Computes "intelligent" differences between two sequenced Enumerables. This is an implementation of the McIlroy-Hunt "diff" algorithm for Enumerable objects that include Diffable.
Based on Mario I. Wolczko's Smalltalk version (1.2, 1993) and Ned Konz's Perl version (Algorithm::Diff 1.15).
require 'diff/lcs' seq1 = %w(a b c e h j l m n p) seq2 = %w(b c d e f j k l m r s t) lcs = Diff::LCS.LCS(seq1, seq2) diffs = Diff::LCS.diff(seq1, seq2) sdiff = Diff::LCS.sdiff(seq1, seq2) seq = Diff::LCS.traverse_sequences(seq1, seq2, callback_obj) bal = Diff::LCS.traverse_balanced(seq1, seq2, callback_obj) seq2 == Diff::LCS.patch(seq1, diffs) seq2 == Diff::LCS.patch!(seq1, diffs) seq1 == Diff::LCS.unpatch(seq2, diffs) seq1 == Diff::LCS.unpatch!(seq2, diffs) seq2 == Diff::LCS.patch(seq1, sdiff) seq2 == Diff::LCS.patch!(seq1, sdiff) seq1 == Diff::LCS.unpatch(seq2, sdiff) seq1 == Diff::LCS.unpatch!(seq2, sdiff)
Alternatively, objects can be extended with Diff::LCS:
seq1.extend(Diff::LCS) lcs = seq1.lcs(seq2) diffs = seq1.diff(seq2) sdiff = seq1.sdiff(seq2) seq = seq1.traverse_sequences(seq2, callback_obj) bal = seq1.traverse_balanced(seq2, callback_obj) seq2 == seq1.patch(diffs) seq2 == seq1.patch!(diffs) seq1 == seq2.unpatch(diffs) seq1 == seq2.unpatch!(diffs) seq2 == seq1.patch(sdiff) seq2 == seq1.patch!(sdiff) seq1 == seq2.unpatch(sdiff) seq1 == seq2.unpatch!(sdiff)
Default extensions are provided for Array and String objects through the use of 'diff/lcs/array' and 'diff/lcs/string'.
The following text is from the Perl documentation. The only changes have been to make the text appear better in Rdoc.
I once read an article written by the authors of diff; they said that they hard worked very hard on the algorithm until they found the right one.
I think what they ended up using (and I hope someone will correct me, because I am not very confident about this) was the `longest common subsequence' method. In the LCS problem, you have two sequences of items:
a b c d f g h j q z a b c d e f g i j k r x y z
and you want to find the longest sequence of items that is present in both original sequences in the same order. That is, you want to find a new sequence S which can be obtained from the first sequence by deleting some items, and from the second sequence by deleting other items. You also want S to be as long as possible. In this case S is:
a b c d f g j z
From there it's only a small step to get diff-like output:
e h i k q r x y + - + + - + + +
This module solves the LCS problem. It also includes a canned function to generate diff-like output.
It might seem from the example above that the LCS of two sequences is always pretty obvious, but that's not always the case, especially when the two sequences have many repeated elements. For example, consider
a x b y c z p d q a b c a x b y c z
A naive approach might start by matching up the a and b that appear at the beginning of each sequence, like this:
a x b y c z p d q a b c a b y c z
This finds the common subsequence +a b c z+. But actually, the LCS is +a x b y c z+:
a x b y c z p d q a b c a x b y c z
This version is by Austin Ziegler <austin@rubyforge.org>.
It is based on the Perl Algorithm::Diff (1.15) by Ned Konz , copyright © 2000–2002 and the Smalltalk diff version by Mario I. Wolczko, copyright © 1993. Documentation includes work by Mark-Jason Dominus.
Copyright © 2004 Austin Ziegler This program is free software; you can redistribute it and/or modify it under the same terms as Ruby, or alternatively under the Perl Artistic licence.
Much of the documentation is taken directly from the Perl Algorithm::Diff implementation and was written originally by Mark-Jason Dominus and later by Ned Konz. The basic Ruby implementation was re-ported from the Smalltalk implementation, available at st.cs.uiuc.edu/pub/Smalltalk/MANCHESTER/manchester/4.0/diff.st
sdiff and traverse_balanced were written for the Perl version by Mike Schilli <m@perlmeister.com>.
