X-Git-Url: https://git.mdrn.pl/pylucene.git/blobdiff_plain/a2e61f0c04805cfcb8706176758d1283c7e3a55c..aaeed5504b982cf3545252ab528713250aa33eed:/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/index/ByteBlockPool.java

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/index/ByteBlockPool.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/index/ByteBlockPool.java
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+package org.apache.lucene.index;
+
+/**
+ * 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.
+ */
+
+/* Class that Posting and PostingVector use to write byte
+ * streams into shared fixed-size byte[] arrays.  The idea
+ * is to allocate slices of increasing lengths For
+ * example, the first slice is 5 bytes, the next slice is
+ * 14, etc.  We start by writing our bytes into the first
+ * 5 bytes.  When we hit the end of the slice, we allocate
+ * the next slice and then write the address of the new
+ * slice into the last 4 bytes of the previous slice (the
+ * "forwarding address").
+ *
+ * Each slice is filled with 0's initially, and we mark
+ * the end with a non-zero byte.  This way the methods
+ * that are writing into the slice don't need to record
+ * its length and instead allocate a new slice once they
+ * hit a non-zero byte. */
+
+import java.util.Arrays;
+import java.util.List;
+import static org.apache.lucene.util.RamUsageEstimator.NUM_BYTES_OBJECT_REF;
+import org.apache.lucene.util.ArrayUtil;
+
+
+final class ByteBlockPool {
+
+  abstract static class Allocator {
+    abstract void recycleByteBlocks(byte[][] blocks, int start, int end);
+    abstract void recycleByteBlocks(List<byte[]> blocks);
+    abstract byte[] getByteBlock();
+  }
+
+  public byte[][] buffers = new byte[10][];
+
+  int bufferUpto = -1;                        // Which buffer we are upto
+  public int byteUpto = DocumentsWriter.BYTE_BLOCK_SIZE;             // Where we are in head buffer
+
+  public byte[] buffer;                              // Current head buffer
+  public int byteOffset = -DocumentsWriter.BYTE_BLOCK_SIZE;          // Current head offset
+
+  private final Allocator allocator;
+
+  public ByteBlockPool(Allocator allocator) {
+    this.allocator = allocator;
+  }
+
+  public void reset() {
+    if (bufferUpto != -1) {
+      // We allocated at least one buffer
+
+      for(int i=0;i<bufferUpto;i++)
+        // Fully zero fill buffers that we fully used
+        Arrays.fill(buffers[i], (byte) 0);
+
+      // Partial zero fill the final buffer
+      Arrays.fill(buffers[bufferUpto], 0, byteUpto, (byte) 0);
+          
+      if (bufferUpto > 0)
+        // Recycle all but the first buffer
+        allocator.recycleByteBlocks(buffers, 1, 1+bufferUpto);
+
+      // Re-use the first buffer
+      bufferUpto = 0;
+      byteUpto = 0;
+      byteOffset = 0;
+      buffer = buffers[0];
+    }
+  }
+
+  public void nextBuffer() {
+    if (1+bufferUpto == buffers.length) {
+      byte[][] newBuffers = new byte[ArrayUtil.oversize(buffers.length+1,
+                                                        NUM_BYTES_OBJECT_REF)][];
+      System.arraycopy(buffers, 0, newBuffers, 0, buffers.length);
+      buffers = newBuffers;
+    }
+    buffer = buffers[1+bufferUpto] = allocator.getByteBlock();
+    bufferUpto++;
+
+    byteUpto = 0;
+    byteOffset += DocumentsWriter.BYTE_BLOCK_SIZE;
+  }
+
+  public int newSlice(final int size) {
+    if (byteUpto > DocumentsWriter.BYTE_BLOCK_SIZE-size)
+      nextBuffer();
+    final int upto = byteUpto;
+    byteUpto += size;
+    buffer[byteUpto-1] = 16;
+    return upto;
+  }
+
+  // Size of each slice.  These arrays should be at most 16
+  // elements (index is encoded with 4 bits).  First array
+  // is just a compact way to encode X+1 with a max.  Second
+  // array is the length of each slice, ie first slice is 5
+  // bytes, next slice is 14 bytes, etc.
+  final static int[] nextLevelArray = {1, 2, 3, 4, 5, 6, 7, 8, 9, 9};
+  final static int[] levelSizeArray = {5, 14, 20, 30, 40, 40, 80, 80, 120, 200};
+  final static int FIRST_LEVEL_SIZE = levelSizeArray[0];
+
+  public int allocSlice(final byte[] slice, final int upto) {
+
+    final int level = slice[upto] & 15;
+    final int newLevel = nextLevelArray[level];
+    final int newSize = levelSizeArray[newLevel];
+
+    // Maybe allocate another block
+    if (byteUpto > DocumentsWriter.BYTE_BLOCK_SIZE-newSize)
+      nextBuffer();
+
+    final int newUpto = byteUpto;
+    final int offset = newUpto + byteOffset;
+    byteUpto += newSize;
+
+    // Copy forward the past 3 bytes (which we are about
+    // to overwrite with the forwarding address):
+    buffer[newUpto] = slice[upto-3];
+    buffer[newUpto+1] = slice[upto-2];
+    buffer[newUpto+2] = slice[upto-1];
+
+    // Write forwarding address at end of last slice:
+    slice[upto-3] = (byte) (offset >>> 24);
+    slice[upto-2] = (byte) (offset >>> 16);
+    slice[upto-1] = (byte) (offset >>> 8);
+    slice[upto] = (byte) offset;
+        
+    // Write new level:
+    buffer[byteUpto-1] = (byte) (16|newLevel);
+
+    return newUpto+3;
+  }
+}
+