~bzr-pqm/bzr/bzr.dev

# Copyright (C) 2005, 2006 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

from cStringIO import StringIO

import codecs

#import traceback

import bzrlib

from bzrlib.decorators import (needs_read_lock,

        needs_write_lock)

import bzrlib.errors as errors

from bzrlib.errors import BzrError

from bzrlib.osutils import file_iterator, safe_unicode

from bzrlib.symbol_versioning import (deprecated_method,

        )

from bzrlib.trace import mutter, note

import bzrlib.transactions as transactions

import bzrlib.urlutils as urlutils

# XXX: The tracking here of lock counts and whether the lock is held is

# somewhat redundant with what's done in LockDir; the main difference is that

# LockableFiles permits reentrancy.

class LockableFiles(object):

    """Object representing a set of related files locked within the same scope.

    These files are used by a WorkingTree, Repository or Branch, and should

    generally only be touched by that object.

    LockableFiles also provides some policy on top of Transport for encoding

    control files as utf-8.

    LockableFiles manage a lock count and can be locked repeatedly by

    a single caller.  (The underlying lock implementation generally does not

    support this.)

    Instances of this class are often called control_files.

    This object builds on top of a Transport, which is used to actually write

    the files to disk, and an OSLock or LockDir, which controls how access to

    the files is controlled.  The particular type of locking used is set when

    the object is constructed.  In older formats OSLocks are used everywhere.

    in newer formats a LockDir is used for Repositories and Branches, and 

    OSLocks for the local filesystem.

    """

    # _lock_mode: None, or 'r' or 'w'

    # _lock_count: If _lock_mode is true, a positive count of the number of

    # times the lock has been taken *by this process*.   

    # If set to False (by a plugin, etc) BzrBranch will not set the

    # mode on created files or directories

    _set_file_mode = True

    _set_dir_mode = True

    def __init__(self, transport, lock_name, lock_class):

        """Create a LockableFiles group

        :param transport: Transport pointing to the directory holding the 

            control files and lock.

        :param lock_name: Name of the lock guarding these files.

        :param lock_class: Class of lock strategy to use: typically

            either LockDir or TransportLock.

        """

        self._transport = transport

        self.lock_name = lock_name

        self._transaction = None

        self._lock_mode = None

        self._lock_count = 0

        self._find_modes()

        esc_name = self._escape(lock_name)

        self._lock = lock_class(transport, esc_name,

                                file_modebits=self._file_mode,

                                dir_modebits=self._dir_mode)

    def create_lock(self):

        """Create the lock.

        This should normally be called only when the LockableFiles directory

        is first created on disk.

        """

        self._lock.create(mode=self._dir_mode)

    def __repr__(self):

        return '%s(%r)' % (self.__class__.__name__,

                           self._transport)

    def __str__(self):

        return 'LockableFiles(%s, %s)' % (self.lock_name, self._transport.base)

    def __del__(self):

        if self.is_locked():

            # XXX: This should show something every time, and be suitable for

            # headless operation and embedding

            from warnings import warn

            warn("file group %r was not explicitly unlocked" % self)

            self._lock.unlock()

    def break_lock(self):

        """Break the lock of this lockable files group if it is held.

        The current ui factory will be used to prompt for user conformation.

        """

        self._lock.break_lock()

    def _escape(self, file_or_path):

        if not isinstance(file_or_path, basestring):

            file_or_path = '/'.join(file_or_path)

        if file_or_path == '':

            return u''

        return urlutils.escape(safe_unicode(file_or_path))

    def _find_modes(self):

        """Determine the appropriate modes for files and directories."""

        try:

            st = self._transport.stat('.')

        except errors.TransportNotPossible:

            self._dir_mode = 0755

            self._file_mode = 0644

        else:

            self._dir_mode = st.st_mode & 07777

            # Remove the sticky and execute bits for files

            self._file_mode = self._dir_mode & ~07111

        if not self._set_dir_mode:

            self._dir_mode = None

        if not self._set_file_mode:

            self._file_mode = None

    def controlfilename(self, file_or_path):

        """Return location relative to branch."""

        return self._transport.abspath(self._escape(file_or_path))

    @needs_read_lock

    def get(self, relpath):

        """Get a file as a bytestream."""

        relpath = self._escape(relpath)

        return self._transport.get(relpath)

    @needs_read_lock

    def get_utf8(self, relpath):

        """Get a file as a unicode stream."""

        relpath = self._escape(relpath)

        # DO NOT introduce an errors=replace here.

        return codecs.getreader('utf-8')(self._transport.get(relpath))

    @needs_write_lock

    def put(self, path, file):

        """Write a file.

        :param path: The path to put the file, relative to the .bzr control

                     directory

        :param f: A file-like or string object whose contents should be copied.

        """

        self._transport.put_file(self._escape(path), file, mode=self._file_mode)

    @needs_write_lock

    def put_bytes(self, path, a_string):

        """Write a string of bytes.

        :param path: The path to put the bytes, relative to the transport root.

        :param string: A string object, whose exact bytes are to be copied.

        """

        self._transport.put_bytes(self._escape(path), a_string,

                                  mode=self._file_mode)

    @needs_write_lock

    def put_utf8(self, path, a_string):

        """Write a string, encoding as utf-8.

        :param path: The path to put the string, relative to the transport root.

        :param string: A string or unicode object whose contents should be copied.

