annotate mercurial/revlogutils/sidedata.py @ 45537:2f8227a12592

rhg: add `--revision` argument to `rhg files`

Add the option to list the tracked files of a revision given its number
or full node id.

Benched on a clone of moz-central
where tip is 1671467:81deaa1a68ebb28db0490954034ab38ab269409d

files -r 81deaa1a68ebb28db0490954034ab38ab269409d > out.txt
hg  0m1.633s
rhg 0m0.157s

files -r 81deaa1a68ebb28db0490954034ab38ab269409d > /dev/null
hg  0m0.415s
rhg 0m0.143s

Differential Revision: https://phab.mercurial-scm.org/D9015

# sidedata.py - Logic around store extra data alongside revlog revisions
#
# Copyright 2019 Pierre-Yves David <[e-mail])
#
# 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, withing the revision rawtext. They
are inserted, 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 enought 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

# 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,
)