--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/tmatesoft/hg/internal/Metadata.java	Mon May 06 17:11:29 2013 +0200
@@ -0,0 +1,209 @@
+/*
+ * 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.internal;
+
+import static org.tmatesoft.hg.util.LogFacility.Severity.Error;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
+
+import org.tmatesoft.hg.core.SessionContext;
+import org.tmatesoft.hg.repo.HgInvalidControlFileException;
+import org.tmatesoft.hg.repo.HgInvalidStateException;
+import org.tmatesoft.hg.util.LogFacility;
+
+/**
+ * Container for metadata recorded as part of file revisions
+ * 
+ * @author Artem Tikhomirov
+ * @author TMate Software Ltd.
+ */
+public final class Metadata {
+	private static class Record {
+		public final int offset;
+		public final MetadataEntry[] entries;
+		
+		public Record(int off, MetadataEntry[] entr) {
+			offset = off;
+			entries = entr;
+		}
+	}
+	// XXX sparse array needed
+	private final IntMap<Metadata.Record> entries = new IntMap<Metadata.Record>(5);
+	
+	private final Metadata.Record NONE = new Record(-1, null); // don't want statics
+
+	private final LogFacility log;
+
+	public Metadata(SessionContext.Source sessionCtx) {
+		log = sessionCtx.getSessionContext().getLog();
+	}
+	
+	// true when there's metadata for given revision
+	public boolean known(int revision) {
+		Metadata.Record i = entries.get(revision);
+		return i != null && NONE != i;
+	}
+
+	// true when revision has been checked for metadata presence.
+	public boolean checked(int revision) {
+		return entries.containsKey(revision);
+	}
+
+	// true when revision has been checked and found not having any metadata
+	public boolean none(int revision) {
+		Metadata.Record i = entries.get(revision);
+		return i == NONE;
+	}
+
+	// mark revision as having no metadata.
+	void recordNone(int revision) {
+		Metadata.Record i = entries.get(revision);
+		if (i == NONE) {
+			return; // already there
+		} 
+		if (i != null) {
+			throw new HgInvalidStateException(String.format("Trying to override Metadata state for revision %d (known offset: %d)", revision, i));
+		}
+		entries.put(revision, NONE);
+	}
+
+	// since this is internal class, callers are supposed to ensure arg correctness (i.e. ask known() before)
+	public int dataOffset(int revision) {
+		return entries.get(revision).offset;
+	}
+	void add(int revision, int dataOffset, Collection<MetadataEntry> e) {
+		assert !entries.containsKey(revision);
+		entries.put(revision, new Record(dataOffset, e.toArray(new MetadataEntry[e.size()])));
+	}
+	
+	/**
+	 * @return <code>true</code> if metadata has been found
+	 */
+	public boolean tryRead(int revisionNumber, DataAccess data) throws IOException, HgInvalidControlFileException {
+		final int daLength = data.length();
+		if (daLength < 4 || data.readByte() != 1 || data.readByte() != 10) {
+			recordNone(revisionNumber);
+			return false;
+		} else {
+			ArrayList<MetadataEntry> _metadata = new ArrayList<MetadataEntry>();
+			int offset = parseMetadata(data, daLength, _metadata);
+			add(revisionNumber, offset, _metadata);
+			return true;
+		}
+	}
+
+	public String find(int revision, String key) {
+		for (MetadataEntry me : entries.get(revision).entries) {
+			if (me.matchKey(key)) {
+				return me.value();
+			}
+		}
+		return null;
+	}
+
+	private int parseMetadata(DataAccess data, final int daLength, ArrayList<MetadataEntry> _metadata) throws IOException, HgInvalidControlFileException {
+		int lastEntryStart = 2;
+		int lastColon = -1;
+		// 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 
+		ByteArrayOutputStream bos = new ByteArrayOutputStream();
+		String key = null, value = null;
+		boolean byteOne = false;
+		boolean metadataIsComplete = false;
+		for (int i = 2; i < daLength; i++) {
+			byte b = data.readByte();
+			if (b == '\n') {
+				if (byteOne) { // i.e. \n follows 1
+					lastEntryStart = i+1;
+					metadataIsComplete = true;
+					// XXX is it possible to have here incomplete key/value (i.e. if last pair didn't end with \n)
+					// if yes, need to set metadataIsComplete to true in that case as well
+					break;
+				}
+				if (key == null || lastColon == -1 || i <= lastColon) {
+					log.dump(getClass(), Error, "Missing key in file revision metadata at index %d", i);
+				}
+				value = new String(bos.toByteArray()).trim();
+				bos.reset();
+				_metadata.add(new MetadataEntry(key, value));
+				key = value = null;
+				lastColon = -1;
+				lastEntryStart = i+1;
+				continue;
+			} 
+			// 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
+			}
+			if (b == (int) ':') {
+				assert value == null;
+				key = new String(bos.toByteArray());
+				bos.reset();
+				lastColon = i;
+			} else if (b == 1) {
+				byteOne = true;
+			} else {
+				bos.write(b);
+			}
+		}
+		// data.isEmpty is not reliable, renamed files of size==0 keep only metadata
+		if (!metadataIsComplete) {
+			// XXX perhaps, worth a testcase (empty file, renamed, read or ask ifCopy
+			throw new HgInvalidControlFileException("Metadata is not closed properly", null, null);
+		}
+		return lastEntryStart;
+	}
+
+	/**
+	 * There may be several entries of metadata per single revision, this class captures single entry
+	 */
+	private static class MetadataEntry {
+		private final String entry;
+		private final int valueStart;
+
+		// key may be null
+		/* package-local */MetadataEntry(String key, String value) {
+			if (key == null) {
+				entry = value;
+				valueStart = -1; // not 0 to tell between key == null and key == ""
+			} else {
+				entry = key + value;
+				valueStart = key.length();
+			}
+		}
+
+		/* package-local */boolean matchKey(String key) {
+			return key == null ? valueStart == -1 : key.length() == valueStart && entry.startsWith(key);
+		}
+
+//			uncomment once/if needed
+//			public String key() {
+//				return entry.substring(0, valueStart);
+//			}
+
+		public String value() {
+			return valueStart == -1 ? entry : entry.substring(valueStart);
+		}
+	}
+}
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