"The algorithm is described in A Fast Algorithm for Computing Longest Common Subsequences, CACM, vol.20, no.5, pp.350-353, May 1977, with a few minor improvements to improve the speed."
An alias for DefaultCallbacks that is used in Diff::LCS#traverse_balanced.
Diff::LCS.LCS(seq1, seq2, Diff::LCS::BalancedCallbacks)
An alias for DefaultCallbacks that is used in Diff::LCS#traverse_sequences.
Diff::LCS.LCS(seq1, seq2, Diff::LCS::SequenceCallbacks)
Given two sequenced Enumerables, LCS returns an Array containing their longest common subsequences.
lcs = Diff::LCS.LCS(seq1, seq2)
This array whose contents is such that:
lcs.each_with_index do |ee, ii| assert(ee.nil? || (seq1[ii] == seq2[ee])) end
If a block is provided, the matching subsequences will be yielded from seq1 in turn and may be modified before they are placed into the returned Array of subsequences.
# File lib/diff/lcs.rb, line 214 def LCS(seq1, seq2, &block) #:yields seq1[ii] for each matched: matches = Diff::LCS.__lcs(seq1, seq2) ret = [] matches.each_with_index do |ee, ii| unless matches[ii].nil? if block_given? ret << (yield seq1[ii]) else ret << seq1[ii] end end end ret end
Examine the patchset and the source to see in which direction the patch should be applied.
WARNING: By default, this examines the whole patch, so this could take some time. This also works better with Diff::LCS::ContextChange or Diff::LCS::Change as its source, as an array will cause the creation of one of the above.
Note: This will be deprecated as a public function in a future release.
# File lib/diff/lcs.rb, line 935 def __diff_direction(src, patchset, limit = nil) count = left = left_miss = right = right_miss = 0 string = src.kind_of?(String) patchset.each do |change| count += 1 case change when Diff::LCS::Change # With a simplistic change, we can't tell the difference between # the left and right on '!' actions, so we ignore those. On '=' # actions, if there's a miss, we miss both left and right. element = string ? src[change.position, 1] : src[change.position] case change.action when '-' if element == change.element left += 1 else left_miss += 1 end when '+' if element == change.element right += 1 else right_miss += 1 end when '=' if element != change.element left_miss += 1 right_miss += 1 end end when Diff::LCS::ContextChange case change.action when '-' # Remove details from the old string element = string ? src[change.old_position, 1] : src[change.old_position] if element == change.old_element left += 1 else left_miss += 1 end when '+' element = string ? src[change.new_position, 1] : src[change.new_position] if element == change.new_element right += 1 else right_miss += 1 end when '=' le = string ? src[change.old_position, 1] : src[change.old_position] re = string ? src[change.new_position, 1] : src[change.new_position] left_miss += 1 if le != change.old_element right_miss += 1 if re != change.new_element when '!' element = string ? src[change.old_position, 1] : src[change.old_position] if element == change.old_element left += 1 else element = string ? src[change.new_position, 1] : src[change.new_position] if element == change.new_element right += 1 else left_miss += 1 right_miss += 1 end end end end break if (not limit.nil?) && (count > limit) end no_left = (left == 0) and (left_miss >= 0) no_right = (right == 0) and (right_miss >= 0) case [no_left, no_right] when [false, true] return :patch when [true, false] return :unpatch else raise "The provided patchset does not appear to apply to the provided value as either source or destination value." end end
If vector maps the matching elements of another collection onto this Enumerable, compute the inverse vector that maps this Enumerable onto the collection. (Currently unused.)
Note: This will be deprecated as a public function in a future release.
# File lib/diff/lcs.rb, line 904 def __inverse_vector(a, vector) inverse = a.dup (0 ... vector.size).each do |ii| inverse[vector[ii]] = ii unless vector[ii].nil? end inverse end
private Compute the longest common subsequence between the sequenced Enumerables a and b. The result is an array whose contents is such that
result = Diff::LCS.__lcs(a, b) result.each_with_index do |e, ii| assert_equal(a[ii], b[e]) unless e.nil? end
Note: This will be deprecated as a public function in a future release.
