branchmap: updating triggers a write
Rather than separate updating and writing, create a subclass that doesn't write
on update. This minimises chances we forget to write out updates somewhere.
This also makes refactoring and improving the branchmap functionality easier.
Differential Revision: https://phab.mercurial-scm.org/D5636
# storageutil.py - Storage functionality agnostic of backend implementation.
#
# Copyright 2018 Gregory Szorc <gregory.szorc@gmail.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
import hashlib
import re
import struct
from ..i18n import _
from ..node import (
bin,
nullid,
nullrev,
)
from .. import (
dagop,
error,
mdiff,
pycompat,
repository,
)
_nullhash = hashlib.sha1(nullid)
def hashrevisionsha1(text, p1, p2):
"""Compute the SHA-1 for revision data and its parents.
This hash combines both the current file contents and its history
in a manner that makes it easy to distinguish nodes with the same
content in the revision graph.
"""
# As of now, if one of the parent node is null, p2 is null
if p2 == nullid:
# deep copy of a hash is faster than creating one
s = _nullhash.copy()
s.update(p1)
else:
# none of the parent nodes are nullid
if p1 < p2:
a = p1
b = p2
else:
a = p2
b = p1
s = hashlib.sha1(a)
s.update(b)
s.update(text)
return s.digest()
METADATA_RE = re.compile(b'\x01\n')
def parsemeta(text):
"""Parse metadata header from revision data.
Returns a 2-tuple of (metadata, offset), where both can be None if there
is no metadata.
"""
# text can be buffer, so we can't use .startswith or .index
if text[:2] != b'\x01\n':
return None, None
s = METADATA_RE.search(text, 2).start()
mtext = text[2:s]
meta = {}
for l in mtext.splitlines():
k, v = l.split(b': ', 1)
meta[k] = v
return meta, s + 2
def packmeta(meta, text):
"""Add metadata to fulltext to produce revision text."""
keys = sorted(meta)
metatext = b''.join(b'%s: %s\n' % (k, meta[k]) for k in keys)
return b'\x01\n%s\x01\n%s' % (metatext, text)
def iscensoredtext(text):
meta = parsemeta(text)[0]
return meta and b'censored' in meta
def filtermetadata(text):
"""Extract just the revision data from source text.
Returns ``text`` unless it has a metadata header, in which case we return
a new buffer without hte metadata.
"""
if not text.startswith(b'\x01\n'):
return text
offset = text.index(b'\x01\n', 2)
return text[offset + 2:]
def filerevisioncopied(store, node):
"""Resolve file revision copy metadata.
Returns ``False`` if the file has no copy metadata. Otherwise a
2-tuple of the source filename and node.
"""
if store.parents(node)[0] != nullid:
return False
meta = parsemeta(store.revision(node))[0]
# copy and copyrev occur in pairs. In rare cases due to old bugs,
# one can occur without the other. So ensure both are present to flag
# as a copy.
if meta and b'copy' in meta and b'copyrev' in meta:
return meta[b'copy'], bin(meta[b'copyrev'])
return False
def filedataequivalent(store, node, filedata):
"""Determines whether file data is equivalent to a stored node.
Returns True if the passed file data would hash to the same value
as a stored revision and False otherwise.
When a stored revision is censored, filedata must be empty to have
equivalence.
When a stored revision has copy metadata, it is ignored as part
of the compare.
"""
if filedata.startswith(b'\x01\n'):
revisiontext = b'\x01\n\x01\n' + filedata
else:
revisiontext = filedata
p1, p2 = store.parents(node)
computednode = hashrevisionsha1(revisiontext, p1, p2)
if computednode == node:
return True
# Censored files compare against the empty file.
if store.iscensored(store.rev(node)):
return filedata == b''
# Renaming a file produces a different hash, even if the data
# remains unchanged. Check if that's the case.
if store.renamed(node):
return store.read(node) == filedata
return False
def iterrevs(storelen, start=0, stop=None):
"""Iterate over revision numbers in a store."""
step = 1
if stop is not None:
if start > stop:
step = -1
stop += step
if stop > storelen:
stop = storelen
else:
stop = storelen
return pycompat.xrange(start, stop, step)
def fileidlookup(store, fileid, identifier):
"""Resolve the file node for a value.
``store`` is an object implementing the ``ifileindex`` interface.
``fileid`` can be:
* A 20 byte binary node.
* An integer revision number
* A 40 byte hex node.
* A bytes that can be parsed as an integer representing a revision number.
