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- /*
- * Copyright (C) 2010, 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
- *
- * 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.storage.pack;
-
- import java.io.EOFException;
- import java.io.IOException;
- import java.io.OutputStream;
- import java.util.zip.Deflater;
-
- import org.eclipse.jgit.errors.IncorrectObjectTypeException;
- import org.eclipse.jgit.errors.LargeObjectException;
- import org.eclipse.jgit.errors.MissingObjectException;
- import org.eclipse.jgit.lib.ObjectReader;
- import org.eclipse.jgit.lib.ProgressMonitor;
- import org.eclipse.jgit.util.TemporaryBuffer;
-
- class DeltaWindow {
- private static final int NEXT_RES = 0;
-
- private static final int NEXT_SRC = 1;
-
- private final PackConfig config;
-
- private final DeltaCache deltaCache;
-
- private final ObjectReader reader;
-
- private final DeltaWindowEntry[] window;
-
- /** Maximum number of bytes to admit to the window at once. */
- private final long maxMemory;
-
- /** Maximum depth we should create for any delta chain. */
- private final int maxDepth;
-
- /** Amount of memory we have loaded right now. */
- private long loaded;
-
- // The object we are currently considering needs a lot of state:
-
- /** Position of {@link #res} within {@link #window} array. */
- private int resSlot;
-
- /**
- * Maximum delta chain depth the current object can have.
- * <p>
- * This can be smaller than {@link #maxDepth}.
- */
- private int resMaxDepth;
-
- /** Window entry of the object we are currently considering. */
- private DeltaWindowEntry res;
-
- /** If we have a delta for {@link #res}, this is the shortest found yet. */
- private TemporaryBuffer.Heap bestDelta;
-
- /** If we have {@link #bestDelta}, the window position it was created by. */
- private int bestSlot;
-
- /** Used to compress cached deltas. */
- private Deflater deflater;
-
- DeltaWindow(PackConfig pc, DeltaCache dc, ObjectReader or) {
- config = pc;
- deltaCache = dc;
- reader = or;
-
- // C Git increases the window size supplied by the user by 1.
- // We don't know why it does this, but if the user asks for
- // window=10, it actually processes with window=11. Because
- // the window size has the largest direct impact on the final
- // pack file size, we match this odd behavior here to give us
- // a better chance of producing a similar sized pack as C Git.
- //
- // We would prefer to directly honor the user's request since
- // PackWriter has a minimum of 2 for the window size, but then
- // users might complain that JGit is creating a bigger pack file.
- //
- window = new DeltaWindowEntry[config.getDeltaSearchWindowSize() + 1];
- for (int i = 0; i < window.length; i++)
- window[i] = new DeltaWindowEntry();
-
- maxMemory = config.getDeltaSearchMemoryLimit();
- maxDepth = config.getMaxDeltaDepth();
- }
-
- void search(ProgressMonitor monitor, ObjectToPack[] toSearch, int off,
- int cnt) throws IOException {
- try {
- for (int end = off + cnt; off < end; off++) {
- res = window[resSlot];
- if (0 < maxMemory) {
- clear(res);
- int tail = next(resSlot);
- final long need = estimateSize(toSearch[off]);
- while (maxMemory < loaded + need && tail != resSlot) {
- clear(window[tail]);
- tail = next(tail);
- }
- }
- res.set(toSearch[off]);
-
- if (res.object.isEdge() || res.object.doNotAttemptDelta()) {
- // We don't actually want to make a delta for
- // them, just need to push them into the window
- // so they can be read by other objects.
- //
- keepInWindow();
- } else {
- // Search for a delta for the current window slot.
- //
- monitor.update(1);
- search();
- }
- }
- } finally {
- if (deflater != null)
- deflater.end();
- }
- }
-
- private static long estimateSize(ObjectToPack ent) {
- return DeltaIndex.estimateIndexSize(ent.getWeight());
- }
-
- private void clear(DeltaWindowEntry ent) {
- if (ent.index != null)
- loaded -= ent.index.getIndexSize();
- else if (res.buffer != null)
- loaded -= ent.buffer.length;
- ent.set(null);
- }
-
- private void search() throws IOException {
- // TODO(spearce) If the object is used as a base for other
- // objects in this pack we should limit the depth we create
- // for ourselves to be the remainder of our longest dependent
- // chain and the configured maximum depth. This can happen
- // when the dependents are being reused out a pack, but we
- // cannot be because we are near the edge of a thin pack.
- //
- resMaxDepth = maxDepth;
-
- // Loop through the window backwards, considering every entry.
- // This lets us look at the bigger objects that came before.
