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The DiffUtils library for computing diffs, applying patches, generationg side-by-side view in Java.
/*
Copyright 2010 Dmitry Naumenko ([email protected])
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package difflib;
import difflib.myers.Equalizer;
import difflib.myers.MyersDiff;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import com.google.common.base.Charsets;
import com.google.common.io.Files;
/**
* Implements the difference and patching engine
*
* @author Dmitry Naumenko
* @version 0.4.1
* @param T
* The type of the compared elements in the 'lines'.
*/
public class DiffUtils {
private static Pattern unifiedDiffChunkRe = Pattern
.compile("^@@\\s+-(?:(\\d+)(?:,(\\d+))?)\\s+\\+(?:(\\d+)(?:,(\\d+))?)\\s+@@$");
@Nonnull
public Patch diff(@Nonnull File original, @Nonnull File revised) throws IOException {
return diff(Files.readLines(original, Charsets.UTF_8), Files.readLines(revised, Charsets.UTF_8));
}
@Nonnull
public Patch diff(@Nonnull File original, @Nonnull File revised, @Nonnull DiffAlgorithm algorithm) throws IOException {
return diff(Files.readLines(original, Charsets.UTF_8), Files.readLines(revised, Charsets.UTF_8), algorithm);
}
@Nonnull
public Patch diff(@Nonnull File original, @Nonnull File revised, @Nullable Equalizer equalizer) throws IOException {
return diff(Files.readLines(original, Charsets.UTF_8), Files.readLines(revised, Charsets.UTF_8), equalizer);
}
/**
* Computes the difference between the original and revised list of elements
* with default diff algorithm
*
* @param original
* The original text. Must not be {@code null}.
* @param revised
* The revised text. Must not be {@code null}.
* @return The patch describing the difference between the original and
* revised sequences. Never {@code null}.
*/
@Nonnull
public static Patch diff(List original, List revised) {
return DiffUtils.diff(original, revised, new MyersDiff());
}
/**
* Computes the difference between the original and revised list of elements
* with default diff algorithm
*
* @param original
* The original text. Must not be {@code null}.
* @param revised
* The revised text. Must not be {@code null}.
*
* @param equalizer
* the equalizer object to replace the default compare algorithm
* (Object.equals). If {@code null} the default equalizer of the
* default algorithm is used..
* @return The patch describing the difference between the original and
* revised sequences. Never {@code null}.
*/
@Nonnull
public static Patch diff(List original, List revised,
Equalizer equalizer) {
if (equalizer != null) {
return DiffUtils.diff(original, revised,
new MyersDiff(equalizer));
}
return DiffUtils.diff(original, revised, new MyersDiff());
}
/**
* Computes the difference between the original and revised list of elements
* with default diff algorithm
*
* @param original
* The original text. Must not be {@code null}.
* @param revised
* The revised text. Must not be {@code null}.
* @param algorithm
* The diff algorithm. Must not be {@code null}.
* @return The patch describing the difference between the original and
* revised sequences. Never {@code null}.
*/
@Nonnull
public static Patch diff(List original, List revised,
DiffAlgorithm algorithm) {
if (original == null) {
throw new IllegalArgumentException("original must not be null");
}
if (revised == null) {
throw new IllegalArgumentException("revised must not be null");
}
if (algorithm == null) {
throw new IllegalArgumentException("algorithm must not be null");
}
return algorithm.diff(original, revised);
}
/**
* Patch the original text with given patch
*
* @param original
* the original text
* @param patch
* the given patch
* @return the revised text
* @throws PatchFailedException
* if can't apply patch
*/
@Nonnull
public static List patch(List original, Patch patch)
throws PatchFailedException {
return patch.applyTo(original);
}
/**
* Unpatch the revised text for a given patch
*
* @param revised
* the revised text
* @param patch
* the given patch
* @return the original text
*/
public static List unpatch(List revised, Patch patch) {
return patch.restore(revised);
}
/**
* Parse the given text in unified format and creates the list of deltas for
* it.
