1 files changed, 264 insertions, 0 deletions
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/WindowCache.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/WindowCache.java
new file mode 100644
index 0000000000..9c21342637
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/WindowCache.java
@@ -0,0 +1,264 @@
+/*
+ * Copyright (C) 2008-2009, Google Inc.
+ * 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.IOException;
+import java.lang.ref.ReferenceQueue;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+
+/**
+ * Caches slices of a {@link PackFile} in memory for faster read access.
+ * <p>
+ * The WindowCache serves as a Java based "buffer cache", loading segments of a
+ * PackFile into the JVM heap prior to use. As JGit often wants to do reads of
+ * only tiny slices of a file, the WindowCache tries to smooth out these tiny
+ * reads into larger block-sized IO operations.
+ */
+public class WindowCache extends OffsetCache<ByteWindow, WindowCache.WindowRef> {
+	private static final int bits(int newSize) {
+		if (newSize < 4096)
+			throw new IllegalArgumentException("Invalid window size");
+		if (Integer.bitCount(newSize) != 1)
+			throw new IllegalArgumentException("Window size must be power of 2");
+		return Integer.numberOfTrailingZeros(newSize);
+	}
+
+	private static volatile WindowCache cache;
+
+	static {
+		reconfigure(new WindowCacheConfig());
+	}
+
+	/**
+	 * Modify the configuration of the window cache.
+	 * <p>
+	 * The new configuration is applied immediately. If the new limits are
+	 * smaller than what what is currently cached, older entries will be purged
+	 * as soon as possible to allow the cache to meet the new limit.
+	 * 
+	 * @param packedGitLimit
+	 *            maximum number of bytes to hold within this instance.
+	 * @param packedGitWindowSize
+	 *            number of bytes per window within the cache.
+	 * @param packedGitMMAP
+	 *            true to enable use of mmap when creating windows.
+	 * @param deltaBaseCacheLimit
+	 *            number of bytes to hold in the delta base cache.
+	 * @deprecated Use {@link WindowCacheConfig} instead.
+	 */
+	public static void reconfigure(final int packedGitLimit,
+			final int packedGitWindowSize, final boolean packedGitMMAP,
+			final int deltaBaseCacheLimit) {
+		final WindowCacheConfig c = new WindowCacheConfig();
+		c.setPackedGitLimit(packedGitLimit);
+		c.setPackedGitWindowSize(packedGitWindowSize);
+		c.setPackedGitMMAP(packedGitMMAP);
+		c.setDeltaBaseCacheLimit(deltaBaseCacheLimit);
+		reconfigure(c);
+	}
+
+	/**
+	 * Modify the configuration of the window cache.
+	 * <p>
+	 * The new configuration is applied immediately. If the new limits are
+	 * smaller than what what is currently cached, older entries will be purged
+	 * as soon as possible to allow the cache to meet the new limit.
+	 *
+	 * @param cfg
+	 *            the new window cache configuration.
+	 * @throws IllegalArgumentException
+	 *             the cache configuration contains one or more invalid
+	 *             settings, usually too low of a limit.
+	 */
+	public static void reconfigure(final WindowCacheConfig cfg) {
+		final WindowCache nc = new WindowCache(cfg);
+		final WindowCache oc = cache;
+		if (oc != null)
+			oc.removeAll();
+		cache = nc;
+		UnpackedObjectCache.reconfigure(cfg);
+	}
+
+	static WindowCache getInstance() {
+		return cache;
+	}
+
+	static final ByteWindow get(final PackFile pack, final long offset)
+			throws IOException {
+		final WindowCache c = cache;
+		final ByteWindow r = c.getOrLoad(pack, c.toStart(offset));
+		if (c != cache) {
+			// The cache was reconfigured while we were using the old one
+			// to load this window. The window is still valid, but our
+			// cache may think its still live. Ensure the window is removed
+			// from the old cache so resources can be released.
+			//
+			c.removeAll();
+		}
+		return r;
+	}
+
+	static final void purge(final PackFile pack) {
+		cache.removeAll(pack);
+	}
+
+	private final int maxFiles;
+
+	private final long maxBytes;
+
+	private final boolean mmap;
+
+	private final int windowSizeShift;
+
+	private final int windowSize;
+
+	private final AtomicInteger openFiles;
+
+	private final AtomicLong openBytes;
+
+	private WindowCache(final WindowCacheConfig cfg) {
+		super(tableSize(cfg), lockCount(cfg));
+		maxFiles = cfg.getPackedGitOpenFiles();
+		maxBytes = cfg.getPackedGitLimit();
+		mmap = cfg.isPackedGitMMAP();
+		windowSizeShift = bits(cfg.getPackedGitWindowSize());
+		windowSize = 1 << windowSizeShift;
+
+		openFiles = new AtomicInteger();
+		openBytes = new AtomicLong();
+
+		if (maxFiles < 1)
+			throw new IllegalArgumentException("Open files must be >= 1");
+		if (maxBytes < windowSize)
+			throw new IllegalArgumentException("Window size must be < limit");
+	}
+
+	int getOpenFiles() {
+		return openFiles.get();
+	}
+
+	long getOpenBytes() {
+		return openBytes.get();
+	}
+
+	@Override
+	protected int hash(final int packHash, final long off) {
+		return packHash + (int) (off >>> windowSizeShift);
+	}
+
+	@Override
+	protected ByteWindow load(final PackFile pack, final long offset)
+			throws IOException {
+		if (pack.beginWindowCache())
+			openFiles.incrementAndGet();
+		try {
+			if (mmap)
+				return pack.mmap(offset, windowSize);
+			return pack.read(offset, windowSize);
+		} catch (IOException e) {
+			close(pack);
+			throw e;
+		} catch (RuntimeException e) {
+			close(pack);
+			throw e;
+		} catch (Error e) {
+			close(pack);
+			throw e;
+		}
+	}
+
+	@Override
+	protected WindowRef createRef(final PackFile p, final long o,
+			final ByteWindow v) {
+		final WindowRef ref = new WindowRef(p, o, v, queue);
+		openBytes.addAndGet(ref.size);
+		return ref;
+	}
+
+	@Override
+	protected void clear(final WindowRef ref) {
+		openBytes.addAndGet(-ref.size);
+		close(ref.pack);
+	}
+
+	private void close(final PackFile pack) {
+		if (pack.endWindowCache())
+			openFiles.decrementAndGet();
+	}
+
+	@Override
+	protected boolean isFull() {
+		return maxFiles < openFiles.get() || maxBytes < openBytes.get();
+	}
+
+	private long toStart(final long offset) {
+		return (offset >>> windowSizeShift) << windowSizeShift;
+	}
+
+	private static int tableSize(final WindowCacheConfig cfg) {
+		final int wsz = cfg.getPackedGitWindowSize();
+		final long limit = cfg.getPackedGitLimit();
+		if (wsz <= 0)
+			throw new IllegalArgumentException("Invalid window size");
+		if (limit < wsz)
+			throw new IllegalArgumentException("Window size must be < limit");
+		return (int) Math.min(5 * (limit / wsz) / 2, 2000000000);
+	}
+
+	private static int lockCount(final WindowCacheConfig cfg) {
+		return Math.max(cfg.getPackedGitOpenFiles(), 32);
+	}
+
+	static class WindowRef extends OffsetCache.Ref<ByteWindow> {
+		final int size;
+
+		WindowRef(final PackFile pack, final long position, final ByteWindow v,
+				final ReferenceQueue<ByteWindow> queue) {
+			super(pack, position, v, queue);
+			size = v.size();
+		}
+	}
+}