--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/tmatesoft/hg/repo/HgBlameFacility.java	Fri Feb 22 20:21:24 2013 +0100
@@ -0,0 +1,905 @@
+/*
+ * Copyright (c) 2013 TMate Software Ltd
+ *  
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * For information on how to redistribute this software under
+ * the terms of a license other than GNU General Public License
+ * contact TMate Software at support@hg4j.com
+ */
+package org.tmatesoft.hg.repo;
+
+import static org.tmatesoft.hg.repo.HgRepository.NO_REVISION;
+import static org.tmatesoft.hg.repo.HgRepository.TIP;
+
+import java.util.BitSet;
+import java.util.LinkedList;
+import java.util.ListIterator;
+
+import org.tmatesoft.hg.core.HgIterateDirection;
+import org.tmatesoft.hg.core.Nodeid;
+import org.tmatesoft.hg.internal.ByteArrayChannel;
+import org.tmatesoft.hg.internal.Callback;
+import org.tmatesoft.hg.internal.DiffHelper;
+import org.tmatesoft.hg.internal.Experimental;
+import org.tmatesoft.hg.internal.IntMap;
+import org.tmatesoft.hg.internal.IntVector;
+import org.tmatesoft.hg.internal.DiffHelper.LineSequence;
+import org.tmatesoft.hg.internal.DiffHelper.LineSequence.ByteChain;
+import org.tmatesoft.hg.repo.HgBlameFacility.RevisionDescriptor.Recipient;
+import org.tmatesoft.hg.util.Adaptable;
+import org.tmatesoft.hg.util.CancelledException;
+import org.tmatesoft.hg.util.Pair;
+
+/**
+ * Facility with diff/annotate functionality.
+ * 
+ * @author Artem Tikhomirov
+ * @author TMate Software Ltd.
+ */
+@Experimental(reason="Unstable API")
+public final class HgBlameFacility {
+	
+	/**
+	 * mimic 'hg diff -r clogRevIndex1 -r clogRevIndex2'
+	 */
+	public void diff(HgDataFile df, int clogRevIndex1, int clogRevIndex2, BlockInspector insp) {
+		int fileRevIndex1 = fileRevIndex(df, clogRevIndex1);
+		int fileRevIndex2 = fileRevIndex(df, clogRevIndex2);
+		FileLinesCache fileInfoCache = new FileLinesCache(df, 5);
+		LineSequence c1 = fileInfoCache.lines(fileRevIndex1);
+		LineSequence c2 = fileInfoCache.lines(fileRevIndex2);
+		DiffHelper<LineSequence> pg = new DiffHelper<LineSequence>();
+		pg.init(c1, c2);
+		pg.findMatchingBlocks(new BlameBlockInspector(fileRevIndex2, insp, clogRevIndex1, clogRevIndex2));
+	}
+	
+	/**
+	 * Walk file history up to revision at given changeset and report changes for each revision
+	 */
+	public void annotate(HgDataFile df, int changelogRevisionIndex, BlockInspector insp, HgIterateDirection iterateOrder) {
+		if (!df.exists()) {
+			return;
+		}
+		// Note, changelogRevisionIndex may be TIP, while #implAnnotateChange doesn't tolerate constants
+		//
+		// XXX df.indexWalk(0, fileRevIndex, ) might be more effective
+		int fileRevIndex = fileRevIndex(df, changelogRevisionIndex);
+		int[] fileRevParents = new int[2];
+		IntVector fileParentRevs = new IntVector((fileRevIndex+1) * 2, 0);
+		fileParentRevs.add(NO_REVISION, NO_REVISION);
+		for (int i = 1; i <= fileRevIndex; i++) {
+			df.parents(i, fileRevParents, null, null);
+			fileParentRevs.add(fileRevParents[0], fileRevParents[1]);
+		}
+		// collect file revisions to visit, from newest to oldest
+		IntVector fileRevsToVisit = new IntVector(fileRevIndex + 1, 0);
+		LinkedList<Integer> queue = new LinkedList<Integer>();
+		BitSet seen = new BitSet(fileRevIndex + 1);
+		queue.add(fileRevIndex);
+		do {
+			int x = queue.removeFirst();
+			if (seen.get(x)) {
+				continue;
+			}
+			seen.set(x);
+			fileRevsToVisit.add(x);
+			int p1 = fileParentRevs.get(2*x);
+			int p2 = fileParentRevs.get(2*x + 1);
+			if (p1 != NO_REVISION) {
+				queue.addLast(p1);
+			}
+			if (p2 != NO_REVISION) {
+				queue.addLast(p2);
+			}
+		} while (!queue.isEmpty());
+		FileLinesCache fileInfoCache = new FileLinesCache(df, 10);
+		// fileRevsToVisit now { r10, r7, r6, r5, r0 }
+		// and we'll iterate it from behind, e.g. old to new unless reversed 
+		if (iterateOrder == HgIterateDirection.NewToOld) {
+			fileRevsToVisit.reverse();
+		}
+		for (int i = fileRevsToVisit.size() - 1; i >= 0; i--) {
+			int fri = fileRevsToVisit.get(i);
+			int clogRevIndex = df.getChangesetRevisionIndex(fri);
+			fileRevParents[0] = fileParentRevs.get(fri * 2);
+			fileRevParents[1] = fileParentRevs.get(fri * 2 + 1);
+			implAnnotateChange(fileInfoCache, clogRevIndex, fri, fileRevParents, insp);
+		}
+	}
+
+	/**
+	 * Annotates changes of the file against its parent(s). 
