Mercurial > hg
view mercurial/revlogutils/sidedata.py @ 47060:fde5bb5d1acf
merge: with stable
author | Augie Fackler <augie@google.com> |
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date | Mon, 03 May 2021 15:14:09 -0400 |
parents | 3d740058b467 |
children | 3aab2330b7d3 |
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# sidedata.py - Logic around store extra data alongside revlog revisions # # Copyright 2019 Pierre-Yves David <pierre-yves.david@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. """core code for "sidedata" support The "sidedata" are stored alongside the revision without actually being part of its content and not affecting its hash. It's main use cases is to cache important information related to a changesets. The current implementation is experimental and subject to changes. Do not rely on it in production. Sidedata are stored in the revlog itself, thanks to a new version of the revlog. The following format is currently used:: initial header: <number of sidedata; 2 bytes> sidedata (repeated N times): <sidedata-key; 2 bytes> <sidedata-entry-length: 4 bytes> <sidedata-content-sha1-digest: 20 bytes> <sidedata-content; X bytes> normal raw text: <all bytes remaining in the rawtext> This is a simple and effective format. It should be enough to experiment with the concept. """ from __future__ import absolute_import import struct from .. import error from ..utils import hashutil ## sidedata type constant # reserve a block for testing purposes. SD_TEST1 = 1 SD_TEST2 = 2 SD_TEST3 = 3 SD_TEST4 = 4 SD_TEST5 = 5 SD_TEST6 = 6 SD_TEST7 = 7 # key to store copies related information SD_P1COPIES = 8 SD_P2COPIES = 9 SD_FILESADDED = 10 SD_FILESREMOVED = 11 SD_FILES = 12 # internal format constant SIDEDATA_HEADER = struct.Struct('>H') SIDEDATA_ENTRY = struct.Struct('>HL20s') def serialize_sidedata(sidedata): sidedata = list(sidedata.items()) sidedata.sort() buf = [SIDEDATA_HEADER.pack(len(sidedata))] for key, value in sidedata: digest = hashutil.sha1(value).digest() buf.append(SIDEDATA_ENTRY.pack(key, len(value), digest)) for key, value in sidedata: buf.append(value) buf = b''.join(buf) return buf def deserialize_sidedata(blob): sidedata = {} offset = 0 (nbentry,) = SIDEDATA_HEADER.unpack(blob[: SIDEDATA_HEADER.size]) offset += SIDEDATA_HEADER.size dataoffset = SIDEDATA_HEADER.size + (SIDEDATA_ENTRY.size * nbentry) for i in range(nbentry): nextoffset = offset + SIDEDATA_ENTRY.size key, size, storeddigest = SIDEDATA_ENTRY.unpack(blob[offset:nextoffset]) offset = nextoffset # read the data associated with that entry nextdataoffset = dataoffset + size entrytext = bytes(blob[dataoffset:nextdataoffset]) readdigest = hashutil.sha1(entrytext).digest() if storeddigest != readdigest: raise error.SidedataHashError(key, storeddigest, readdigest) sidedata[key] = entrytext dataoffset = nextdataoffset return sidedata