Mercurial > hg
changeset 39330:655b5b465953
revlog: split functionality related to deltas computation in a new module
The revlog module is getting big and this logic is getting more and more
advanced. Moving it to `mercurial.revlogutils.deltas` split a lot off
revlog.py and will help this logic to become less interleaved with revlog.
The code is simply moved without modification (but for namespace changes).
Refactoring and improvement will be made in later changesets.
| author | Boris Feld <boris.feld@octobus.net> |
|---|---|
| date | Thu, 16 Aug 2018 02:53:42 +0200 |
| parents | 729082bb9938 |
| children | fd0150a3c2fe |
| files | mercurial/debugcommands.py mercurial/revlog.py mercurial/revlogutils/constants.py mercurial/revlogutils/deltas.py |
| diffstat | 4 files changed, 748 insertions(+), 704 deletions(-) [+] |
line wrap: on
line diff
--- a/mercurial/debugcommands.py Thu Aug 16 02:08:13 2018 +0200 +++ b/mercurial/debugcommands.py Thu Aug 16 02:53:42 2018 +0200 @@ -88,6 +88,10 @@ stringutil, ) +from .revlogutils import ( + deltas as deltautil +) + release = lockmod.release command = registrar.command() @@ -706,7 +710,7 @@ largestblock = 0 srchunks = 0 - for revschunk in revlog._slicechunk(r, chain): + for revschunk in deltautil.slicechunk(r, chain): srchunks += 1 blkend = start(revschunk[-1]) + length(revschunk[-1]) blksize = blkend - start(revschunk[0])
--- a/mercurial/revlog.py Thu Aug 16 02:08:13 2018 +0200 +++ b/mercurial/revlog.py Thu Aug 16 02:53:42 2018 +0200 @@ -17,7 +17,6 @@ import contextlib import errno import hashlib -import heapq import os import re import struct @@ -39,7 +38,6 @@ from .revlogutils.constants import ( FLAG_GENERALDELTA, FLAG_INLINE_DATA, - LIMIT_DELTA2TEXT, REVIDX_DEFAULT_FLAGS, REVIDX_ELLIPSIS, REVIDX_EXTSTORED, @@ -69,6 +67,9 @@ templatefilters, util, ) +from .revlogutils import ( + deltas as deltautil, +) from .utils import ( interfaceutil, stringutil, @@ -211,610 +212,6 @@ s.update(text) return s.digest() -class _testrevlog(object): - """minimalist fake revlog to use in doctests""" - - def __init__(self, data, density=0.5, mingap=0): - """data is an list of revision payload boundaries""" - self._data = data - self._srdensitythreshold = density - self._srmingapsize = mingap - - def start(self, rev): - if rev == 0: - return 0 - return self._data[rev - 1] - - def end(self, rev): - return self._data[rev] - - def length(self, rev): - return self.end(rev) - self.start(rev) - - def __len__(self): - return len(self._data) - -def _trimchunk(revlog, revs, startidx, endidx=None): - """returns revs[startidx:endidx] without empty trailing revs - - Doctest Setup - >>> revlog = _testrevlog([ - ... 5, #0 - ... 10, #1 - ... 12, #2 - ... 12, #3 (empty) - ... 17, #4 - ... 21, #5 - ... 21, #6 (empty) - ... ]) - - Contiguous cases: - >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 0) - [0, 1, 2, 3, 4, 5] - >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 0, 5) - [0, 1, 2, 3, 4] - >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 0, 4) - [0, 1, 2] - >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 2, 4) - [2] - >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 3) - [3, 4, 5] - >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 3, 5) - [3, 4] - - Discontiguous cases: - >>> _trimchunk(revlog, [1, 3, 5, 6], 0) - [1, 3, 5] - >>> _trimchunk(revlog, [1, 3, 5, 6], 0, 2) - [1] - >>> _trimchunk(revlog, [1, 3, 5, 6], 1, 3) - [3, 5] - >>> _trimchunk(revlog, [1, 3, 5, 6], 1) - [3, 5] - """ - length = revlog.length - - if endidx is None: - endidx = len(revs) - - # If we have a non-emtpy delta candidate, there are nothing to trim - if revs[endidx - 1] < len(revlog): - # Trim empty revs at the end, except the very first revision of a chain - while (endidx > 1 - and endidx > startidx - and length(revs[endidx - 1]) == 0): - endidx -= 1 - - return revs[startidx:endidx] - -def _segmentspan(revlog, revs, deltainfo=None): - """Get the byte span of a segment of revisions - - revs is a sorted array of revision numbers - - >>> revlog = _testrevlog([ - ... 5, #0 - ... 10, #1 - ... 12, #2 - ... 12, #3 (empty) - ... 17, #4 - ... ]) - - >>> _segmentspan(revlog, [0, 1, 2, 3, 4]) - 17 - >>> _segmentspan(revlog, [0, 4]) - 17 - >>> _segmentspan(revlog, [3, 4]) - 5 - >>> _segmentspan(revlog, [1, 2, 3,]) - 7 - >>> _segmentspan(revlog, [1, 3]) - 7 - """ - if not revs: - return 0 - if deltainfo is not None and len(revlog) <= revs[-1]: - if len(revs) == 1: - return deltainfo.deltalen - offset = revlog.end(len(revlog) - 1) - end = deltainfo.deltalen + offset - else: - end = revlog.end(revs[-1]) - return end - revlog.start(revs[0]) - -def _slicechunk(revlog, revs, deltainfo=None, targetsize=None): - """slice revs to reduce the amount of unrelated data to be read from disk. - - ``revs`` is sliced into groups that should be read in one time. - Assume that revs are sorted. - - The initial chunk is sliced until the overall density (payload/chunks-span - ratio) is above `revlog._srdensitythreshold`. No gap smaller than - `revlog._srmingapsize` is skipped. - - If `targetsize` is set, no chunk larger than `targetsize` will be yield. - For consistency with other slicing choice, this limit won't go lower than - `revlog._srmingapsize`. - - If individual revisions chunk are larger than this limit, they will still - be raised individually. - - >>> revlog = _testrevlog([ - ... 5, #00 (5) - ... 10, #01 (5) - ... 12, #02 (2) - ... 12, #03 (empty) - ... 27, #04 (15) - ... 31, #05 (4) - ... 31, #06 (empty) - ... 42, #07 (11) - ... 47, #08 (5) - ... 47, #09 (empty) - ... 48, #10 (1) - ... 51, #11 (3) - ... 74, #12 (23) - ... 85, #13 (11) - ... 86, #14 (1) - ... 