+	 * Unlike {@link #annotate(HgDataFile, int, BlockInspector, HgIterateDirection)}, doesn't
+	 * walk file history, looks at the specified revision only. Handles both parents (if merge revision).
+	 */
+	public void annotateSingleRevision(HgDataFile df, int changelogRevisionIndex, BlockInspector insp) {
+		// TODO detect if file is text/binary (e.g. looking for chars < ' ' and not \t\r\n\f
+		int fileRevIndex = fileRevIndex(df, changelogRevisionIndex);
+		int[] fileRevParents = new int[2];
+		df.parents(fileRevIndex, fileRevParents, null, null);
+		if (changelogRevisionIndex == TIP) {
+			changelogRevisionIndex = df.getChangesetRevisionIndex(fileRevIndex);
+		}
+		implAnnotateChange(new FileLinesCache(df, 5), changelogRevisionIndex, fileRevIndex, fileRevParents, insp);
+	}
+
+	private void implAnnotateChange(FileLinesCache fl, int csetRevIndex, int fileRevIndex, int[] fileParentRevs, BlockInspector insp) {
+		final LineSequence fileRevLines = fl.lines(fileRevIndex);
+		if (fileParentRevs[0] != NO_REVISION && fileParentRevs[1] != NO_REVISION) {
+			LineSequence p1Lines = fl.lines(fileParentRevs[0]);
+			LineSequence p2Lines = fl.lines(fileParentRevs[1]);
+			int p1ClogIndex = fl.getChangesetRevisionIndex(fileParentRevs[0]);
+			int p2ClogIndex = fl.getChangesetRevisionIndex(fileParentRevs[1]);
+			DiffHelper<LineSequence> pg = new DiffHelper<LineSequence>();
+			pg.init(p2Lines, fileRevLines);
+			EqualBlocksCollector p2MergeCommon = new EqualBlocksCollector();
+			pg.findMatchingBlocks(p2MergeCommon);
+			//
+			pg.init(p1Lines);
+			BlameBlockInspector bbi = new BlameBlockInspector(fileRevIndex, insp, p1ClogIndex, csetRevIndex);
+			bbi.setMergeParent2(p2MergeCommon, p2ClogIndex);
+			pg.findMatchingBlocks(bbi);
+		} else if (fileParentRevs[0] == fileParentRevs[1]) {
+			// may be equal iff both are unset
+			assert fileParentRevs[0] == NO_REVISION;
+			// everything added
+			BlameBlockInspector bbi = new BlameBlockInspector(fileRevIndex, insp, NO_REVISION, csetRevIndex);
+			bbi.begin(LineSequence.newlines(new byte[0]), fileRevLines);
+			bbi.match(0, fileRevLines.chunkCount()-1, 0);
+			bbi.end();
+		} else {
+			int soleParent = fileParentRevs[0] == NO_REVISION ? fileParentRevs[1] : fileParentRevs[0];
+			assert soleParent != NO_REVISION;
+			LineSequence parentLines = fl.lines(soleParent);
+			
+			int parentChangesetRevIndex = fl.getChangesetRevisionIndex(soleParent);
+			DiffHelper<LineSequence> pg = new DiffHelper<LineSequence>();
+			pg.init(parentLines, fileRevLines);
+			pg.findMatchingBlocks(new BlameBlockInspector(fileRevIndex, insp, parentChangesetRevIndex, csetRevIndex));
+		}
+	}
+
+	private static int fileRevIndex(HgDataFile df, int csetRevIndex) {
+		Nodeid fileRev = df.getRepo().getManifest().getFileRevision(csetRevIndex, df.getPath());
+		return df.getRevisionIndex(fileRev);
+	}
+
+	private static class FileLinesCache {
+		private final HgDataFile df;
+		private final LinkedList<Pair<Integer, LineSequence>> lruCache;
+		private final int limit;
+		private IntMap<Integer> fileToClogIndexMap = new IntMap<Integer>(20);
+
+		public FileLinesCache(HgDataFile file, int lruLimit) {
