# 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, within the revision rawtext. They
are inserted and removed from it using the flagprocessors mechanism. 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 sidedatawriteprocessor(rl, text, sidedata):
sidedata = list(sidedata.items())
sidedata.sort()
rawtext = [SIDEDATA_HEADER.pack(len(sidedata))]
for key, value in sidedata:
digest = hashutil.sha1(value).digest()
rawtext.append(SIDEDATA_ENTRY.pack(key, len(value), digest))
for key, value in sidedata:
rawtext.append(value)
rawtext.append(bytes(text))
return b''.join(rawtext), False
def sidedatareadprocessor(rl, text):
sidedata = {}
offset = 0
(nbentry,) = SIDEDATA_HEADER.unpack(text[: 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(text[offset:nextoffset])
offset = nextoffset
# read the data associated with that entry
nextdataoffset = dataoffset + size
entrytext = text[dataoffset:nextdataoffset]
readdigest = hashutil.sha1(entrytext).digest()
if storeddigest != readdigest:
raise error.SidedataHashError(key, storeddigest, readdigest)
sidedata[key] = entrytext
dataoffset = nextdataoffset
text = text[dataoffset:]
return text, True, sidedata
def sidedatarawprocessor(rl, text):
# side data modifies rawtext and prevent rawtext hash validation
return False
processors = (
sidedatareadprocessor,
sidedatawriteprocessor,
sidedatarawprocessor,
)