91, #15 (5) - ... ]) - - >>> list(_slicechunk(revlog, list(range(16)))) - [[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]] - >>> list(_slicechunk(revlog, [0, 15])) - [[0], [15]] - >>> list(_slicechunk(revlog, [0, 11, 15])) - [[0], [11], [15]] - >>> list(_slicechunk(revlog, [0, 11, 13, 15])) - [[0], [11, 13, 15]] - >>> list(_slicechunk(revlog, [1, 2, 3, 5, 8, 10, 11, 14])) - [[1, 2], [5, 8, 10, 11], [14]] - - Slicing with a maximum chunk size - >>> list(_slicechunk(revlog, [0, 11, 13, 15], targetsize=15)) - [[0], [11], [13], [15]] - >>> list(_slicechunk(revlog, [0, 11, 13, 15], targetsize=20)) - [[0], [11], [13, 15]] - """ - if targetsize is not None: - targetsize = max(targetsize, revlog._srmingapsize) - # targetsize should not be specified when evaluating delta candidates: - # * targetsize is used to ensure we stay within specification when reading, - # * deltainfo is used to pick are good delta chain when writing. - if not (deltainfo is None or targetsize is None): - msg = 'cannot use `targetsize` with a `deltainfo`' - raise error.ProgrammingError(msg) - for chunk in _slicechunktodensity(revlog, revs, - deltainfo, - revlog._srdensitythreshold, - revlog._srmingapsize): - for subchunk in _slicechunktosize(revlog, chunk, targetsize): - yield subchunk - -def _slicechunktosize(revlog, revs, targetsize=None): - """slice revs to match the target size - - This is intended to be used on chunk that density slicing selected by that - are still too large compared to the read garantee of revlog. This might - happens when "minimal gap size" interrupted the slicing or when chain are - built in a way that create large blocks next to each other. - - >>> revlog = _testrevlog([ - ... 3, #0 (3) - ... 5, #1 (2) - ... 6, #2 (1) - ... 8, #3 (2) - ... 8, #4 (empty) - ... 11, #5 (3) - ... 12, #6 (1) - ... 13, #7 (1) - ... 14, #8 (1) - ... ]) - - Cases where chunk is already small enough - >>> list(_slicechunktosize(revlog, [0], 3)) - [[0]] - >>> list(_slicechunktosize(revlog, [6, 7], 3)) - [[6, 7]] - >>> list(_slicechunktosize(revlog, [0], None)) - [[0]] - >>> list(_slicechunktosize(revlog, [6, 7], None)) - [[6, 7]] - - cases where we need actual slicing - >>> list(_slicechunktosize(revlog, [0, 1], 3)) - [[0], [1]] - >>> list(_slicechunktosize(revlog, [1, 3], 3)) - [[1], [3]] - >>> list(_slicechunktosize(revlog, [1, 2, 3], 3)) - [[1, 2], [3]] - >>> list(_slicechunktosize(revlog, [3, 5], 3)) - [[3], [5]] - >>> list(_slicechunktosize(revlog, [3, 4, 5], 3)) - [[3], [5]] - >>> list(_slicechunktosize(revlog, [5, 6, 7, 8], 3)) - [[5], [6, 7, 8]] - >>> list(_slicechunktosize(revlog, [0, 1, 2, 3, 4, 5, 6, 7, 8], 3)) - [[0], [1, 2], [3], [5], [6, 7, 8]] - - Case with too large individual chunk (must return valid chunk) - >>> list(_slicechunktosize(revlog, [0, 1], 2)) - [[0], [1]] - >>> list(_slicechunktosize(revlog, [1, 3], 1)) - [[1], [3]] - >>> list(_slicechunktosize(revlog, [3, 4, 5], 2)) - [[3], [5]] - """ - assert targetsize is None or 0 <= targetsize - if targetsize is None or _segmentspan(revlog, revs) <= targetsize: - yield revs - return - - startrevidx = 0 - startdata = revlog.start(revs[0]) - endrevidx = 0 - iterrevs = enumerate(revs) - next(iterrevs) # skip first rev. - for idx, r in iterrevs: - span = revlog.end(r) - startdata - if span <= targetsize: - endrevidx = idx - else: - chunk = _trimchunk(revlog, revs, startrevidx, endrevidx + 1) - if chunk: - yield chunk - startrevidx = idx - startdata = revlog.start(r) - endrevidx = idx - yield _trimchunk(revlog, revs, startrevidx) - -def _slicechunktodensity(revlog, revs, deltainfo=None, targetdensity=0.5, - mingapsize=0): - """slice revs to reduce the amount of unrelated data to be read from disk. - - ``revs`` is sliced into groups that should be read in one time. - Assume that revs are sorted. - - ``deltainfo`` is a _deltainfo instance of a revision that we would append - to the top of the revlog. - - The initial chunk is sliced until the overall density (payload/chunks-span - ratio) is above `targetdensity`. No gap smaller than `mingapsize` is - skipped. - - >>> revlog = _testrevlog([ - ... 5, #00 (5) - ... 10, #01 (5) - ... 12, #02 (2) - ... 12, #03 (empty) - ... 27, #04 (15) - ... 31, #05 (4) - ... 31, #06 (empty) - ... 42, #07 (11) - ... 47, #08 (5) - ... 47, #09 (empty) - ... 48, #10 (1) - ... 51, #11 (3) - ... 74, #12 (23) - ... 85, #13 (11) - ... 86, #14 (1) - ... 91, #15 (5) - ... ]) - - >>> list(_slicechunktodensity(revlog, list(range(16)))) - [[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]] - >>> list(_slicechunktodensity(revlog, [0, 15])) - [[0], [15]] - >>> list(_slicechunktodensity(revlog, [0, 11, 15])) - [[0], [11], [15]] - >>> list(_slicechunktodensity(revlog, [0, 11, 13, 15])) - [[0], [11, 13, 15]] - >>> list(_slicechunktodensity(revlog, [1, 2, 3, 5, 8, 10, 11, 14])) - [[1, 2], [5, 8, 10, 11], [14]] - >>> list(_slicechunktodensity(revlog, [1, 2, 3, 5, 8, 10, 11, 14], - ... mingapsize=20)) - [[1, 2, 3, 5, 8, 10, 11], [14]] - >>> list(_slicechunktodensity(revlog, [1, 2, 3, 5, 8, 10, 11, 14], - ... targetdensity=0.95)) - [[1, 2], [5], [8, 10, 11], [14]] - >>> list(_slicechunktodensity(revlog, [1, 2, 3, 5, 8, 10, 11, 14], - ... targetdensity=0.95, mingapsize=12)) - [[1, 2], [5, 8, 10, 11], [14]] - """ - start = revlog.start - length = revlog.length - - if len(revs) <= 1: - yield revs - return - - nextrev = len(revlog) - nextoffset = revlog.end(nextrev - 1) - - if deltainfo is None: - deltachainspan = _segmentspan(revlog, revs) - chainpayload = sum(length(r) for r in revs) - else: - deltachainspan = deltainfo.distance - chainpayload = deltainfo.compresseddeltalen - - if deltachainspan < mingapsize: - yield revs - return - - readdata = deltachainspan - - if deltachainspan: - density = chainpayload / float(deltachainspan) - else: - density = 1.0 - - if density >= targetdensity: - yield revs - return - - if