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package org.apache.lucene.store.bytebuffer;
/**
* 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 org.apache.lucene.store.IndexInput;
import java.io.EOFException;
import java.io.IOException;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;
/**
*/
public class ByteBufferIndexInput extends IndexInput {
private final static ByteBuffer EMPTY_BUFFER = ByteBuffer.allocate(0).asReadOnlyBuffer();
private final ByteBufferFile file;
private final long length;
private ByteBuffer currentBuffer;
private int currentBufferIndex;
private long bufferStart;
private final int BUFFER_SIZE;
private volatile boolean closed = false;
public ByteBufferIndexInput(String name, ByteBufferFile file) throws IOException {
super("BBIndexInput(name=" + name + ")");
this.file = file;
this.file.incRef();
this.length = file.getLength();
this.BUFFER_SIZE = file.bufferSize;
// make sure that we switch to the
// first needed buffer lazily
currentBufferIndex = -1;
currentBuffer = EMPTY_BUFFER;
}
@Override
public void close() {
// we protected from double closing the index input since
// some tests do that...
if (closed) {
return;
}
closed = true;
file.decRef();
}
@Override
public long length() {
return length;
}
@Override
public short readShort() throws IOException {
try {
currentBuffer.mark();
return currentBuffer.getShort();
} catch (BufferUnderflowException e) {
currentBuffer.reset();
return super.readShort();
}
}
@Override
public int readInt() throws IOException {
try {
currentBuffer.mark();
return currentBuffer.getInt();
} catch (BufferUnderflowException e) {
currentBuffer.reset();
return super.readInt();
}
}
@Override
public long readLong() throws IOException {
try {
currentBuffer.mark();
return currentBuffer.getLong();
} catch (BufferUnderflowException e) {
currentBuffer.reset();
return super.readLong();
}
}
@Override
public byte readByte() throws IOException {
if (!currentBuffer.hasRemaining()) {
currentBufferIndex++;
switchCurrentBuffer(true);
}
return currentBuffer.get();
}
@Override
public void readBytes(byte[] b, int offset, int len) throws IOException {
while (len > 0) {
if (!currentBuffer.hasRemaining()) {
currentBufferIndex++;
switchCurrentBuffer(true);
}
int remainInBuffer = currentBuffer.remaining();
int bytesToCopy = len < remainInBuffer ? len : remainInBuffer;
currentBuffer.get(b, offset, bytesToCopy);
offset += bytesToCopy;
len -= bytesToCopy;
}
}
@Override
public long getFilePointer() {
return currentBufferIndex < 0 ? 0 : bufferStart + currentBuffer.position();
}
@Override
public void seek(long pos) throws IOException {
if (currentBuffer == EMPTY_BUFFER || pos < bufferStart || pos >= bufferStart + BUFFER_SIZE) {
currentBufferIndex = (int) (pos / BUFFER_SIZE);
switchCurrentBuffer(false);
}
try {
currentBuffer.position((int) (pos % BUFFER_SIZE));
// Grrr, need to wrap in IllegalArgumentException since tests (if not other places)
// expect an IOException...
} catch (IllegalArgumentException e) {
IOException ioException = new IOException("seeking past position");
ioException.initCause(e);
throw ioException;
}
}
private void switchCurrentBuffer(boolean enforceEOF) throws IOException {
if (currentBufferIndex >= file.numBuffers()) {
// end of file reached, no more buffers left
if (enforceEOF) {
throw new EOFException("Read past EOF (resource: " + this + ")");
} else {
// Force EOF if a read takes place at this position
currentBufferIndex--;
currentBuffer.position(currentBuffer.limit());
}
} else {
ByteBuffer buffer = file.getBuffer(currentBufferIndex);
// we must duplicate (and make it read only while we are at it) since we need position and such to be independent
currentBuffer = buffer.asReadOnlyBuffer();
currentBuffer.position(0);
bufferStart = (long) BUFFER_SIZE * (long) currentBufferIndex;
// if we are at the tip, limit the current buffer to only whats available to read
long buflen = length - bufferStart;
if (buflen < BUFFER_SIZE) {
currentBuffer.limit((int) buflen);
}
// we need to enforce EOF here as well...
if (!currentBuffer.hasRemaining()) {
if (enforceEOF) {
throw new EOFException("Read past EOF (resource: " + this + ")");
} else {
// Force EOF if a read takes place at this position
currentBufferIndex--;
currentBuffer.position(currentBuffer.limit());
}
}
}
}
@Override
public IndexInput clone() {
ByteBufferIndexInput cloned = (ByteBufferIndexInput) super.clone();
cloned.file.incRef(); // inc ref on cloned one
if (currentBuffer != EMPTY_BUFFER) {
cloned.currentBuffer = currentBuffer.asReadOnlyBuffer();
cloned.currentBuffer.position(currentBuffer.position());
}
return cloned;
}
}
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