/*
    * Copyright (C) 2017, Google Inc.
    * and other copyright owners as documented in the project's IP log.
    *
    * This program and the accompanying materials are made available
    * under the terms of the Eclipse Distribution License v1.0 which
    * accompanies this distribution, is reproduced below, and is
    * available at http://www.eclipse.org/org/documents/edl-v10.php
    *
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  package org.eclipse.jgit.internal.fsck;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.channels.Channels;
  import java.text.MessageFormat;
  import java.util.Arrays;
  import java.util.HashSet;
  import java.util.Set;
  import java.util.zip.CRC32;
  
  import org.eclipse.jgit.errors.CorruptObjectException;
  import org.eclipse.jgit.errors.CorruptPackIndexException;
  import org.eclipse.jgit.errors.CorruptPackIndexException.ErrorType;
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.internal.fsck.FsckError.CorruptObject;
  import org.eclipse.jgit.internal.storage.dfs.ReadableChannel;
  import org.eclipse.jgit.internal.storage.file.PackIndex;
  import org.eclipse.jgit.internal.storage.file.PackIndex.MutableEntry;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.ObjectDatabase;
  import org.eclipse.jgit.lib.ObjectIdOwnerMap;
  import org.eclipse.jgit.transport.PackParser;
  import org.eclipse.jgit.transport.PackedObjectInfo;
  
  /**
   * A read-only pack parser for object validity checking.
   */
  public class FsckPackParser extends PackParser {
  	private final CRC32 crc;
  
  	private final ReadableChannel channel;
  
  	private final Set<CorruptObject> corruptObjects = new HashSet<>();
  
  	private long expectedObjectCount = -1L;
  
  	private long offset;
  
  	private int blockSize;
  
  	/**
  	 * Constructor for FsckPackParser
  	 *
  	 * @param db
  	 *            the object database which stores repository's data.
  	 * @param channel
  	 *            readable channel of the pack file.
  	 */
  	public FsckPackParser(ObjectDatabase db, ReadableChannel channel) {
  		super(db, Channels.newInputStream(channel));
  		this.channel = channel;
  		setCheckObjectCollisions(false);
  		this.crc = new CRC32();
  		this.blockSize = channel.blockSize() > 0 ? channel.blockSize() : 65536;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void onPackHeader(long objCnt) throws IOException {
 		if (expectedObjectCount >= 0) {
 			// Some DFS pack files don't contain the correct object count, e.g.
 			// INSERT/RECEIVE packs don't always contain the correct object
 			// count in their headers. Overwrite the expected object count
 			// after parsing the pack header.
 			setExpectedObjectCount(expectedObjectCount);
 		}
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void onBeginWholeObject(long streamPosition, int type,
 			long inflatedSize) throws IOException {
 		crc.reset();
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void onObjectHeader(Source src, byte[] raw, int pos, int len)
 			throws IOException {
 		crc.update(raw, pos, len);
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void onObjectData(Source src, byte[] raw, int pos, int len)
 			throws IOException {
 		crc.update(raw, pos, len);
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void onEndWholeObject(PackedObjectInfo info) throws IOException {
 		info.setCRC((int) crc.getValue());
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void onBeginOfsDelta(long deltaStreamPosition,
 			long baseStreamPosition, long inflatedSize) throws IOException {
 		crc.reset();
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void onBeginRefDelta(long deltaStreamPosition, AnyObjectId baseId,
 			long inflatedSize) throws IOException {
 		crc.reset();
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected UnresolvedDelta onEndDelta() throws IOException {
 		UnresolvedDelta delta = new UnresolvedDelta();
 		delta.setCRC((int) crc.getValue());
 		return delta;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void onInflatedObjectData(PackedObjectInfo obj, int typeCode,
 			byte[] data) throws IOException {
 		// FsckPackParser ignores this event.
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void verifySafeObject(final AnyObjectId id, final int type,
 			final byte[] data) {
 		try {
 			super.verifySafeObject(id, type, data);
 		} catch (CorruptObjectException e) {
 			corruptObjects.add(
 					new CorruptObject(id.toObjectId(), type, e.getErrorType()));
 		}
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void onPackFooter(byte[] hash) throws IOException {
 		// Do nothing.
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected boolean onAppendBase(int typeCode, byte[] data,
 			PackedObjectInfo info) throws IOException {
 		// Do nothing.
 		return false;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void onEndThinPack() throws IOException {
 		// Do nothing.
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected ObjectTypeAndSize seekDatabase(PackedObjectInfo obj,
 			ObjectTypeAndSize info) throws IOException {
 		crc.reset();
 		offset = obj.getOffset();
 		return readObjectHeader(info);
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected ObjectTypeAndSize seekDatabase(UnresolvedDelta delta,
 			ObjectTypeAndSize info) throws IOException {
 		crc.reset();
 		offset = delta.getOffset();
 		return readObjectHeader(info);
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected int readDatabase(byte[] dst, int pos, int cnt)
 			throws IOException {
 		// read from input instead of database.
 		int n = read(offset, dst, pos, cnt);
 		if (n > 0) {
 			offset += n;
 		}
 		return n;
 	}
 
