00000000, # DWORD nNumberOfBytesToLockHigh

                                 p_overlapped, # lpOverlapped

                                )

            if result == 0:

                self._clear_f()

                last_err = _GetLastError()

                if last_err in (ERROR_LOCK_VIOLATION,):

                    raise errors.LockContention(filename)

                raise errors.LockError('Unknown locking error: %s'

                                       % (last_err,))

        def unlock(self):

            overlapped = OVERLAPPED()

            p_overlapped = ctypes.pointer(overlapped)

            result = _UnlockFileEx(self.hfile, # HANDLE hFile

                                   0,          # DWORD dwReserved

                                   0x7fffffff, # DWORD nNumberOfBytesToLockLow

                                   0x00000000, # DWORD nNumberOfBytesToLockHigh

                                   p_overlapped, # lpOverlapped

                                  )

            self._clear_f()

            if result == 0:

                self._clear_f()

                last_err = _GetLastError()

                raise errors.LockError('Unknown unlocking error: %s'

                                       % (last_err,))

    class _ctypes_ReadLock(_ctypes_FileLock):

        def __init__(self, filename):

            super(_ctypes_ReadLock, self).__init__()

            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)

    class _ctypes_WriteLock(_ctypes_FileLock):

        def __init__(self, filename):

            super(_ctypes_WriteLock, self).__init__()

            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)

    _lock_classes.append(('ctypes', _ctypes_WriteLock, _ctypes_ReadLock))

if len(_lock_classes) == 0:

    raise NotImplementedError(

        "We must have one of fcntl, pywin32, or ctypes available"

        " to support OS locking."

        )

# We default to using the first available lock class.

_lock_type, WriteLock, ReadLock = _lock_classes[0]