streamclone: define first iteration of version 2 of stream format
(This patch is based on a first draft from Gregory Szorc, with deeper rework)
Version 1 of the stream clone format was invented many years ago and suffers
from a few deficiencies:
1) Filenames are stored in store-encoded (on filesystem) form rather than in
their internal form. This makes future compatibility with new store
filename encodings more difficult.
2) File entry "headers" consist of a newline of the file name followed by the
string file size. Converting strings to integers is avoidable overhead. We
can't store filenames with newlines (manifests have this limitation as
well, so it isn't a major concern). But the big concern here is the
necessity for readline(). Scanning for newlines means reading ahead and
that means extra buffer allocations and slicing (in Python) and this makes
performance suffer.
3) Filenames aren't compressed optimally. Filenames should be compressed well
since there is a lot of repeated data. However, since they are scattered
all over the stream (with revlog data in between), they typically fall
outside the window size of the compressor and don't compress.
4) It can only exchange stored based content, being able to exchange caches
too would be nice.
5) It is limited to a stream-based protocol and isn't suitable for an on-disk
format for general repository reading because the offset of individual file
entries requires scanning the entire file to find file records.
As part of enabling streaming clones to work in bundle2, #2 proved to have a
significant negative impact on performance. Since bundle2 provides the
opportunity to start fresh, Gregory Szorc figured he would take the
opportunity to invent a new streaming clone data format.
The new format devised in this series addresses #1, #2, and #4. It punts on #3
because it was complex without yielding a significant gain and on #5 because
devising a new store format that "packs" multiple revlogs into a single
"packed revlog" is massive scope bloat. However, this v2 format might be
suitable for streaming into a "packed revlog" with minimal processing. If it
works, great. If not, we can always invent stream format when it is needed.
This patch only introduces the bases of the format. We'll get it usable through
bundle2 first, then we'll extend the format in future patches to bring it to its
full potential (especially #4).
# mdiff.py - diff and patch routines for mercurial
#
# Copyright 2005, 2006 Matt Mackall <mpm@selenic.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 re
import struct
import zlib
from .i18n import _
from . import (
error,
policy,
pycompat,
util,
)
bdiff = policy.importmod(r'bdiff')
mpatch = policy.importmod(r'mpatch')
blocks = bdiff.blocks
fixws = bdiff.fixws
patches = mpatch.patches
patchedsize = mpatch.patchedsize
textdiff = bdiff.bdiff
def splitnewlines(text):
'''like str.splitlines, but only split on newlines.'''
lines = [l + '\n' for l in text.split('\n')]
if lines:
if lines[-1] == '\n':
lines.pop()
else:
lines[-1] = lines[-1][:-1]
return lines
class diffopts(object):
'''context is the number of context lines
text treats all files as text
showfunc enables diff -p output
git enables the git extended patch format
nodates removes dates from diff headers
nobinary ignores binary files
noprefix disables the 'a/' and 'b/' prefixes (ignored in plain mode)
ignorews ignores all whitespace changes in the diff
ignorewsamount ignores changes in the amount of whitespace
ignoreblanklines ignores changes whose lines are all blank
upgrade generates git diffs to avoid data loss
'''
defaults = {
'context': 3,
'text': False,
'showfunc': False,
'git': False,
'nodates': False,
'nobinary': False,
'noprefix': False,
'index': 0,
'ignorews': False,
'ignorewsamount': False,
'ignorewseol': False,
'ignoreblanklines': False,
'upgrade': False,
'showsimilarity': False,
'worddiff': False,
}
def __init__(self, **opts):
opts = pycompat.byteskwargs(opts)
for k in self.defaults.keys():
v = opts.get(k)
if v is None:
v = self.defaults[k]
setattr(self, k, v)
try:
self.context = int(self.context)
except ValueError:
raise error.Abort(_('diff context lines count must be '
'an integer, not %r') % self.context)
def copy(self, **kwargs):
opts = dict((k, getattr(self, k)) for k in self.defaults)
opts = pycompat.strkwargs(opts)
opts.update(kwargs)
return diffopts(**opts)
defaultopts = diffopts()
def wsclean(opts, text, blank=True):
if opts.ignorews:
text = bdiff.fixws(text, 1)
elif opts.ignorewsamount:
text = bdiff.fixws(text, 0)
if blank and opts.ignoreblanklines:
text = re.sub('\n+', '\n', text).strip('\n')
if opts.ignorewseol:
text = re.sub(br'[ \t\r\f]+\n', r'\n', text)
return text
def splitblock(base1, lines1, base2, lines2, opts):