# File lib/diff/lcs.rb, line 804 def __lcs(a, b) a_start = b_start = 0 a_finish = a.size - 1 b_finish = b.size - 1 vector = [] # Prune off any common elements at the beginning... while (a_start <= a_finish) and (b_start <= b_finish) and (a[a_start] == b[b_start]) vector[a_start] = b_start a_start += 1 b_start += 1 end # Now the end... while (a_start <= a_finish) and (b_start <= b_finish) and (a[a_finish] == b[b_finish]) vector[a_finish] = b_finish a_finish -= 1 b_finish -= 1 end # Now, compute the equivalence classes of positions of elements. b_matches = Diff::LCS.__position_hash(b, b_start .. b_finish) thresh = [] links = [] (a_start .. a_finish).each do |ii| ai = a.kind_of?(String) ? a[ii, 1] : a[ii] bm = b_matches[ai] kk = nil bm.reverse_each do |jj| if kk and (thresh[kk] > jj) and (thresh[kk - 1] < jj) thresh[kk] = jj else kk = Diff::LCS.__replace_next_larger(thresh, jj, kk) end links[kk] = [ (kk > 0) ? links[kk - 1] : nil, ii, jj ] unless kk.nil? end end unless thresh.empty? link = links[thresh.size - 1] while not link.nil? vector[link[1]] = link[2] link = link[0] end end vector end
Normalize the patchset. A patchset is always a sequence of changes, but how those changes are represented may vary, depending on how they were generated. In all cases we support, we also support the array representation of the changes. The formats are:
[ # patchset <- Diff::LCS.diff(a, b) [ # one or more hunks Diff::LCS::Change # one or more changes ] ] [ # patchset, equivalent to the above [ # one or more hunks [ action, line, value ] # one or more changes ] ] [ # patchset <- Diff::LCS.diff(a, b, Diff::LCS::ContextDiffCallbacks) # OR <- Diff::LCS.sdiff(a, b, Diff::LCS::ContextDiffCallbacks) [ # one or more hunks Diff::LCS::ContextChange # one or more changes ] ] [ # patchset, equivalent to the above [ # one or more hunks [ action, [ old line, old value ], [ new line, new value ] ] # one or more changes ] ] [ # patchset <- Diff::LCS.sdiff(a, b) # OR <- Diff::LCS.diff(a, b, Diff::LCS::SDiffCallbacks) Diff::LCS::ContextChange # one or more changes ] [ # patchset, equivalent to the above [ action, [ old line, old value ], [ new line, new value ] ] # one or more changes ]
The result of this will be either of the following.
[ # patchset Diff::LCS::ContextChange # one or more changes ] [ # patchset Diff::LCS::Change # one or more changes ]
If either of the above is provided, it will be returned as such.
Note: This will be deprecated as a public function in a future release.
# File lib/diff/lcs.rb, line 1072 def __normalize_patchset(patchset) patchset.map do |hunk| case hunk when Diff::LCS::ContextChange, Diff::LCS::Change hunk when Array if (not hunk[0].kind_of?(Array)) and hunk[1].kind_of?(Array) and hunk[2].kind_of?(Array) Diff::LCS::ContextChange.from_a(hunk) else hunk.map do |change| case change when Diff::LCS::ContextChange, Diff::LCS::Change change when Array # change[1] will ONLY be an array in a ContextChange#to_a call. # In Change#to_a, it represents the line (singular). if change[1].kind_of?(Array) Diff::LCS::ContextChange.from_a(change) else Diff::LCS::Change.from_a(change) end end end end else raise ArgumentError, "Cannot normalise a hunk of class #{hunk.class}." end end.flatten end
Returns a hash mapping each element of an Enumerable to the set of positions it occupies in the Enumerable, optionally restricted to the elements specified in the range of indexes specified by interval.
Note: This will be deprecated as a public function in a future release.
