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diff_match_patch.rb
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diff_match_patch.rb
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require 'uri'
module DMPTextEncode
def encodeText(text)
URI.encode(text, /[^0-9A-Za-z_.;!~*'(),\/?:@&=+$\#-]/)
end
def decodeText(text)
URI.decode(text.force_encoding(Encoding::UTF_8))
end
end
# Class representing one diff operation (delete, equal or insert)
Diff = Struct.new(:op, :text)
# Class representing one patch operation
class Patch
include DMPTextEncode
attr_accessor :start1, :start2
attr_accessor :length1, :length2
attr_accessor :diffs
# Constructor
def initialize
@start1 = @start2 = nil
@length1 = @length2 = 0
@diffs = []
end
# Emulate GNU diff's format
# Header: @@ -382,8 +481,9 @@
# Indices are printed as 1-based, not 0-based.
def to_s
if length1 == 0
coords1 = start1.to_s + ",0"
elsif length1 == 1
coords1 = (start1 + 1).to_s
else
coords1 = (start1 + 1).to_s + "," + length1.to_s
end
if length2 == 0
coords2 = start2.to_s + ",0"
elsif length2 == 1
coords2 = (start2 + 1).to_s
else
coords2 = (start2 + 1).to_s + "," + length2.to_s
end
text = '@@ -' + coords1 + ' +' + coords2 + " @@\n"
# Encode the body of the patch with %xx notation.
text += diffs.map do |diff|
op = case diff.op
when :insert; '+'
when :delete; '-'
when :equal ; ' '
end
op + encodeText(diff.text) + "\n"
end.join.gsub('%20', ' ')
end
end
class DiffPatchMatch
include DMPTextEncode
attr_accessor :diff_timeout
attr_accessor :diff_editCost
attr_accessor :match_threshold
attr_accessor :match_distance
attr_accessor :patch_deleteThreshold
attr_accessor :patch_margin
attr_reader :match_maxBits
def initialize
# Defaults.
# Redefine these in your program to override the defaults.
# Number of seconds to map a diff before giving up (0 for infinity).
@diff_timeout = 1
# Cost of an empty edit operation in terms of edit characters.
@diff_editCost = 4
# At what point is no match declared (0.0 = perfection, 1.0 = very loose).
@match_threshold = 0.5
# How far to search for a match (0 = exact location, 1000+ = broad match).
# A match this many characters away from the expected location will add
# 1.0 to the score (0.0 is a perfect match).
@match_distance = 1000
# When deleting a large block of text (over ~64 characters), how close does
# the contents have to match the expected contents. (0.0 = perfection,
# 1.0 = very loose). Note that match_threshold controls how closely the
# end points of a delete need to match.
@patch_deleteThreshold = 0.5
# Chunk size for context length.
@patch_margin = 4
@match_maxBits = 32
end
# Determine the common prefix of two strings.
def diff_commonPrefix(text1, text2)
# Quick check for common null cases.
return 0 if text1.empty? || text2.empty? || text1[0] != text2[0]
# Binary search.
# Performance analysis: http://neil.fraser.name/news/2007/10/09/
# See diff_patch_match_bench.rb
pointer_min = 0
pointer_max = [text1.length, text2.length].min
pointer_mid = pointer_max
pointer_start = 0
while pointer_min < pointer_mid
if text1[pointer_start...pointer_mid] ==
text2[pointer_start...pointer_mid]
pointer_min = pointer_mid
pointer_start = pointer_min
else
pointer_max = pointer_mid
end
pointer_mid = (pointer_max - pointer_min) / 2 + pointer_min
end
pointer_mid
end
# Determine the common suffix of two strings.
def diff_commonSuffix(text1, text2)
# Quick check for common null cases.
return 0 if text1.empty? || text2.empty? || text1[-1] != text2[-1]
# Binary search.
# Performance analysis: http://neil.fraser.name/news/2007/10/09/
# See diff_patch_match_bench.rb
pointer_min = 0
pointer_max = [text1.length, text2.length].min
pointer_mid = pointer_max
pointer_end = 0
while pointer_min < pointer_mid
if text1[-pointer_mid..(-pointer_end-1)] ==
text2[-pointer_mid..(-pointer_end-1)]
pointer_min = pointer_mid
pointer_end = pointer_min
else
pointer_max = pointer_mid
end
pointer_mid = (pointer_max - pointer_min) / 2 + pointer_min
end
pointer_mid
end
# Determine if the suffix of one string is the prefix of another.
def diff_commonOverlap(text1, text2)
# Cache the text lengths to prevent multiple calls.
text1_length = text1.length
text2_length = text2.length
# Eliminate the null case.
return 0 if text1_length.zero? || text2_length.zero?