# The input lines matches except for interwoven blank lines. We
# transform it into a sequence of matching blocks and blank blocks.
lines1 = [(wsclean(opts, l) and 1 or 0) for l in lines1]
lines2 = [(wsclean(opts, l) and 1 or 0) for l in lines2]
s1, e1 = 0, len(lines1)
s2, e2 = 0, len(lines2)
while s1 < e1 or s2 < e2:
i1, i2, btype = s1, s2, '='
if (i1 >= e1 or lines1[i1] == 0
or i2 >= e2 or lines2[i2] == 0):
# Consume the block of blank lines
btype = '~'
while i1 < e1 and lines1[i1] == 0:
i1 += 1
while i2 < e2 and lines2[i2] == 0:
i2 += 1
else:
# Consume the matching lines
while i1 < e1 and lines1[i1] == 1 and lines2[i2] == 1:
i1 += 1
i2 += 1
yield [base1 + s1, base1 + i1, base2 + s2, base2 + i2], btype
s1 = i1
s2 = i2
def hunkinrange(hunk, linerange):
"""Return True if `hunk` defined as (start, length) is in `linerange`
defined as (lowerbound, upperbound).
>>> hunkinrange((5, 10), (2, 7))
True
>>> hunkinrange((5, 10), (6, 12))
True
>>> hunkinrange((5, 10), (13, 17))
True
>>> hunkinrange((5, 10), (3, 17))
True
>>> hunkinrange((5, 10), (1, 3))
False
>>> hunkinrange((5, 10), (18, 20))
False
>>> hunkinrange((5, 10), (1, 5))
False
>>> hunkinrange((5, 10), (15, 27))
False
"""
start, length = hunk
lowerbound, upperbound = linerange
return lowerbound < start + length and start < upperbound
def blocksinrange(blocks, rangeb):
"""filter `blocks` like (a1, a2, b1, b2) from items outside line range
`rangeb` from ``(b1, b2)`` point of view.
Return `filteredblocks, rangea` where:
* `filteredblocks` is list of ``block = (a1, a2, b1, b2), stype`` items of
`blocks` that are inside `rangeb` from ``(b1, b2)`` point of view; a
block ``(b1, b2)`` being inside `rangeb` if
``rangeb[0] < b2 and b1 < rangeb[1]``;
* `rangea` is the line range w.r.t. to ``(a1, a2)`` parts of `blocks`.
"""
lbb, ubb = rangeb
lba, uba = None, None
filteredblocks = []
for block in blocks:
(a1, a2, b1, b2), stype = block
if lbb >= b1 and ubb <= b2 and stype == '=':
# rangeb is within a single "=" hunk, restrict back linerange1
# by offsetting rangeb
lba = lbb - b1 + a1
uba = ubb - b1 + a1
else:
if b1 <= lbb < b2:
if stype == '=':
lba = a2 - (b2 - lbb)
else:
lba = a1
if b1 < ubb <= b2:
if stype == '=':
uba = a1 + (ubb - b1)
else:
uba = a2
if hunkinrange((b1, (b2 - b1)), rangeb):
filteredblocks.append(block)
if lba is None or uba is None or uba < lba:
raise error.Abort(_('line range exceeds file size'))
return filteredblocks, (lba, uba)
def allblocks(text1, text2, opts=None, lines1=None, lines2=None):
"""Return (block, type) tuples, where block is an mdiff.blocks
line entry. type is '=' for blocks matching exactly one another
(bdiff blocks), '!' for non-matching blocks and '~' for blocks
matching only after having filtered blank lines.
line1 and line2 are text1 and text2 split with splitnewlines() if
they are already available.