+			df = file;
+			limit = lruLimit;
+			lruCache = new LinkedList<Pair<Integer, LineSequence>>();
+		}
+		
+		public int getChangesetRevisionIndex(int fileRevIndex) {
+			Integer cached = fileToClogIndexMap.get(fileRevIndex);
+			if (cached == null) {
+				cached = df.getChangesetRevisionIndex(fileRevIndex);
+				fileToClogIndexMap.put(fileRevIndex, cached);
+			}
+			return cached.intValue();
+		}
+
+		public LineSequence lines(int fileRevIndex) {
+			Pair<Integer, LineSequence> cached = checkCache(fileRevIndex);
+			if (cached != null) {
+				return cached.second();
+			}
+			try {
+				ByteArrayChannel c;
+				df.content(fileRevIndex, c = new ByteArrayChannel());
+				LineSequence rv = LineSequence.newlines(c.toArray());
+				lruCache.addFirst(new Pair<Integer, LineSequence>(fileRevIndex, rv));
+				if (lruCache.size() > limit) {
+					lruCache.removeLast();
+				}
+				return rv;
+			} catch (CancelledException ex) {
+				// TODO likely it was bad idea to throw cancelled exception from content()
+				// deprecate and provide alternative?
+				HgInvalidStateException ise = new HgInvalidStateException("ByteArrayChannel never throws CancelledException");
+				ise.initCause(ex);
+				throw ise;
+			}
+		}
+		
+		private Pair<Integer,LineSequence> checkCache(int fileRevIndex) {
+			Pair<Integer, LineSequence> rv = null;
+			for (ListIterator<Pair<Integer, LineSequence>> it = lruCache.listIterator(); it.hasNext(); ) {
+				Pair<Integer, LineSequence> p = it.next();
+				if (p.first() == fileRevIndex) {
+					rv = p;
+					it.remove();
+					break;
+				}
+			}
+			if (rv != null) {
+				lruCache.addFirst(rv);
+			}
+			return rv;
+		}
+	}
+
+	/**
+	 * Client's sink for revision differences.
+	 * 
+	 * When implemented, clients shall not expect new {@link Block blocks} instances in each call.
+	 * 
+	 * In case more information about annotated revision is needed, inspector instances may supply 
+	 * {@link RevisionDescriptor.Recipient} through {@link Adaptable}.  
+	 */
+	@Callback
+	public interface BlockInspector {
+		void same(EqualBlock block);
+		void added(AddBlock block);
+		void changed(ChangeBlock block);
+		void deleted(DeleteBlock block);
+	}
+	
+	/**
+	 * Represents content of a block, either as a sequence of bytes or a 
+	 * sequence of smaller blocks (lines), if appropriate (according to usage context).
+	 * 
+	 * This approach allows line-by-line access to content data along with complete byte sequence for the whole block, i.e.
+	 * <pre>
+	 *    BlockData bd = addBlock.addedLines()
+	 *    // bd describes data from the addition completely.
+	 *    // elements of the BlockData are lines
+	 *    bd.elementCount() == addBlock.totalAddedLines();
+	 *    // one cat obtain complete addition with
+	 *    byte[] everythingAdded = bd.asArray();
+	 *    // or iterate line by line
+	 *    for (int i = 0; i < bd.elementCount(); i++) {
+	 *    	 byte[] lineContent = bd.elementAt(i);
+	 *       String line = new String(lineContent, fileEncodingCharset);
+	 *    }
+	 *    where bd.elementAt(0) is the line at index addBlock.firstAddedLine() 
+	 * </pre> 
+	 * 
+	 * LineData or ChunkData? 
