1 files changed, 134 insertions, 0 deletions
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/DeltaCache.java b/org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/DeltaCache.java
new file mode 100644
index 0000000000..b6a7436f16
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/DeltaCache.java
@@ -0,0 +1,134 @@
+/*
+ * 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.lang.ref.ReferenceQueue;
+import java.lang.ref.SoftReference;
+
+class DeltaCache {
+	private final long size;
+
+	private final int entryLimit;
+
+	private final ReferenceQueue<byte[]> queue;
+
+	private long used;
+
+	DeltaCache(PackWriter pw) {
+		size = pw.getDeltaCacheSize();
+		entryLimit = pw.getDeltaCacheLimit();
+		queue = new ReferenceQueue<byte[]>();
+	}
+
+	boolean canCache(int length, ObjectToPack src, ObjectToPack res) {
+		// If the cache would overflow, don't store.
+		//
+		if (0 < size && size < used + length) {
+			checkForGarbageCollectedObjects();
+			if (0 < size && size < used + length)
+				return false;
+		}
+
+		if (length < entryLimit) {
+			used += length;
+			return true;
+		}
+
+		// If the combined source files are multiple megabytes but the delta
+		// is on the order of a kilobyte or two, this was likely costly to
+		// construct. Cache it anyway, even though its over the limit.
+		//
+		if (length >> 10 < (src.getWeight() >> 20) + (res.getWeight() >> 21)) {
+			used += length;
+			return true;
+		}
+
+		return false;
+	}
+
+	void credit(int reservedSize) {
+		used -= reservedSize;
+	}
+
+	Ref cache(byte[] data, int actLen, int reservedSize) {
+		// The caller may have had to allocate more space than is
+		// required. If we are about to waste anything, shrink it.
+		//
+		data = resize(data, actLen);
+
+		// When we reserved space for this item we did it for the
+		// inflated size of the delta, but we were just given the
+		// compressed version. Adjust the cache cost to match.
+		//
+		if (reservedSize != data.length) {
+			used -= reservedSize;
+			used += data.length;
+		}
+		return new Ref(data, queue);
+	}
+
+	byte[] resize(byte[] data, int actLen) {
+		if (data.length != actLen) {
+			byte[] nbuf = new byte[actLen];
+			System.arraycopy(data, 0, nbuf, 0, actLen);
+			data = nbuf;
+		}
+		return data;
+	}
+
+	private void checkForGarbageCollectedObjects() {
+		Ref r;
+		while ((r = (Ref) queue.poll()) != null)
+			used -= r.cost;
+	}
+
+	static class Ref extends SoftReference<byte[]> {
+		final int cost;
+
+		Ref(byte[] array, ReferenceQueue<byte[]> queue) {
+			super(array, queue);
+			cost = array.length;
+		}
+	}
+}