- //
- for (int srcSlot = prior(resSlot); srcSlot != resSlot; srcSlot = prior(srcSlot)) {
- DeltaWindowEntry src = window[srcSlot];
- if (src.empty())
- break;
- if (delta(src, srcSlot) == NEXT_RES) {
- bestDelta = null;
- return;
- }
- }
-
- // We couldn't find a suitable delta for this object, but it may
- // still be able to act as a base for another one.
- //
- if (bestDelta == null) {
- keepInWindow();
- return;
- }
-
- // Select this best matching delta as the base for the object.
- //
- ObjectToPack srcObj = window[bestSlot].object;
- ObjectToPack resObj = res.object;
- if (srcObj.isEdge()) {
- // The source (the delta base) is an edge object outside of the
- // pack. Its part of the common base set that the peer already
- // has on hand, so we don't want to send it. We have to store
- // an ObjectId and *NOT* an ObjectToPack for the base to ensure
- // the base isn't included in the outgoing pack file.
- //
- resObj.setDeltaBase(srcObj.copy());
- } else {
- // The base is part of the pack we are sending, so it should be
- // a direct pointer to the base.
- //
- resObj.setDeltaBase(srcObj);
- }
- resObj.setDeltaDepth(srcObj.getDeltaDepth() + 1);
- resObj.clearReuseAsIs();
- cacheDelta(srcObj, resObj);
-
- // Discard the cached best result, otherwise it leaks.
- //
- bestDelta = null;
-
- // If this should be the end of a chain, don't keep
- // it in the window. Just move on to the next object.
- //
- if (resObj.getDeltaDepth() == maxDepth)
- return;
-
- shuffleBaseUpInPriority();
- keepInWindow();
- }
-
- private int delta(final DeltaWindowEntry src, final int srcSlot)
- throws IOException {
- // Objects must use only the same type as their delta base.
- // If we are looking at something where that isn't true we
- // have exhausted everything of the correct type and should
- // move on to the next thing to examine.
- //
- if (src.type() != res.type()) {
- keepInWindow();
- return NEXT_RES;
- }
-
- // Only consider a source with a short enough delta chain.
- if (src.depth() > resMaxDepth)
- return NEXT_SRC;
-
- // Estimate a reasonable upper limit on delta size.
- int msz = deltaSizeLimit(res, resMaxDepth, src);
- if (msz <= 8)
- return NEXT_SRC;
-
- // If we have to insert a lot to make this work, find another.
- if (res.size() - src.size() > msz)
- return NEXT_SRC;
-
- // If the sizes are radically different, this is a bad pairing.
- if (res.size() < src.size() / 16)
- return NEXT_SRC;
-
- DeltaIndex srcIndex;
- try {
- srcIndex = index(src);
- } catch (LargeObjectException tooBig) {
- // If the source is too big to work on, skip it.
- dropFromWindow(srcSlot);
- return NEXT_SRC;
- } catch (IOException notAvailable) {
- if (src.object.isEdge()) {
- // This is an edge that is suddenly not available.
- dropFromWindow(srcSlot);
- return NEXT_SRC;
- } else {
- throw notAvailable;
- }
- }
-
- byte[] resBuf;
- try {
- resBuf = buffer(res);
- } catch (LargeObjectException tooBig) {
- // If its too big, move on to another item.
- return NEXT_RES;
- }
-
- // If we already have a delta for the current object, abort
- // encoding early if this new pairing produces a larger delta.
- if (bestDelta != null && bestDelta.length() < msz)
- msz = (int) bestDelta.length();
-
- TemporaryBuffer.Heap delta = new TemporaryBuffer.Heap(msz);
- try {
- if (!srcIndex.encode(delta, resBuf, msz))
- return NEXT_SRC;
- } catch (IOException deltaTooBig) {
- // This only happens when the heap overflows our limit.
- return NEXT_SRC;
- }
-
- if (isBetterDelta(src, delta)) {
- bestDelta = delta;
- bestSlot = srcSlot;
- }
-
- return NEXT_SRC;
- }
-
- private void cacheDelta(ObjectToPack srcObj, ObjectToPack resObj) {
- if (Integer.MAX_VALUE < bestDelta.length())
- return;
-
- int rawsz = (int) bestDelta.length();
- if (deltaCache.canCache(rawsz, srcObj, resObj)) {
- try {
- byte[] zbuf = new byte[deflateBound(rawsz)];
-
- ZipStream zs = new ZipStream(deflater(), zbuf);
- bestDelta.writeTo(zs, null);
- bestDelta = null;
- int len = zs.finish();
-
- resObj.setCachedDelta(deltaCache.cache(zbuf, len, rawsz));
- resObj.setCachedSize(rawsz);
- } catch (IOException err) {
- deltaCache.credit(rawsz);
- } catch (OutOfMemoryError err) {
- deltaCache.credit(rawsz);
- }
- }
- }
-
- private static int deflateBound(int insz) {
- return insz + ((insz + 7) >> 3) + ((insz + 63) >> 6) + 11;
- }
-
- private void shuffleBaseUpInPriority() {
- // Shuffle the entire window so that the best match we just used
- // is at our current index, and our current object is at the index
- // before it. Slide any entries in between to make space.
