pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / src / java / org / apache / lucene / util / RecyclingByteBlockAllocator.java

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/util/RecyclingByteBlockAllocator.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/util/RecyclingByteBlockAllocator.java
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+++ b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/util/RecyclingByteBlockAllocator.java
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+package org.apache.lucene.util;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+import org.apache.lucene.util.ByteBlockPool.Allocator;
+
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * A {@link ByteBlockPool.Allocator} implementation that recycles unused byte
+ * blocks in a buffer and reuses them in subsequent calls to
+ * {@link #getByteBlock()}.
+ * 
+ * @lucene.internal
+ */
+public final class RecyclingByteBlockAllocator extends ByteBlockPool.Allocator {
+  private byte[][] freeByteBlocks;
+  private final int maxBufferedBlocks;
+  private int freeBlocks = 0;
+  private final AtomicLong bytesUsed;
+  public static final int DEFAULT_BUFFERED_BLOCKS = 64;
+
+  /**
+   * Creates a new {@link RecyclingByteBlockAllocator}
+   * 
+   * @param blockSize
+   *          the block size in bytes
+   * @param maxBufferedBlocks
+   *          maximum number of buffered byte block
+   * @param bytesUsed
+   *          {@link AtomicLong} reference counting internally allocated bytes
+   * 
+   * @see DummyConcurrentLock
+   */
+  public RecyclingByteBlockAllocator(int blockSize, int maxBufferedBlocks,
+      AtomicLong bytesUsed) {
+    super(blockSize);
+    freeByteBlocks = new byte[Math.min(10, maxBufferedBlocks)][];
+    this.maxBufferedBlocks = maxBufferedBlocks;
+    this.bytesUsed = bytesUsed;
+  }
+
+  /**
+   * Creates a new {@link RecyclingByteBlockAllocator} with a
+   * {@link DummyConcurrentLock} instance.
+   * 
+   * @param blockSize
+   *          the block size in bytes
+   * @param maxBufferedBlocks
+   *          maximum number of buffered byte block
+   */
+  public RecyclingByteBlockAllocator(int blockSize, int maxBufferedBlocks) {
+    this(blockSize, maxBufferedBlocks, new AtomicLong());
+  }
+
+  /**
+   * Creates a new {@link RecyclingByteBlockAllocator} with a block size of
+   * {@link ByteBlockPool#BYTE_BLOCK_SIZE}, upper buffered docs limit of
+   * {@link #DEFAULT_BUFFERED_BLOCKS} ({@value #DEFAULT_BUFFERED_BLOCKS}) and a
+   * {@link DummyConcurrentLock} instance.
+   * 
+   */
+  public RecyclingByteBlockAllocator() {
+    this(ByteBlockPool.BYTE_BLOCK_SIZE, 64, new AtomicLong());
+  }
+
+  @Override
+  public synchronized byte[] getByteBlock() {
+    if (freeBlocks == 0) {
+      bytesUsed.addAndGet(blockSize);
+      return new byte[blockSize];
+    }
+    final byte[] b = freeByteBlocks[--freeBlocks];
+    freeByteBlocks[freeBlocks] = null;
+    return b;
+  }
+
+  @Override
+  public synchronized void recycleByteBlocks(byte[][] blocks, int start, int end) {
+    final int numBlocks = Math.min(maxBufferedBlocks - freeBlocks, end - start);
+    final int size = freeBlocks + numBlocks;
+    if (size >= freeByteBlocks.length) {
+      final byte[][] newBlocks = new byte[ArrayUtil.oversize(size,
+          RamUsageEstimator.NUM_BYTES_OBJECT_REF)][];
+      System.arraycopy(freeByteBlocks, 0, newBlocks, 0, freeBlocks);
+      freeByteBlocks = newBlocks;
+    }
+    final int stop = start + numBlocks;
+    for (int i = start; i < stop; i++) {
+      freeByteBlocks[freeBlocks++] = blocks[i];
+      blocks[i] = null;
+    }
+    for (int i = stop; i < end; i++) {
+      blocks[i] = null;
+    }
+    bytesUsed.addAndGet(-(end - stop) * blockSize);
+    assert bytesUsed.get() >= 0;
+  }
+
+  /**
+   * @return the number of currently buffered blocks
+   */
+  public synchronized int numBufferedBlocks() {
+    return freeBlocks;
+  }
+
+  /**
+   * @return the number of bytes currently allocated by this {@link Allocator}
+   */
+  public long bytesUsed() {
+    return bytesUsed.get();
+  }
+
+  /**
+   * @return the maximum number of buffered byte blocks
+   */
+  public int maxBufferedBlocks() {
+    return maxBufferedBlocks;
+  }
+
+  /**
+   * Removes the given number of byte blocks from the buffer if possible.
+   * 
+   * @param num
+   *          the number of byte blocks to remove
+   * @return the number of actually removed buffers
+   */
+  public synchronized int freeBlocks(int num) {
+    assert num >= 0;
+    final int stop;
+    final int count;
+    if (num > freeBlocks) {
+      stop = 0;
+      count = freeBlocks;
+    } else {
+      stop = freeBlocks - num;
+      count = num;
+    }
+    while (freeBlocks > stop) {
+      freeByteBlocks[--freeBlocks] = null;
+    }
+    bytesUsed.addAndGet(-count*blockSize);
+    assert bytesUsed.get() >= 0;
+    return count;
+  }
+}
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