# File lib/diff/lcs.rb, line 917 def __position_hash(enum, interval = 0 .. -1) hash = Hash.new { |hh, kk| hh[kk] = [] } interval.each do |ii| kk = enum.kind_of?(String) ? enum[ii, 1] : enum[ii] hash[kk] << ii end hash end
Find the place at which value would normally be inserted into the Enumerable. If that place is already occupied by value, do nothing and return nil. If the place does not exist (i.e., it is off the end of the Enumerable), add it to the end. Otherwise, replace the element at that point with value. It is assumed that the Enumerable's values are numeric.
This operation preserves the sort order.
Note: This will be deprecated as a public function in a future release.
# File lib/diff/lcs.rb, line 869 def __replace_next_larger(enum, value, last_index = nil) # Off the end? if enum.empty? or (value > enum[-1]) enum << value return enum.size - 1 end # Binary search for the insertion point last_index ||= enum.size first_index = 0 while (first_index <= last_index) ii = (first_index + last_index) >> 1 found = enum[ii] if value == found return nil elsif value > found first_index = ii + 1 else last_index = ii - 1 end end # The insertion point is in first_index; overwrite the next larger # value. enum[first_index] = value return first_index end
Diff::LCS.diff computes the smallest set of additions and deletions necessary to turn the first sequence into the second, and returns a description of these changes.
See Diff::LCS::DiffCallbacks for the default behaviour. An alternate behaviour may be implemented with Diff::LCS::ContextDiffCallbacks. If a Class argument is provided for callbacks, diff will attempt to initialise it. If the callbacks object (possibly initialised) responds to finish, it will be called.
# File lib/diff/lcs.rb, line 238 def diff(seq1, seq2, callbacks = nil, &block) # :yields diff changes: callbacks ||= Diff::LCS::DiffCallbacks if callbacks.kind_of?(Class) cb = callbacks.new rescue callbacks callbacks = cb end traverse_sequences(seq1, seq2, callbacks) callbacks.finish if callbacks.respond_to?(:finish) if block_given? res = callbacks.diffs.map do |hunk| if hunk.kind_of?(Array) hunk = hunk.map { |hunk_block| yield hunk_block } else yield hunk end end res else callbacks.diffs end end
Given a patchset, convert the current version to the new version. If direction is not specified (must be :patch or :unpatch), then discovery of the direction of the patch will be attempted.
# File lib/diff/lcs.rb, line 682 def patch(src, patchset, direction = nil) string = src.kind_of?(String) # Start with a new empty type of the source's class res = src.class.new # Normalize the patchset. patchset = __normalize_patchset(patchset) direction ||= Diff::LCS.__diff_direction(src, patchset) direction ||= :patch ai = bj = 0 patchset.each do |change| # Both Change and ContextChange support #action action = PATCH_MAP[direction][change.action] case change when Diff::LCS::ContextChange case direction when :patch el = change.new_element op = change.old_position np = change.new_position when :unpatch el = change.old_element op = change.new_position np = change.old_position end case action when '-' # Remove details from the old string while ai < op res << (string ? src[ai, 1] : src[ai]) ai += 1 bj += 1 end ai += 1 when '+' while bj < np res << (string ? src[ai, 1] : src[ai]) ai += 1 bj += 1 end res << el bj += 1 when '=' # This only appears in sdiff output with the SDiff callback. # Therefore, we only need to worry about dealing with a single # element. res << el ai += 1 bj += 1 when '!' while ai < op res << (string ? src[ai, 1] : src[ai]) ai += 1 bj += 1 end bj += 1 ai += 1 res << el end when Diff::LCS::Change case action when '-' while ai < change.position res << (string ? src[ai, 1] : src[ai]) ai += 1 bj += 1 end ai += 1 when '+' while bj < change.position res << (string ? src[ai, 1] : src[ai]) ai += 1 bj += 1 end bj += 1 res << change.element end end end while ai < src.size res << (string ? src[ai, 1] : src[ai]) ai += 1 bj += 1 end res end
Given a set of patchset, convert the current version to the next version. Does no auto-discovery.
# File lib/diff/lcs.rb, line 789 def patch!(src, patchset) Diff::LCS.patch(src, patchset, :patch) end
Diff::LCS.sdiff computes all necessary components to show two sequences and their minimized differences side by side, just like the Unix utility sdiff does:
old < - same same before | after - > new
See Diff::LCS::SDiffCallbacks for the default behaviour. An alternate behaviour may be implemented with Diff::LCS::ContextDiffCallbacks. If a Class argument is provided for callbacks, diff will attempt to initialise it. If the callbacks object (possibly initialised) responds to finish, it will be called.
