pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / contrib / facet / src / java / org / apache / lucene / util / encoding / EightFlagsIntDecoder.java

diff --git a/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/encoding/EightFlagsIntDecoder.java b/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/encoding/EightFlagsIntDecoder.java
new file mode 100644 (file)
index 0000000..5f8e22b
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+++ b/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/encoding/EightFlagsIntDecoder.java
@@ -0,0 +1,91 @@
+package org.apache.lucene.util.encoding;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * 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.
+ */
+
+/**
+ * Decodes data which was encoded by {@link EightFlagsIntEncoder}. Scans
+ * the <code>indicator</code>, one flag (1-bits) at a time, and decodes extra
+ * data using {@link VInt8IntDecoder}.
+ * 
+ * @see EightFlagsIntEncoder
+ * @lucene.experimental
+ */
+public class EightFlagsIntDecoder extends IntDecoder {
+
+  /**
+   * Holds all combinations of <i>indicator</i> for fast decoding (saves time
+   * on real-time bit manipulation)
+   */
+  private static final byte[][] decodeTable = new byte[256][8];
+
+  /** Generating all combinations of <i>indicator</i> into separate flags. */
+  static {
+    for (int i = 256; i != 0;) {
+      --i;
+      for (int j = 8; j != 0;) {
+        --j;
+        decodeTable[i][j] = (byte) ((i >>> j) & 0x1);
+      }
+    }
+  }
+
+  private final IntDecoder decoder = new VInt8IntDecoder();
+
+  /** The indicator for decoding a chunk of 8 integers. */
+  private int indicator;
+
+  /** Used as an ordinal of 0 - 7, as the decoder decodes chunks of 8 integers. */
+  private int ordinal = 0;
+
+  @Override
+  public long decode() throws IOException { 
+    // If we've decoded 8 integers, read the next indicator.
+    if ((ordinal & 0x7) == 0) {
+      indicator = in.read();
+      if (indicator < 0) {
+        return EOS;
+      }
+      ordinal = 0;
+    }
+
+    if (decodeTable[indicator][ordinal++] == 0) {
+      // decode the value from the stream.
+      long decode = decoder.decode();
+      return decode == EOS ? EOS : decode + 2;
+    }
+
+    return 1;
+  }
+
+  @Override
+  public void reInit(InputStream in) {
+    super.reInit(in);
+    decoder.reInit(in);
+    ordinal = 0;
+    indicator = 0;
+  }
+
+  @Override
+  public String toString() {
+    return "EightFlags (VInt8)";
+  }
+
+}