# Truncate the longer string.
if text1_length > text2_length
text1 = text1[-text2_length..-1]
else
text2 = text2[0...text1_length]
end
text_length = [text1_length, text2_length].min
# Quick check for the whole case.
return text_length if text1 == text2
# Start by looking for a single character match
# and increase length until no match is found.
# Performance analysis: http://neil.fraser.name/news/2010/11/04/
best, length = 0, 1
loop do
pattern = text1[(text_length - length)..-1]
found = text2.index(pattern)
return best if found.nil?
length += found
if found == 0 || text1[(text_length - length)..-1] == text2[0..length]
best = length
length += 1
end
end
end
# Does a substring of shorttext exist within longtext such that the substring
# is at least half the length of longtext?
def diff_halfMatchI(longtext, shorttext, i)
# Start with a 1/4 length Substring at position i as a seed.
seed = longtext[i, longtext.length / 4]
j = -1
best_common = ''
while j = shorttext.index(seed, j + 1)
prefix_length = diff_commonPrefix(longtext[i..-1], shorttext[j..-1])
suffix_length = diff_commonSuffix(longtext[0...i], shorttext[0...j])
if best_common.length < suffix_length + prefix_length
best_common = shorttext[(j - suffix_length)...j] +
shorttext[j...(j + prefix_length)]
best_longtext_a = longtext[0...(i - suffix_length)]
best_longtext_b = longtext[(i + prefix_length)..-1]
best_shorttext_a = shorttext[0...(j - suffix_length)]
best_shorttext_b = shorttext[(j + prefix_length)..-1]
end
end
if best_common.length * 2 >= longtext.length
[best_longtext_a, best_longtext_b, best_shorttext_a, best_shorttext_b,
best_common]
end
end
# Do the two texts share a substring which is at least half the length of the
# longer text?
# This speedup can produce non-minimal diffs.
def diff_halfMatch(text1, text2)
# Don't risk returning a non-optimal diff if we have unlimited time
return nil if diff_timeout <= 0
shorttext, longtext = [text1, text2].sort_by(&:length)
if longtext.length < 4 || shorttext.length * 2 < longtext.length
return nil # Pointless.
end
# First check if the second quarter is the seed for a half-match.
hm1 = diff_halfMatchI(longtext, shorttext, (longtext.length / 4.0).ceil)
# Check again based on the third quarter.
hm2 = diff_halfMatchI(longtext, shorttext, (longtext.length / 2.0).ceil)
if hm1.nil? && hm2.nil?
return nil
elsif hm2.nil?
hm = hm1
elsif hm1.nil?
hm = hm2
else
# Both matched. Select the longest.
hm = hm1[4].length > hm2[4].length ? hm1 : hm2
end
# A half-match was found, sort out the return data.
if text1.length > text2.length
text1_a, text1_b, text2_a, text2_b = hm
else
text2_a, text2_b, text1_a, text1_b = hm
end
mid_common = hm[4]
[text1_a, text1_b, text2_a, text2_b, mid_common]
end
# Split two texts into an array of strings. Reduce the texts to a string of
# hashes where each Unicode character represents one line.
def diff_linesToChars(text1, text2)
line_array = [''] # e.g. line_array[4] == "Hello\n"
line_hash = {} # e.g. line_hash["Hello\n"] == 4
[text1, text2].map do |text|
# Split text into an array of strings. Reduce the text to a string of
# hashes where each Unicode character represents one line.
chars = ''
text.each_line do |line|
if line_hash[line]
chars += line_hash[line].chr(Encoding::UTF_8)
else
chars += line_array.length.chr(Encoding::UTF_8)
line_hash[line] = line_array.length
line_array.push(line)
end
end
chars
end.push(line_array)
end
# Rehydrate the text in a diff from a string of line hashes to real lines of
# text.
def diff_charsToLines(diffs, line_array)
diffs.each do |diff|
diff.text = diff.text.chars.map{ |c| line_array[c.ord] }.join
end
end
# Reorder and merge like edit sections. Merge equalities.
# Any edit section can move as long as it doesn't cross an equality.
def diff_cleanupMerge(diffs)
diffs.push(Diff.new(:equal, '')) # Add a dummy entry at the end.