+	 */
+	public interface BlockData {
+		BlockData elementAt(int index);
+		int elementCount();
+		byte[] asArray();
+	}
+	
+	/**
+	 * {@link BlockInspector} may optionally request extra information about revisions
+	 * being inspected, denoting itself as a {@link RevisionDescriptor.Recipient}. This class 
+	 * provides complete information about file revision under annotation now. 
+	 */
+	public interface RevisionDescriptor {
+		/**
+		 * @return complete source of the diff origin, never <code>null</code>
+		 */
+		BlockData origin();
+		/**
+		 * @return complete source of the diff target, never <code>null</code>
+		 */
+		BlockData target();
+		/**
+		 * @return changeset revision index of original file, or {@link HgRepository#NO_REVISION} if it's the very first revision
+		 */
+		int originChangesetIndex();
+		/**
+		 * @return changeset revision index of the target file
+		 */
+		int targetChangesetIndex();
+		/**
+		 * @return <code>true</code> if this revision is merge
+		 */
+		boolean isMerge();
+		/**
+		 * @return changeset revision index of the second, merged parent
+		 */
+		int mergeChangesetIndex();
+		/**
+		 * @return revision index of the change in target file's revlog
+		 */
+		int fileRevisionIndex();
+
+		/**
+		 * Implement to indicate interest in {@link RevisionDescriptor}.
+		 * 
+		 * Note, instance of {@link RevisionDescriptor} is the same for 
+		 * {@link #start(RevisionDescriptor)} and {@link #done(RevisionDescriptor)} 
+		 * methods, and not necessarily a new one (i.e. <code>==</code>) for the next
+		 * revision announced.
+		 */
+		@Callback
+		public interface Recipient {
+			/**
+			 * Comes prior to any change {@link Block blocks}
+			 */
+			void start(RevisionDescriptor revisionDescription);
+			/**
+			 * Comes after all change {@link Block blocks} were dispatched
+			 */
+			void done(RevisionDescriptor revisionDescription);
+		}
+	}
+	
+	/**
+	 * Each change block comes from a single origin, blocks that are result of a merge
+	 * have {@link #originChangesetIndex()} equal to {@link RevisionDescriptor#mergeChangesetIndex()}.
+	 */
+	public interface Block {
+		int originChangesetIndex();
+		int targetChangesetIndex();
+	}
+	
+	public interface EqualBlock extends Block {
+		int originStart();
+		int targetStart();
+		int length();
+		BlockData content();
+	}
+	
+	public interface AddBlock extends Block {
+		/**
+		 * @return line index in the origin where this block is inserted
+		 */
+		int insertedAt();  
+		/**
+		 * @return line index of the first added line in the target revision
+		 */
+		int firstAddedLine();
+		/**
+		 * @return number of added lines in this block
+		 */
+		int totalAddedLines();
+		/**
+		 * @return content of added lines
+		 */
+		BlockData addedLines();
+	}
+	public interface DeleteBlock extends Block {
+		/**
+		 * @return line index in the target revision were this deleted block would be
+		 */
+		int removedAt();
+		/**
+		 * @return line index of the first removed line in the original revision
+		 */
+		int firstRemovedLine();
+		/**
+		 * @return number of deleted lines in this block
+		 */
+		int totalRemovedLines();
+		/**
+		 * @return content of deleted lines
+		 */
+		BlockData removedLines();
+	}
+	public interface ChangeBlock extends AddBlock, DeleteBlock {
+	}
+	
+	private static class BlameBlockInspector extends DiffHelper.DeltaInspector<LineSequence> {
+		private final BlockInspector insp;
+		private final int csetOrigin;
+		private final int csetTarget;
+		private EqualBlocksCollector p2MergeCommon;
+		private int csetMergeParent;
+		private IntVector mergeRanges;
+		private final AnnotateRev annotatedRevision;
+
+		public BlameBlockInspector(int fileRevIndex, BlockInspector inspector, int originCset, int targetCset) {
+			assert inspector != null;
+			insp = inspector;
+			annotatedRevision = new AnnotateRev();
