mirror of https://github.com/python/cpython
Tim Peters writes:
Attached is a cleaned-up version of ndiff (added useful module docstring, now echo'ed in case of cmd line mistake); added -q option to suppress initial file identification lines; + other minor cleanups, & a slightly faster match engine.
This commit is contained in:
Guido van Rossum
parent
806a467fbf
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@ -1,16 +1,50 @@
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#! /usr/bin/env python
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# Released to the public domain $JustDate: 3/16/98 $,
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# by Tim Peters (email tim_one@email.msn.com).
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# Module ndiff version 1.3.0
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# Released to the public domain 26-Mar-1999,
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# by Tim Peters (tim_one@email.msn.com).
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# ndiff file1 file2 -- a human-friendly file differencer.
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# Provided as-is; use at your own risk; no warranty; no promises; enjoy!
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# $Revision$
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"""ndiff [-q] file1 file2
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Print a human-friendly file difference report to stdout. Both inter-
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and intra-line differences are noted.
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If -q ("quiet") is not specified, the first two lines of output are
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-: file1
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+: file2
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Each remaining line begins with a two-letter code:
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"- " line unique to file1
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"+ " line unique to file2
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" " line common to both files
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"? " line not present in either input file
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Lines beginning with "? " attempt to guide the eye to intraline
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differences, and were not present in either input file.
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The first file can be recovered by retaining only lines that begin with
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" " or "- ", and deleting those 2-character prefixes.
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The second file can be recovered similarly, but by retaining only " "
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and "+ " lines. On Unix, the second file can be recovered by piping the
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output through
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sed -n '/^[+ ] /s/^..//p'
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Modifications to recover the first file are left as an exercise for
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the reader.
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See module comments for details and programmatic interface.
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"""
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__version__ = 1, 3, 0
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# SequenceMatcher tries to compute a "human-friendly diff" between
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# two sequences (chiefly picturing a file as a sequence of lines,
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# and a line as a sequence of characters, here). Unlike UNIX(tm) diff,
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# e.g., the fundamental notion is the longest *contiguous* & junk-free
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# and a line as a sequence of characters, here). Unlike e.g. UNIX(tm)
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# diff, the fundamental notion is the longest *contiguous* & junk-free
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# matching subsequence. That's what catches peoples' eyes. The
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# Windows(tm) windiff has another interesting notion, pairing up elements
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# that appear uniquely in each sequence. That, and the method here,
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@ -26,11 +60,11 @@
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# apart. Restricting synch points to contiguous matches preserves some
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# notion of locality, at the occasional cost of producing a longer diff.
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#
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# With respect to junk, an earlier verion of ndiff simply refused to
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# With respect to junk, an earlier version of ndiff simply refused to
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# *start* a match with a junk element. The result was cases like this:
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# before: private Thread currentThread;
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# after: private volatile Thread currentThread;
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# If you consider whitespace to be junk, the longest continguous match
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# If you consider whitespace to be junk, the longest contiguous match
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# not starting with junk is "e Thread currentThread". So ndiff reported
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# that "e volatil" was inserted between the 't' and the 'e' in "private".
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# While an accurate view, to people that's absurd. The current version
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@ -40,23 +74,9 @@
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# preceding blank; then "private" is matched, and extended to suck up the
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# following blank; then "Thread" is matched; and finally ndiff reports
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# that "volatile " was inserted before "Thread". The only quibble
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# remaining is that perhaps it was really the case that " volative"
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# remaining is that perhaps it was really the case that " volatile"
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# was inserted after "private". I can live with that <wink>.
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#
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# NOTE on the output: From an ndiff report,
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# 1) The first file can be recovered by retaining only lines that begin
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# with " " or "- ", and deleting those 2-character prefixes.
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# 2) The second file can be recovered similarly, but by retaining only
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# " " and "+ " lines.
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# 3) Lines beginning with "? " attempt to guide the eye to intraline
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# differences, and were not present in either input file.
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#
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# COROLLARY:
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# On Unix, the second file can be recovered by piping the output through
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# sed -n '/^[+ ] /s/^..//p'
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# Modifications to recover the first file are left as an exercise for
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# the reader.
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#
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# NOTE on junk: the module-level names
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# IS_LINE_JUNK
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# IS_CHARACTER_JUNK
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@ -70,8 +90,8 @@
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#
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# After setting those, you can call fcompare(f1name, f2name) with the
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# names of the files you want to compare. The difference report
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# is sent to stdout. Or you can call main(), which expects to find
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# (exactly) the two file names in sys.argv.