pointer = 0
count_delete = count_insert = 0
text_delete, text_insert = '', ''
while pointer < diffs.length
case diffs[pointer].op
when :insert
count_insert += 1
text_insert += diffs[pointer].text
pointer += 1
when :delete
count_delete += 1
text_delete += diffs[pointer].text
pointer += 1
when :equal
# Upon reaching an equality, check for prior redundancies.
if count_delete + count_insert > 1
if count_delete != 0 && count_insert != 0
# Factor out any common prefixies.
common_length = diff_commonPrefix(text_insert, text_delete)
if common_length != 0
if (pointer - count_delete - count_insert) > 0 &&
diffs[pointer - count_delete - count_insert - 1].op == :equal
diffs[pointer - count_delete - count_insert - 1].text +=
text_insert[0...common_length]
else
diffs.unshift(Diff.new(:equal, text_insert[0...common_length]))
pointer += 1
end
text_insert = text_insert[common_length..-1]
text_delete = text_delete[common_length..-1]
end
# Factor out any common suffixies.
common_length = diff_commonSuffix(text_insert, text_delete)
if common_length != 0
diffs[pointer].text = text_insert[-common_length..-1] +
diffs[pointer].text
text_insert = text_insert[0...-common_length]
text_delete = text_delete[0...-common_length]
end
end
# Delete the offending records and add the merged ones.
if count_delete.zero?
diffs[
pointer - count_delete - count_insert,
count_delete + count_insert
] = [Diff.new(:insert, text_insert)]
elsif count_insert.zero?
diffs[
pointer - count_delete - count_insert,
count_delete + count_insert
] = [Diff.new(:delete, text_delete)]
else
diffs[
pointer - count_delete - count_insert,
count_delete + count_insert
] = [Diff.new(:delete, text_delete), Diff.new(:insert, text_insert)]
end
pointer = pointer - count_delete - count_insert +
(count_delete.zero? ? 0 : 1) + (count_insert.zero? ? 0 : 1) + 1
elsif pointer != 0 && diffs[pointer - 1].op == :equal
# Merge this equality with the previous one.
diffs[pointer - 1].text += diffs[pointer].text
diffs[pointer, 1] = []
else
pointer += 1
end
count_insert = count_delete = 0
text_delete, text_insert = '', ''
end # case
end # while
if diffs.last.text.empty?
diffs.pop # Remove the dummy entry at the end.
end
# Second pass: look for single edits surrounded on both sides by equalities
# which can be shifted sideways to eliminate an equality.
# e.g: A<ins>BA</ins>C -> <ins>AB</ins>AC
changes = false
pointer = 1
# Intentionally ignore the first and last element (don't need checking).
while pointer < diffs.length - 1
if diffs[pointer - 1].op == :equal && diffs[pointer + 1].op == :equal
# This is a single edit surrounded by equalities.
if diffs[pointer].text[-diffs[pointer - 1].text.length..-1] ==
diffs[pointer - 1].text
# Shift the edit over the previous equality.
diffs[pointer].text = diffs[pointer - 1].text +
diffs[pointer].text[0...-diffs[pointer - 1].text.length]
diffs[pointer + 1].text = diffs[pointer - 1].text +
diffs[pointer + 1].text
diffs[pointer - 1, 1] = []
changes = true
elsif diffs[pointer].text[0...diffs[pointer + 1].text.length] ==
diffs[pointer + 1].text
# Shift the edit over the next equality.
diffs[pointer - 1].text += diffs[pointer + 1].text
diffs[pointer].text =
diffs[pointer].text[diffs[pointer + 1].text.length..-1] +
diffs[pointer + 1].text
diffs[pointer + 1, 1] = []
changes = true
end
end
pointer += 1
end # while
# If shifts were made, the diff needs reordering and another shift sweep.
if changes
diff_cleanupMerge(diffs)
end
end
# Given two strings, compute a score representing whether the internal
# boundary falls on logical boundaries.
# Scores range from 5 (best) to 0 (worst).
def diff_cleanupSemanticScore(one, two)
if one.empty? || two.empty?