- //
- window[resSlot] = window[bestSlot];
-
- DeltaWindowEntry next = res;
- int slot = prior(resSlot);
- for (; slot != bestSlot; slot = prior(slot)) {
- DeltaWindowEntry e = window[slot];
- window[slot] = next;
- next = e;
- }
- window[slot] = next;
- }
-
- private void keepInWindow() {
- resSlot = next(resSlot);
- }
-
- private int next(int slot) {
- if (++slot == window.length)
- return 0;
- return slot;
- }
-
- private int prior(int slot) {
- if (slot == 0)
- return window.length - 1;
- return slot - 1;
- }
-
- private void dropFromWindow(@SuppressWarnings("unused") int srcSlot) {
- // We should drop the current source entry from the window,
- // it is somehow invalid for us to work with.
- }
-
- private boolean isBetterDelta(DeltaWindowEntry src,
- TemporaryBuffer.Heap resDelta) {
- if (bestDelta == null)
- return true;
-
- // If both delta sequences are the same length, use the one
- // that has a shorter delta chain since it would be faster
- // to access during reads.
- //
- if (resDelta.length() == bestDelta.length())
- return src.depth() < window[bestSlot].depth();
-
- return resDelta.length() < bestDelta.length();
- }
-
- private static int deltaSizeLimit(DeltaWindowEntry res, int maxDepth,
- DeltaWindowEntry src) {
- // Ideally the delta is at least 50% of the original size,
- // but we also want to account for delta header overhead in
- // the pack file (to point to the delta base) so subtract off
- // some of those header bytes from the limit.
- //
- final int limit = res.size() / 2 - 20;
-
- // Distribute the delta limit over the entire chain length.
- // This is weighted such that deeper items in the chain must
- // be even smaller than if they were earlier in the chain, as
- // they cost significantly more to unpack due to the increased
- // number of recursive unpack calls.
- //
- final int remainingDepth = maxDepth - src.depth();
- return (limit * remainingDepth) / maxDepth;
- }
-
- private DeltaIndex index(DeltaWindowEntry ent)
- throws MissingObjectException, IncorrectObjectTypeException,
- IOException, LargeObjectException {
- DeltaIndex idx = ent.index;
- if (idx == null) {
- try {
- idx = new DeltaIndex(buffer(ent));
- } catch (OutOfMemoryError noMemory) {
- LargeObjectException.OutOfMemory e;
- e = new LargeObjectException.OutOfMemory(noMemory);
- e.setObjectId(ent.object);
- throw e;
- }
- if (0 < maxMemory)
- loaded += idx.getIndexSize() - idx.getSourceSize();
- ent.index = idx;
- }
- return idx;
- }
-
- private byte[] buffer(DeltaWindowEntry ent) throws MissingObjectException,
- IncorrectObjectTypeException, IOException, LargeObjectException {
- byte[] buf = ent.buffer;
- if (buf == null) {
- buf = PackWriter.buffer(config, reader, ent.object);
- if (0 < maxMemory)
- loaded += buf.length;
- ent.buffer = buf;
- }
- return buf;
- }
-
- private Deflater deflater() {
- if (deflater == null)
- deflater = new Deflater(config.getCompressionLevel());
- else
- deflater.reset();
- return deflater;
- }
-
- static final class ZipStream extends OutputStream {
- private final Deflater deflater;
-
- private final byte[] zbuf;
-
- private int outPtr;
-
- ZipStream(Deflater deflater, byte[] zbuf) {
- this.deflater = deflater;
- this.zbuf = zbuf;
- }
-
- int finish() throws IOException {
- deflater.finish();
- for (;;) {
- if (outPtr == zbuf.length)
- throw new EOFException();
-
- int n = deflater.deflate(zbuf, outPtr, zbuf.length - outPtr);
- if (n == 0) {
- if (deflater.finished())
- return outPtr;
- throw new IOException();
- }
- outPtr += n;
- }
- }
-
- @Override
- public void write(byte[] b, int off, int len) throws IOException {
- deflater.setInput(b, off, len);
- for (;;) {
- if (outPtr == zbuf.length)
- throw new EOFException();
-
- int n = deflater.deflate(zbuf, outPtr, zbuf.length - outPtr);
- if (n == 0) {
- if (deflater.needsInput())
- break;
- throw new IOException();
- }
- outPtr += n;
- }
- }
-
- @Override
- public void write(int b) throws IOException {
- throw new UnsupportedOperationException();
- }
- }
- }
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