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# is sent to stdout. Or you can call main(args), passing what would
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# have been in sys.argv[1:] had the cmd-line form been used.
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import string
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TRACE = 0
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@ -148,7 +168,7 @@ class SequenceMatcher:
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self.fullbcount = None
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self.__chain_b()
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# for each element x in b, set b2j[x] to a list of the indices in
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# For each element x in b, set b2j[x] to a list of the indices in
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# b where x appears; the indices are in increasing order; note that
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# the number of times x appears in b is len(b2j[x]) ...
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# when self.isjunk is defined, junk elements don't show up in this
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@ -173,7 +193,7 @@ class SequenceMatcher:
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b = self.b
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self.b2j = b2j = {}
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self.b2jhas = b2jhas = b2j.has_key
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for i in xrange(0, len(b)):
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for i in xrange(len(b)):
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elt = b[i]
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if b2jhas(elt):
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b2j[elt].append(i)
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@ -210,9 +230,9 @@ class SequenceMatcher:
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k >= k'
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i <= i'
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and if i == i', j <= j'
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In other words, of all maximal matching blocks, returns one
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In other words, of all maximal matching blocks, return one
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that starts earliest in a, and of all those maximal matching
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blocks that start earliest in a, returns the one that starts
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blocks that start earliest in a, return the one that starts
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earliest in b.
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If isjunk is defined, first the longest matching block is
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@ -223,7 +243,7 @@ class SequenceMatcher:
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as identical junk happens to be adjacent to an "interesting"
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match.
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If no blocks match, returns (alo, blo, 0).
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If no blocks match, return (alo, blo, 0).
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"""
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# CAUTION: stripping common prefix or suffix would be incorrect.
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@ -238,40 +258,28 @@ class SequenceMatcher:
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# Windiff ends up at the same place as diff, but by pairing up
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# the unique 'b's and then matching the first two 'a's.
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# find longest junk-free match
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a, b, b2j, isbjunk = self.a, self.b, self.b2j, self.isbjunk
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besti, bestj, bestsize = alo, blo, 0
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# find longest junk-free match
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# during an iteration of the loop, j2len[j] = length of longest
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# junk-free match ending with a[i-1] and b[j]
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j2len = {}
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nothing = []
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for i in xrange(alo, ahi):
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# check for longest match starting at a[i]
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if i + bestsize >= ahi:
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# we're too far right to get a new best
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break
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# look at all instances of a[i] in b; note that because
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# b2j has no junk keys, the loop is skipped if a[i] is junk
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for j in b2j.get(a[i], []):
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j2lenget = j2len.get
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newj2len = {}
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for j in b2j.get(a[i], nothing):
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# a[i] matches b[j]
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if j < blo:
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continue
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if j + bestsize >= bhi:
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# we're too far right to get a new best, here or
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# anywhere to the right
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if j >= bhi:
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break
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if a[i + bestsize] != b[j + bestsize]:
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# can't be longer match; this test is not necessary
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# for correctness, but is a huge win for efficiency
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continue
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# set k to length of match
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k = 1 # a[i] == b[j] already known
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while i + k < ahi and j + k < bhi and \
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a[i+k] == b[j+k] and not isbjunk(b[j+k]):
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k = k + 1
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k = newj2len[j] = j2lenget(j-1, 0) + 1
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if k > bestsize:
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besti, bestj, bestsize = i, j, k
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if i + bestsize >= ahi:
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# only time in my life I really wanted a
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# labelled break <wink> -- we're done with
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# both loops now
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break
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besti, bestj, bestsize = i-k+1, j-k+1, k
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j2len = newj2len
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# Now that we have a wholly interesting match (albeit possibly
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# empty!), we may as well suck up the matching junk on each
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print " returns", besti, bestj, bestsize
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return besti, bestj, bestsize
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# A different implementation, using a binary doubling technique that
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# does far fewer element compares (trades 'em for integer compares),
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# and has n*lg n worst-case behavior. Alas, the code is much harder
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# to follow (the details are tricky!), and in most cases I've seen,
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# it takes at least 50% longer than the "clever dumb" method above;
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# probably due to creating layers of small dicts.
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# NOTE: this no longer matches the version above wrt junk; remains
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# too unpromising to update it; someday, though ...
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# def find_longest_match(self, alo, ahi, blo, bhi):
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# """Find longest matching block in a[alo:ahi] and b[blo:bhi].
