# HG changeset patch
# User Artem Tikhomirov <tikhomirov.artem@gmail.com>
# Date 1314652499 -7200
# Node ID 74e7493a042a6fdb28b5d7214065f5fe99437710
# Parent  6355ecda1f0861f5956c8594b55b00872336fa44
Favor delegation over generalization

diff -r 6355ecda1f08 -r 74e7493a042a src/org/tmatesoft/hg/repo/HgDataFile.java
--- a/src/org/tmatesoft/hg/repo/HgDataFile.java	Mon Aug 29 22:15:12 2011 +0200
+++ b/src/org/tmatesoft/hg/repo/HgDataFile.java	Mon Aug 29 23:14:59 2011 +0200
@@ -34,6 +34,7 @@
 import org.tmatesoft.hg.core.Nodeid;
 import org.tmatesoft.hg.internal.DataAccess;
 import org.tmatesoft.hg.internal.FilterByteChannel;
+import org.tmatesoft.hg.internal.FilterDataAccess;
 import org.tmatesoft.hg.internal.IntMap;
 import org.tmatesoft.hg.internal.RevlogStream;
 import org.tmatesoft.hg.util.ByteChannel;
@@ -201,14 +202,14 @@
 		if (metadata == null) {
 			metadata = new Metadata();
 		}
-		ContentPipe insp;
+		ErrorHandlingInspector insp;
 		if (metadata.none(revision)) {
 			insp = new ContentPipe(sink, 0);
 		} else if (metadata.known(revision)) {
 			insp = new ContentPipe(sink, metadata.dataOffset(revision));
 		} else {
 			// do not know if there's metadata
-			insp = new MetadataContentPipe(sink, metadata, getPath());
+			insp = new MetadataInspector(metadata, getPath(), new ContentPipe(sink, 0));
 		}
 		insp.checkCancelled();
 		super.content.iterate(revision, revision, true, insp);
@@ -409,28 +410,47 @@
 		}
 	}
 
-	private static class MetadataContentPipe extends ContentPipe {
-
+	private static class MetadataInspector extends ErrorHandlingInspector implements RevlogStream.Inspector {
 		private final Metadata metadata;
 		private final Path fname; // need this only for error reporting
+		private final RevlogStream.Inspector delegate;
 
-		public MetadataContentPipe(ByteChannel sink, Metadata _metadata, Path file) {
-			super(sink, 0);
+		public MetadataInspector(Metadata _metadata, Path file, RevlogStream.Inspector chain) {
 			metadata = _metadata;
 			fname = file;
+			delegate = chain;
+			setCancelSupport(CancelSupport.Factory.get(chain));
 		}
 