+			annotatedRevision.set(fileRevIndex);
+			csetOrigin = originCset;
+			csetTarget = targetCset;
+		}
+		
+		public void setMergeParent2(EqualBlocksCollector p2Merge, int parentCset2) {
+			p2MergeCommon = p2Merge;
+			csetMergeParent = parentCset2;
+			mergeRanges = new IntVector(3*10, 3*10);
+		}
+		
+		@Override
+		public void begin(LineSequence s1, LineSequence s2) {
+			super.begin(s1, s2);
+			ContentBlock originContent = new ContentBlock(s1);
+			ContentBlock targetContent = new ContentBlock(s2);
+			annotatedRevision.set(originContent, targetContent);
+			annotatedRevision.set(csetOrigin, csetTarget, p2MergeCommon != null ? csetMergeParent : NO_REVISION);
+			Recipient curious = Adaptable.Factory.getAdapter(insp, Recipient.class, null);
+			if (curious != null) {
+				curious.start(annotatedRevision);
+			}
+		}
+		
+		@Override
+		public void end() {
+			super.end();
+			Recipient curious = Adaptable.Factory.getAdapter(insp, Recipient.class, null);
+			if (curious != null) {
+				curious.done(annotatedRevision);
+			}
+			p2MergeCommon = null;
+		}
+
+		@Override
+		protected void changed(int s1From, int s1To, int s2From, int s2To) {
+			if (p2MergeCommon != null) {
+				mergeRanges.clear();
+				p2MergeCommon.combineAndMarkRangesWithTarget(s2From, s2To - s2From, csetOrigin, csetMergeParent, mergeRanges);
+				
+				/*
+				 * Usecases:
+				 * 3 lines changed to 10 lines. range of 10 lines breaks down to 2 from p2, 3 from p1, and 5 from p2.
+				 * We report: 2 lines changed to 2(p2), then 1 line changed with 3(p1) and 5 lines added from p2.
+				 * 
+				 * 10 lines changed to 3 lines, range of 3 lines breaks down to 2 line from p1 and 1 line from p2.
+				 * We report: 2 lines changed to 2(p1) and 8 lines changed to 1(p2) 
+				 */
+				int s1TotalLines = s1To - s1From, s1ConsumedLines = 0, s1Start = s1From;
+				
+				for (int i = 0; i < mergeRanges.size(); i += 3) {
+					final int rangeOrigin = mergeRanges.get(i);
+					final int rangeStart = mergeRanges.get(i+1);
+					final int rangeLen = mergeRanges.get(i+2);
+					final boolean lastRange = i+3 >= mergeRanges.size();
+					final int s1LinesLeft = s1TotalLines - s1ConsumedLines;
+					// how many lines we may reported as changed (don't use more than in range unless it's the very last range)
+					final int s1LinesToBorrow = lastRange ? s1LinesLeft : Math.min(s1LinesLeft, rangeLen);
+					if (s1LinesToBorrow > 0) {
+						ChangeBlockImpl block = getChangeBlock(s1Start, s1LinesToBorrow, rangeStart, rangeLen);
+						block.setOriginAndTarget(rangeOrigin, csetTarget);
+						insp.changed(block);
+						s1ConsumedLines += s1LinesToBorrow;
+						s1Start += s1LinesToBorrow;
+					} else {
+						ChangeBlockImpl block = getAddBlock(rangeStart, rangeLen, s1Start);
+						block.setOriginAndTarget(rangeOrigin, csetTarget);
+						insp.added(block);
+					}
+				}
+				if (s1ConsumedLines != s1TotalLines) {
+					throw new HgInvalidStateException(String.format("Expected to process %d lines, but actually was %d", s1TotalLines, s1ConsumedLines));
+				}
+			} else {
+				ChangeBlockImpl block = getChangeBlock(s1From, s1To - s1From, s2From, s2To - s2From);
+				block.setOriginAndTarget(csetOrigin, csetTarget);
+				insp.changed(block);
+			}
+		}
+		
+		@Override
+		protected void added(int s1InsertPoint, int s2From, int s2To) {
+			if (p2MergeCommon != null) {
+				mergeRanges.clear();
+				p2MergeCommon.combineAndMarkRangesWithTarget(s2From, s2To - s2From, csetOrigin, csetMergeParent, mergeRanges);
+				int insPoint = s1InsertPoint; // track changes to insertion point
+				for (int i = 0; i < mergeRanges.size(); i += 3) {
+					int rangeOrigin = mergeRanges.get(i);
+					int rangeStart = mergeRanges.get(i+1);
+					int rangeLen = mergeRanges.get(i+2);
+					ChangeBlockImpl block = getAddBlock(rangeStart, rangeLen, insPoint);