# Edges are the best
return 5
end
# Define some regex patterns for matching boundaries.
punctuation = /[^a-zA-Z0-9]/
whitespace = /\s/
linebreak = /[\r\n]/
blanklineEnd = /\n\r?\n$/
blanklineStart = /^\r?\n\r?\n/
# Each port of this function behaves slightly differently due to
# subtle differences in each language's definition of things like
# 'whitespace'. Since this function's purpose is largely cosmetic,
# the choice has been made to use each language's native features
# rather than force total conformity.
score = 0
# One point for non-alphanumeric.
if one[-1] =~ punctuation || two[0] =~ punctuation
score += 1
# Two points for whitespace.
if one[-1] =~ whitespace || two[0] =~ whitespace
score += 1
# Three points for line breaks.
if one[-1] =~ linebreak || two[0] =~ linebreak
score += 1
# Four points for blank lines.
if one =~ blanklineEnd || two =~ blanklineStart
score += 1
end
end
end
end
score
end
# Look for single edits surrounded on both sides by equalities
# which can be shifted sideways to align the edit to a word boundary.
# e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.
def diff_cleanupSemanticLossless(diffs)
pointer = 1
# Intentionally ignore the first and last element (don't need checking).
while pointer < diffs.length - 1
if diffs[pointer - 1].op == :equal && diffs[pointer + 1].op == :equal
# This is a single edit surrounded by equalities.
equality1 = diffs[pointer - 1].text
edit = diffs[pointer].text
equality2 = diffs[pointer + 1].text
# First, shift the edit as far left as possible.
common_offset = diff_commonSuffix(equality1, edit)
if common_offset != 0
common_string = edit[-common_offset..-1]
equality1 = equality1[0...-common_offset]
edit = common_string + edit[0...-common_offset]
equality2 = common_string + equality2
end
# Second, step character by character right, looking for the best fit.
bestEquality1 = equality1
bestEdit = edit
bestEquality2 = equality2
bestScore = diff_cleanupSemanticScore(equality1, edit) +
diff_cleanupSemanticScore(edit, equality2)
while edit[0] == equality2[0]
equality1 += edit[0]
edit = edit[1..-1] + equality2[0]
equality2 = equality2[1..-1]
score = diff_cleanupSemanticScore(equality1, edit) +
diff_cleanupSemanticScore(edit, equality2)
# The >= encourages trailing rather than leading whitespace on edits.
if score >= bestScore
bestScore = score
bestEquality1 = equality1
bestEdit = edit
bestEquality2 = equality2
end
end
if diffs[pointer - 1].text != bestEquality1
# We have an improvement, save it back to the diff.
if bestEquality1.empty?
diffs[pointer - 1, 1] = []
pointer -= 1
else
diffs[pointer - 1].text = bestEquality1
end
diffs[pointer].text = bestEdit
if bestEquality2.empty?
diffs[pointer + 1, 1] = []
pointer -= 1
else
diffs[pointer + 1].text = bestEquality2
end
end
end
pointer += 1
end
end
# Reduce the number of edits by eliminating semantically trivial equalities.
def diff_cleanupSemantic(diffs)
changes = false
equalities = [] # Stack of indices where equalities are found.
last_equality = nil # Always equal to equalities.last[1]
pointer = 0 # Index of current position.
# Number of characters that changed prior to the equality.
length_insertions1 = length_deletions1 = 0
# Number of characters that changed after the equality.
length_insertions2 = length_deletions2 = 0
while pointer < diffs.length
if diffs[pointer].op == :equal # Equality found.
equalities.push(pointer)
length_insertions1 = length_insertions2
length_deletions1 = length_deletions2
length_insertions2 = length_deletions2 = 0
last_equality = diffs[pointer].text
else # An insertion or deletion.
if diffs[pointer].op == :insert
length_insertions2 += diffs[pointer].text.length
else
length_deletions2 += diffs[pointer].text.length
end
if last_equality &&
last_equality.length <= [length_insertions1, length_deletions1].max &&
last_equality.length <= [length_insertions2, length_deletions2].max
# Duplicate record.
diffs[equalities.last, 0] = [Diff.new(:delete, last_equality)]
# Change second copy to insert.
diffs[equalities.last + 1].op = :insert
# Throw away the equality we just deleted.
equalities.pop
# Throw away the previous equality (it needs to be reevaluated).
equalities.pop
pointer = equalities.last || -1
length_insertions1 = length_deletions1 = 0 # Reset the counters.
