pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / src / java / org / apache / lucene / store / ChecksumIndexOutput.java

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/store/ChecksumIndexOutput.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/store/ChecksumIndexOutput.java
new file mode 100644 (file)
index 0000000..1805893
--- /dev/null
+++ b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/store/ChecksumIndexOutput.java
@@ -0,0 +1,102 @@
+package org.apache.lucene.store;
+
+/**
+ * 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.
+ */
+
+import java.io.IOException;
+import java.util.zip.CRC32;
+import java.util.zip.Checksum;
+
+/** Writes bytes through to a primary IndexOutput, computing
+ *  checksum.  Note that you cannot use seek().
+ *
+ * @lucene.internal
+ */
+public class ChecksumIndexOutput extends IndexOutput {
+  IndexOutput main;
+  Checksum digest;
+
+  public ChecksumIndexOutput(IndexOutput main) {
+    this.main = main;
+    digest = new CRC32();
+  }
+
+  @Override
+  public void writeByte(byte b) throws IOException {
+    digest.update(b);
+    main.writeByte(b);
+  }
+
+  @Override
+  public void writeBytes(byte[] b, int offset, int length) throws IOException {
+    digest.update(b, offset, length);
+    main.writeBytes(b, offset, length);
+  }
+
+  public long getChecksum() {
+    return digest.getValue();
+  }
+
+  @Override
+  public void flush() throws IOException {
+    main.flush();
+  }
+
+  @Override
+  public void close() throws IOException {
+    main.close();
+  }
+
+  @Override
+  public long getFilePointer() {
+    return main.getFilePointer();
+  }
+
+  @Override
+  public void seek(long pos) {
+    throw new RuntimeException("not allowed");    
+  }
+
+  /**
+   * Starts but does not complete the commit of this file (=
+   * writing of the final checksum at the end).  After this
+   * is called must call {@link #finishCommit} and the
+   * {@link #close} to complete the commit.
+   */
+  public void prepareCommit() throws IOException {
+    final long checksum = getChecksum();
+    // Intentionally write a mismatched checksum.  This is
+    // because we want to 1) test, as best we can, that we
+    // are able to write a long to the file, but 2) not
+    // actually "commit" the file yet.  This (prepare
+    // commit) is phase 1 of a two-phase commit.
+    final long pos = main.getFilePointer();
+    main.writeLong(checksum-1);
+    main.flush();
+    main.seek(pos);
+  }
+
+  /** See {@link #prepareCommit} */
+  public void finishCommit() throws IOException {
+    main.writeLong(getChecksum());
+  }
+
+  @Override
+  public long length() throws IOException {
+    return main.length();
+  }
+}