"""
if opts is None:
opts = defaultopts
if opts.ignorews or opts.ignorewsamount or opts.ignorewseol:
text1 = wsclean(opts, text1, False)
text2 = wsclean(opts, text2, False)
diff = bdiff.blocks(text1, text2)
for i, s1 in enumerate(diff):
# The first match is special.
# we've either found a match starting at line 0 or a match later
# in the file. If it starts later, old and new below will both be
# empty and we'll continue to the next match.
if i > 0:
s = diff[i - 1]
else:
s = [0, 0, 0, 0]
s = [s[1], s1[0], s[3], s1[2]]
# bdiff sometimes gives huge matches past eof, this check eats them,
# and deals with the special first match case described above
if s[0] != s[1] or s[2] != s[3]:
type = '!'
if opts.ignoreblanklines:
if lines1 is None:
lines1 = splitnewlines(text1)
if lines2 is None:
lines2 = splitnewlines(text2)
old = wsclean(opts, "".join(lines1[s[0]:s[1]]))
new = wsclean(opts, "".join(lines2[s[2]:s[3]]))
if old == new:
type = '~'
yield s, type
yield s1, '='
def unidiff(a, ad, b, bd, fn1, fn2, opts=defaultopts):
"""Return a unified diff as a (headers, hunks) tuple.
If the diff is not null, `headers` is a list with unified diff header
lines "--- <original>" and "+++ <new>" and `hunks` is a generator yielding
(hunkrange, hunklines) coming from _unidiff().
Otherwise, `headers` and `hunks` are empty.
"""
def datetag(date, fn=None):
if not opts.git and not opts.nodates:
return '\t%s' % date
if fn and ' ' in fn:
return '\t'
return ''
sentinel = [], ()
if not a and not b:
return sentinel
if opts.noprefix:
aprefix = bprefix = ''
else:
aprefix = 'a/'
bprefix = 'b/'
epoch = util.datestr((0, 0))
fn1 = util.pconvert(fn1)
fn2 = util.pconvert(fn2)
def checknonewline(lines):
for text in lines:
if text[-1:] != '\n':
text += "\n\ No newline at end of file\n"
yield text
if not opts.text and (util.binary(a) or util.binary(b)):
if a and b and len(a) == len(b) and a == b:
return sentinel
headerlines = []
hunks = (None, ['Binary file %s has changed\n' % fn1]),
elif not a:
b = splitnewlines(b)
if a is None:
l1 = '--- /dev/null%s' % datetag(epoch)
else:
l1 = "--- %s%s%s" % (aprefix, fn1, datetag(ad, fn1))
l2 = "+++ %s%s" % (bprefix + fn2, datetag(bd, fn2))
headerlines = [l1, l2]
size = len(b)
hunkrange = (0, 0, 1, size)
hunklines = ["@@ -0,0 +1,%d @@\n" % size] + ["+" + e for e in b]
hunks = (hunkrange, checknonewline(hunklines)),
elif not b:
a = splitnewlines(a)
l1 = "--- %s%s%s" % (aprefix, fn1, datetag(ad, fn1))
if b is None:
l2 = '+++ /dev/null%s' % datetag(epoch)
else:
l2 = "+++ %s%s%s" % (bprefix, fn2, datetag(bd, fn2))
headerlines = [l1, l2]
size = len(a)
hunkrange = (1, size, 0, 0)
hunklines = ["@@ -1,%d +0,0 @@\n" % size] + ["-" + e for e in a]
hunks = (hunkrange, checknonewline(hunklines)),
else:
diffhunks = _unidiff(a, b, opts=opts)
try:
hunkrange, hunklines = next(diffhunks)
except StopIteration:
return sentinel
headerlines = [
"--- %s%s%s" % (aprefix, fn1, datetag(ad, fn1)),
"+++ %s%s%s" % (bprefix, fn2, datetag(bd, fn2)),
]
def rewindhunks():
yield hunkrange, checknonewline(hunklines)
for hr, hl in diffhunks:
yield hr, checknonewline(hl)
hunks = rewindhunks()
return headerlines, hunks
def _unidiff(t1, t2, opts=defaultopts):
"""Yield hunks of a headerless unified diff from t1 and t2 texts.
Each hunk consists of a (hunkrange, hunklines) tuple where `hunkrange` is a
tuple (s1, l1, s2, l2) representing the range information of the hunk to
form the '@@ -s1,l1 +s2,l2 @@' header and `hunklines` is a list of lines
of the hunk combining said header followed by line additions and
deletions.