deltainfo is not None and deltainfo.deltalen: - revs = list(revs) - revs.append(nextrev) - - # Store the gaps in a heap to have them sorted by decreasing size - gapsheap = [] - heapq.heapify(gapsheap) - prevend = None - for i, rev in enumerate(revs): - if rev < nextrev: - revstart = start(rev) - revlen = length(rev) - else: - revstart = nextoffset - revlen = deltainfo.deltalen - - # Skip empty revisions to form larger holes - if revlen == 0: - continue - - if prevend is not None: - gapsize = revstart - prevend - # only consider holes that are large enough - if gapsize > mingapsize: - heapq.heappush(gapsheap, (-gapsize, i)) - - prevend = revstart + revlen - - # Collect the indices of the largest holes until the density is acceptable - indicesheap = [] - heapq.heapify(indicesheap) - while gapsheap and density < targetdensity: - oppgapsize, gapidx = heapq.heappop(gapsheap) - - heapq.heappush(indicesheap, gapidx) - - # the gap sizes are stored as negatives to be sorted decreasingly - # by the heap - readdata -= (-oppgapsize) - if readdata > 0: - density = chainpayload / float(readdata) - else: - density = 1.0 - - # Cut the revs at collected indices - previdx = 0 - while indicesheap: - idx = heapq.heappop(indicesheap) - - chunk = _trimchunk(revlog, revs, previdx, idx) - if chunk: - yield chunk - - previdx = idx - - chunk = _trimchunk(revlog, revs, previdx) - if chunk: - yield chunk - -@attr.s(slots=True, frozen=True) -class _deltainfo(object): - distance = attr.ib() - deltalen = attr.ib() - data = attr.ib() - base = attr.ib() - chainbase = attr.ib() - chainlen = attr.ib() - compresseddeltalen = attr.ib() - snapshotdepth = attr.ib() - -class _deltacomputer(object): - def __init__(self, revlog): - self.revlog = revlog - - def _getcandidaterevs(self, p1, p2, cachedelta): - """ - Provides revisions that present an interest to be diffed against, - grouped by level of easiness. - """ - revlog = self.revlog - gdelta = revlog._generaldelta - curr = len(revlog) - prev = curr - 1 - p1r, p2r = revlog.rev(p1), revlog.rev(p2) - - # should we try to build a delta? - if prev != nullrev and revlog._storedeltachains: - tested = set() - # This condition is true most of the time when processing - # changegroup data into a generaldelta repo. The only time it - # isn't true is if this is the first revision in a delta chain - # or if ``format.generaldelta=true`` disabled ``lazydeltabase``. - if cachedelta and gdelta and revlog._lazydeltabase: - # Assume what we received from the server is a good choice - # build delta will reuse the cache - yield (cachedelta[0],) - tested.add(cachedelta[0]) - - if gdelta: - # exclude already lazy tested base if any - parents = [p for p in (p1r, p2r) - if p != nullrev and p not in tested] - - if not revlog._deltabothparents and len(parents) == 2: - parents.sort() - # To minimize the chance of having to build a fulltext, - # pick first whichever parent is closest to us (max rev) - yield (parents[1],) - # then the other one (min rev) if the first did not fit - yield (parents[0],) - tested.update(parents) - elif len(parents) > 0: - # Test all parents (1 or 2), and keep the best candidate - yield parents - tested.update(parents) - - if prev not in tested: - # other approach failed try against prev to hopefully save us a - # fulltext. - yield (prev,) - tested.add(prev) - - def buildtext(self, revinfo, fh): - """Builds a fulltext version of a revision - - revinfo: _revisioninfo instance that contains all needed info - fh: file handle to either the .i or the .d revlog file, - depending on whether it is inlined or not - """ - btext = revinfo.btext - if btext[0] is not None: - return btext[0] - - revlog = self.revlog - cachedelta = revinfo.cachedelta - flags = revinfo.flags - node = revinfo.node - - baserev = cachedelta[0] - delta = cachedelta[1] - # special case deltas which replace entire base; no need to decode - # base revision. this neatly avoids censored bases, which throw when - # they're decoded. - hlen = struct.calcsize(">lll") - if delta[:hlen] == mdiff.replacediffheader(revlog.rawsize(baserev), - len(delta) - hlen): - btext[0] = delta[hlen:] - else: - # deltabase is rawtext before changed by flag processors, which is - # equivalent to non-raw text - basetext = revlog.revision(baserev, _df=fh, raw=False) - btext[0] = mdiff.patch(basetext, delta) - - try: - res = revlog._processflags(btext[0], flags, 'read', raw=True) - btext[0], validatehash = res - if validatehash: - revlog.checkhash(btext[0], node, p1=revinfo.p1, p2=revinfo.p2) - if flags & REVIDX_ISCENSORED: - raise RevlogError(_('node %s is not censored') % node) - except CensoredNodeError: - # must pass the censored index flag to add censored revisions - if not flags & REVIDX_ISCENSORED: - raise - return btext[0] - - def _builddeltadiff(self, base, revinfo, fh): - revlog = self.revlog - t = self.buildtext(revinfo, fh) - if revlog.iscensored(base): - # deltas based on a censored revision must replace the - # full content in one patch, so delta works everywhere - header = mdiff.replacediffheader(revlog.rawsize(base), len(t)) - delta = header + t - else: - ptext = revlog.revision(base, _df=fh, raw=True) - delta = mdiff.textdiff(ptext, t) - - return delta - - def _builddeltainfo(self, revinfo, base, fh): - # can we use the cached delta? - if revinfo.cachedelta and revinfo.cachedelta[0] == base: - delta = revinfo.cachedelta[1] - else: - delta = self._builddeltadiff(base, revinfo, fh) - revlog = self.revlog - header, data = revlog.compress(delta) - deltalen = len(header) + len(data) - chainbase = revlog.chainbase(base) - offset = revlog.end(len(revlog) - 1) - dist = deltalen + offset - revlog.start(chainbase) - if revlog._generaldelta: - deltabase = base - else: - deltabase = chainbase - chainlen, compresseddeltalen = revlog._chaininfo(base) - chainlen += 1 - compresseddeltalen += deltalen - - revlog = self.revlog - snapshotdepth = None - if deltabase == nullrev: - snapshotdepth = 0 - elif revlog._sparserevlog and revlog.issnapshot(deltabase): - # A delta chain should always be one full snapshot, - # zero or more semi-snapshots, and zero or more deltas - p1, p2 = revlog.rev(revinfo.p1), revlog.rev(revinfo.p2) - if deltabase not in (p1, p2) and revlog.issnapshot(deltabase): - snapshotdepth = len(revlog._deltachain(deltabase)[0]) - - return _deltainfo(dist, deltalen, (header, data), deltabase, - chainbase, chainlen, compresseddeltalen, - snapshotdepth) - - def finddeltainfo(self, revinfo, fh): - """Find an acceptable delta against a candidate revision - - revinfo: information about the revision (instance of _revisioninfo) - fh: file handle to either the .i or the .d revlog file, - depending on whether it is inlined or not - - Returns the first acceptable candidate revision, as ordered by - _getcandidaterevs - """ - if not revinfo.textlen: - return None # empty file do not need delta - - cachedelta = revinfo.cachedelta - p1 = revinfo.p1 - p2 = revinfo.p2 - revlog = self.revlog - - deltalength = self.revlog.length - deltaparent = self.revlog.deltaparent - - deltainfo = None - deltas_limit = revinfo.textlen * LIMIT_DELTA2TEXT - for candidaterevs in self._getcandidaterevs(p1, p2, cachedelta): - # filter out delta base that will never produce good delta - candidaterevs = [r for r in candidaterevs - if self.revlog.length(r) <= deltas_limit] - nominateddeltas = [] - for candidaterev in candidaterevs: - # skip over empty delta (no need to include them in a chain) - while candidaterev != nullrev and not deltalength(candidaterev): - candidaterev = deltaparent(candidaterev) - # no need to try a delta against nullid, this will be handled - # by fulltext later. - if candidaterev == nullrev: - continue - # no delta for rawtext-changing revs (see "candelta" for why) - if revlog.flags(candidaterev) & REVIDX_RAWTEXT_CHANGING_FLAGS: - continue - candidatedelta = self._builddeltainfo(revinfo, candidaterev, fh) - if revlog._isgooddeltainfo(candidatedelta, revinfo): - nominateddeltas.append(candidatedelta) - if nominateddeltas: - deltainfo = min(nominateddeltas, key=lambda x: x.deltalen) - break - - return deltainfo - @attr.s(slots=True, frozen=True) class _revisioninfo(object): """Information about a revision that allows building its fulltext @@ -2095,7 +1492,8 @@ if not self._withsparseread: slicedchunks = (revs,) else: - slicedchunks = _slicechunk(self, revs, targetsize=targetsize) + slicedchunks = deltautil.slicechunk(self, revs, + targetsize=targetsize) for revschunk in slicedchunks: firstrev = revschunk[0] @@ -2393,7 +1791,7 @@ computed by default as hash(text, p1, p2), however subclasses might use different hashing method (and override checkhash() in such case) flags - the known flags to set on the revision - deltacomputer - an optional _deltacomputer instance shared between + deltacomputer - an optional deltacomputer instance shared between multiple calls """ if link == nullrev: @@ -2516,95 +1914,6 @@ return compressor.decompress(data) - def _isgooddeltainfo(self, deltainfo, revinfo): - """Returns True if the given delta is good. Good means that it is within - the disk span, disk size, and chain length bounds that we know to be - performant.""" - if deltainfo is None: - return False - - # - 'deltainfo.distance' is the distance from the base revision -- - # bounding it limits the amount of I/O we need to do. - # - 'deltainfo.compresseddeltalen' is the sum of the total size of - # deltas we need to apply -- bounding it limits the amount of CPU - # we consume. - - if self._sparserevlog: - # As sparse-read will be used, we can consider that the distance, - # instead of being the span of the whole chunk, - # is the span of the largest read chunk - base = deltainfo.base - - if base != nullrev: - deltachain = self._deltachain(base)[0] - else: - deltachain = [] - - # search for the first non-snapshot revision - for idx, r in enumerate(deltachain): - if not self.issnapshot(r): - break - deltachain = deltachain[idx:] - chunks = _slicechunk(self, deltachain, deltainfo) - all_span = [_segmentspan(self, revs, deltainfo) for revs in chunks] - distance = max(all_span) - else: - distance = deltainfo.distance - - textlen = revinfo.textlen - defaultmax = textlen * 4 - maxdist = self._maxdeltachainspan - if not maxdist: - maxdist = distance # ensure the conditional pass - maxdist = max(maxdist, defaultmax) - if self._sparserevlog and maxdist < self._srmingapsize: - # In multiple place, we are ignoring irrelevant data range below a - # certain size. Be also apply this tradeoff here and relax span - # constraint for small enought content. - maxdist = self._srmingapsize - - # Bad delta from read span: - # - # If the span of data read is larger than the maximum allowed. - if maxdist < distance: - return False - - # Bad delta from new delta size: - # - # If the delta size is larger than the target text, storing the - # delta will be inefficient. - if textlen < deltainfo.deltalen: - return False - - # Bad delta from cumulated payload size: - # - # If the sum of delta get larger than K * target text length. - if textlen * LIMIT_DELTA2TEXT < deltainfo.compresseddeltalen: - return False - - # Bad delta from chain length: - # - # If the number of delta in the chain gets too high. - if self._maxchainlen and self._maxchainlen < deltainfo.chainlen: - return False - - # bad delta from intermediate snapshot size limit - # - # If an intermediate snapshot size is higher than the limit. The - # limit exist to prevent endless chain of intermediate delta to be - # created. - if (deltainfo.snapshotdepth is not None