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#
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# Return (i,j,k) such that a[i:i+k] is equal to b[j:j+k], where
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# alo <= i <= i+k <= ahi
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# blo <= j <= j+k <= bhi
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# and for all (i',j',k') meeting those conditions,
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# k >= k'
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# i <= i'
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# and if i == i', j <= j'
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# In other words, of all maximal matching blocks, returns one
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# that starts earliest in a, and of all those maximal matching
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# blocks that start earliest in a, returns the one that starts
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# earliest in b.
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#
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# If no blocks match, returns (alo, blo, 0).
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# """
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#
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# a, b2j = self.a, self.b2j
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# # alljs[size][i] is a set of all j's s.t. a[i:i+len] matches
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# # b[j:j+len]
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# alljs = {}
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# alljs[1] = js = {}
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# ahits = {}
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# for i in xrange(alo, ahi):
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# elt = a[i]
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# if ahits.has_key(elt):
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# js[i] = ahits[elt]
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# continue
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# if b2j.has_key(elt):
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# in_range = {}
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# for j in b2j[elt]:
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# if j >= blo:
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# if j >= bhi:
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# break
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# in_range[j] = 1
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# if in_range:
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# ahits[elt] = js[i] = in_range
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# del ahits
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# size = 1
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# while js:
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# oldsize = size
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# size = size + size
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# oldjs = js
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# alljs[size] = js = {}
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# for i in oldjs.keys():
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# # i has matches of size oldsize
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# if not oldjs.has_key(i + oldsize):
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# # can't double it
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# continue
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# second_js = oldjs[i + oldsize]
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# answer = {}
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# for j in oldjs[i].keys():
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# if second_js.has_key(j + oldsize):
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# answer[j] = 1
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# if answer:
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# js[i] = answer
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# del alljs[size]
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# size = size >> 1 # max power of 2 with a match
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# if not size:
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# return alo, blo, 0
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# besti, bestj, bestsize = alo, blo, 0
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# fatis = alljs[size].keys()
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# fatis.sort()
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# for i in fatis:
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# # figure out longest match starting at a[i]
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# totalsize = halfsize = size
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# # i has matches of len totalsize at the indices in js
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# js = alljs[size][i].keys()
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# while halfsize > 1:
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# halfsize = halfsize >> 1
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# # is there a match of len halfsize starting at
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# # i + totalsize?
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# newjs = []
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# if alljs[halfsize].has_key(i + totalsize):
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# second_js = alljs[halfsize][i + totalsize]
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# for j in js:
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# if second_js.has_key(j + totalsize):
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# newjs.append(j)
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# if newjs:
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# totalsize = totalsize + halfsize
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# js = newjs
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# if totalsize > bestsize:
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# besti, bestj, bestsize = i, min(js), totalsize
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# return besti, bestj, bestsize
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def get_matching_blocks(self):
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if self.matching_blocks is not None:
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return self.matching_blocks
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try:
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return open(fname, 'r')
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except IOError, detail:
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print "couldn't open " + fname + ": " + `detail`
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print "couldn't open " + fname + ": " + str(detail)
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return 0
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# open two files & spray the diff to stdout; return false iff a problem
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return 1
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# get file names from argv & compare; return false iff a problem
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def main():
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from sys import argv
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if len(argv) != 3:
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print 'need 2 args'
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# crack args (sys.argv[1:] is normal) & compare;
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# return false iff a problem
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def main(args):
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import getopt
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try:
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opts, args = getopt.getopt(args, "q")
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except getopt.error, detail:
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print str(detail)
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print __doc__
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return 0
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[f1name, f2name] = argv[1:3]
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print '-:', f1name
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print '+:', f2name
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noisy = 1
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for opt, val in opts:
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if opt == "-q":
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noisy = 0
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if len(args) != 2:
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print 'need 2 args'
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print __doc__
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return 0
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f1name, f2name = args
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if noisy:
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print '-:', f1name
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print '+:', f2name
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return fcompare(f1name, f2name)
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if __name__ == '__main__':
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import sys
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args = sys.argv[1:]
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if 1:
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main()
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main(args)
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else:
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import profile, pstats
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statf = "ndiff.pro"
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profile.run("main()", statf)
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profile.run("main(args)", statf)
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stats = pstats.Stats(statf)
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stats.strip_dirs().sort_stats('time').print_stats()
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Reference in New Issue