length_insertions2 = length_deletions2 = 0
last_equality = nil
changes = true
end
end
pointer += 1
end
# Normalize the diff.
if changes
diff_cleanupMerge(diffs)
end
diff_cleanupSemanticLossless(diffs)
# Find any overlaps between deletions and insertions.
# e.g: <del>abcxx</del><ins>xxdef</ins>
# -> <del>abc</del>xx<ins>def</ins>
pointer = 1
while pointer < diffs.length
if diffs[pointer - 1].op == :delete && diffs[pointer].op == :insert
deletion = diffs[pointer - 1].text
insertion = diffs[pointer].text
overlap_length = diff_commonOverlap(deletion, insertion)
if overlap_length != 0
# Overlap found. Insert an equality and trim the surrounding edits.
diffs[pointer, 0] = [Diff.new(:equal, insertion[0...overlap_length])]
diffs[pointer - 1].text = deletion[0...-overlap_length]
diffs[pointer + 1].text = insertion[overlap_length..-1]
pointer += 1
end
pointer += 1
end
pointer += 1
end
end
# Reduce the number of edits by eliminating operationally trivial equalities.
def diff_cleanupEfficiency(diffs)
changes = false
equalities = [] # Stack of indices where equalities are found.
last_equality = '' # Always equal to equalities.last[1]
pointer = 0 # Index of current position.
# Is there an insertion operation before the last equality.
pre_ins = false
# Is there a deletion operation before the last equality.
pre_del = false
# Is there an insertion operation after the last equality.
post_ins = false
# Is there a deletion operation after the last equality.
post_del = false
while pointer < diffs.length
if diffs[pointer].op == :equal # Equality found.
if diffs[pointer].text.length < diff_editCost && (post_ins || post_del)
# Candidate found.
equalities.push(pointer)
pre_ins = post_ins
pre_del = post_del
last_equality = diffs[pointer].text
else
# Not a candidate, and can never become one.
equalities.clear
last_equality = ''
end
post_ins = post_del = false
else # An insertion or deletion.
if diffs[pointer].op == :delete
post_del = true
else
post_ins = true
end
# Five types to be split:
# <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>
# <ins>A</ins>X<ins>C</ins><del>D</del>
# <ins>A</ins><del>B</del>X<ins>C</ins>
# <ins>A</del>X<ins>C</ins><del>D</del>
# <ins>A</ins><del>B</del>X<del>C</del>
#/
if !last_equality.empty? &&
((pre_ins && pre_del && post_ins && post_del) ||
((last_equality.length < diff_editCost / 2) &&
[pre_ins, pre_del, post_ins, post_del].count(true) == 3))
# Duplicate record.
diffs[equalities.last, 0] = [Diff.new(:delete, last_equality)]
# Change second copy to insert.
diffs[equalities.last + 1].op = :insert
equalities.pop # Throw away the equality we just deleted
last_equality = ''
if pre_ins && pre_del
# No changes made which could affect previous entry, keep going.
post_ins = post_del = true
equalities.clear
else
equalities.pop # Throw away the previous equality.
pointer = equalities.last || -1
post_ins = post_del = false
end
changes = true
end
end
pointer += 1
end
if changes
diff_cleanupMerge(diffs)
end
end
# Convert a diff array into a pretty HTML report.
def diff_prettyHtml(diffs)
diffs.map do |diff|
text = diff.text.gsub('&', '&').gsub('<', '<').gsub('>', '>').
gsub('\n', '¶<br>')
case diff.op
when :insert
"<ins style=\"background:#e6ffe6;\">#{text}</ins>"
when :delete
"<del style=\"background:#ffe6e6;\">#{text}</del>"
when :equal
"<span>#{text}</span>"
end
end.join
end
# Compute and return the source text (all equalities and deletions).
#
def diff_text1(diffs)
diffs.map do |diff|
if diff.op == :insert
''
else
diff.text
end
end.join
end
# Compute and return the destination text (all equalities and insertions).
def diff_text2(diffs)
diffs.map do |diff|
if diff.op == :delete
''