# File lib/diff/lcs.rb, line 275 def sdiff(seq1, seq2, callbacks = nil, &block) #:yields diff changes: callbacks ||= Diff::LCS::SDiffCallbacks if callbacks.kind_of?(Class) cb = callbacks.new rescue callbacks callbacks = cb end traverse_balanced(seq1, seq2, callbacks) callbacks.finish if callbacks.respond_to?(:finish) if block_given? res = callbacks.diffs.map do |hunk| if hunk.kind_of?(Array) hunk = hunk.map { |hunk_block| yield hunk_block } else yield hunk end end res else callbacks.diffs end end
traverse_balanced is an alternative to traverse_sequences. It uses a different algorithm to iterate through the entries in the computed longest common subsequence. Instead of viewing the changes as insertions or deletions from one of the sequences, traverse_balanced will report changes between the sequences. To represent a
The arguments to traverse_balanced are the two sequences to traverse and a callback object, like this:
traverse_balanced(seq1, seq2, Diff::LCS::ContextDiffCallbacks.new)
sdiff is implemented with traverse_balanced.
Optional callback methods are emphasized.
callbacksmatch |
Called when a and b are pointing to common elements in A and B. |
callbacksdiscard_a |
Called when a is pointing to an element not in B. |
callbacksdiscard_b |
Called when b is pointing to an element not in A. |
callbackschange |
Called when a and b are pointing to the same relative position, but A[a] and B[b] are not the same; a change has occurred. |
traverse_balanced might be a bit slower than traverse_sequences, noticable only while processing huge amounts of data.
The sdiff function of this module is implemented as call to traverse_balanced.
a---+ v A = a b c e h j l m n p B = b c d e f j k l m r s t ^ b---+
If there are two arrows (a and b) pointing to elements of sequences A and B, the arrows will initially point to the first elements of their respective sequences. traverse_sequences will advance the arrows through the sequences one element at a time, calling a method on the user-specified callback object before each advance. It will advance the arrows in such a way that if there are elements A[ii] and B[jj] which are both equal and part of the longest common subsequence, there will be some moment during the execution of traverse_sequences when arrow a is pointing to A[ii] and arrow b is pointing to B[jj]. When this happens, traverse_sequences will call callbacks#match and then it will advance both arrows.
Otherwise, one of the arrows is pointing to an element of its sequence that is not part of the longest common subsequence. traverse_sequences will advance that arrow and will call callbacks#discard_a or callbacks#discard_b, depending on which arrow it advanced.
If both a and b point to elements that are not part of the longest common subsequence, then traverse_sequences will try to call callbacks#change and advance both arrows. If callbacks#change is not implemented, then callbacks#discard_a and callbacks#discard_b will be called in turn.
The methods for callbacks#match, callbacks#discard_a, callbacks#discard_b, and callbacks#change are invoked with an event comprising the action ("=", "+", "-", or "!", respectively), the indicies ii and jj, and the elements A[ii] and B[jj]. Return values are discarded by traverse_balanced.
Note that ii and jj may not be the same index position, even if a and b are considered to be pointing to matching or changed elements.