 	int read(long channelPosition, byte[] dst, int pos, int cnt)
 			throws IOException {
 		long block = channelPosition / blockSize;
 		byte[] bytes = readFromChannel(block);
 		if (bytes == null) {
 			return -1;
 		}
 		int offs = (int) (channelPosition - block * blockSize);
 		int bytesToCopy = Math.min(cnt, bytes.length - offs);
 		if (bytesToCopy < 1) {
 			return -1;
 		}
 		System.arraycopy(bytes, offs, dst, pos, bytesToCopy);
 		return bytesToCopy;
 	}
 
 	private byte[] readFromChannel(long block) throws IOException {
 		channel.position(block * blockSize);
 		ByteBuffer buf = ByteBuffer.allocate(blockSize);
 		int totalBytesRead = 0;
 		while (totalBytesRead < blockSize) {
 			int bytesRead = channel.read(buf);
 			if (bytesRead == -1) {
 				if (totalBytesRead == 0) {
 					return null;
 				}
 				return Arrays.copyOf(buf.array(), totalBytesRead);
 			}
 			totalBytesRead += bytesRead;
 		}
 		return buf.array();
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected boolean checkCRC(int oldCRC) {
 		return oldCRC == (int) crc.getValue();
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void onStoreStream(byte[] raw, int pos, int len)
 			throws IOException {
 		// Do nothing.
 	}
 
 	/**
 	 * Get corrupt objects reported by
 	 * {@link org.eclipse.jgit.lib.ObjectChecker}
 	 *
 	 * @return corrupt objects that are reported by
 	 *         {@link org.eclipse.jgit.lib.ObjectChecker}.
 	 */
 	public Set<CorruptObject> getCorruptObjects() {
 		return corruptObjects;
 	}
 
 	/**
 	 * Verify the existing index file with all objects from the pack.
 	 *
 	 * @param idx
 	 *            index file associate with the pack
 	 * @throws org.eclipse.jgit.errors.CorruptPackIndexException
 	 *             when the index file is corrupt.
 	 */
 	public void verifyIndex(PackIndex idx)
 			throws CorruptPackIndexException {
 		ObjectIdOwnerMap<ObjFromPack> inPack = new ObjectIdOwnerMap<>();
 		for (int i = 0; i < getObjectCount(); i++) {
 			PackedObjectInfo entry = getObject(i);
 			inPack.add(new ObjFromPack(entry));
 
 			long offs = idx.findOffset(entry);
 			if (offs == -1) {
 				throw new CorruptPackIndexException(
 						MessageFormat.format(JGitText.get().missingObject,
 								Integer.valueOf(entry.getType()),
 								entry.getName()),
 						ErrorType.MISSING_OBJ);
 			} else if (offs != entry.getOffset()) {
 				throw new CorruptPackIndexException(MessageFormat
 						.format(JGitText.get().mismatchOffset, entry.getName()),
 						ErrorType.MISMATCH_OFFSET);
 			}
 
 			try {
 				if (idx.hasCRC32Support()
 						&& (int) idx.findCRC32(entry) != entry.getCRC()) {
 					throw new CorruptPackIndexException(
 							MessageFormat.format(JGitText.get().mismatchCRC,
 									entry.getName()),
 							ErrorType.MISMATCH_CRC);
 				}
 			} catch (MissingObjectException e) {
 				throw new CorruptPackIndexException(MessageFormat
 						.format(JGitText.get().missingCRC, entry.getName()),
 						ErrorType.MISSING_CRC);
 			}
 		}
 
 		for (MutableEntry entry : idx) {
 			if (!inPack.contains(entry.toObjectId())) {
 				throw new CorruptPackIndexException(MessageFormat.format(
 						JGitText.get().unknownObjectInIndex, entry.name()),
 						ErrorType.UNKNOWN_OBJ);
 			}
 		}
 	}
 
 	/**
 	 * Set the object count for overwriting the expected object count from pack
 	 * header.
 	 *
 	 * @param objectCount
 	 *            the actual expected object count.
 	 */
 	public void overwriteObjectCount(long objectCount) {
 		this.expectedObjectCount = objectCount;
 	}
 
 	static class ObjFromPack extends ObjectIdOwnerMap.Entry {
 		ObjFromPack(AnyObjectId id) {
 			super(id);
 		}
 	}
 }