*
* @param diff
* the text in unified format
* @return the patch with deltas.
*/
public static Patch parseUnifiedDiff(List diff) {
boolean inPrelude = true;
List rawChunk = new ArrayList();
Patch patch = new Patch();
int old_ln = 0, new_ln = 0;
String tag;
String rest;
for (String line : diff) {
// Skip leading lines until after we've seen one starting with '+++'
if (inPrelude) {
if (line.startsWith("+++")) {
inPrelude = false;
}
continue;
}
Matcher m = unifiedDiffChunkRe.matcher(line);
if (m.find()) {
// Process the lines in the previous chunk
if (rawChunk.size() != 0) {
List oldChunkLines = new ArrayList();
List newChunkLines = new ArrayList();
for (String[] raw_line : rawChunk) {
tag = raw_line[0];
rest = raw_line[1];
if (tag.equals(" ") || tag.equals("-")) {
oldChunkLines.add(rest);
}
if (tag.equals(" ") || tag.equals("+")) {
newChunkLines.add(rest);
}
}
patch.addDelta(new ChangeDelta(new Chunk(
old_ln - 1, oldChunkLines), new Chunk(
new_ln - 1, newChunkLines)));
rawChunk.clear();
}
// Parse the @@ header
old_ln = m.group(1) == null ? 1 : Integer.parseInt(m.group(1));
new_ln = m.group(3) == null ? 1 : Integer.parseInt(m.group(3));
if (old_ln == 0) {
old_ln += 1;
}
if (new_ln == 0) {
new_ln += 1;
}
} else {
if (line.length() > 0) {
tag = line.substring(0, 1);
rest = line.substring(1);
if (tag.equals(" ") || tag.equals("+") || tag.equals("-")) {
rawChunk.add(new String[] { tag, rest });
}
} else {
rawChunk.add(new String[] { " ", "" });
}
}
}
// Process the lines in the last chunk
if (rawChunk.size() != 0) {
List oldChunkLines = new ArrayList();
List newChunkLines = new ArrayList();
for (String[] raw_line : rawChunk) {
tag = raw_line[0];
rest = raw_line[1];
if (tag.equals(" ") || tag.equals("-")) {
oldChunkLines.add(rest);
}
if (tag.equals(" ") || tag.equals("+")) {
newChunkLines.add(rest);
}
}
patch.addDelta(new ChangeDelta(new Chunk(
old_ln - 1, oldChunkLines), new Chunk(new_ln - 1,
newChunkLines)));
rawChunk.clear();
}
return patch;
}
/**
* generateUnifiedDiff takes a Patch and some other arguments, returning the
* Unified Diff format text representing the Patch.
*
* @param original
* - Filename of the original (unrevised file)
* @param revised
* - Filename of the revised file
* @param originalLines
* - Lines of the original file
* @param patch
* - Patch created by the diff() function
* @param contextSize
* - number of lines of context output around each difference in
* the file.
* @return List of strings representing the Unified Diff representation of
* the Patch argument.
* @author Bill James ([email protected])
*/
public static List generateUnifiedDiff(String original,
String revised, List originalLines, Patch patch,
int contextSize) {
if (!patch.getDeltas().isEmpty()) {
List ret = new ArrayList();
ret.add("--- " + original);
ret.add("+++ " + revised);
List> patchDeltas = new ArrayList>(
patch.getDeltas());
// code outside the if block also works for single-delta issues.
List> deltas = new ArrayList>(); // current
// list
// of
// Delta's to
// process
Delta delta = patchDeltas.get(0);
deltas.add(delta); // add the first Delta to the current set
// if there's more than 1 Delta, we may need to output them together
if (patchDeltas.size() > 1) {
for (int i = 1; i < patchDeltas.size(); i++) {
int position = delta.getOriginal().getPosition(); // store
// the
// current
// position
// of
// the first Delta
// Check if the next Delta is too close to the current
// position.
