~bzr-pqm/bzr/bzr.dev

# Copyright (C) 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

"""Common code for generating file or revision ids."""

from bzrlib.lazy_import import lazy_import

lazy_import(globals(), """

import time

import unicodedata

from bzrlib import (

    config,

    errors,

    osutils,

    )

""")

from bzrlib import (

    lazy_regex,

    )

# the regex removes any weird characters; we don't escape them 

# but rather just pull them out

_file_id_chars_re = lazy_regex.lazy_compile(r'[^\w.]')

_rev_id_chars_re = lazy_regex.lazy_compile(r'[^-\w.+@]')

_gen_file_id_suffix = None

_gen_file_id_serial = 0

def _next_id_suffix():

    """Create a new file id suffix that is reasonably unique.

    On the first call we combine the current time with 64 bits of randomness to

    give a highly probably globally unique number. Then each call in the same

    process adds 1 to a serial number we append to that unique value.

    """

    # XXX TODO: change bzrlib.add.smart_add_tree to call workingtree.add() rather 

    # than having to move the id randomness out of the inner loop like this.

    # XXX TODO: for the global randomness this uses we should add the thread-id

    # before the serial #.

    # XXX TODO: jam 20061102 I think it would be good to reset every 100 or

    #           1000 calls, or perhaps if time.time() increases by a certain

    #           amount. time.time() shouldn't be terribly expensive to call,

    #           and it means that long-lived processes wouldn't use the same

    #           suffix forever.

    global _gen_file_id_suffix, _gen_file_id_serial

    if _gen_file_id_suffix is None:

        _gen_file_id_suffix = "-%s-%s-" % (osutils.compact_date(time.time()),

                                           osutils.rand_chars(16))

    _gen_file_id_serial += 1

    return _gen_file_id_suffix + str(_gen_file_id_serial)

def gen_file_id(name):

    """Return new file id for the basename 'name'.

    The uniqueness is supplied from _next_id_suffix.

    """

    # The real randomness is in the _next_id_suffix, the

    # rest of the identifier is just to be nice.

    # So we:

    # 1) Remove non-ascii word characters to keep the ids portable

    # 2) squash to lowercase, so the file id doesn't have to

    #    be escaped (case insensitive filesystems would bork for ids

    #    that only differ in case without escaping).

    # 3) truncate the filename to 20 chars. Long filenames also bork on some

    #    filesystems

    # 4) Removing starting '.' characters to prevent the file ids from

    #    being considered hidden.

    ascii_word_only = str(_file_id_chars_re.sub('', name.lower()))

    short_no_dots = ascii_word_only.lstrip('.')[:20]

    return short_no_dots + _next_id_suffix()

def gen_root_id():

    """Return a new tree-root file id."""

    return gen_file_id('tree_root')

def gen_revision_id(username, timestamp=None):

    """Return new revision-id.

    :param username: This is the value returned by config.username(), which is

        typically a real name, followed by an email address. If found, we will

        use just the email address portion. Otherwise we flatten the real name,

        and use that.

    :return: A new revision id.

    """

    try:

        user_or_email = config.extract_email_address(username)

    except errors.NoEmailInUsername:

        user_or_email = username

    user_or_email = user_or_email.lower()

    user_or_email = user_or_email.replace(' ', '_')

    user_or_email = _rev_id_chars_re.sub('', user_or_email)

    # This gives 36^16 ~= 2^82.7 ~= 83 bits of entropy

    unique_chunk = osutils.rand_chars(16)

    if timestamp is None:

        timestamp = time.time()

    rev_id = u'-'.join((user_or_email,

                        osutils.compact_date(timestamp),

                        unique_chunk))

    return rev_id.encode('utf8')