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# sidedata.py - Logic around store extra data alongside revlog revisions
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#
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# Copyright 2019 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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"""core code for "sidedata" support
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The "sidedata" are stored alongside the revision without actually being part of
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its content and not affecting its hash. It's main use cases is to cache
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important information related to a changesets.
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The current implementation is experimental and subject to changes. Do not rely
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on it in production.
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Sidedata are stored in the revlog itself, withing the revision rawtext. They
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are inserted, removed from it using the flagprocessors mechanism. The following
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format is currently used::
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initial header:
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<number of sidedata; 2 bytes>
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sidedata (repeated N times):
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<sidedata-key; 2 bytes>
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<sidedata-entry-length: 4 bytes>
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<sidedata-content-sha1-digest: 20 bytes>
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<sidedata-content; X bytes>
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normal raw text:
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<all bytes remaining in the rawtext>
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This is a simple and effective format. It should be enought to experiment with
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the concept.
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"""
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from __future__ import absolute_import
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import hashlib
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import struct
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from .. import error
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## sidedata type constant
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# reserve a block for testing purposes.
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SD_TEST1 = 1
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SD_TEST2 = 2
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SD_TEST3 = 3
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SD_TEST4 = 4
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SD_TEST5 = 5
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SD_TEST6 = 6
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SD_TEST7 = 7
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# key to store copies related information
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SD_P1COPIES = 8
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SD_P2COPIES = 9
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SD_FILESADDED = 10
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SD_FILESREMOVED = 11
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# internal format constant
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SIDEDATA_HEADER = struct.Struct(r'>H')
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SIDEDATA_ENTRY = struct.Struct(r'>HL20s')
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def sidedatawriteprocessor(rl, text, sidedata):
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sidedata = list(sidedata.items())
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sidedata.sort()
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rawtext = [SIDEDATA_HEADER.pack(len(sidedata))]
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for key, value in sidedata:
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digest = hashlib.sha1(value).digest()
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rawtext.append(SIDEDATA_ENTRY.pack(key, len(value), digest))
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for key, value in sidedata:
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rawtext.append(value)
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rawtext.append(bytes(text))
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return b''.join(rawtext), False
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def sidedatareadprocessor(rl, text):
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sidedata = {}
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offset = 0
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(nbentry,) = SIDEDATA_HEADER.unpack(text[: SIDEDATA_HEADER.size])
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offset += SIDEDATA_HEADER.size
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dataoffset = SIDEDATA_HEADER.size + (SIDEDATA_ENTRY.size * nbentry)
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for i in range(nbentry):
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nextoffset = offset + SIDEDATA_ENTRY.size
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key, size, storeddigest = SIDEDATA_ENTRY.unpack(text[offset:nextoffset])
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offset = nextoffset
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# read the data associated with that entry
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nextdataoffset = dataoffset + size
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entrytext = text[dataoffset:nextdataoffset]
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readdigest = hashlib.sha1(entrytext).digest()
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if storeddigest != readdigest:
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raise error.SidedataHashError(key, storeddigest, readdigest)
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sidedata[key] = entrytext
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dataoffset = nextdataoffset
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text = text[dataoffset:]
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return text, True, sidedata
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def sidedatarawprocessor(rl, text):
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# side data modifies rawtext and prevent rawtext hash validation
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return False
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processors = (
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sidedatareadprocessor,
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sidedatawriteprocessor,
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sidedatarawprocessor,
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)
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