module Diff::LCS::Internals
Public Class Methods
analyze_patchset(patchset, depth = 0)
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This method will analyze the provided patchset to provide a single-pass normalization (conversion of the array form of Diff::LCS::Change objects to the object form of same) and detection of whether the patchset represents changes to be made.
# File lib/diff/lcs/internals.rb, line 99 def analyze_patchset(patchset, depth = 0) raise "Patchset too complex" if depth > 1 has_changes = false # Format: # [ # patchset # # hunk (change) # [ # hunk # # change # ] # ] patchset = patchset.map do |hunk| case hunk when Diff::LCS::Change has_changes ||= !hunk.unchanged? hunk when Array # Detect if the 'hunk' is actually an array-format # Change object. if Diff::LCS::Change.valid_action? hunk[0] hunk = Diff::LCS::Change.from_a(hunk) has_changes ||= !hunk.unchanged? hunk else with_changes, hunk = analyze_patchset(hunk, depth + 1) has_changes ||= with_changes hunk.flatten end else raise ArgumentError, "Cannot normalise a hunk of class #{hunk.class}." end end [ has_changes, patchset.flatten(1) ] end
intuit_diff_direction(src, patchset, limit = nil)
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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.
# File lib/diff/lcs/internals.rb, line 144 def intuit_diff_direction(src, patchset, limit = nil) string = src.kind_of?(String) count = left_match = left_miss = right_match = right_miss = 0 patchset.each do |change| count += 1 case change when Diff::LCS::ContextChange le = string ? src[change.old_position, 1] : src[change.old_position] re = string ? src[change.new_position, 1] : src[change.new_position] case change.action when '-' # Remove details from the old string if le == change.old_element left_match += 1 else left_miss += 1 end when '+' if re == change.new_element right_match += 1 else right_miss += 1 end when '=' left_miss += 1 if le != change.old_element right_miss += 1 if re != change.new_element when '!' if le == change.old_element left_match += 1 else if re == change.new_element right_match += 1 else left_miss += 1 right_miss += 1 end end end 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_match += 1 else left_miss += 1 end when '+' if element == change.element right_match += 1 else right_miss += 1 end when '=' if element != change.element left_miss += 1 right_miss += 1 end end end break if (not limit.nil?) && (count > limit) end no_left = (left_match == 0) && (left_miss > 0) no_right = (right_match == 0) && (right_miss > 0) case [ no_left, no_right ] when [ false, true ] :patch when [ true, false ] :unpatch else case left_match <=> right_match when 1 if left_miss.zero? :patch else :unpatch end when -1 if right_miss.zero? :unpatch else :patch end else raise "The provided patchset does not appear to apply to the provided enumerable as either source or destination value." end end end
lcs(a, b)
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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::Internals.lcs(a, b) result.each_with_index do |e, i| assert_equal(a[i], b[e]) unless e.nil? end
# File lib/diff/lcs/internals.rb, line 40 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 b_start = a_start # 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 = position_hash(b, b_start..b_finish) thresh = [] links = [] string = a.kind_of?(String) (a_start .. a_finish).each do |i| ai = string ? a[i, 1] : a[i] bm = b_matches[ai] k = nil bm.reverse_each do |j| if k and (thresh[k] > j) and (thresh[k - 1] < j) thresh[k] = j else k = replace_next_larger(thresh, j, k) end links[k] = [ (k > 0) ? links[k - 1] : nil, i, j ] unless k.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