// And if it is, add it to the current set
Delta nextDelta = patchDeltas.get(i);
if ((position + delta.getOriginal().size() + contextSize) >= (nextDelta
.getOriginal().getPosition() - contextSize)) {
deltas.add(nextDelta);
} else {
// if it isn't, output the current set,
// then create a new set and add the current Delta to
// it.
List curBlock = processDeltas(originalLines,
deltas, contextSize);
ret.addAll(curBlock);
deltas.clear();
deltas.add(nextDelta);
}
delta = nextDelta;
}
}
// don't forget to process the last set of Deltas
List curBlock = processDeltas(originalLines, deltas,
contextSize);
ret.addAll(curBlock);
return ret;
}
return new ArrayList();
}
/**
* processDeltas takes a list of Deltas and outputs them together in a
* single block of Unified-Diff-format text.
*
* @param origLines
* - the lines of the original file
* @param deltas
* - the Deltas to be output as a single block
* @param contextSize
* - the number of lines of context to place around block
* @return
* @author Bill James ([email protected])
*/
private static List processDeltas(List origLines,
List> deltas, int contextSize) {
List buffer = new ArrayList();
int origTotal = 0; // counter for total lines output from Original
int revTotal = 0; // counter for total lines output from Original
int line;
Delta curDelta = deltas.get(0);
// NOTE: +1 to overcome the 0-offset Position
int origStart = curDelta.getOriginal().getPosition() + 1 - contextSize;
if (origStart < 1) {
origStart = 1;
}
int revStart = curDelta.getRevised().getPosition() + 1 - contextSize;
if (revStart < 1) {
revStart = 1;
}
// find the start of the wrapper context code
int contextStart = curDelta.getOriginal().getPosition() - contextSize;
if (contextStart < 0) {
contextStart = 0; // clamp to the start of the file
}
// output the context before the first Delta
for (line = contextStart; line < curDelta.getOriginal().getPosition(); line++) { //
buffer.add(" " + origLines.get(line));
origTotal++;
revTotal++;
}
// output the first Delta
buffer.addAll(getDeltaText(curDelta));
origTotal += curDelta.getOriginal().getLines().size();
revTotal += curDelta.getRevised().getLines().size();
int deltaIndex = 1;
while (deltaIndex < deltas.size()) { // for each of the other Deltas
Delta nextDelta = deltas.get(deltaIndex);
int intermediateStart = curDelta.getOriginal().getPosition()
+ curDelta.getOriginal().getLines().size();
for (line = intermediateStart; line < nextDelta.getOriginal()
.getPosition(); line++) {
// output the code between the last Delta and this one
buffer.add(" " + origLines.get(line));
origTotal++;
revTotal++;
}
buffer.addAll(getDeltaText(nextDelta)); // output the Delta
origTotal += nextDelta.getOriginal().getLines().size();
revTotal += nextDelta.getRevised().getLines().size();
curDelta = nextDelta;
deltaIndex++;
}
// Now output the post-Delta context code, clamping the end of the file
contextStart = curDelta.getOriginal().getPosition()
+ curDelta.getOriginal().getLines().size();
for (line = contextStart; (line < (contextStart + contextSize))
&& (line < origLines.size()); line++) {
buffer.add(" " + origLines.get(line));
origTotal++;
revTotal++;
}
// Create and insert the block header, conforming to the Unified Diff
// standard
StringBuffer header = new StringBuffer();
header.append("@@ -");
header.append(origStart);
header.append(",");
header.append(origTotal);
header.append(" +");
header.append(revStart);
header.append(",");
header.append(revTotal);
header.append(" @@");
buffer.add(0, header.toString());
return buffer;
}
/**
* getDeltaText returns the lines to be added to the Unified Diff text from
* the Delta parameter
*
* @param delta
* - the Delta to output
* @return list of String lines of code.
* @author Bill James ([email protected])
*/
private static List getDeltaText(Delta delta) {
List buffer = new ArrayList();
for (String line : delta.getOriginal().getLines()) {
buffer.add("-" + line);
}
for (String line : delta.getRevised().getLines()) {
buffer.add("+" + line);
}
return buffer;
}
}