``identifier`` is used to populate ``error.LookupError`` with an identifier
for the store.
Raises ``error.LookupError`` on failure.
"""
if isinstance(fileid, int):
try:
return store.node(fileid)
except IndexError:
raise error.LookupError('%d' % fileid, identifier,
_('no match found'))
if len(fileid) == 20:
try:
store.rev(fileid)
return fileid
except error.LookupError:
pass
if len(fileid) == 40:
try:
rawnode = bin(fileid)
store.rev(rawnode)
return rawnode
except TypeError:
pass
try:
rev = int(fileid)
if b'%d' % rev != fileid:
raise ValueError
try:
return store.node(rev)
except (IndexError, TypeError):
pass
except (ValueError, OverflowError):
pass
raise error.LookupError(fileid, identifier, _('no match found'))
def resolvestripinfo(minlinkrev, tiprev, headrevs, linkrevfn, parentrevsfn):
"""Resolve information needed to strip revisions.
Finds the minimum revision number that must be stripped in order to
strip ``minlinkrev``.
Returns a 2-tuple of the minimum revision number to do that and a set
of all revision numbers that have linkrevs that would be broken
by that strip.
``tiprev`` is the current tip-most revision. It is ``len(store) - 1``.
``headrevs`` is an iterable of head revisions.
``linkrevfn`` is a callable that receives a revision and returns a linked
revision.
``parentrevsfn`` is a callable that receives a revision number and returns
an iterable of its parent revision numbers.
"""
brokenrevs = set()
strippoint = tiprev + 1
heads = {}
futurelargelinkrevs = set()
for head in headrevs:
headlinkrev = linkrevfn(head)
heads[head] = headlinkrev
if headlinkrev >= minlinkrev:
futurelargelinkrevs.add(headlinkrev)
# This algorithm involves walking down the rev graph, starting at the
# heads. Since the revs are topologically sorted according to linkrev,
# once all head linkrevs are below the minlink, we know there are
# no more revs that could have a linkrev greater than minlink.
# So we can stop walking.
while futurelargelinkrevs:
strippoint -= 1
linkrev = heads.pop(strippoint)
if linkrev < minlinkrev:
brokenrevs.add(strippoint)
else:
futurelargelinkrevs.remove(linkrev)
for p in parentrevsfn(strippoint):
if p != nullrev:
plinkrev = linkrevfn(p)
heads[p] = plinkrev
if plinkrev >= minlinkrev:
futurelargelinkrevs.add(plinkrev)
return strippoint, brokenrevs
def emitrevisions(store, nodes, nodesorder, resultcls, deltaparentfn=None,
candeltafn=None, rawsizefn=None, revdifffn=None, flagsfn=None,
deltamode=repository.CG_DELTAMODE_STD,
revisiondata=False, assumehaveparentrevisions=False):
"""Generic implementation of ifiledata.emitrevisions().
Emitting revision data is subtly complex. This function attempts to
encapsulate all the logic for doing so in a backend-agnostic way.
``store``
Object conforming to ``ifilestorage`` interface.
``nodes``
List of revision nodes whose data to emit.
``resultcls``
A type implementing the ``irevisiondelta`` interface that will be
constructed and returned.
``deltaparentfn`` (optional)
Callable receiving a revision number and returning the revision number
of a revision that the internal delta is stored against. This delta
will be preferred over computing a new arbitrary delta.
If not defined, a delta will always be computed from raw revision
data.
``candeltafn`` (optional)
Callable receiving a pair of revision numbers that returns a bool
indicating whether a delta between them can be produced.
If not defined, it is assumed that any two revisions can delta with
each other.
``rawsizefn`` (optional)
Callable receiving a revision number and returning the length of the
``store.revision(rev, raw=True)``.
If not defined, ``len(store.revision(rev, raw=True))`` will be called.
``revdifffn`` (optional)
Callable receiving a pair of revision numbers that returns a delta
between them.
If not defined, a delta will be computed by invoking mdiff code
on ``store.revision()`` results.
Defining this function allows a precomputed or stored delta to be
used without having to compute on.
``flagsfn`` (optional)
Callable receiving a revision number and returns the integer flags
value for it. If not defined, flags value will be 0.
``deltamode``
constaint on delta to be sent:
* CG_DELTAMODE_STD - normal mode, try to reuse storage deltas,
* CG_DELTAMODE_PREV - only delta against "prev",
* CG_DELTAMODE_FULL - only issue full snapshot.