else
diff.text
end
end.join
end
# Crush the diff into an encoded string which describes the operations
# required to transform text1 into text2.
# E.g. =3\t-2\t+ing -> Keep 3 chars, delete 2 chars, insert 'ing'.
# Operations are tab-separated. Inserted text is escaped using %xx notation.
def diff_toDelta(diffs)
diffs.map do |diff|
case diff.op
when :insert
'+' + encodeText(diff.text)
when :delete
'-' + diff.text.length.to_s
when :equal
'=' + diff.text.length.to_s
end
end.join("\t").gsub('%20', ' ')
end
# Given the original text1, and an encoded string which describes the
# operations required to transform text1 into text2, compute the full diff.
def diff_fromDelta(text1, delta)
diffs = []
pointer = 0 # Cursor in text1
delta.split("\t").each do |token|
# Each token begins with a one character parameter which specifies the
# operation of this token (delete, insert, equality).
param = token[1..-1]
case token[0]
when '+'
diffs.push(Diff.new(:insert, decodeText(param)))
when '-', '='
begin
n = Integer(param)
raise if n < 0
text = text1[pointer...(pointer += n)]
if token[0] == '='
diffs.push(Diff.new(:equal, text))
else
diffs.push(Diff.new(:delete, text))
end
rescue ArgumentError => e
raise ArgumentError.new(
"Invalid number in diff_fromDelta: #{param.inspect}")
end
else
# Blank tokens are ok (from a trailing \t).
# Anything else is an error.
if !token.empty?
raise ArgumentError.new(
"Invalid diff operation in diff_fromDelta: #{token.inspect}")
end
end
end
if pointer != text1.length
raise ArgumentError.new("Delta length (#{pointer}) does not equal " +
"source text length #{text1.length}")
end
diffs
end
# loc is a location in text1, compute and return the equivalent location in
# text2.
# e.g. 'The cat' vs 'The big cat', 1->1, 5->8
def diff_xIndex(diffs, loc)
chars1 = chars2 = 0
last_chars1 = last_chars2 = 0
x = diffs.index do |diff|
if diff.op != :insert # Equality or deletion.
chars1 += diff.text.length
end
if diff.op != :delete # Equality or insertion.
chars2 += diff.text.length
end
if chars1 > loc # Overshot the location.
true
else
last_chars1 = chars1
last_chars2 = chars2
false
end
end
# Was the location deleted?
if x && diffs[x].op == :delete
last_chars2
else
# Add the remaining character length.
last_chars2 + (loc - last_chars1)
end
end
def diff_levenshtein(diffs)
levenshtein = insertions = deletions = 0
diffs.each do |diff|
case diff.op
when :insert
insertions += diff.text.length
when :delete
deletions += diff.text.length
when :equal
# A deletion and an insertion is one substitution.
levenshtein += [insertions, deletions].max
insertions = deletions = 0
end
end
levenshtein + [insertions, deletions].max
end
# Find the 'middle snake' of a diff, split the problem in two
# and return the recursively constructed diff.
# See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.
def diff_bisect(text1, text2, deadline)
# Cache the text lengths to prevent multiple calls.
text1_length = text1.length
text2_length = text2.length
max_d = (text1_length + text2_length + 1) / 2
v_offset = max_d
v_length = 2 * max_d
v1 = Array.new(v_length, -1)
v2 = Array.new(v_length, -1)
v1[v_offset + 1] = 0
v2[v_offset + 1] = 0
delta = text1_length - text2_length
# If the total number of characters is odd, then the front path will collide
# with the reverse path.
front = (delta % 2 != 0)
# Offsets for start and end of k loop.
# Prevents mapping of space beyond the grid.
k1start = 0
k1end = 0
k2start = 0
k2end = 0
max_d.times do |d|
# Bail out if deadline is reached.
if deadline && Time.now >= deadline
break
end
# Walk the front path one step.
(-d + k1start).step(d - k1end, 2) do |k1|
k1_offset = v_offset + k1
if k1 == -d || k1 != d && v1[k1_offset - 1] < v1[k1_offset + 1]
x1 = v1[k1_offset + 1]
else
x1 = v1[k1_offset - 1] + 1
end
y1 = x1 - k1
while x1 < text1_length && y1 < text2_length && text1[x1] == text2[y1]
x1 += 1
y1 += 1
end
v1[k1_offset] = x1
if x1 > text1_length
# Ran off the right of the graph.
k1end += 2
elsif y1 > text2_length
# Ran off the bottom of the graph.
k1start += 2
elsif front
k2_offset = v_offset + delta - k1
if k2_offset >= 0 && k2_offset < v_length && v2[k2_offset] != -1
# Mirror x2 onto top-left coordinate system.
x2 = text1_length - v2[k2_offset]
if x1 >= x2
# Overlap detected.
return diff_bisectSplit(text1, text2, x1, y1, deadline)
