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;
/** Base implementation class for buffered {@link IndexOutput}. */
public abstract class BufferedIndexOutput extends IndexOutput {
static final int BUFFER_SIZE = 16384;
private final byte[] buffer = new byte[BUFFER_SIZE];
private long bufferStart = 0; // position in file of buffer
private int bufferPosition = 0; // position in buffer
/** Writes a single byte.
* @see IndexInput#readByte()
*/
@Override
public void writeByte(byte b) throws IOException {
if (bufferPosition >= BUFFER_SIZE)
flush();
buffer[bufferPosition++] = b;
}
/** Writes an array of bytes.
* @param b the bytes to write
* @param length the number of bytes to write
* @see IndexInput#readBytes(byte[],int,int)
*/
@Override
public void writeBytes(byte[] b, int offset, int length) throws IOException {
int bytesLeft = BUFFER_SIZE - bufferPosition;
// is there enough space in the buffer?
if (bytesLeft >= length) {
// we add the data to the end of the buffer
System.arraycopy(b, offset, buffer, bufferPosition, length);
bufferPosition += length;
// if the buffer is full, flush it
if (BUFFER_SIZE - bufferPosition == 0)
flush();
} else {
// is data larger then buffer?
if (length > BUFFER_SIZE) {
// we flush the buffer
if (bufferPosition > 0)
flush();
// and write data at once
flushBuffer(b, offset, length);
bufferStart += length;
} else {
// we fill/flush the buffer (until the input is written)
int pos = 0; // position in the input data
int pieceLength;
while (pos < length) {
pieceLength = (length - pos < bytesLeft) ? length - pos : bytesLeft;
System.arraycopy(b, pos + offset, buffer, bufferPosition, pieceLength);
pos += pieceLength;
bufferPosition += pieceLength;
// if the buffer is full, flush it
bytesLeft = BUFFER_SIZE - bufferPosition;
if (bytesLeft == 0) {
flush();
bytesLeft = BUFFER_SIZE;
}
}
}
}
}
/** Forces any buffered output to be written. */
@Override
public void flush() throws IOException {
flushBuffer(buffer, bufferPosition);
bufferStart += bufferPosition;
bufferPosition = 0;
}
/** Expert: implements buffer write. Writes bytes at the current position in
* the output.
* @param b the bytes to write
* @param len the number of bytes to write
*/
private void flushBuffer(byte[] b, int len) throws IOException {
flushBuffer(b, 0, len);
}
/** Expert: implements buffer write. Writes bytes at the current position in
* the output.
* @param b the bytes to write
* @param offset the offset in the byte array
* @param len the number of bytes to write
*/
protected abstract void flushBuffer(byte[] b, int offset, int len) throws IOException;
/** Closes this stream to further operations. */
@Override
public void close() throws IOException {
flush();
}
/** Returns the current position in this file, where the next write will
* occur.
* @see #seek(long)
*/
@Override
public long getFilePointer() {
return bufferStart + bufferPosition;
}
/** Sets current position in this file, where the next write will occur.
* @see #getFilePointer()
*/
@Override
public void seek(long pos) throws IOException {
flush();
bufferStart = pos;
}
/** The number of bytes in the file. */
@Override
public abstract long length() throws IOException;
}