org.apache.lucene.store.IndexInput Maven / Gradle / Ivy
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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.Closeable;
import java.io.IOException;
/** Abstract base class for input from a file in a {@link Directory}. A
* random-access input stream. Used for all Lucene index input operations.
*
* {@code IndexInput} may only be used from one thread, because it is not
* thread safe (it keeps internal state like file position). To allow
* multithreaded use, every {@code IndexInput} instance must be cloned before
* used in another thread. Subclasses must therefore implement {@link #clone()},
* returning a new {@code IndexInput} which operates on the same underlying
* resource, but positioned independently. Lucene never closes cloned
* {@code IndexInput}s, it will only do this on the original one.
* The original instance must take care that cloned instances throw
* {@link AlreadyClosedException} when the original one is closed.
* @see Directory
*/
public abstract class IndexInput extends DataInput implements Cloneable,Closeable {
private final String resourceDescription;
/** resourceDescription should be a non-null, opaque string
* describing this resource; it's returned from
* {@link #toString}. */
protected IndexInput(String resourceDescription) {
if (resourceDescription == null) {
throw new IllegalArgumentException("resourceDescription must not be null");
}
this.resourceDescription = resourceDescription;
}
/** Closes the stream to further operations. */
@Override
public abstract void close() throws IOException;
/** Returns the current position in this file, where the next read will
* occur.
* @see #seek(long)
*/
public abstract long getFilePointer();
/** Sets current position in this file, where the next read will occur.
* @see #getFilePointer()
*/
public abstract void seek(long pos) throws IOException;
/** The number of bytes in the file. */
public abstract long length();
@Override
public String toString() {
return resourceDescription;
}
/** {@inheritDoc}
*
Warning: Lucene never closes cloned
* {@code IndexInput}s, it will only do this on the original one.
* The original instance must take care that cloned instances throw
* {@link AlreadyClosedException} when the original one is closed.
*/
@Override
public IndexInput clone() {
return (IndexInput) super.clone();
}
}