end
end
end
end
# Walk the reverse path one step.
(-d + k2start).step(d - k2end, 2) do |k2|
k2_offset = v_offset + k2
if k2 == -d || k2 != d && v2[k2_offset - 1] < v2[k2_offset + 1]
x2 = v2[k2_offset + 1]
else
x2 = v2[k2_offset - 1] + 1
end
y2 = x2 - k2
while x2 < text1_length && y2 < text2_length && text1[-x2-1] == text2[-y2-1]
x2 += 1
y2 += 1
end
v2[k2_offset] = x2
if x2 > text1_length
# Ran off the left of the graph.
k2end += 2
elsif y2 > text2_length
# Ran off the top of the graph.
k2start += 2
elsif !front
k1_offset = v_offset + delta - k2
if k1_offset >= 0 && k1_offset < v_length && v1[k1_offset] != -1
x1 = v1[k1_offset]
y1 = v_offset + x1 - k1_offset
# Mirror x2 onto top-left coordinate system.
x2 = text1_length - x2
if x1 >= x2
# Overlap detected.
return diff_bisectSplit(text1, text2, x1, y1, deadline)
end
end
end
end
end
# Diff took too long and hit the deadline or
# number of diffs equals number of characters, no commonality at all.
[Diff.new(:delete, text1), Diff.new(:insert, text2)]
end
# Given the location of the 'middle snake', split the diff in two parts
# and recurse.
def diff_bisectSplit(text1, text2, x, y, deadline)
text1a = text1[0...x]
text2a = text2[0...y]
text1b = text1[x..-1]
text2b = text2[y..-1]
# Compute both diffs serially.
diffs = diff_main(text1a, text2a, false, deadline)
diffsb = diff_main(text1b, text2b, false, deadline)
diffs + diffsb
end
# Find the differences between two texts. Simplifies the problem by stripping
# any common prefix or suffix off the texts before diffing.
def diff_main(text1, text2, checklines=nil, deadline=nil)
# Set a deadline by which time the diff must be complete.
if deadline.nil? && diff_timeout > 0
deadline = Time.now + diff_timeout
end
# Check for null inputs.
if text1.nil? || text2.nil?
raise ArgumentError.new('Null input. (diff_main)')
end
# Check for equality (speedup).
if text1 == text2
if text1.empty?
return []
else
return [Diff.new(:equal, text1)]
end
end
# Default to checklines == true
if checklines.nil?
checklines = true
end
# Trim off common prefix (speedup).
common_length = diff_commonPrefix(text1, text2)
if common_length.nonzero?
common_prefix = text1[0...common_length]
text1 = text1[common_length..-1]
text2 = text2[common_length..-1]
end
# Trim off common suffix (speedup).
common_length = diff_commonSuffix(text1, text2)
if common_length.nonzero?
common_suffix = text1[-common_length..-1]
text1 = text1[0...-common_length]
text2 = text2[0...-common_length]
end
# Compute the diff on the middle block.
diffs = diff_compute(text1, text2, checklines, deadline)
# Restore the prefix and suffix.
if common_prefix
diffs.unshift(Diff.new(:equal, common_prefix))
end
if common_suffix
diffs.push(Diff.new(:equal, common_suffix))
end
diff_cleanupMerge(diffs)
diffs
end
# Find the differences between two texts. Assumes that the texts do not
# have any common prefix or suffix.
def diff_compute(text1, text2, checklines, deadline)
if text1.empty?
# Just add some text (speedup).
return [Diff.new(:insert, text2)]
end
if text2.empty?
# Just delete some text (speedup).
return [Diff.new(:delete, text1)]
end
shorttext, longtext = [text1, text2].sort_by(&:length)
if i = longtext.index(shorttext)
# Shorter text is inside the longer text (speedup).
diffs = [Diff.new(:insert, longtext[0...i]),
Diff.new(:equal, shorttext),
Diff.new(:insert, longtext[(i + shorttext.length)..-1])]
# Swap insertions for deletions if diff is reversed.
if text1.length > text2.length
diffs[0].op = diffs[2].op = :delete
end
return diffs
end
if shorttext.length == 1
# Single character string.
# After the previous speedup, the character can't be an equality.
return [Diff.new(:delete, text1), Diff.new(:insert, text2)]