/*
 * Copyright (C) 2008-2009, Google Inc.
 * Copyright (C) 2008, Marek Zawirski <marek.zawirski@gmail.com>
 * 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
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.eclipse.jgit.internal.storage.pack;

import static org.eclipse.jgit.lib.Constants.OBJ_OFS_DELTA;
import static org.eclipse.jgit.lib.Constants.OBJ_REF_DELTA;
import static org.eclipse.jgit.lib.Constants.PACK_SIGNATURE;

import java.io.IOException;
import java.io.OutputStream;
import java.security.MessageDigest;

import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ProgressMonitor;
import org.eclipse.jgit.util.NB;

Custom output stream to support PackWriter. /**
 * Custom output stream to support
 * {@link org.eclipse.jgit.internal.storage.pack.PackWriter}.
 */
public final class PackOutputStream extends OutputStream {
	private static final int BYTES_TO_WRITE_BEFORE_CANCEL_CHECK = 128 * 1024;

	private final ProgressMonitor writeMonitor;

	private final OutputStream out;

	private final PackWriter packWriter;

	private final MessageDigest md = Constants.newMessageDigest();

	private long count;

	private final byte[] headerBuffer = new byte[32];

	private final byte[] copyBuffer = new byte[64 << 10];

	private long checkCancelAt;

	private boolean ofsDelta;

	
Initialize a pack output stream.
 This constructor is exposed to support debugging the JGit library only. Application or storage level code should not create a PackOutputStream, instead use PackWriter, and let the writer create the stream. 
Params:
writeMonitor – 
           monitor to update on object output progress.
out – 
           target stream to receive all object contents.
pw – 
           packer that is going to perform the output./**
	 * Initialize a pack output stream.
	 * <p>
	 * This constructor is exposed to support debugging the JGit library only.
	 * Application or storage level code should not create a PackOutputStream,
	 * instead use {@link org.eclipse.jgit.internal.storage.pack.PackWriter},
	 * and let the writer create the stream.
	 *
	 * @param writeMonitor
	 *            monitor to update on object output progress.
	 * @param out
	 *            target stream to receive all object contents.
	 * @param pw
	 *            packer that is going to perform the output.
	 */
	public PackOutputStream(final ProgressMonitor writeMonitor,
			final OutputStream out, final PackWriter pw) {
		this.writeMonitor = writeMonitor;
		this.out = out;
		this.packWriter = pw;
		this.checkCancelAt = BYTES_TO_WRITE_BEFORE_CANCEL_CHECK;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public final void write(int b) throws IOException {
		count++;
		out.write(b);
		md.update((byte) b);
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public final void write(byte[] b, int off, int len)
			throws IOException {
		while (0 < len) {
			final int n = Math.min(len, BYTES_TO_WRITE_BEFORE_CANCEL_CHECK);
			count += n;

			if (checkCancelAt <= count) {
				if (writeMonitor.isCancelled()) {
					throw new IOException(
							JGitText.get().packingCancelledDuringObjectsWriting);
				}
				checkCancelAt = count + BYTES_TO_WRITE_BEFORE_CANCEL_CHECK;
			}

			out.write(b, off, n);
			md.update(b, off, n);

			off += n;
			len -= n;
		}
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public void flush() throws IOException {
		out.flush();
	}

	final void writeFileHeader(int version, long objectCount)
			throws IOException {
		System.arraycopy(PACK_SIGNATURE, 0, headerBuffer, 0, 4);
		NB.encodeInt32(headerBuffer, 4, version);
		NB.encodeInt32(headerBuffer, 8, (int) objectCount);
		write(headerBuffer, 0, 12);
		ofsDelta = packWriter.isDeltaBaseAsOffset();
	}

	
Write one object.
If the object was already written, this method does nothing and returns
quickly. This case occurs whenever an object was written out of order in
order to ensure the delta base occurred before the object that needs it.
Params:
otp – 
           the object to write.
Throws:
IOException – 
            the object cannot be read from the object reader, or the
            output stream is no longer accepting output. Caller must
            examine the type of exception and possibly its message to
            distinguish between these cases./**
	 * Write one object.
	 *
	 * If the object was already written, this method does nothing and returns
	 * quickly. This case occurs whenever an object was written out of order in
	 * order to ensure the delta base occurred before the object that needs it.
	 *
	 * @param otp
	 *            the object to write.
	 * @throws java.io.IOException
	 *             the object cannot be read from the object reader, or the
	 *             output stream is no longer accepting output. Caller must
	 *             examine the type of exception and possibly its message to
	 *             distinguish between these cases.
	 */
	public final void writeObject(ObjectToPack otp) throws IOException {
		packWriter.writeObject(this, otp);
	}

	
Commits the object header onto the stream.

