pylucene 3.5.0-3

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

diff --git a/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/UnsafeByteArrayInputStream.java b/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/UnsafeByteArrayInputStream.java
new file mode 100644 (file)
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+++ b/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/UnsafeByteArrayInputStream.java
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+package org.apache.lucene.util;
+
+import java.io.ByteArrayInputStream;
+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.
+ */
+
+/**
+ * This class, much like {@link ByteArrayInputStream} uses a given buffer as a
+ * source of an InputStream. Unlike ByteArrayInputStream, this class does not
+ * "waste" memory by creating a local copy of the given buffer, but rather uses
+ * the given buffer as is. Hence the name Unsafe. While using this class one
+ * should remember that the byte[] buffer memory is shared and might be changed
+ * from outside.
+ * 
+ * For reuse-ability, a call for {@link #reInit(byte[])} can be called, and
+ * initialize the stream with a new buffer.
+ * 
+ * @lucene.experimental
+ */
+public class UnsafeByteArrayInputStream extends InputStream {
+
+  private byte[] buffer;
+  private int markIndex;
+  private int upperLimit;
+  private int index;
+
+  /**
+   * Creates a new instance by not using any byte[] up front. If you use this
+   * constructor, you MUST call either of the {@link #reInit(byte[]) reInit}
+   * methods before you consume any byte from this instance.<br>
+   * This constructor is for convenience purposes only, so that if one does not
+   * have the byte[] at the moment of creation, one is not forced to pass a
+   * <code>new byte[0]</code> or something. Obviously in that case, one will
+   * call either {@link #reInit(byte[]) reInit} methods before using the class.
+   */
+  public UnsafeByteArrayInputStream() {
+    markIndex = upperLimit = index = 0;
+  }
+
+  /**
+   * Creates an UnsafeByteArrayInputStream which uses a given byte array as
+   * the source of the stream. Default range is [0 , buffer.length)
+   * 
+   * @param buffer
+   *            byte array used as the source of this stream
+   */
+  public UnsafeByteArrayInputStream(byte[] buffer) {
+    reInit(buffer, 0, buffer.length);
+  }
+
+  /**
+   * Creates an UnsafeByteArrayInputStream which uses a given byte array as
+   * the source of the stream, at the specific range: [startPos, endPos)
+   * 
+   * @param buffer
+   *            byte array used as the source of this stream
+   * @param startPos
+   *            first index (inclusive) to the data lying in the given buffer
+   * @param endPos
+   *            an index (exclusive) where the data ends. data @
+   *            buffer[endPos] will never be read
+   */
+  public UnsafeByteArrayInputStream(byte[] buffer, int startPos, int endPos) {
+    reInit(buffer, startPos, endPos);
+  }
+
+  @Override
+  public void mark(int readlimit) {
+    markIndex = index;
+  }
+
+  @Override
+  public boolean markSupported() {
+    return true;
+  }
+
+  /**
+   * Initialize the stream with a given buffer, using the default limits of
+   * [0, buffer.length)
+   * 
+   * @param buffer
+   *            byte array used as the source of this stream
+   */
+  public void reInit(byte[] buffer) {
+    reInit(buffer, 0, buffer.length);
+  }
+
+  /**
+   * Initialize the stream with a given byte array as the source of the
+   * stream, at the specific range: [startPos, endPos)
+   * 
+   * @param buffer
+   *            byte array used as the source of this stream
+   * @param startPos
+   *            first index (inclusive) to the data lying in the given buffer
+   * @param endPos
+   *            an index (exclusive) where the data ends. data @
+   *            buffer[endPos] will never be read
+   */
+  public void reInit(byte[] buffer, int startPos, int endPos) {
+    this.buffer = buffer;
+    markIndex = startPos;
+    upperLimit = endPos;
+    index = markIndex;
+  }
+
+  @Override
+  public int available() throws IOException {
+    return upperLimit - index;
+  }
+
+  /**
+   * Read a byte. Data returned as an integer [0,255] If end of stream
+   * reached, returns -1
+   */
+  @Override
+  public int read() throws IOException {
+    return index < upperLimit ? buffer[index++] & 0xff : -1;
+  }
+
+  /**
+   * Resets the stream back to its original state. Basically - moving the
+   * index back to start position.
+   */
+  @Override
+  public void reset() throws IOException {
+    index = markIndex;
+  }
+
+}