and - (textlen >> deltainfo.snapshotdepth) < deltainfo.deltalen): - return False - - # bad delta if new intermediate snapshot is larger than the previous - # snapshot - if (deltainfo.snapshotdepth - and self.length(deltainfo.base) < deltainfo.deltalen): - return False - - return True - def _addrevision(self, node, rawtext, transaction, link, p1, p2, flags, cachedelta, ifh, dfh, alwayscache=False, deltacomputer=None): @@ -2652,7 +1961,7 @@ textlen = len(rawtext) if deltacomputer is None: - deltacomputer = _deltacomputer(self) + deltacomputer = deltautil.deltacomputer(self) revinfo = _revisioninfo(node, p1, p2, btext, textlen, cachedelta, flags) @@ -2754,7 +2063,7 @@ dfh.flush() ifh.flush() try: - deltacomputer = _deltacomputer(self) + deltacomputer = deltautil.deltacomputer(self) # loop through our set of deltas for data in deltas: node, p1, p2, linknode, deltabase, delta, flags = data @@ -3127,7 +2436,7 @@ populatecachedelta = deltareuse in (self.DELTAREUSEALWAYS, self.DELTAREUSESAMEREVS) - deltacomputer = _deltacomputer(destrevlog) + deltacomputer = deltautil.deltacomputer(destrevlog) index = self.index for rev in self: entry = index[rev]
--- a/mercurial/revlogutils/constants.py Thu Aug 16 02:08:13 2018 +0200 +++ b/mercurial/revlogutils/constants.py Thu Aug 16 02:53:42 2018 +0200 @@ -41,6 +41,3 @@ REVIDX_KNOWN_FLAGS = util.bitsfrom(REVIDX_FLAGS_ORDER) # bitmark for flags that could cause rawdata content change REVIDX_RAWTEXT_CHANGING_FLAGS = REVIDX_ISCENSORED | REVIDX_EXTSTORED - -# maximum <delta-chain-data>/<revision-text-length> ratio -LIMIT_DELTA2TEXT = 2
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mercurial/revlogutils/deltas.py Thu Aug 16 02:53:42 2018 +0200 @@ -0,0 +1,734 @@ +# revlogdeltas.py - Logic around delta computation for revlog +# +# Copyright 2005-2007 Matt Mackall <mpm@selenic.com> +# Copyright 2018 Octobus <contact@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. +"""Helper class to compute deltas stored inside revlogs""" + +from __future__ import absolute_import + +import heapq +import struct + +# import stuff from node for others to import from revlog +from ..node import ( + nullrev, +) +from ..i18n import _ + +from .constants import ( + REVIDX_ISCENSORED, + REVIDX_RAWTEXT_CHANGING_FLAGS, +) + +from ..thirdparty import ( + attr, +) + +from .. import ( + error, + mdiff, +) + +RevlogError = error.RevlogError +CensoredNodeError = error.CensoredNodeError + +# maximum <delta-chain-data>/<revision-text-length> ratio +LIMIT_DELTA2TEXT = 2 + +class _testrevlog(object): + """minimalist fake revlog to use in doctests""" + + def __init__(self, data, density=0.5, mingap=0): + """data is an list of revision payload boundaries""" + self._data = data + self._srdensitythreshold = density + self._srmingapsize = mingap + + def start(self, rev): + if rev == 0: + return 0 + return self._data[rev - 1] + + def end(self, rev): + return self._data[rev] + + def length(self, rev): + return self.end(rev) - self.start(rev) + + def __len__(self): + return len(self._data) + +def slicechunk(revlog, revs, deltainfo=None, targetsize=None): + """slice revs to reduce the amount of unrelated data to be read from disk. + + ``revs`` is sliced into groups that should be read in one time. + Assume that revs are sorted. + + The initial chunk is sliced until the overall density (payload/chunks-span + ratio) is above `revlog._srdensitythreshold`. No gap smaller than + `revlog._srmingapsize` is skipped. + + If `targetsize` is set, no chunk larger than `targetsize` will be yield. + For consistency with other slicing choice, this limit won't go lower than + `revlog._srmingapsize`. + + If individual revisions chunk are larger than this limit, they will still + be raised individually. + + >>> revlog = _testrevlog([ + ... 5, #00 (5) + ... 10, #01 (5) + ... 12, #02 (2) + ... 12, #03 (empty) + ... 27, #04 (15) + ... 31, #05 (4) + ... 31, #06 (empty) + ... 42, #07 (11) + ... 47, #08 (5) + ... 47, #09 (empty) + ... 48, #10 (1) + ... 51, #11 (3) + ... 74, #12 (23) + ... 85, #13 (11) + ... 86, #14 (1) + ... 91, #15 (5) + ... ]) + + >>> list(slicechunk(revlog, list(range(16)))) + [[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]] + >>> list(slicechunk(revlog, [0, 15])) + [[0], [15]] + >>> list(slicechunk(revlog, [0, 11, 15])) + [[0], [11], [15]] + >>> list(slicechunk(revlog, [0, 11, 13, 15])) + [[0], [11, 13, 15]] + >>> list(slicechunk(revlog, [1, 2, 3, 5, 8, 10, 11, 14])) + [[1, 2], [5, 8, 10, 11], [14]] + + Slicing with a maximum chunk size + >>> list(slicechunk(revlog, [0, 11, 13, 15], targetsize=15)) + [[0], [11], [13], [15]] + >>> list(slicechunk(revlog, [0, 11, 13, 15], targetsize=20)) + [[0], [11], [13, 15]] + """ + if targetsize is not None: + targetsize = max(targetsize, revlog._srmingapsize) + # targetsize should not be specified when evaluating delta candidates: + # * targetsize is used to ensure we stay within specification when reading, + # * deltainfo is used to pick are good delta chain when writing. + if not (deltainfo is None or targetsize is None): + msg = 'cannot use `targetsize` with a `deltainfo`' + raise error.ProgrammingError(msg) + for chunk in _slicechunktodensity(revlog, revs, + deltainfo, + revlog._srdensitythreshold, + revlog._srmingapsize): + for subchunk in _slicechunktosize(revlog, chunk, targetsize): + yield subchunk + +def _slicechunktosize(revlog, revs, targetsize=None): + """slice revs to match the target size + + This is intended to be used on chunk that density slicing selected by that + are still too large compared to the read garantee of revlog. This might + happens when "minimal gap size" interrupted the slicing or when chain are + built in a way that create large blocks next to each other. + + >>> revlog = _testrevlog([ + ... 