# File lib/diff/lcs.rb, line 570 def traverse_balanced(seq1, seq2, callbacks = Diff::LCS::BalancedCallbacks) matches = Diff::LCS.__lcs(seq1, seq2) a_size = seq1.size b_size = seq2.size ai = bj = mb = 0 ma = -1 string = seq1.kind_of?(String) # Process all the lines in the match vector. loop do # Find next match indices +ma+ and +mb+ loop do ma += 1 break unless ma < matches.size and matches[ma].nil? end break if ma >= matches.size # end of matches? mb = matches[ma] # Change(seq2) while (ai < ma) or (bj < mb) ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[bj, 1] : seq2[bj] case [(ai < ma), (bj < mb)] when [true, true] if callbacks.respond_to?(:change) event = Diff::LCS::ContextChange.new('!', ai, ax, bj, bx) event = yield event if block_given? callbacks.change(event) ai += 1 bj += 1 else event = Diff::LCS::ContextChange.new('-', ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) ai += 1 ax = string ? seq1[ai, 1] : seq1[ai] event = Diff::LCS::ContextChange.new('+', ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) bj += 1 end when [true, false] event = Diff::LCS::ContextChange.new('-', ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) ai += 1 when [false, true] event = Diff::LCS::ContextChange.new('+', ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) bj += 1 end end # Match ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new('=', ai, ax, bj, bx) event = yield event if block_given? callbacks.match(event) ai += 1 bj += 1 end while (ai < a_size) or (bj < b_size) ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[bj, 1] : seq2[bj] case [(ai < a_size), (bj < b_size)] when [true, true] if callbacks.respond_to?(:change) event = Diff::LCS::ContextChange.new('!', ai, ax, bj, bx) event = yield event if block_given? callbacks.change(event) ai += 1 bj += 1 else event = Diff::LCS::ContextChange.new('-', ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) ai += 1 ax = string ? seq1[ai, 1] : seq1[ai] event = Diff::LCS::ContextChange.new('+', ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) bj += 1 end when [true, false] event = Diff::LCS::ContextChange.new('-', ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) ai += 1 when [false, true] event = Diff::LCS::ContextChange.new('+', ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) bj += 1 end end end
Diff::LCS.traverse_sequences is the most general facility provided by this module; diff and LCS are implemented as calls to it.
The arguments to traverse_sequences are the two sequences to traverse, and a callback object, like this:
traverse_sequences(seq1, seq2, Diff::LCS::ContextDiffCallbacks.new)
diff is implemented with traverse_sequences.
Optional callback methods are emphasized.
callbacksmatch |
Called when a and b are pointing to common elements in A and B. |
callbacksdiscard_a |
Called when a is pointing to an element not in B. |
callbacksdiscard_b |
Called when b is pointing to an element not in A. |
callbacksfinished_a |
Called when a has reached the end of sequence A. |
callbacksfinished_b |
Called when b has reached the end of sequence B. |
a---+ v A = a b c e h j l m n p B = b c d e f j k l m r s t ^ b---+
If there are two arrows (a and b) pointing to elements of sequences A and B, the arrows will initially point to the first elements of their respective sequences. traverse_sequences will advance the arrows through the sequences one element at a time, calling a method on the user-specified callback object before each advance. It will advance the arrows in such a way that if there are elements A[ii] and B[jj] which are both equal and part of the longest common subsequence, there will be some moment during the execution of traverse_sequences when arrow a is pointing to A[ii] and arrow b is pointing to B[jj]. When this happens, traverse_sequences will call callbacks#match and then it will advance both arrows.
Otherwise, one of the arrows is pointing to an element of its sequence that is not part of the longest common subsequence. traverse_sequences will advance that arrow and will call callbacks#discard_a or callbacks#discard_b, depending on which arrow it advanced. If both arrows point to elements that are not part of the longest common subsequence, then traverse_sequences will advance one of them and call the appropriate callback, but it is not specified which it will call.
The methods for callbacks#match, callbacks#discard_a, and callbacks#discard_b are invoked with an event comprising the action ("=", "+", or "-", respectively), the indicies ii and jj, and the elements A[ii] and B[jj]. Return values are discarded by traverse_sequences.
If arrow a reaches the end of its sequence before arrow b does, traverse_sequence will try to call callbacks#finished_a with the last index and element of A (A[-1]) and the current index and element of B (B[jj]). If callbacks#finished_a does not exist, then callbacks#discard_b will be called on each element of B until the end of the sequence is reached (the call will be done with A[-1] and B[jj] for each element).
If b reaches the end of B before a reaches the end of A, callbacks#finished_b will be called with the current index and element of A (A[ii]) and the last index and element of B (A[-1]). Again, if callbacks#finished_b does not exist on the callback object, then callbacks#discard_a will be called on each element of A until the end of the sequence is reached (A[ii] and B[-1]).
There is a chance that one additional callbacks#discard_a or callbacks#discard_b will be called after the end of the sequence is reached, if a has not yet reached the end of A or b has not yet reached the end of B.