+					block.setOriginAndTarget(rangeOrigin, csetTarget);
+					insp.added(block);
+					// indicate insPoint moved down number of lines we just reported
+					insPoint += rangeLen;
+				}
+			} else {
+				ChangeBlockImpl block = getAddBlock(s2From, s2To - s2From, s1InsertPoint);
+				block.setOriginAndTarget(csetOrigin, csetTarget);
+				insp.added(block);
+			}
+		}
+		
+		@Override
+		protected void deleted(int s2DeletePoint, int s1From, int s1To) {
+			ChangeBlockImpl block = new ChangeBlockImpl(annotatedRevision.origin, null, s1From, s1To - s1From, -1, -1, -1, s2DeletePoint);
+			block.setOriginAndTarget(csetOrigin, csetTarget);
+			insp.deleted(block);
+		}
+
+		@Override
+		protected void unchanged(int s1From, int s2From, int length) {
+			EqualBlockImpl block = new EqualBlockImpl(s1From, s2From, length, annotatedRevision.target);
+			block.setOriginAndTarget(csetOrigin, csetTarget);
+			insp.same(block);
+		}
+		
+		private ChangeBlockImpl getAddBlock(int start, int len, int insPoint) {
+			return new ChangeBlockImpl(null, annotatedRevision.target, -1, -1, start, len, insPoint, -1);
+		}
+		
+		private ChangeBlockImpl getChangeBlock(int start1, int len1, int start2, int len2) {
+			return new ChangeBlockImpl(annotatedRevision.origin, annotatedRevision.target, start1, len1, start2, len2, start1, start2);
+		}
+	}
+	
+	private static class BlockImpl implements Block {
+		private int originCset;
+		private int targetCset;
+
+		void setOriginAndTarget(int originChangesetIndex, int targetChangesetIndex) {
+			// XXX perhaps, shall be part of Inspector API, rather than Block's
+			// as they don't change between blocks (although the moment about merged revisions)
+			// is not yet clear to me
+			originCset = originChangesetIndex;
+			targetCset = targetChangesetIndex;
+		}
+
+		public int originChangesetIndex() {
+			return originCset;
+		}
+
+		public int targetChangesetIndex() {
+			return targetCset;
+		}
+	}
+
+	private static class EqualBlockImpl extends BlockImpl implements EqualBlock {
+		private final int start1, start2;
+		private final int length;
+		private final ContentBlock fullContent;
+		private FilterBlock myContent;
+		
+		EqualBlockImpl(int blockStartSeq1, int blockStartSeq2, int blockLength, ContentBlock targetContent) {
+			start1 = blockStartSeq1;
+			start2 = blockStartSeq2;
+			length = blockLength;
+			fullContent = targetContent;
+		}
+
+		public int originStart() {
+			return start1;
+		}
+
+		public int targetStart() {
+			return start2;
+		}
+
+		public int length() {
+			return length;
+		}
+		
+		public BlockData content() {
+			if (myContent == null) {
+				myContent = new FilterBlock(fullContent, start2, length);
+			}
+			return myContent;
+		}
+		
+		@Override
+		public String toString() {
+			return String.format("@@ [%d..%d) == [%d..%d) @@", start1, start1+length, start2, start2+length);
+		}
+	}
+	
+	private static class ChangeBlockImpl extends BlockImpl implements ChangeBlock {
+		private final ContentBlock oldContent;
+		private final ContentBlock newContent;
+		private final int s1Start;
+		private final int s1Len;
+		private final int s2Start;
+		private final int s2Len;
+		private final int s1InsertPoint;
+		private final int s2DeletePoint;
+		private FilterBlock addedBlock, removedBlock;
+
+		public ChangeBlockImpl(ContentBlock c1, ContentBlock c2, int s1Start, int s1Len, int s2Start, int s2Len, int s1InsertPoint, int s2DeletePoint) {
+			oldContent = c1;
+			newContent = c2;
+			this.s1Start = s1Start;
+			this.s1Len = s1Len;
+			this.s2Start = s2Start;
+			this.s2Len = s2Len;
+			this.s1InsertPoint = s1InsertPoint;
+			this.s2DeletePoint = s2DeletePoint;
+		}
+		
+		public int insertedAt() {
+			return s1InsertPoint;
+		}
+
+		public int firstAddedLine() {
+			return s2Start;
+		}
+
+		public int totalAddedLines() {
+			return s2Len;
+		}
+
+		public BlockData addedLines() {
