view mercurial/mdiff.py @ 14365:a8e3931e3fb5

revlog: linearize created changegroups in generaldelta revlogs

This greatly improves the speed of the bundling process, and often reduces the
bundle size considerably. (Although if the repository is already ordered, this
has little effect on both time and bundle size.)

For non-generaldelta clients, the reduced bundle size translates to a reduced
repository size, similar to shrinking the revlogs (which uses the exact same
algorithm). For generaldelta clients the difference is minor.

When the new bundle format comes, reordering will not be necessary since we
can then store the deltaparent relationsships directly. The eventual default
behavior for clients and servers is presented in the table below, where "new"
implies support for GD as well as the new bundle format:

                    old client                    new client
old server          old bundle, no reorder        old bundle, no reorder
new server, non-GD  old bundle, no reorder[1]     old bundle, no reorder[2]
new server, GD      old bundle, reorder[3]        new bundle, no reorder[4]

[1] reordering is expensive on the server in this case, skip it
[2] client can choose to do its own redelta here
[3] reordering is needed because otherwise the pull does a lot of extra
    work on the server
[4] reordering isn't needed because client can get deltabase in bundle
    format

Currently, the default is to reorder on GD-servers, and not otherwise. A new
setting, bundle.reorder, has been added to override the default reordering
behavior. It can be set to either 'auto' (the default), or any true or false
value as a standard boolean setting, to either force the reordering on or off
regardless of generaldelta.


Some timing data from a relatively branch test repository follows. All
bundling is done with --all --type none options.

Non-generaldelta, non-shrunk repo:
-----------------------------------
Size: 276M

Without reorder (default):
Bundle time: 14.4 seconds
Bundle size: 939M

With reorder:
Bundle time: 1 minute, 29.3 seconds
Bundle size: 381M

Generaldelta, non-shrunk repo:
-----------------------------------
Size: 87M

Without reorder:
Bundle time: 2 minutes, 1.4 seconds
Bundle size: 939M

With reorder (default):
Bundle time: 25.5 seconds
Bundle size: 381M

# mdiff.py - diff and patch routines for mercurial
#
# Copyright 2005, 2006 Matt Mackall <[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.

from i18n import _
import bdiff, mpatch, util
import re, struct

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
    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,
        'ignorews': False,
        'ignorewsamount': False,
        'ignoreblanklines': False,
        'upgrade': False,
        }

    __slots__ = defaults.keys()

    def __init__(self, **opts):
        for k in self.__slots__:
            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 util.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.update(kwargs)
        return diffopts(**opts)

defaultopts = diffopts()

def wsclean(opts, text, blank=True):
    if opts.ignorews:
        text = re.sub('[ \t\r]+', '', text)
    elif opts.ignorewsamount:
        text = re.sub('[ \t\r]+', ' ', text)
        text = text.replace(' \n', '\n')
    if blank and opts.ignoreblanklines:
        text = re.sub('\n+', '', text)
    return text

def diffline(revs, a, b, opts):
    parts = ['diff']
    if opts.git:
        parts.append('--git')
    if revs and not opts.git:
        parts.append(' '.join(["-r %s" % rev for rev in revs]))
    if opts.git:
        parts.append('a/%s' % a)
        parts.append('b/%s' % b)
    else:
        parts.append(a)
    return ' '.join(parts) + '\n'

def unidiff(a, ad, b, bd, fn1, fn2, r=None, opts=defaultopts):
    def datetag(date, addtab=True):
        if not opts.git and not opts.nodates:
            return '\t%s\n' % date
        if addtab and ' ' in fn1:
            return '\t\n'
        return '\n'

    if not a and not b:
        return ""
    epoch = util.datestr((0, 0))

    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 ""
        l = ['Binary file %s has changed\n' % fn1]
    elif not a:
        b = splitnewlines(b)
        if a is None:
            l1 = '--- /dev/null%s' % datetag(epoch, False)
        else:
            l1 = "--- %s%s" % ("a/" + fn1, datetag(ad))
        l2 = "+++ %s%s" % ("b/" + fn2, datetag(bd))
        l3 = "@@ -0,0 +1,%d @@\n" % len(b)
        l = [l1, l2, l3] + ["+" + e for e in b]
    elif not b:
        a = splitnewlines(a)
        l1 = "--- %s%s" % ("a/" + fn1, datetag(ad))
        if b is None:
            l2 = '+++ /dev/null%s' % datetag(epoch, False)
        else:
            l2 = "+++ %s%s" % ("b/" + fn2, datetag(bd))
        l3 = "@@ -1,%d +0,0 @@\n" % len(a)
        l = [l1, l2, l3] + ["-" + e for e in a]
    else:
        al = splitnewlines(a)
        bl = splitnewlines(b)
        l = list(_unidiff(a, b, al, bl, opts=opts))
        if not l:
            return ""

        l.insert(0, "--- a/%s%s" % (fn1, datetag(ad)))
        l.insert(1, "+++ b/%s%s" % (fn2, datetag(bd)))

    for ln in xrange(len(l)):
        if l[ln][-1] != '\n':
            l[ln] += "\n\ No newline at end of file\n"

    if r:
        l.insert(0, diffline(r, fn1, fn2, opts))

    return "".join(l)

# creates a headerless unified diff
# t1 and t2 are the text to be diffed
# l1 and l2 are the text broken up into lines
def _unidiff(t1, t2, l1, l2, opts=defaultopts):
    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

    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:
            # walk backwards from the start of the context
            # to find a line starting with an alphanumeric char.
            for x in xrange(astart - 1, -1, -1):
                t = l1[x].rstrip()
                if funcre.match(t):
                    func = ' ' + t[:40]
                    break

        yield "@@ -%d,%d +%d,%d @@%s\n" % (astart + 1, alen,
                                           bstart + 1, blen, func)
        for x in delta:
            yield x
        for x in xrange(a2, aend):
            yield ' ' + l1[x]

    if opts.showfunc:
        funcre = re.compile('\w')

    # 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.
    #
    if opts.ignorews or opts.ignorewsamount:
        t1 = wsclean(opts, t1, False)
        t2 = wsclean(opts, t2, False)

    diff = bdiff.blocks(t1, t2)
    hunk = None
    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]
        delta = []
        a1 = s[1]
        a2 = s1[0]
        b1 = s[3]
        b2 = s1[2]

        old = l1[a1:a2]
        new = l2[b1:b2]

        # bdiff sometimes gives huge matches past eof, this check eats them,
        # and deals with the special first match case described above
        if not old and not new:
            continue

        if opts.ignoreblanklines:
            if wsclean(opts, "".join(old)) == wsclean(opts, "".join(new)):
                continue

        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 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 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)

patches = mpatch.patches
patchedsize = mpatch.patchedsize
textdiff = bdiff.bdiff