"""
l1 = splitnewlines(t1)
l2 = splitnewlines(t2)
def contextend(l, len):
ret = l + opts.context
if ret > len:
ret = len
return ret
def contextstart(l):
ret = l - opts.context
if ret < 0:
return 0
return ret
lastfunc = [0, '']
def yieldhunk(hunk):
(astart, a2, bstart, b2, delta) = hunk
aend = contextend(a2, len(l1))
alen = aend - astart
blen = b2 - bstart + aend - a2
func = ""
if opts.showfunc:
lastpos, func = lastfunc
# walk backwards from the start of the context up to the start of
# the previous hunk context until we find a line starting with an
# alphanumeric char.
for i in xrange(astart - 1, lastpos - 1, -1):
if l1[i][0:1].isalnum():
func = ' ' + l1[i].rstrip()[:40]
lastfunc[1] = func
break
# by recording this hunk's starting point as the next place to
# start looking for function lines, we avoid reading any line in
# the file more than once.
lastfunc[0] = astart
# zero-length hunk ranges report their start line as one less
if alen:
astart += 1
if blen:
bstart += 1
hunkrange = astart, alen, bstart, blen
hunklines = (
["@@ -%d,%d +%d,%d @@%s\n" % (hunkrange + (func,))]
+ delta
+ [' ' + l1[x] for x in xrange(a2, aend)]
)
yield hunkrange, hunklines
# bdiff.blocks gives us the matching sequences in the files. The loop
# below finds the spaces between those matching sequences and translates
# them into diff output.
#
hunk = None
ignoredlines = 0
for s, stype in allblocks(t1, t2, opts, l1, l2):
a1, a2, b1, b2 = s
if stype != '!':
if stype == '~':
# The diff context lines are based on t1 content. When
# blank lines are ignored, the new lines offsets must
# be adjusted as if equivalent blocks ('~') had the
# same sizes on both sides.
ignoredlines += (b2 - b1) - (a2 - a1)
continue
delta = []
old = l1[a1:a2]
new = l2[b1:b2]
b1 -= ignoredlines
b2 -= ignoredlines
astart = contextstart(a1)
bstart = contextstart(b1)
prev = None
if hunk:
# join with the previous hunk if it falls inside the context
if astart < hunk[1] + opts.context + 1:
prev = hunk
astart = hunk[1]
bstart = hunk[3]
else:
for x in yieldhunk(hunk):
yield x
if prev:
# we've joined the previous hunk, record the new ending points.
hunk[1] = a2
hunk[3] = b2
delta = hunk[4]
else:
# create a new hunk
hunk = [astart, a2, bstart, b2, delta]
delta[len(delta):] = [' ' + x for x in l1[astart:a1]]
delta[len(delta):] = ['-' + x for x in old]
delta[len(delta):] = ['+' + x for x in new]
if hunk:
for x in yieldhunk(hunk):
yield x
def b85diff(to, tn):
'''print base85-encoded binary diff'''
def fmtline(line):
l = len(line)
if l <= 26:
l = chr(ord('A') + l - 1)
else:
l = chr(l - 26 + ord('a') - 1)
return '%c%s\n' % (l, util.b85encode(line, True))
def chunk(text, csize=52):
l = len(text)
i = 0
while i < l:
yield text[i:i + csize]
i += csize
if to is None:
to = ''
if tn is None:
tn = ''
if to == tn:
return ''
# TODO: deltas
ret = []
ret.append('GIT binary patch\n')
ret.append('literal %d\n' % len(tn))
for l in chunk(zlib.compress(tn)):
ret.append(fmtline(l))
ret.append('\n')
return ''.join(ret)
def patchtext(bin):
pos = 0
t = []
while pos < len(bin):
p1, p2, l = struct.unpack(">lll", bin[pos:pos + 12])
pos += 12
t.append(bin[pos:pos + l])
pos += l
return "".join(t)
def patch(a, bin):
if len(a) == 0:
# skip over trivial delta header
return util.buffer(bin, 12)
return mpatch.patches(a, [bin])
# similar to difflib.SequenceMatcher.get_matching_blocks
def get_matching_blocks(a, b):
return [(d[0], d[2], d[1] - d[0]) for d in bdiff.blocks(a, b)]
def trivialdiffheader(length):
return struct.pack(">lll", 0, 0, length) if length else ''
def replacediffheader(oldlen, newlen):
return struct.pack(">lll", 0, oldlen, newlen)