Once the header has been written, the object representation must be fully
output, or packing must abort abnormally.
Params:
otp – 
           the object to pack. Header information is obtained.
rawLength – 
           number of bytes of the inflated content. For an object that is
           in whole object format, this is the same as the object size.
           For an object that is in a delta format, this is the size of
           the inflated delta instruction stream.
Throws:
IOException – 
            the underlying stream refused to accept the header./**
	 * Commits the object header onto the stream.
	 * <p>
	 * Once the header has been written, the object representation must be fully
	 * output, or packing must abort abnormally.
	 *
	 * @param otp
	 *            the object to pack. Header information is obtained.
	 * @param rawLength
	 *            number of bytes of the inflated content. For an object that is
	 *            in whole object format, this is the same as the object size.
	 *            For an object that is in a delta format, this is the size of
	 *            the inflated delta instruction stream.
	 * @throws java.io.IOException
	 *             the underlying stream refused to accept the header.
	 */
	@SuppressWarnings("ShortCircuitBoolean")
	public final void writeHeader(ObjectToPack otp, long rawLength)
			throws IOException {
		ObjectToPack b = otp.getDeltaBase();
		if (b != null && (b.isWritten() & ofsDelta)) { // Non-short-circuit logic is intentional
			int n = objectHeader(rawLength, OBJ_OFS_DELTA, headerBuffer);
			n = ofsDelta(count - b.getOffset(), headerBuffer, n);
			write(headerBuffer, 0, n);
		} else if (otp.isDeltaRepresentation()) {
			int n = objectHeader(rawLength, OBJ_REF_DELTA, headerBuffer);
			otp.getDeltaBaseId().copyRawTo(headerBuffer, n);
			write(headerBuffer, 0, n + 20);
		} else {
			int n = objectHeader(rawLength, otp.getType(), headerBuffer);
			write(headerBuffer, 0, n);
		}
	}

	private static final int objectHeader(long len, int type, byte[] buf) {
		byte b = (byte) ((type << 4) | (len & 0x0F));
		int n = 0;
		for (len >>>= 4; len != 0; len >>>= 7) {
			buf[n++] = (byte) (0x80 | b);
			b = (byte) (len & 0x7F);
		}
		buf[n++] = b;
		return n;
	}

	private static final int ofsDelta(long diff, byte[] buf, int p) {
		p += ofsDeltaVarIntLength(diff);
		int n = p;
		buf[--n] = (byte) (diff & 0x7F);
		while ((diff >>>= 7) != 0)
			buf[--n] = (byte) (0x80 | (--diff & 0x7F));
		return p;
	}

	private static final int ofsDeltaVarIntLength(long v) {
		int n = 1;
		for (; (v >>>= 7) != 0; n++)
			--v;
		return n;
	}

	
Get a temporary buffer writers can use to copy data with.
Returns:
a temporary buffer writers can use to copy data with./**
	 * Get a temporary buffer writers can use to copy data with.
	 *
	 * @return a temporary buffer writers can use to copy data with.
	 */
	public final byte[] getCopyBuffer() {
		return copyBuffer;
	}

	void endObject() {
		writeMonitor.update(1);
	}

	
Get total number of bytes written since stream start.
Returns:
total number of bytes written since stream start./**
	 * Get total number of bytes written since stream start.
	 *
	 * @return total number of bytes written since stream start.
	 */
	public final long length() {
		return count;
	}

	
Returns:
obtain the current SHA-1 digest./** @return obtain the current SHA-1 digest. */
	final byte[] getDigest() {
		return md.digest();
	}
}