mercurial/pure/bdiff.py
author Martin von Zweigbergk <martinvonz@google.com>
Tue, 05 Apr 2022 12:06:32 -0700
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parent 48966 6000f5b25c9b
child 49733 594fc56c0af7
permissions -rw-r--r--
rust-revlog: add methods for getting parent revs and entries Differential Revision: https://phab.mercurial-scm.org/D12442
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# bdiff.py - Python implementation of bdiff.c
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#
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# Copyright 2009 Olivia Mackall <olivia@selenic.com> and others
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#
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# This software may be used and distributed according to the terms of the
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# GNU General Public License version 2 or any later version.
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import difflib
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import re
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import struct
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def splitnewlines(text):
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    '''like str.splitlines, but only split on newlines.'''
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    lines = [l + b'\n' for l in text.split(b'\n')]
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    if lines:
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        if lines[-1] == b'\n':
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            lines.pop()
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        else:
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            lines[-1] = lines[-1][:-1]
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    return lines
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def _normalizeblocks(a, b, blocks):
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    prev = None
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    r = []
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    for curr in blocks:
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        if prev is None:
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            prev = curr
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            continue
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        shift = 0
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        a1, b1, l1 = prev
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        a1end = a1 + l1
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        b1end = b1 + l1
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        a2, b2, l2 = curr
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        a2end = a2 + l2
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        b2end = b2 + l2
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        if a1end == a2:
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            while (
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                a1end + shift < a2end and a[a1end + shift] == b[b1end + shift]
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            ):
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                shift += 1
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        elif b1end == b2:
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            while (
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                b1end + shift < b2end and a[a1end + shift] == b[b1end + shift]
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            ):
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                shift += 1
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        r.append((a1, b1, l1 + shift))
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        prev = a2 + shift, b2 + shift, l2 - shift
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    if prev is not None:
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        r.append(prev)
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    return r
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def bdiff(a, b):
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    a = bytes(a).splitlines(True)
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    b = bytes(b).splitlines(True)
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    if not a:
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        s = b"".join(b)
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        return s and (struct.pack(b">lll", 0, 0, len(s)) + s)
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    bin = []
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    p = [0]
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    for i in a:
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        p.append(p[-1] + len(i))
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    d = difflib.SequenceMatcher(None, a, b).get_matching_blocks()
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    d = _normalizeblocks(a, b, d)
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    la = 0
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    lb = 0
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    for am, bm, size in d:
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        s = b"".join(b[lb:bm])
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        if am > la or s:
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            bin.append(struct.pack(b">lll", p[la], p[am], len(s)) + s)
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        la = am + size
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        lb = bm + size
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    return b"".join(bin)
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def blocks(a, b):
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    an = splitnewlines(a)
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    bn = splitnewlines(b)
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    d = difflib.SequenceMatcher(None, an, bn).get_matching_blocks()
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    d = _normalizeblocks(an, bn, d)
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    return [(i, i + n, j, j + n) for (i, j, n) in d]
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def fixws(text, allws):
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    if allws:
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        text = re.sub(b'[ \t\r]+', b'', text)
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    else:
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        text = re.sub(b'[ \t\r]+', b' ', text)
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        text = text.replace(b' \n', b'\n')
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    return text