-		@Override
-		protected void prepare(int revisionNumber, DataAccess da) throws HgException, IOException {
-			final int daLength = da.length();
-			if (daLength < 4 || da.readByte() != 1 || da.readByte() != 10) {
-				metadata.recordNone(revisionNumber);
-				da.reset();
-				return;
+		public void next(int revisionNumber, int actualLen, int baseRevision, int linkRevision, int parent1Revision, int parent2Revision, byte[] nodeid, DataAccess data) {
+			try {
+				final int daLength = data.length();
+				if (daLength < 4 || data.readByte() != 1 || data.readByte() != 10) {
+					metadata.recordNone(revisionNumber);
+					data.reset();
+				} else {
+					ArrayList<MetadataEntry> _metadata = new ArrayList<MetadataEntry>();
+					int offset = parseMetadata(data, daLength, _metadata);
+					metadata.add(revisionNumber, offset, _metadata);
+					// da is in prepared state (i.e. we consumed all bytes up to metadata end).
+					// However, it's not safe to assume delegate won't call da.reset() for some reason,
+					// and we need to ensure predictable result.
+					data.reset();
+					data = new FilterDataAccess(data, offset, daLength - offset);
+				}
+				if (delegate != null) {
+					delegate.next(revisionNumber, actualLen, baseRevision, linkRevision, parent1Revision, parent2Revision, nodeid, data);
+				}
+			} catch (IOException ex) {
+				recordFailure(ex);
+			} catch (HgDataStreamException ex) {
+				recordFailure(ex.setRevisionNumber(revisionNumber));
 			}
+		}
+
+		private int parseMetadata(DataAccess data, final int daLength, ArrayList<MetadataEntry> _metadata) throws IOException, HgDataStreamException {
 			int lastEntryStart = 2;
 			int lastColon = -1;
-			ArrayList<MetadataEntry> _metadata = new ArrayList<MetadataEntry>();
 			// XXX in fact, need smth like ByteArrayBuilder, similar to StringBuilder,
 			// which can't be used here because we can't convert bytes to chars as we read them
 			// (there might be multi-byte encoding), and we need to collect all bytes before converting to string 
@@ -438,7 +458,7 @@
 			String key = null, value = null;
 			boolean byteOne = false;
 			for (int i = 2; i < daLength; i++) {
-				byte b = da.readByte();
+				byte b = data.readByte();
 				if (b == '\n') {
 					if (byteOne) { // i.e. \n follows 1
 						lastEntryStart = i+1;
@@ -456,12 +476,12 @@
 					lastEntryStart = i+1;
 					continue;
 				} 
-				// byteOne has to be consumed up to this line, if not jet, consume it
+				// byteOne has to be consumed up to this line, if not yet, consume it
 				if (byteOne) {
 					// insert 1 we've read on previous step into the byte builder
 					bos.write(1);
+					byteOne = false;
 					// fall-through to consume current byte
-					byteOne = false;
 				}
 				if (b == (int) ':') {
 					assert value == null;
@@ -474,11 +494,10 @@
 					bos.write(b);
 				}
 			}
-			metadata.add(revisionNumber, lastEntryStart, _metadata);
-			if (da.isEmpty() || !byteOne) {
-				throw new HgDataStreamException(fname, String.format("Metadata for revision %d is not closed properly", revisionNumber), null);
+			if (data.isEmpty() || !byteOne) {
+				throw new HgDataStreamException(fname, "Metadata is not closed properly", null);
 			}
-			// da is in prepared state (i.e. we consumed all bytes up to metadata end).
+			return lastEntryStart;
 		}
 	}
 }
diff -r 6355ecda1f08 -r 74e7493a042a src/org/tmatesoft/hg/repo/Revlog.java
--- a/src/org/tmatesoft/hg/repo/Revlog.java	Mon Aug 29 22:15:12 2011 +0200
+++ b/src/org/tmatesoft/hg/repo/Revlog.java	Mon Aug 29 23:14:59 2011 +0200
@@ -449,58 +449,13 @@
 		}
 	}
 
-
-	protected static class ContentPipe implements RevlogStream.Inspector, CancelSupport {
-		private final ByteChannel sink;
-		private final CancelSupport cancelSupport;
+	protected abstract static class ErrorHandlingInspector implements RevlogStream.Inspector, CancelSupport {
 		private Exception failure;
-		private final int offset;
-
-		/**
-		 * @param _sink - cannot be <code>null</code>
-		 * @param seekOffset - when positive, orders to pipe bytes to the sink starting from specified offset, not from the first byte available in DataAccess
-		 */
-		public ContentPipe(ByteChannel _sink, int seekOffset) {
-			assert _sink != null;
-			sink = _sink;
-			cancelSupport = CancelSupport.Factory.get(_sink);
-			offset = seekOffset;
-		}
+		private CancelSupport cancelSupport;
 		