Whether to send fulltext revisions instead of deltas, if allowed.
``nodesorder``
``revisiondata``
``assumehaveparentrevisions``
"""
fnode = store.node
frev = store.rev
if nodesorder == 'nodes':
revs = [frev(n) for n in nodes]
elif nodesorder == 'linear':
revs = set(frev(n) for n in nodes)
revs = dagop.linearize(revs, store.parentrevs)
else: # storage and default
revs = sorted(frev(n) for n in nodes)
prevrev = None
if deltamode == repository.CG_DELTAMODE_PREV or assumehaveparentrevisions:
prevrev = store.parentrevs(revs[0])[0]
# Set of revs available to delta against.
available = set()
for rev in revs:
if rev == nullrev:
continue
node = fnode(rev)
p1rev, p2rev = store.parentrevs(rev)
if deltaparentfn:
deltaparentrev = deltaparentfn(rev)
else:
deltaparentrev = nullrev
# Forced delta against previous mode.
if deltamode == repository.CG_DELTAMODE_PREV:
baserev = prevrev
# We're instructed to send fulltext. Honor that.
elif deltamode == repository.CG_DELTAMODE_FULL:
baserev = nullrev
# We're instructed to use p1. Honor that
elif deltamode == repository.CG_DELTAMODE_P1:
baserev = p1rev
# There is a delta in storage. We try to use that because it
# amounts to effectively copying data from storage and is
# therefore the fastest.
elif deltaparentrev != nullrev:
# Base revision was already emitted in this group. We can
# always safely use the delta.
if deltaparentrev in available:
baserev = deltaparentrev
# Base revision is a parent that hasn't been emitted already.
# Use it if we can assume the receiver has the parent revision.
elif (assumehaveparentrevisions
and deltaparentrev in (p1rev, p2rev)):
baserev = deltaparentrev
# No guarantee the receiver has the delta parent. Send delta
# against last revision (if possible), which in the common case
# should be similar enough to this revision that the delta is
# reasonable.
elif prevrev is not None:
baserev = prevrev
else:
baserev = nullrev
# Storage has a fulltext revision.
# Let's use the previous revision, which is as good a guess as any.
# There is definitely room to improve this logic.
elif prevrev is not None:
baserev = prevrev
else:
baserev = nullrev
# But we can't actually use our chosen delta base for whatever
# reason. Reset to fulltext.
if baserev != nullrev and (candeltafn and not candeltafn(baserev, rev)):
baserev = nullrev
revision = None
delta = None
baserevisionsize = None
if revisiondata:
if store.iscensored(baserev) or store.iscensored(rev):
try:
revision = store.revision(node, raw=True)
except error.CensoredNodeError as e:
revision = e.tombstone
if baserev != nullrev:
if rawsizefn:
baserevisionsize = rawsizefn(baserev)
else:
baserevisionsize = len(store.revision(baserev,
raw=True))
elif (baserev == nullrev
and deltamode != repository.CG_DELTAMODE_PREV):
revision = store.revision(node, raw=True)
available.add(rev)
else:
if revdifffn:
delta = revdifffn(baserev, rev)
else:
delta = mdiff.textdiff(store.revision(baserev, raw=True),
store.revision(rev, raw=True))
available.add(rev)
yield resultcls(
node=node,
p1node=fnode(p1rev),
p2node=fnode(p2rev),
basenode=fnode(baserev),
flags=flagsfn(rev) if flagsfn else 0,
baserevisionsize=baserevisionsize,
revision=revision,
delta=delta)
prevrev = rev
def deltaiscensored(delta, baserev, baselenfn):
"""Determine if a delta represents censored revision data.
``baserev`` is the base revision this delta is encoded against.
``baselenfn`` is a callable receiving a revision number that resolves the
length of the revision fulltext.
Returns a bool indicating if the result of the delta represents a censored
revision.
"""
# Fragile heuristic: unless new file meta keys are added alphabetically
# preceding "censored", all censored revisions are prefixed by
# "\1\ncensored:". A delta producing such a censored revision must be a
# full-replacement delta, so we inspect the first and only patch in the
# delta for this prefix.
hlen = struct.calcsize(">lll")
if len(delta) <= hlen:
return False
oldlen = baselenfn(baserev)
newlen = len(delta) - hlen
if delta[:hlen] != mdiff.replacediffheader(oldlen, newlen):
return False
add = "\1\ncensored:"
addlen = len(add)
return newlen >= addlen and delta[hlen:hlen + addlen] == add