Mercurial > hg
view mercurial/revlogutils/constants.py @ 47249:130c9f7ed914
revlog: add a "data compression mode" entry in the index tuple
That will make it possible to keep track of compression information in the
revlog index, opening the way to more efficient revision restoration (in native
code, but the python usage is already defeating performance work).
We start with adding a new entry to the index tuple, using a value matching the
current behavior. We will introduce storage and other value in later changesets.
Differential Revision: https://phab.mercurial-scm.org/D10646
author | Pierre-Yves David <pierre-yves.david@octobus.net> |
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date | Mon, 03 May 2021 18:19:16 +0200 |
parents | 616b8f412676 |
children | 6bfa6c2c5f15 |
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# revlogdeltas.py - constant used for revlog logic. # # Copyright 2005-2007 Olivia Mackall <olivia@selenic.com> # Copyright 2018 Octobus <contact@octobus.net> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. """Helper class to compute deltas stored inside revlogs""" from __future__ import absolute_import import struct from ..interfaces import repository ### Internal utily constants KIND_CHANGELOG = 1001 # over 256 to not be comparable with a bytes KIND_MANIFESTLOG = 1002 KIND_FILELOG = 1003 KIND_OTHER = 1004 ALL_KINDS = { KIND_CHANGELOG, KIND_MANIFESTLOG, KIND_FILELOG, KIND_OTHER, } ### main revlog header INDEX_HEADER = struct.Struct(b">I") ## revlog version REVLOGV0 = 0 REVLOGV1 = 1 # Dummy value until file format is finalized. REVLOGV2 = 0xDEAD ## global revlog header flags # Shared across v1 and v2. FLAG_INLINE_DATA = 1 << 16 # Only used by v1, implied by v2. FLAG_GENERALDELTA = 1 << 17 REVLOG_DEFAULT_FLAGS = FLAG_INLINE_DATA REVLOG_DEFAULT_FORMAT = REVLOGV1 REVLOG_DEFAULT_VERSION = REVLOG_DEFAULT_FORMAT | REVLOG_DEFAULT_FLAGS REVLOGV0_FLAGS = 0 REVLOGV1_FLAGS = FLAG_INLINE_DATA | FLAG_GENERALDELTA REVLOGV2_FLAGS = FLAG_INLINE_DATA ### individual entry ## index v0: # 4 bytes: offset # 4 bytes: compressed length # 4 bytes: base rev # 4 bytes: link rev # 20 bytes: parent 1 nodeid # 20 bytes: parent 2 nodeid # 20 bytes: nodeid INDEX_ENTRY_V0 = struct.Struct(b">4l20s20s20s") ## index v1 # 6 bytes: offset # 2 bytes: flags # 4 bytes: compressed length # 4 bytes: uncompressed length # 4 bytes: base rev # 4 bytes: link rev # 4 bytes: parent 1 rev # 4 bytes: parent 2 rev # 32 bytes: nodeid INDEX_ENTRY_V1 = struct.Struct(b">Qiiiiii20s12x") assert INDEX_ENTRY_V1.size == 32 * 2 # 6 bytes: offset # 2 bytes: flags # 4 bytes: compressed length # 4 bytes: uncompressed length # 4 bytes: base rev # 4 bytes: link rev # 4 bytes: parent 1 rev # 4 bytes: parent 2 rev # 32 bytes: nodeid # 8 bytes: sidedata offset # 4 bytes: sidedata compressed length # 20 bytes: Padding to align to 96 bytes (see RevlogV2Plan wiki page) INDEX_ENTRY_V2 = struct.Struct(b">Qiiiiii20s12xQi20x") assert INDEX_ENTRY_V2.size == 32 * 3 # revlog index flags # For historical reasons, revlog's internal flags were exposed via the # wire protocol and are even exposed in parts of the storage APIs. # revision has censor metadata, must be verified REVIDX_ISCENSORED = repository.REVISION_FLAG_CENSORED # revision hash does not match data (narrowhg) REVIDX_ELLIPSIS = repository.REVISION_FLAG_ELLIPSIS # revision data is stored externally REVIDX_EXTSTORED = repository.REVISION_FLAG_EXTSTORED # revision changes files in a way that could affect copy tracing. REVIDX_HASCOPIESINFO = repository.REVISION_FLAG_HASCOPIESINFO REVIDX_DEFAULT_FLAGS = 0 # stable order in which flags need to be processed and their processors applied REVIDX_FLAGS_ORDER = [ REVIDX_ISCENSORED, REVIDX_ELLIPSIS, REVIDX_EXTSTORED, REVIDX_HASCOPIESINFO, ] # bitmark for flags that could cause rawdata content change REVIDX_RAWTEXT_CHANGING_FLAGS = REVIDX_ISCENSORED | REVIDX_EXTSTORED ## chunk compression mode constants: # These constants are used in revlog version >=2 to denote the compression used # for a chunk. # Chunk use a compression mode stored "inline" at the start of the chunk # itself. This is the mode always used for revlog version "0" and "1" COMP_MODE_INLINE = 2 SUPPORTED_FLAGS = { REVLOGV0: REVLOGV0_FLAGS, REVLOGV1: REVLOGV1_FLAGS, REVLOGV2: REVLOGV2_FLAGS, } _no = lambda flags: False _yes = lambda flags: True def _from_flag(flag): return lambda flags: bool(flags & flag) FEATURES_BY_VERSION = { REVLOGV0: { b'inline': _no, b'generaldelta': _no, b'sidedata': False, b'docket': False, }, REVLOGV1: { b'inline': _from_flag(FLAG_INLINE_DATA), b'generaldelta': _from_flag(FLAG_GENERALDELTA), b'sidedata': False, b'docket': False, }, REVLOGV2: { # The point of inline-revlog is to reduce the number of files used in # the store. Using a docket defeat this purpose. So we needs other # means to reduce the number of files for revlogv2. b'inline': _no, b'generaldelta': _yes, b'sidedata': True, b'docket': True, }, } SPARSE_REVLOG_MAX_CHAIN_LENGTH = 1000