        """

        # IterableFile would not be needed if Transport.put took iterables

        # instead of files.  ADHB 2005-12-25

        # RBC 20060103 surely its not needed anyway, with codecs transcode

        # file support ?

        # JAM 20060103 We definitely don't want encode(..., 'replace')

        # these are valuable files which should have exact contents.

        if not isinstance(a_string, basestring):

            raise errors.BzrBadParameterNotString(a_string)

        self.put_bytes(path, a_string.encode('utf-8'))

    def leave_in_place(self):

        """Set this LockableFiles to not clear the physical lock on unlock."""

        self._lock.leave_in_place()

    def dont_leave_in_place(self):

        """Set this LockableFiles to clear the physical lock on unlock."""

        self._lock.dont_leave_in_place()

    def lock_write(self, token=None):

        """Lock this group of files for writing.

        :param token: if this is already locked, then lock_write will fail

            unless the token matches the existing lock.

        :returns: a token if this instance supports tokens, otherwise None.

        :raises TokenLockingNotSupported: when a token is given but this

            instance doesn't support using token locks.

        :raises MismatchedToken: if the specified token doesn't match the token

            of the existing lock.

        A token should be passed in if you know that you have locked the object

        some other way, and need to synchronise this object's state with that

        fact.

        """

        # mutter("lock write: %s (%s)", self, self._lock_count)

        # TODO: Upgrade locking to support using a Transport,

        # and potentially a remote locking protocol

        if self._lock_mode:

            if self._lock_mode != 'w' or not self.get_transaction().writeable():

                raise errors.ReadOnlyError(self)

            self._lock.validate_token(token)

            self._lock_count += 1

            return self._token_from_lock

        else:

            token_from_lock = self._lock.lock_write(token=token)

            #note('write locking %s', self)

            #traceback.print_stack()

            self._lock_mode = 'w'

            self._lock_count = 1

            self._set_transaction(transactions.WriteTransaction())

            self._token_from_lock = token_from_lock

            return token_from_lock

    def lock_read(self):

        # mutter("lock read: %s (%s)", self, self._lock_count)

        if self._lock_mode:

            assert self._lock_mode in ('r', 'w'), \

                   "invalid lock mode %r" % self._lock_mode

            self._lock_count += 1

        else:

            self._lock.lock_read()

            #note('read locking %s', self)

            #traceback.print_stack()

            self._lock_mode = 'r'

            self._lock_count = 1

            self._set_transaction(transactions.ReadOnlyTransaction())

            # 5K may be excessive, but hey, its a knob.

            self.get_transaction().set_cache_size(5000)

    def unlock(self):

        # mutter("unlock: %s (%s)", self, self._lock_count)

        if not self._lock_mode:

            raise errors.LockNotHeld(self)

        if self._lock_count > 1:

            self._lock_count -= 1

        else:

            #note('unlocking %s', self)

            #traceback.print_stack()

            self._finish_transaction()

            try:

                self._lock.unlock()

            finally:

                self._lock_mode = self._lock_count = None

    def is_locked(self):

        """Return true if this LockableFiles group is locked"""

        return self._lock_count >= 1

    def get_physical_lock_status(self):

        """Return physical lock status.

        Returns true if a lock is held on the transport. If no lock is held, or

        the underlying locking mechanism does not support querying lock

        status, false is returned.

        """

        try:

            return self._lock.peek() is not None

        except NotImplementedError:

            return False

    def get_transaction(self):

        """Return the current active transaction.

        If no transaction is active, this returns a passthrough object

        for which all data is immediately flushed and no caching happens.

        """

        if self._transaction is None:

            return transactions.PassThroughTransaction()

        else:

            return self._transaction

    def _set_transaction(self, new_transaction):

        """Set a new active transaction."""

        if self._transaction is not None:

            raise errors.LockError('Branch %s is in a transaction already.' %

                                   self)

        self._transaction = new_transaction

    def _finish_transaction(self):

        """Exit the current transaction."""

        if self._transaction is None:

            raise errors.LockError('Branch %s is not in a transaction' %

                                   self)

        transaction = self._transaction

        self._transaction = None

        transaction.finish()

class TransportLock(object):

    """Locking method which uses transport-dependent locks.

    On the local filesystem these transform into OS-managed locks.

    These do not guard against concurrent access via different

    transports.

    This is suitable for use only in WorkingTrees (which are at present

    always local).

    """

    def __init__(self, transport, escaped_name, file_modebits, dir_modebits):

        self._transport = transport

        self._escaped_name = escaped_name

        self._file_modebits = file_modebits

        self._dir_modebits = dir_modebits

    def break_lock(self):

        raise NotImplementedError(self.break_lock)

    def leave_in_place(self):

        raise NotImplementedError(self.leave_in_place)

    def dont_leave_in_place(self):

        raise NotImplementedError(self.dont_leave_in_place)

    def lock_write(self, token=None):

        if token is not None:

            raise errors.TokenLockingNotSupported(self)

        self._lock = self._transport.lock_write(self._escaped_name)

    def lock_read(self):

        self._lock = self._transport.lock_read(self._escaped_name)

    def unlock(self):

        self._lock.unlock()

        self._lock = None

    def peek(self):

        raise NotImplementedError()

    def create(self, mode=None):

        """Create lock mechanism"""

        # for old-style locks, create the file now

        self._transport.put_bytes(self._escaped_name, '',

                            mode=self._file_modebits)

    def validate_token(self, token):

        if token is not None:

            raise errors.TokenLockingNotSupported(self)