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- /*
- * Copyright (C) 2008, Robin Rosenberg <robin.rosenberg@dewire.com>
- * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
- * 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.lib;
-
- import java.io.BufferedOutputStream;
- import java.io.IOException;
- import java.io.OutputStream;
- import java.security.DigestOutputStream;
- import java.util.List;
-
- import org.eclipse.jgit.transport.PackedObjectInfo;
- import org.eclipse.jgit.util.NB;
-
- /**
- * Creates a table of contents to support random access by {@link PackFile}.
- * <p>
- * Pack index files (the <code>.idx</code> suffix in a pack file pair)
- * provides random access to any object in the pack by associating an ObjectId
- * to the byte offset within the pack where the object's data can be read.
- */
- public abstract class PackIndexWriter {
- /** Magic constant indicating post-version 1 format. */
- protected static final byte[] TOC = { -1, 't', 'O', 'c' };
-
- /**
- * Create a new writer for the oldest (most widely understood) format.
- * <p>
- * This method selects an index format that can accurate describe the
- * supplied objects and that will be the most compatible format with older
- * Git implementations.
- * <p>
- * Index version 1 is widely recognized by all Git implementations, but
- * index version 2 (and later) is not as well recognized as it was
- * introduced more than a year later. Index version 1 can only be used if
- * the resulting pack file is under 4 gigabytes in size; packs larger than
- * that limit must use index version 2.
- *
- * @param dst
- * the stream the index data will be written to. If not already
- * buffered it will be automatically wrapped in a buffered
- * stream. Callers are always responsible for closing the stream.
- * @param objs
- * the objects the caller needs to store in the index. Entries
- * will be examined until a format can be conclusively selected.
- * @return a new writer to output an index file of the requested format to
- * the supplied stream.
- * @throws IllegalArgumentException
- * no recognized pack index version can support the supplied
- * objects. This is likely a bug in the implementation.
- */
- @SuppressWarnings("fallthrough")
- public static PackIndexWriter createOldestPossible(final OutputStream dst,
- final List<? extends PackedObjectInfo> objs) {
- int version = 1;
- LOOP: for (final PackedObjectInfo oe : objs) {
- switch (version) {
- case 1:
- if (PackIndexWriterV1.canStore(oe))
- continue;
- version = 2;
- case 2:
- break LOOP;
- }
- }
- return createVersion(dst, version);
- }
-
- /**
- * Create a new writer instance for a specific index format version.
- *
- * @param dst
- * the stream the index data will be written to. If not already
- * buffered it will be automatically wrapped in a buffered
- * stream. Callers are always responsible for closing the stream.
- * @param version
- * index format version number required by the caller. Exactly
- * this formatted version will be written.
- * @return a new writer to output an index file of the requested format to
- * the supplied stream.
- * @throws IllegalArgumentException
- * the version requested is not supported by this
- * implementation.
- */
- public static PackIndexWriter createVersion(final OutputStream dst,
- final int version) {
- switch (version) {
- case 1:
- return new PackIndexWriterV1(dst);
- case 2:
- return new PackIndexWriterV2(dst);
- default:
- throw new IllegalArgumentException(
- "Unsupported pack index version " + version);
- }
- }
-
- /** The index data stream we are responsible for creating. */
- protected final DigestOutputStream out;
-
- /** A temporary buffer for use during IO to {link #out}. */
- protected final byte[] tmp;
-
- /** The entries this writer must pack. */
- protected List<? extends PackedObjectInfo> entries;
-
- /** SHA-1 checksum for the entire pack data. */
- protected byte[] packChecksum;
-
- /**
- * Create a new writer instance.
- *
- * @param dst
- * the stream this instance outputs to. If not already buffered
- * it will be automatically wrapped in a buffered stream.
- */
- protected PackIndexWriter(final OutputStream dst) {
- out = new DigestOutputStream(dst instanceof BufferedOutputStream ? dst
- : new BufferedOutputStream(dst), Constants.newMessageDigest());
- tmp = new byte[4 + Constants.OBJECT_ID_LENGTH];
- }
-
- /**
- * Write all object entries to the index stream.
- * <p>
- * After writing the stream passed to the factory is flushed but remains
- * open. Callers are always responsible for closing the output stream.
- *
- * @param toStore
- * sorted list of objects to store in the index. The caller must
- * have previously sorted the list using {@link PackedObjectInfo}'s
- * native {@link Comparable} implementation.
- * @param packDataChecksum
- * checksum signature of the entire pack data content. This is
- * traditionally the last 20 bytes of the pack file's own stream.
- * @throws IOException
- * an error occurred while writing to the output stream, or this
- * index format cannot store the object data supplied.
- */
- public void write(final List<? extends PackedObjectInfo> toStore,
- final byte[] packDataChecksum) throws IOException {
- entries = toStore;
- packChecksum = packDataChecksum;
- writeImpl();
- out.flush();
- }
-
- /**
- * Writes the index file to {@link #out}.
- * <p>
- * Implementations should go something like:
- *
- * <pre>
- * writeFanOutTable();
- * for (final PackedObjectInfo po : entries)
- * writeOneEntry(po);
- * writeChecksumFooter();
- * </pre>
- *
- * <p>
- * Where the logic for <code>writeOneEntry</code> is specific to the index
- * format in use. Additional headers/footers may be used if necessary and
- * the {@link #entries} collection may be iterated over more than once if
- * necessary. Implementors therefore have complete control over the data.
- *
- * @throws IOException
- * an error occurred while writing to the output stream, or this
- * index format cannot store the object data supplied.
- */
- protected abstract void writeImpl() throws IOException;
-
- /**
- * Output the version 2 (and later) TOC header, with version number.
- * <p>
- * Post version 1 all index files start with a TOC header that makes the
- * file an invalid version 1 file, and then includes the version number.
- * This header is necessary to recognize a version 1 from a version 2
- * formatted index.
- *
- * @param version
- * version number of this index format being written.
- * @throws IOException
- * an error occurred while writing to the output stream.
- */
- protected void writeTOC(final int version) throws IOException {
- out.write(TOC);
- NB.encodeInt32(tmp, 0, version);
- out.write(tmp, 0, 4);
- }
-
- /**
- * Output the standard 256 entry first-level fan-out table.
- * <p>
- * The fan-out table is 4 KB in size, holding 256 32-bit unsigned integer
- * counts. Each count represents the number of objects within this index
- * whose {@link ObjectId#getFirstByte()} matches the count's position in the
- * fan-out table.
- *
- * @throws IOException
- * an error occurred while writing to the output stream.
- */
- protected void writeFanOutTable() throws IOException {
- final int[] fanout = new int[256];
- for (final PackedObjectInfo po : entries)
- fanout[po.getFirstByte() & 0xff]++;
- for (int i = 1; i < 256; i++)
- fanout[i] += fanout[i - 1];
- for (final int n : fanout) {
- NB.encodeInt32(tmp, 0, n);
- out.write(tmp, 0, 4);
- }
- }
-
- /**
- * Output the standard two-checksum index footer.
- * <p>
- * The standard footer contains two checksums (20 byte SHA-1 values):
- * <ol>
- * <li>Pack data checksum - taken from the last 20 bytes of the pack file.</li>
- * <li>Index data checksum - checksum of all index bytes written, including
- * the pack data checksum above.</li>
- * </ol>
- *
- * @throws IOException
- * an error occurred while writing to the output stream.
- */
- protected void writeChecksumFooter() throws IOException {
- out.write(packChecksum);
- out.on(false);
- out.write(out.getMessageDigest().digest());
- }
- }
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