PackOutputStream.java
/*
* Copyright (C) 2008-2009, Google Inc.
* Copyright (C) 2008, Marek Zawirski <marek.zawirski@gmail.com> and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
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
* {@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.
* <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} */
@Override
public final void write(int b) throws IOException {
count++;
out.write(b);
md.update((byte) b);
}
/** {@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} */
@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.
*
* @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.
* <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.
*
* @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.
*
* @return total number of bytes written since stream start.
*/
public final long length() {
return count;
}
/** @return obtain the current SHA-1 digest. */
final byte[] getDigest() {
return md.digest();
}
}