+			if (addedBlock == null) {
+				addedBlock = new FilterBlock(newContent, firstAddedLine(), totalAddedLines());
+			}
+			return addedBlock;
+		}
+		
+		public int removedAt() {
+			return s2DeletePoint;
+		}
+
+		public int firstRemovedLine() {
+			return s1Start;
+		}
+
+		public int totalRemovedLines() {
+			return s1Len;
+		}
+
+		public BlockData removedLines() {
+			if (removedBlock == null) {
+				removedBlock = new FilterBlock(oldContent, firstRemovedLine(), totalRemovedLines());
+			}
+			return removedBlock;
+		}
+		
+		@Override
+		public String toString() {
+			if (s2DeletePoint == -1) {
+				return String.format("@@ -%d,0 +%d,%d @@", insertedAt(), firstAddedLine(), totalAddedLines());
+			} else if (s1InsertPoint == -1) {
+				// delete only
+				return String.format("@@ -%d,%d +%d,0 @@", firstRemovedLine(), totalRemovedLines(), removedAt());
+			}
+			return String.format("@@ -%d,%d +%d,%d @@", firstRemovedLine(), totalRemovedLines(), firstAddedLine(), totalAddedLines());
+		}
+	}
+	
+	private static class SingleLine implements BlockData {
+		private final ByteChain line;
+
+		public SingleLine(ByteChain lineContent) {
+			line = lineContent;
+		}
+
+		public BlockData elementAt(int index) {
+			assert false;
+			return null;
+		}
+
+		public int elementCount() {
+			return 0;
+		}
+
+		public byte[] asArray() {
+			return line.data();
+		}
+	}
+	
+	private static class ContentBlock implements BlockData {
+		private final LineSequence seq;
+
+		public ContentBlock(LineSequence sequence) {
+			seq = sequence;
+		}
+
+		public BlockData elementAt(int index) {
+			return new SingleLine(seq.chunk(index));
+		}
+
+		public int elementCount() {
+			return seq.chunkCount() - 1;
+		}
+
+		public byte[] asArray() {
+			return seq.data(0, seq.chunkCount() - 1);
+		}
+	}
+	
+	private static class FilterBlock implements BlockData {
+		private final ContentBlock contentBlock;
+		private final int from;
+		private final int length;
+
+		public FilterBlock(ContentBlock bd, int startFrom, int len) {
+			assert bd != null;
+			assert startFrom + len < bd.seq.chunkCount(); // there's one extra chunk in the end, so strict less is ok
+			contentBlock = bd;
+			from = startFrom;
+			length = len;
+		}
+
+		public BlockData elementAt(int index) {
+			if (index < 0 || index >= length) {
+				throw new IllegalArgumentException(String.format("Expected value from [0..%d), got %d", length, index));
+			}
+			return contentBlock.elementAt(from + index);
+		}
+
+		public int elementCount() {
+			return length;
+		}
+
+		public byte[] asArray() {
+			return contentBlock.seq.data(from, from + length);
+		}
+	}
+	
+
+	static class EqualBlocksCollector implements DiffHelper.MatchInspector<LineSequence> {
+		private final IntVector matches = new IntVector(10*3, 2*3);
+
+		public void begin(LineSequence s1, LineSequence s2) {
+		}
+
+		public void match(int startSeq1, int startSeq2, int matchLength) {
+			matches.add(startSeq1);
+			matches.add(startSeq2);
+			matches.add(matchLength);
+		}
+
+		public void end() {
+		}
+		
+		// true when specified line in origin is equal to a line in target
+		public boolean includesOriginLine(int ln) {
+			return includes(ln, 0);
+		}
+		
+		// true when specified line in target is equal to a line in origin
+		public boolean includesTargetLine(int ln) {
+			return includes(ln, 1);
+		}
+		
+		public void intersectWithTarget(int start, int length, IntVector result) {
+			int s = start;
+			for (int l = start, x = start + length; l < x; l++) {
+				if (!includesTargetLine(l)) {
+					if (l - s > 0) {
+						result.add(s);
+						result.add(l - s);
+					}
+					s = l+1;
+				}
+			}
+			if (s < start+length) {
+				result.add(s);
+				result.add((start + length) - s);
+			}
+		}
+		
+		/*
+		 * intersects [start..start+length) with ranges of target lines, and based on the intersection 
