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Diff.scala
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Diff.scala
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/*
* Copyright (c) 2011, Owen Stephens
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Owen Stephens nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL Owen Stephens BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package OwenDiff
import scala.collection.immutable.HashMap
object Diff {
type IndexPair = (Int, Int)
// Find the LCS of common, unique lines.
def uniqueLCS(lines1 : Seq[String], lines2 : Seq[String])
: Traversable[IndexPair] = {
type LineToIndex = HashMap[String,Int]
type LineAndIndex = (String, Int)
// Insert into, or mark as duplicate, the line in the map.
def updateLineMap(map : LineToIndex, lineAndIndex : LineAndIndex) = {
val (line, index) = lineAndIndex
map + ((line, if (map.contains(line)) -1 else index))
}
val lines1Indices =
(new LineToIndex() /: lines1.view.zipWithIndex)(updateLineMap)
// Remove any duplicated entries (marked by value of -1)
val uniques1 = lines1Indices.filter(kv => kv._2 >= 0)
// Represents the current state of the mapping fold.
// Tuple is (file1Uniques, line#In2ToLine#In1, file2Uniques)
type MappingState =
(LineToIndex,HashMap[Int,Int], LineToIndex)
def updateUniqueMaps(state : MappingState, lineAndIndex : LineAndIndex) = {
val (uniques1, line2ToLine1, uniqueIndices2) = state
val (line, index) = lineAndIndex
// Only pay attention to common lines.
if (uniques1.contains(line)) {
val newTuple = if (uniqueIndices2.contains(line)) {
(uniques1 - line,// Ensure we don't match this line again
line2ToLine1 - uniqueIndices2(line),// Not unique, so unset.
uniqueIndices2)
} else {
(uniques1,
line2ToLine1 + ((index,uniques1(line))),
uniqueIndices2 + ((line,index)))
}
newTuple
} else {
state
}
}
// Find indices of all unique line2s and create mapping between files.
val lineMaps = (uniques1, HashMap.empty[Int, Int], new LineToIndex())
val (_,line2ToLine1,_) =
(lineMaps /: lines2.view.zipWithIndex)(updateUniqueMaps)
// Order the pairs by the line order in file2.
val indices1OrderedBy2 = line2ToLine1.toList.sortBy(p => p._1)
// Create an Ordered[IndexPair], so that pairs are ordered small-big by
// their 2nd element (line # in file1).
implicit def IndexPairOrdered(thisVal : IndexPair) = new
Ordered[IndexPair] {
def compare(thatVal : IndexPair) = thisVal._2 compare thatVal._2
}
// Obtain the LCS of the line pairs by finding the LIS
// of the pairs.
val lcs = PatienceSort.LIS(indices1OrderedBy2)(IndexPairOrdered)
// Swap the returned tuples' order, so we return pairs: (line1#, line2#)
lcs.map(t => (t._2, t._1))
}
def recursiveMatch(lines1 : Seq[String], lines2 : Seq[String],
bounds1 : (Int, Int), bounds2 : (Int, Int)) : List[IndexPair] = {
// Catch base-case bounds.
if (bounds1._1 == bounds1._2 || bounds2._1 == bounds2._2) {
return Nil
}
// Obtain a list of line pairs that form the LCS
val equalLineIndices = uniqueLCS(lines1.slice(bounds1._1, bounds1._2),
lines2.slice(bounds2._1, bounds2._2))
def processIndexPair(lastPosAndMatches : ((Int, Int), List[IndexPair]),
pair : IndexPair) = {
val offsetPos1 = pair._1 + bounds1._1
val offsetPos2 = pair._2 + bounds2._1
val (lastPos1, lastPos2) = lastPosAndMatches._1
// Check if we're in a sequence of matching lines, if not, recurse.
val localResults = if (lastPos1 + 1 != offsetPos1 ||
lastPos2 + 1 != offsetPos2) {
recursiveMatch(lines1, lines2, (lastPos1 + 1, offsetPos1),
(lastPos2 + 1, offsetPos2))
} else {
List()
}
((offsetPos1, offsetPos2), lastPosAndMatches._2 ++
localResults :+ (offsetPos1, offsetPos2))
}
// Fold up the list of matched line equalLineIndices, recursing between
// groups of matching lines.
val initialTuple = ((bounds1._1 - 1, bounds2._1), List[IndexPair]())
val (lastPos, returnList) =
(initialTuple /: equalLineIndices)(processIndexPair)
val extraList = if (returnList.length > 0) {
// If we matched at all, look for matches between the last match
// and the end.
recursiveMatch(lines1, lines2, (lastPos._1 + 1, bounds1._2),
(lastPos._2 + 1, bounds2._2))
} else if (lines1(bounds1._1) == lines2(bounds2._1)) {
// Find matches at the "start". Catches non-unique, yet equal lines.