# File lib/diff/lcs.rb, line 380 def traverse_sequences(seq1, seq2, callbacks = Diff::LCS::SequenceCallbacks, &block) #:yields change events: matches = Diff::LCS.__lcs(seq1, seq2) run_finished_a = run_finished_b = false string = seq1.kind_of?(String) a_size = seq1.size b_size = seq2.size ai = bj = 0 (0 .. matches.size).each do |ii| b_line = matches[ii] ax = string ? seq1[ii, 1] : seq1[ii] bx = string ? seq2[bj, 1] : seq2[bj] if b_line.nil? unless ax.nil? event = Diff::LCS::ContextChange.new('-', ii, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) end else loop do break unless bj < b_line bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new('+', ii, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) bj += 1 end bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new('=', ii, ax, bj, bx) event = yield event if block_given? callbacks.match(event) bj += 1 end ai = ii end ai += 1 # The last entry (if any) processed was a match. +ai+ and +bj+ point # just past the last matching lines in their sequences. while (ai < a_size) or (bj < b_size) # last A? if ai == a_size and bj < b_size if callbacks.respond_to?(:finished_a) and not run_finished_a ax = string ? seq1[-1, 1] : seq1[-1] bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new('>', (a_size - 1), ax, bj, bx) event = yield event if block_given? callbacks.finished_a(event) run_finished_a = true else ax = string ? seq1[ai, 1] : seq1[ai] loop do bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new('+', ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) bj += 1 break unless bj < b_size end end end # last B? if bj == b_size and ai < a_size if callbacks.respond_to?(:finished_b) and not run_finished_b ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[-1, 1] : seq2[-1] event = Diff::LCS::ContextChange.new('<', ai, ax, (b_size - 1), bx) event = yield event if block_given? callbacks.finished_b(event) run_finished_b = true else bx = string ? seq2[bj, 1] : seq2[bj] loop do ax = string ? seq1[ai, 1] : seq1[ai] event = Diff::LCS::ContextChange.new('-', ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) ai += 1 break unless bj < b_size end end end if ai < a_size ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new('-', ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) ai += 1 end if bj < b_size ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new('+', ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) bj += 1 end end end
Returns the difference set between self and other. See Diff::LCS#diff.
# File lib/diff/lcs.rb, line 148 def diff(other, callbacks = nil, &block) Diff::LCS::diff(self, other, callbacks, &block) end
Attempts to patch a copy of self with the provided patchset. See Diff::LCS#patch.
# File lib/diff/lcs.rb, line 175 def patch(patchset) Diff::LCS::patch(self.dup, patchset) end
Attempts to patch self with the provided patchset. See Diff::LCS#patch!. Does no autodiscovery.
# File lib/diff/lcs.rb, line 187 def patch!(patchset) Diff::LCS::patch!(self, patchset) end
Returns the balanced ("side-by-side") difference set between self and other. See Diff::LCS#sdiff.
# File lib/diff/lcs.rb, line 154 def sdiff(other, callbacks = nil, &block) Diff::LCS::sdiff(self, other, callbacks, &block) end
Traverses the discovered longest common subsequences between self and other using the alternate, balanced algorithm. See Diff::LCS#traverse_balanced.
# File lib/diff/lcs.rb, line 168 def traverse_balanced(other, callbacks = nil, &block) traverse_balanced(self, other, callbacks || Diff::LCS::YieldingCallbacks, &block) end
Traverses the discovered longest common subsequences between self and other. See Diff::LCS#traverse_sequences.
# File lib/diff/lcs.rb, line 160 def traverse_sequences(other, callbacks = nil, &block) traverse_sequences(self, other, callbacks || Diff::LCS::YieldingCallbacks, &block) end
Attempts to unpatch a copy of self with the provided patchset. See Diff::LCS#patch.
# File lib/diff/lcs.rb, line 181 def unpatch(patchset) Diff::LCS::unpatch(self.dup, patchset) end
Attempts to unpatch self with the provided patchset. See Diff::LCS#unpatch. Does no autodiscovery.
# File lib/diff/lcs.rb, line 193 def unpatch!(patchset) Diff::LCS::unpatch!(self, patchset) end
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