Module: Diff::LCS::Internals
- Defined in:
- lib/diff/lcs/internals.rb
Overview
:nodoc:
Class Method Summary collapse
-
.analyze_patchset(patchset, depth = 0) ⇒ Object
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.
-
.intuit_diff_direction(src, patchset, limit = nil) ⇒ Object
Examine the patchset and the source to see in which direction the patch should be applied.
-
.inverse_vector(a, vector) ⇒ Object
If
vector
maps the matching elements of another collection onto this Enumerable, compute the inverse ofvector
that maps this Enumerable onto the collection. -
.lcs(a, b) ⇒ Object
Compute the longest common subsequence between the sequenced Enumerables
a
andb
. -
.position_hash(enum, interval) ⇒ Object
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
. -
.replace_next_larger(enum, value, last_index = nil) ⇒ Object
Find the place at which
value
would normally be inserted into the Enumerable.
Class Method Details
.analyze_patchset(patchset, depth = 0) ⇒ Object
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.
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# 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) ⇒ Object
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.
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# File 'lib/diff/lcs/internals.rb', line 146 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 :patch when -1 :unpatch else raise "The provided patchset does not appear to apply to the provided value as either source or destination value." end end end |
.inverse_vector(a, vector) ⇒ Object
If vector
maps the matching elements of another collection onto this Enumerable, compute the inverse of vector
that maps this Enumerable onto the collection. (Currently unused.)
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# File 'lib/diff/lcs/internals.rb', line 278 def inverse_vector(a, vector) inverse = a.dup (0...vector.size).each do |i| inverse[vector[i]] = i unless vector[i].nil? end inverse end |
.lcs(a, b) ⇒ Object
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# File 'lib/diff/lcs/internals.rb', line 41 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 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 |
.position_hash(enum, interval) ⇒ Object
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
.
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# File 'lib/diff/lcs/internals.rb', line 290 def position_hash(enum, interval) string = enum.kind_of?(String) hash = Hash.new { |h, k| h[k] = [] } interval.each do |i| k = string ? enum[i, 1] : enum[i] hash[k] << i end hash end |
.replace_next_larger(enum, value, last_index = nil) ⇒ Object
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.
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# File 'lib/diff/lcs/internals.rb', line 244 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) i = (first_index + last_index) >> 1 found = enum[i] if value == found return nil elsif value > found first_index = i + 1 else last_index = i - 1 end end # The insertion point is in first_index; overwrite the next larger # value. enum[first_index] = value return first_index end |