3, #0 (3) + ... 5, #1 (2) + ... 6, #2 (1) + ... 8, #3 (2) + ... 8, #4 (empty) + ... 11, #5 (3) + ... 12, #6 (1) + ... 13, #7 (1) + ... 14, #8 (1) + ... ]) + + Cases where chunk is already small enough + >>> list(_slicechunktosize(revlog, [0], 3)) + [[0]] + >>> list(_slicechunktosize(revlog, [6, 7], 3)) + [[6, 7]] + >>> list(_slicechunktosize(revlog, [0], None)) + [[0]] + >>> list(_slicechunktosize(revlog, [6, 7], None)) + [[6, 7]] + + cases where we need actual slicing + >>> list(_slicechunktosize(revlog, [0, 1], 3)) + [[0], [1]] + >>> list(_slicechunktosize(revlog, [1, 3], 3)) + [[1], [3]] + >>> list(_slicechunktosize(revlog, [1, 2, 3], 3)) + [[1, 2], [3]] + >>> list(_slicechunktosize(revlog, [3, 5], 3)) + [[3], [5]] + >>> list(_slicechunktosize(revlog, [3, 4, 5], 3)) + [[3], [5]] + >>> list(_slicechunktosize(revlog, [5, 6, 7, 8], 3)) + [[5], [6, 7, 8]] + >>> list(_slicechunktosize(revlog, [0, 1, 2, 3, 4, 5, 6, 7, 8], 3)) + [[0], [1, 2], [3], [5], [6, 7, 8]] + + Case with too large individual chunk (must return valid chunk) + >>> list(_slicechunktosize(revlog, [0, 1], 2)) + [[0], [1]] + >>> list(_slicechunktosize(revlog, [1, 3], 1)) + [[1], [3]] + >>> list(_slicechunktosize(revlog, [3, 4, 5], 2)) + [[3], [5]] + """ + assert targetsize is None or 0 <= targetsize + if targetsize is None or segmentspan(revlog, revs) <= targetsize: + yield revs + return + + startrevidx = 0 + startdata = revlog.start(revs[0]) + endrevidx = 0 + iterrevs = enumerate(revs) + next(iterrevs) # skip first rev. + for idx, r in iterrevs: + span = revlog.end(r) - startdata + if span <= targetsize: + endrevidx = idx + else: + chunk = _trimchunk(revlog, revs, startrevidx, endrevidx + 1) + if chunk: + yield chunk + startrevidx = idx + startdata = revlog.start(r) + endrevidx = idx + yield _trimchunk(revlog, revs, startrevidx) + +def _slicechunktodensity(revlog, revs, deltainfo=None, targetdensity=0.5, + mingapsize=0): + """slice revs to reduce the amount of unrelated data to be read from disk. + + ``revs`` is sliced into groups that should be read in one time. + Assume that revs are sorted. + + ``deltainfo`` is a _deltainfo instance of a revision that we would append + to the top of the revlog. + + The initial chunk is sliced until the overall density (payload/chunks-span + ratio) is above `targetdensity`. No gap smaller than `mingapsize` is + skipped. + + >>> revlog = _testrevlog([ + ... 5, #00 (5) + ... 10, #01 (5) + ... 12, #02 (2) + ... 12, #03 (empty) + ... 27, #04 (15) + ... 31, #05 (4) + ... 31, #06 (empty) + ... 42, #07 (11) + ... 47, #08 (5) + ... 47, #09 (empty) + ... 48, #10 (1) + ... 51, #11 (3) + ... 74, #12 (23) + ... 85, #13 (11) + ... 86, #14 (1) + ... 91, #15 (5) + ... ]) + + >>> list(_slicechunktodensity(revlog, list(range(16)))) + [[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]] + >>> list(_slicechunktodensity(revlog, [0, 15])) + [[0], [15]] + >>> list(_slicechunktodensity(revlog, [0, 11, 15])) + [[0], [11], [15]] + >>> list(_slicechunktodensity(revlog, [0, 11, 13, 15])) + [[0], [11, 13, 15]] + >>> list(_slicechunktodensity(revlog, [1, 2, 3, 5, 8, 10, 11, 14])) + [[1, 2], [5, 8, 10, 11], [14]] + >>> list(_slicechunktodensity(revlog, [1, 2, 3, 5, 8, 10, 11, 14], + ... mingapsize=20)) + [[1, 2, 3, 5, 8, 10, 11], [14]] + >>> list(_slicechunktodensity(revlog, [1, 2, 3, 5, 8, 10, 11, 14], + ... targetdensity=0.95)) + [[1, 2], [5], [8, 10, 11], [14]] + >>> list(_slicechunktodensity(revlog, [1, 2, 3, 5, 8, 10, 11, 14], + ... targetdensity=0.95, mingapsize=12)) + [[1, 2], [5, 8, 10, 11], [14]] + """ + start = revlog.start + length = revlog.length + + if len(revs) <= 1: + yield revs + return + + nextrev = len(revlog) + nextoffset = revlog.end(nextrev - 1) + + if deltainfo is None: + deltachainspan = segmentspan(revlog, revs) + chainpayload = sum(length(r) for r in revs) + else: + deltachainspan = deltainfo.distance + chainpayload = deltainfo.compresseddeltalen + + if deltachainspan < mingapsize: + yield revs + return + + readdata = deltachainspan + + if deltachainspan: + density = chainpayload / float(deltachainspan) + else: + density = 1.0 + + if density >= targetdensity: + yield revs + return + + if deltainfo is not None and deltainfo.deltalen: + revs = list(revs) + revs.append(nextrev) + + # Store the gaps in a heap to have them sorted by decreasing size + gapsheap = [] + heapq.heapify(gapsheap) + prevend = None + for i, rev in enumerate(revs): + if rev < nextrev: + revstart = start(rev) + revlen = length(rev) + else: + revstart = nextoffset + revlen = deltainfo.deltalen + + # Skip empty revisions to form larger holes + if revlen == 0: + continue + + if prevend is not None: + gapsize = revstart - prevend + # only consider holes that are large enough + if gapsize > mingapsize: + heapq.heappush(gapsheap, (-gapsize, i)) + + prevend = revstart + revlen + + # Collect the indices of the largest holes until the density is acceptable + indicesheap = [] + heapq.heapify(indicesheap) + while gapsheap and density < targetdensity: + oppgapsize, gapidx = heapq.heappop(gapsheap) + + heapq.heappush(indicesheap, gapidx) + + # the gap sizes are stored as negatives to be sorted decreasingly + # by the heap + readdata -= (-oppgapsize) + if readdata > 0: + density = chainpayload / float(readdata) + else: + density = 1.0 + + # Cut the revs at collected indices + previdx = 0 + while indicesheap: + idx = heapq.heappop(indicesheap) + + chunk = _trimchunk(revlog, revs, previdx, idx) + if chunk: + yield chunk + + previdx = idx + + chunk = _trimchunk(revlog, revs, previdx) + if chunk: + yield chunk + +def _trimchunk(revlog, revs, startidx, endidx=None): + """returns revs[startidx:endidx] without empty trailing revs + + Doctest Setup + >>> revlog = _testrevlog([ + ... 5, #0 + ... 10, #1 + ... 12, #2 + ... 