+		 * breaks initial range into smaller ranges and records them into result, with marker to indicate
+		 * whether the range is from initial range (markerSource) or is a result of the intersection with target
+		 * (markerTarget)
+		 */
+		public void combineAndMarkRangesWithTarget(int start, int length, int markerSource, int markerTarget, IntVector result) {
+			int sourceStart = start, targetStart = start, sourceEnd = start + length;
+			for (int l = sourceStart; l < sourceEnd; l++) {
+				if (includesTargetLine(l)) {
+					// l is from target
+					if (sourceStart < l) {
+						// few lines from source range were not in the target, report them
+						result.add(markerSource);
+						result.add(sourceStart);
+						result.add(l - sourceStart);
+					}
+					// indicate the earliest line from source range to use
+					sourceStart = l + 1;
+				} else {
+					// l is not in target
+					if (targetStart < l) {
+						// report lines from target range
+						result.add(markerTarget);
+						result.add(targetStart);
+						result.add(l - targetStart);
+					}
+					// next line *may* be from target
+					targetStart = l + 1;
+				}
+			}
+			// if source range end with line from target, sourceStart would be == sourceEnd, and we need to add range with markerTarget
+			// if source range doesn't end with target line, targetStart == sourceEnd, while sourceStart < sourceEnd
+			if (sourceStart < sourceEnd) {
+				assert targetStart == sourceEnd;
+				// something left from the source range
+				result.add(markerSource);
+				result.add(sourceStart);
+				result.add(sourceEnd - sourceStart);
+			} else if (targetStart < sourceEnd) {
+				assert sourceStart == sourceEnd;
+				result.add(markerTarget);
+				result.add(targetStart);
+				result.add(sourceEnd - targetStart);
+			}
+		}
+		
+		private boolean includes(int ln, int o) {
+			for (int i = 2; i < matches.size(); o += 3, i+=3) {
+				int rangeStart = matches.get(o);
+				if (rangeStart > ln) {
+					return false;
+				}
+				int rangeLen = matches.get(i);
+				if (rangeStart + rangeLen > ln) {
+					return true;
+				}
+			}
+			return false;
+		}
+	}
+
+	private static class AnnotateRev implements RevisionDescriptor {
+		public ContentBlock origin, target;
+		public int originCset, targetCset, mergeCset, fileRevIndex;
+		
+		public void set(int fileRev) {
+			fileRevIndex = fileRev;
+		}
+		public void set(ContentBlock o, ContentBlock t) {
+			origin = o;
+			target = t;
+		}
+		public void set(int o, int t, int m) {
+			originCset = o;
+			targetCset = t;
+			mergeCset = m;
+		}
+		
+		public BlockData origin() {
+			return origin;
+		}
+
+		public BlockData target() {
+			return target;
+		}
+
+		public int originChangesetIndex() {
+			return originCset;
+		}
+
+		public int targetChangesetIndex() {
+			return targetCset;
+		}
+
+		public boolean isMerge() {
+			return mergeCset != NO_REVISION;
+		}
+
+		public int mergeChangesetIndex() {
+			return mergeCset;
+		}
+
+		public int fileRevisionIndex() {
+			return fileRevIndex;
+		}
+	}
+
+	public static void main(String[] args) {
+		EqualBlocksCollector bc = new EqualBlocksCollector();
+		bc.match(-1, 5, 3);
+		bc.match(-1, 10, 2);
+		bc.match(-1, 15, 3);
+		bc.match(-1, 20, 3);
+		assert !bc.includesTargetLine(4);
+		assert bc.includesTargetLine(7);
+		assert !bc.includesTargetLine(8);
+		assert bc.includesTargetLine(10);
+		assert !bc.includesTargetLine(12);
+		IntVector r = new IntVector();
+		bc.intersectWithTarget(7, 10, r);
+		for (int i = 0; i < r.size(); i+=2) {
+			System.out.printf("[%d..%d) ", r.get(i), r.get(i) + r.get(i+1));
+		}
+		System.out.println();
+		r.clear();
+		bc.combineAndMarkRangesWithTarget(0, 16, 508, 514, r);
+		for (int i = 0; i < r.size(); i+=3) {
+			System.out.printf("%d:[%d..%d)  ", r.get(i), r.get(i+1), r.get(i+1) + r.get(i+2));
+		}
+	}
+}