// Collect matches until we pass the bounds or lines don't match.
def findStartMatches(pos1 : Int, pos2 : Int,
acc : List[IndexPair]) : (Int, Int, List[IndexPair]) = {
if (pos1 >= bounds1._2 || pos2 >= bounds2._2 ||
lines1(pos1) != lines2(pos2)) {
return (pos1, pos2, acc)
}
return findStartMatches(pos1 + 1, pos2 + 1, acc :+ (pos1, pos2))
}
val (pos1, pos2, startList) =
findStartMatches(bounds1._1, bounds2._1, Nil)
// Recurse between the last match at the start and the end.
startList ++ recursiveMatch(lines1, lines2, (pos1, bounds1._2),
(pos2, bounds2._2))
} else if (lines1(bounds1._2 - 1) == lines2(bounds2._2 - 1)) {
// Find matches at the end of the lines. Catches non-unique, yet
// equal lines.
def findEndMatches(pos1 : Int, pos2 : Int, acc : List[IndexPair])
: (Int, Int, List[IndexPair]) = {
if (pos1 <= bounds1._1 || pos2 <= bounds2._1 ||
lines1(pos1 - 1) != lines2(pos2 - 1)) {
return (pos1, pos2, acc)
} else {
return findEndMatches(pos1 - 1, pos2 - 1,
acc :+ (pos1, pos2))
}
}
val (pos1, pos2, endList) = findEndMatches(bounds1._2 - 1,
bounds2._2 - 1, Nil)
// Find any matches between end matches and last position.
val endGapList = recursiveMatch(lines1, lines2, (lastPos._1 + 1,
pos1), (lastPos._2, pos2))
// Add any matches between end matched and last match first
// to retain correct ordering.
endGapList ++ endList
} else {
Nil
}
returnList ++ extraList
}
// Turn increasing sequences of matched lines into a single MatchResult
def coalesceResults(results : Seq[IndexPair]) : List[MatchResult] = {
def processMatchResult(acc : ((Int, Int, Int), List[MatchResult]),
res : IndexPair) = {
val (index1, index2) = res
val (offset1, offset2, length) = acc._1
val list = acc._2
// Don't match at the start.
val notFirst = offset1 != -1
if (notFirst && index1 == offset1 + length &&
index2 == offset2 + length) {
((offset1, offset2, length + 1), list)
} else {
val nextList = if (notFirst) {
new MatchResult(offset1, offset2, length) :: list
} else {
list
}
((index1, index2, 1), nextList)
}
}
// Fold up the list of matchingLines to join adjacent matches.
val ((offset1, offset2, length), list) =
(((-1, -1, 0), List[MatchResult]()) /: results)(processMatchResult)
// Create a match for anything at the end.
val finalList = if (length > 0) {
new MatchResult(offset1, offset2, length) :: list
} else {
list
}
finalList.reverse
}
def diff(lines1 : Seq[String], lines2 : Seq[String])
: Traversable[DiffResult] = {
val matchLines = recursiveMatch(lines1, lines2,
(0, lines1.length), (0, lines2.length))
val matchBlocks = coalesceResults(matchLines) :+
MatchResult(lines1.length, lines2.length, 0)
// Calculate the actual differences, using the equal line indices.
def processMatchBlock(acc : (IndexPair, List[DiffResult]),
block : MatchResult) = {
val index1 = block.file1Index
val index2 = block.file2Index
val blockLen = block.length
val (pos1, pos2) = acc._1
val list = acc._2
// Update the change list, by calculating which sort of change
// has happened, based on line positions.
val modificationList = if (pos1 < index1 && pos2 < index2) {
new Modify(pos1, pos2, (index1 - pos1, index2 - pos2),
lines1.slice(pos1,index1), lines2.slice(pos2,index2)) :: list
} else if (pos1 < index1) {
new Delete(pos1, pos2, (index1 - pos1, 0),
lines1.slice(pos1, index1)) :: list
} else if (pos2 < index2) {
new Insert(pos1, pos2, (0, index2 - pos2),
lines2.slice(pos2, index2)) :: list
} else {
list
}
val newPos@(newPos1, newPos2) =
(index1 + blockLen, index2 + blockLen)
val returnList = if (blockLen > 0) {
new Equal(newPos1, newPos2, (blockLen, blockLen),
lines1.slice(newPos1 - blockLen, newPos1)) :: modificationList
} else {
modificationList
}
(newPos, returnList)
}
// Fold up a current line tuple with a list of
// line changes that describe going from file1 to file2.
// Reverse, since we cons'd to create the list
var initialTuple = ((0, 0), List[DiffResult]())
(initialTuple /: matchBlocks)(processMatchBlock)._2.reverse
}
}
/*
* Used to represent a match result between two files.
* file1[file1Index:file1Index + length] ==
* file2[file2Index:file2Index + length]
*/
case class MatchResult(file1Index : Int, file2Index : Int, length : Int)