12, #3 (empty) + ... 17, #4 + ... 21, #5 + ... 21, #6 (empty) + ... ]) + + Contiguous cases: + >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 0) + [0, 1, 2, 3, 4, 5] + >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 0, 5) + [0, 1, 2, 3, 4] + >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 0, 4) + [0, 1, 2] + >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 2, 4) + [2] + >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 3) + [3, 4, 5] + >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 3, 5) + [3, 4] + + Discontiguous cases: + >>> _trimchunk(revlog, [1, 3, 5, 6], 0) + [1, 3, 5] + >>> _trimchunk(revlog, [1, 3, 5, 6], 0, 2) + [1] + >>> _trimchunk(revlog, [1, 3, 5, 6], 1, 3) + [3, 5] + >>> _trimchunk(revlog, [1, 3, 5, 6], 1) + [3, 5] + """ + length = revlog.length + + if endidx is None: + endidx = len(revs) + + # If we have a non-emtpy delta candidate, there are nothing to trim + if revs[endidx - 1] < len(revlog): + # Trim empty revs at the end, except the very first revision of a chain + while (endidx > 1 + and endidx > startidx + and length(revs[endidx - 1]) == 0): + endidx -= 1 + + return revs[startidx:endidx] + +def segmentspan(revlog, revs, deltainfo=None): + """Get the byte span of a segment of revisions + + revs is a sorted array of revision numbers + + >>> revlog = _testrevlog([ + ... 5, #0 + ... 10, #1 + ... 12, #2 + ... 12, #3 (empty) + ... 17, #4 + ... ]) + + >>> segmentspan(revlog, [0, 1, 2, 3, 4]) + 17 + >>> segmentspan(revlog, [0, 4]) + 17 + >>> segmentspan(revlog, [3, 4]) + 5 + >>> segmentspan(revlog, [1, 2, 3,]) + 7 + >>> segmentspan(revlog, [1, 3]) + 7 + """ + if not revs: + return 0 + if deltainfo is not None and len(revlog) <= revs[-1]: + if len(revs) == 1: + return deltainfo.deltalen + offset = revlog.end(len(revlog) - 1) + end = deltainfo.deltalen + offset + else: + end = revlog.end(revs[-1]) + return end - revlog.start(revs[0]) + +@attr.s(slots=True, frozen=True) +class _deltainfo(object): + distance = attr.ib() + deltalen = attr.ib() + data = attr.ib() + base = attr.ib() + chainbase = attr.ib() + chainlen = attr.ib() + compresseddeltalen = attr.ib() + snapshotdepth = attr.ib() + +def isgooddeltainfo(revlog, deltainfo, revinfo): + """Returns True if the given delta is good. Good means that it is within + the disk span, disk size, and chain length bounds that we know to be + performant.""" + if deltainfo is None: + return False + + # - 'deltainfo.distance' is the distance from the base revision -- + # bounding it limits the amount of I/O we need to do. + # - 'deltainfo.compresseddeltalen' is the sum of the total size of + # deltas we need to apply -- bounding it limits the amount of CPU + # we consume. + + if revlog._sparserevlog: + # As sparse-read will be used, we can consider that the distance, + # instead of being the span of the whole chunk, + # is the span of the largest read chunk + base = deltainfo.base + + if base != nullrev: + deltachain = revlog._deltachain(base)[0] + else: + deltachain = [] + + # search for the first non-snapshot revision + for idx, r in enumerate(deltachain): + if not revlog.issnapshot(r): + break + deltachain = deltachain[idx:] + chunks = slicechunk(revlog, deltachain, deltainfo) + all_span = [segmentspan(revlog, revs, deltainfo) + for revs in chunks] + distance = max(all_span) + else: + distance = deltainfo.distance + + textlen = revinfo.textlen + defaultmax = textlen * 4 + maxdist = revlog._maxdeltachainspan + if not maxdist: + maxdist = distance # ensure the conditional pass + maxdist = max(maxdist, defaultmax) + if revlog._sparserevlog and maxdist < revlog._srmingapsize: + # In multiple place, we are ignoring irrelevant data range below a + # certain size. Be also apply this tradeoff here and relax span + # constraint for small enought content. + maxdist = revlog._srmingapsize + + # Bad delta from read span: + # + # If the span of data read is larger than the maximum allowed. + if maxdist < distance: + return False + + # Bad delta from new delta size: + # + # If the delta size is larger than the target text, storing the + # delta will be inefficient. + if textlen < deltainfo.deltalen: + return False + + # Bad delta from cumulated payload size: + # + # If the sum of delta get larger than K * target text length. + if textlen * LIMIT_DELTA2TEXT < deltainfo.compresseddeltalen: + return False + + # Bad delta from chain length: + # + # If the number of delta in the chain gets too high. + if (revlog._maxchainlen + and revlog._maxchainlen < deltainfo.chainlen): + return False + + # bad delta from intermediate snapshot size limit + # + # If an intermediate snapshot size is higher than the limit. The + # limit exist to prevent endless chain of intermediate delta to be + # created. + if (deltainfo.snapshotdepth is not None and + (textlen >> deltainfo.snapshotdepth) < deltainfo.deltalen): + return False + + # bad delta if new intermediate snapshot is larger than the previous + # snapshot + if (deltainfo.snapshotdepth + and revlog.length(deltainfo.base) < deltainfo.deltalen): + return False + + return True + +class deltacomputer(object): + def __init__(self, revlog): + self.revlog = revlog + + def _getcandidaterevs(self, p1, p2, cachedelta): + """ + Provides revisions that present an interest to be diffed against, + grouped by level of easiness. + """ + revlog = self.revlog + gdelta = revlog._generaldelta + curr = len(revlog) + prev = curr - 1 + p1r, p2r = revlog.rev(p1), revlog.rev(p2) + + # should we try to build a delta? + if prev != nullrev and revlog._storedeltachains: + tested = set() + # This condition is true most of the time when processing + # changegroup data into a generaldelta repo. The only time it + # isn't true is if this is the first revision in a delta chain + # or if ``format.generaldelta=true`` disabled ``lazydeltabase``. + if cachedelta and gdelta and revlog._lazydeltabase: + # Assume what we received from the server is a good choice + # build delta will reuse the cache + yield (cachedelta[0],) + tested.add(cachedelta[0]) + + if gdelta: + # exclude already lazy tested base if any + parents = [p for p in (p1r, p2r) + if p != nullrev and p not in tested] + + if not revlog._deltabothparents and len(parents) == 2: + parents.sort() + # To minimize the chance of having to build a fulltext, + # pick first whichever parent is closest to us (max rev) + yield (parents[1],) + # then the other one (min rev) if the first did not fit + yield (parents[0],) + tested.update(parents) + elif len(parents) > 0: + # Test all parents (1 or 2), and keep the best candidate + yield parents + tested.update(parents) + + if prev not in tested: + # other approach failed try against prev to hopefully save us a + # fulltext. + yield (prev,) + tested.add(prev) + + def buildtext(self, revinfo, fh): + """Builds a fulltext version of a revision + + revinfo: _revisioninfo instance that contains all needed info + fh: file handle to either the .i or the .d revlog file, + depending on whether it is inlined or not + """ + btext = revinfo.btext + if btext[0] is not None: + return btext[0] + + revlog = self.revlog + cachedelta = revinfo.cachedelta + flags = revinfo.flags + node = revinfo.node + + baserev = cachedelta[0] + delta = cachedelta[1] + # special case deltas which replace entire base; no need to decode + # base revision. this neatly avoids censored bases, which throw when + # they're decoded. + hlen = struct.calcsize(">lll") + if delta[:hlen] == mdiff.replacediffheader(revlog.rawsize(baserev), + len(delta) - hlen): + btext[0] = delta[hlen:] + else: + # deltabase is rawtext before changed by flag processors, which is + # equivalent to non-raw text + basetext = revlog.revision(baserev, _df=fh, raw=False) + btext[0] = mdiff.patch(basetext, delta) + + try: + res = revlog._processflags(btext[0], flags, 'read', raw=True) + btext[0], validatehash = res + if validatehash: + revlog.checkhash(btext[0], node, p1=revinfo.p1, p2=revinfo.p2) + if flags & REVIDX_ISCENSORED: + raise RevlogError(_('node %s is not censored') % node) + except CensoredNodeError: + # must pass the censored index flag to add censored revisions + if not flags & REVIDX_ISCENSORED: + raise + return btext[0] + + def _builddeltadiff(self, base, revinfo, fh): + revlog = self.revlog + t = self.buildtext(revinfo, fh) + if revlog.iscensored(base): + # deltas based on a censored revision must replace the + # full content in one patch, so delta works everywhere + header = mdiff.replacediffheader(revlog.rawsize(base), len(t)) + delta = header + t + else: + ptext = revlog.revision(base, _df=fh, raw=True) + delta = mdiff.textdiff(ptext, t) + + return delta + + def _builddeltainfo(self, revinfo, base, fh): + # can we use the cached delta? + if revinfo.cachedelta and revinfo.cachedelta[0] == base: + delta = revinfo.cachedelta[1] + else: + delta = self._builddeltadiff(base, revinfo, fh) + revlog = self.revlog + header, data = revlog.compress(delta) + deltalen = len(header) + len(data) + chainbase = revlog.chainbase(base) + offset = revlog.end(len(revlog) - 1) + dist = deltalen + offset - revlog.start(chainbase) + if revlog._generaldelta: + deltabase = base + else: + deltabase = chainbase + chainlen, compresseddeltalen = revlog._chaininfo(base) + chainlen += 1 + compresseddeltalen += deltalen + + revlog = self.revlog + snapshotdepth = None + if deltabase == nullrev: + snapshotdepth = 0 + elif revlog._sparserevlog and revlog.issnapshot(deltabase): + # A delta chain should always be one full snapshot, + # zero or more semi-snapshots, and zero or more deltas + p1, p2 = revlog.rev(revinfo.p1), revlog.rev(revinfo.p2) + if deltabase not in (p1, p2) and revlog.issnapshot(deltabase): + snapshotdepth = len(revlog._deltachain(deltabase)[0]) + + return _deltainfo(dist, deltalen, (header, data), deltabase, + chainbase, chainlen, compresseddeltalen, + snapshotdepth) + + def finddeltainfo(self, revinfo, fh): + """Find an acceptable delta against a candidate revision + + revinfo: information about the revision (instance of _revisioninfo) + fh: file handle to either the .i or the .d revlog file, + depending on whether it is inlined or not + + Returns the first acceptable candidate revision, as ordered by + _getcandidaterevs + """ + if not revinfo.textlen: + return None # empty file do not need delta + + cachedelta = revinfo.cachedelta + p1 = revinfo.p1 + p2 = revinfo.p2 + revlog = self.revlog + + deltalength = self.revlog.length + deltaparent = self.revlog.deltaparent + + deltainfo = None + deltas_limit = revinfo.textlen * LIMIT_DELTA2TEXT + for candidaterevs in self._getcandidaterevs(p1, p2, cachedelta): + # filter out delta base that will never produce good delta + candidaterevs = [r for r in candidaterevs + if self.revlog.length(r) <= deltas_limit] + nominateddeltas = [] + for candidaterev in candidaterevs: + # skip over empty delta (no need to include them in a chain) + while candidaterev != nullrev and not deltalength(candidaterev): + candidaterev = deltaparent(candidaterev) + # no need to try a delta against nullid, this will be handled + # by fulltext later. + if candidaterev == nullrev: + continue + # no delta for rawtext-changing revs (see "candelta" for why) + if revlog.flags(candidaterev) & REVIDX_RAWTEXT_CHANGING_FLAGS: + continue + candidatedelta = self._builddeltainfo(revinfo, candidaterev, fh) + if isgooddeltainfo(self.revlog, candidatedelta, revinfo): + nominateddeltas.append(candidatedelta) + if nominateddeltas: + deltainfo = min(nominateddeltas, key=lambda x: x.deltalen) + break + + return deltainfo