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# docket - code related to revlog "docket"
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#
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# Copyright 2021 Pierre-Yves David <pierre-yves.david@octobus.net>
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#
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# This software may be used and distributed according to the terms of the
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# GNU General Public License version 2 or any later version.
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### Revlog docket file
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#
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# The revlog is stored on disk using multiple files:
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#
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# * a small docket file, containing metadata and a pointer,
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#
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# * an index file, containing fixed width information about revisions,
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#
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# * a data file, containing variable width data for these revisions,
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from __future__ import absolute_import
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import errno
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import os
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import random
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import struct
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from .. import (
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encoding,
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error,
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node,
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pycompat,
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util,
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)
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from . import (
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constants,
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)
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def make_uid(id_size=8):
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"""return a new unique identifier.
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The identifier is random and composed of ascii characters."""
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# size we "hex" the result we need half the number of bits to have a final
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# uuid of size ID_SIZE
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return node.hex(os.urandom(id_size // 2))
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# some special test logic to avoid anoying random output in the test
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stable_docket_file = encoding.environ.get(b'HGTEST_UUIDFILE')
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if stable_docket_file:
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def make_uid(id_size=8):
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try:
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with open(stable_docket_file, mode='rb') as f:
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seed = f.read().strip()
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except IOError as inst:
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if inst.errno != errno.ENOENT:
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raise
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seed = b'04' # chosen by a fair dice roll. garanteed to be random
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if pycompat.ispy3:
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iter_seed = iter(seed)
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else:
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iter_seed = (ord(c) for c in seed)
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# some basic circular sum hashing on 64 bits
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int_seed = 0
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low_mask = int('1' * 35, 2)
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for i in iter_seed:
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high_part = int_seed >> 35
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low_part = (int_seed & low_mask) << 28
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int_seed = high_part + low_part + i
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r = random.Random()
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if pycompat.ispy3:
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r.seed(int_seed, version=1)
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else:
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r.seed(int_seed)
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# once we drop python 3.8 support we can simply use r.randbytes
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raw = r.getrandbits(id_size * 4)
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assert id_size == 8
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p = struct.pack('>L', raw)
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new = node.hex(p)
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with open(stable_docket_file, 'wb') as f:
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f.write(new)
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return new
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# Docket format
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#
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# * 4 bytes: revlog version
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# | This is mandatory as docket must be compatible with the previous
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# | revlog index header.
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# * 1 bytes: size of index uuid
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# * 1 bytes: size of data uuid
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# * 8 bytes: size of index-data
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# * 8 bytes: pending size of index-data
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# * 8 bytes: size of data
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# * 8 bytes: pending size of data
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# * 1 bytes: default compression header
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S_HEADER = struct.Struct(constants.INDEX_HEADER.format + 'BBLLLLc')
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class RevlogDocket(object):
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"""metadata associated with revlog"""
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def __init__(
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self,
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revlog,
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use_pending=False,
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version_header=None,
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index_uuid=None,
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data_uuid=None,
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index_end=0,
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pending_index_end=0,
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data_end=0,
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pending_data_end=0,
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default_compression_header=None,
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):
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self._version_header = version_header
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self._read_only = bool(use_pending)
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self._dirty = False
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self._radix = revlog.radix
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self._path = revlog._docket_file
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self._opener = revlog.opener
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self._index_uuid = index_uuid
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self._data_uuid = data_uuid
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# thes asserts should be True as long as we have a single index filename
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assert index_end <= pending_index_end
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assert data_end <= pending_data_end
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self._initial_index_end = index_end
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self._pending_index_end = pending_index_end
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self._initial_data_end = data_end
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self._pending_data_end = pending_data_end
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if use_pending:
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self._index_end = self._pending_index_end
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self._data_end = self._pending_data_end
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else:
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self._index_end = self._initial_index_end
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self._data_end = self._initial_data_end
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self.default_compression_header = default_compression_header
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def index_filepath(self):
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"""file path to the current index file associated to this docket"""
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# very simplistic version at first
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if self._index_uuid is None:
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self._index_uuid = make_uid()
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return b"%s-%s.idx" % (self._radix, self._index_uuid)
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def data_filepath(self):
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"""file path to the current index file associated to this docket"""
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# very simplistic version at first
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if self._data_uuid is None:
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self._data_uuid = make_uid()
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return b"%s-%s.dat" % (self._radix, self._data_uuid)
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@property
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def index_end(self):
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return self._index_end
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@index_end.setter
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def index_end(self, new_size):
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if new_size != self._index_end:
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self._index_end = new_size
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self._dirty = True
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@property
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def data_end(self):
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return self._data_end
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@data_end.setter
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def data_end(self, new_size):
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if new_size != self._data_end:
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self._data_end = new_size
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self._dirty = True
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def write(self, transaction, pending=False, stripping=False):
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"""write the modification of disk if any
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This make the new content visible to all process"""
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if not self._dirty:
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return False
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else:
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if self._read_only:
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msg = b'writing read-only docket: %s'
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msg %= self._path
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raise error.ProgrammingError(msg)
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if not stripping:
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# XXX we could, leverage the docket while stripping. However it
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# is not powerfull enough at the time of this comment
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transaction.addbackup(self._path, location=b'store')
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with self._opener(self._path, mode=b'w', atomictemp=True) as f:
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f.write(self._serialize(pending=pending))
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# if pending we still need to the write final data eventually
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self._dirty = pending
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return True
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def _serialize(self, pending=False):
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if pending:
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official_index_end = self._initial_index_end
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official_data_end = self._initial_data_end
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else:
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official_index_end = self._index_end
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official_data_end = self._data_end
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# this assert should be True as long as we have a single index filename
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assert official_data_end <= self._data_end
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data = (
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self._version_header,
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len(self._index_uuid),
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len(self._data_uuid),
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official_index_end,
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self._index_end,
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official_data_end,
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self._data_end,
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self.default_compression_header,
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)
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s = []
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s.append(S_HEADER.pack(*data))
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s.append(self._index_uuid)
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s.append(self._data_uuid)
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return b''.join(s)
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def default_docket(revlog, version_header):
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"""given a revlog version a new docket object for the given revlog"""
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rl_version = version_header & 0xFFFF
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if rl_version not in (constants.REVLOGV2, constants.CHANGELOGV2):
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return None
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comp = util.compengines[revlog._compengine].revlogheader()
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docket = RevlogDocket(
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revlog,
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version_header=version_header,
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default_compression_header=comp,
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)
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docket._dirty = True
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return docket
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def parse_docket(revlog, data, use_pending=False):
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"""given some docket data return a docket object for the given revlog"""
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header = S_HEADER.unpack(data[: S_HEADER.size])
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offset = S_HEADER.size
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iheader = iter(header)
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version_header = next(iheader)
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index_uuid_size = next(iheader)
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index_uuid = data[offset : offset + index_uuid_size]
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offset += index_uuid_size
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data_uuid_size = next(iheader)
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data_uuid = data[offset : offset + data_uuid_size]
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offset += data_uuid_size
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index_size = next(iheader)
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pending_index_size = next(iheader)
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data_size = next(iheader)
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pending_data_size = next(iheader)
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default_compression_header = next(iheader)
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docket = RevlogDocket(
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revlog,
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use_pending=use_pending,
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version_header=version_header,
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index_uuid=index_uuid,
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data_uuid=data_uuid,
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index_end=index_size,
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pending_index_end=pending_index_size,
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data_end=data_size,
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pending_data_end=pending_data_size,
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default_compression_header=default_compression_header,
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)
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return docket
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