-		protected void prepare(int revisionNumber, DataAccess da) throws HgException, IOException {
-			if (offset > 0) { // save few useless reset/rewind operations
-				da.seek(offset);
-			}
-		}
-
-		public void next(int revisionNumber, int actualLen, int baseRevision, int linkRevision, int parent1Revision, int parent2Revision, byte[] nodeid, DataAccess da) {
-			try {
-				prepare(revisionNumber, da); // XXX perhaps, prepare shall return DA (sliced, if needed)
-				final ProgressSupport progressSupport = ProgressSupport.Factory.get(sink);
-				ByteBuffer buf = ByteBuffer.allocate(512);
-				progressSupport.start(da.length());
-				while (!da.isEmpty()) {
-					cancelSupport.checkCancelled();
-					da.readBytes(buf);
-					buf.flip();
-					// XXX I may not rely on returned number of bytes but track change in buf position instead.
-					int consumed = sink.write(buf); 
-					// FIXME in fact, bad sink implementation (that consumes no bytes) would result in endless loop. Need to account for this 
-					buf.compact();
-					progressSupport.worked(consumed);
-				}
-				progressSupport.done(); // XXX shall specify whether #done() is invoked always or only if completed successfully.
-			} catch (IOException ex) {
-				recordFailure(ex);
-			} catch (CancelledException ex) {
-				recordFailure(ex);
-			} catch (HgException ex) {
-				recordFailure(ex);
-			}
-		}
-		
-		public void checkCancelled() throws CancelledException {
-			cancelSupport.checkCancelled();
+		protected void setCancelSupport(CancelSupport cs) {
+			assert cancelSupport == null; // no reason to set it twice
+			cancelSupport = cs;
 		}
 
 		protected void recordFailure(Exception ex) {
@@ -523,5 +478,59 @@
 			}
 			throw new HgBadStateException(failure);
 		}
+
+		public void checkCancelled() throws CancelledException {
+			if (cancelSupport != null) {
+				cancelSupport.checkCancelled();
+			}
+		}
+	}
+
+	protected static class ContentPipe extends ErrorHandlingInspector implements RevlogStream.Inspector, CancelSupport {
+		private final ByteChannel sink;
+		private final int offset;
+
+		/**
+		 * @param _sink - cannot be <code>null</code>
+		 * @param seekOffset - when positive, orders to pipe bytes to the sink starting from specified offset, not from the first byte available in DataAccess
+		 */
+		public ContentPipe(ByteChannel _sink, int seekOffset) {
+			assert _sink != null;
+			sink = _sink;
+			setCancelSupport(CancelSupport.Factory.get(_sink));
+			offset = seekOffset;
+		}
+		
+		protected void prepare(int revisionNumber, DataAccess da) throws HgException, IOException {
+			if (offset > 0) { // save few useless reset/rewind operations
+				da.seek(offset);
+			}
+		}
+
+		public void next(int revisionNumber, int actualLen, int baseRevision, int linkRevision, int parent1Revision, int parent2Revision, byte[] nodeid, DataAccess da) {
+			try {
+				prepare(revisionNumber, da); // XXX perhaps, prepare shall return DA (sliced, if needed)
+				final ProgressSupport progressSupport = ProgressSupport.Factory.get(sink);
+				ByteBuffer buf = ByteBuffer.allocate(512);
+				progressSupport.start(da.length());
+				while (!da.isEmpty()) {
+					checkCancelled();
+					da.readBytes(buf);
+					buf.flip();
+					// XXX I may not rely on returned number of bytes but track change in buf position instead.
+					int consumed = sink.write(buf); 
+					// FIXME in fact, bad sink implementation (that consumes no bytes) would result in endless loop. Need to account for this 
+					buf.compact();
+					progressSupport.worked(consumed);
+				}
+				progressSupport.done(); // XXX shall specify whether #done() is invoked always or only if completed successfully.
+			} catch (IOException ex) {
+				recordFailure(ex);
+			} catch (CancelledException ex) {
+				recordFailure(ex);
+			} catch (HgException ex) {
+				recordFailure(ex);
+			}
+		}
 	}
 }