/* XXL: The eXtensible and fleXible Library for data processing
Copyright (C) 2000-2011 Prof. Dr. Bernhard Seeger
Head of the Database Research Group
Department of Mathematics and Computer Science
University of Marburg
Germany
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; If not, see <http://www.gnu.org/licenses/>.
http://code.google.com/p/xxl/
*/
package xxl.core.io.converters;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
/**
* This class provides a converter that is able to read and write arrays of
* <code>long</code> values. First the converter reads or writes the length of
* the <code>long</code> array. Thereafter the <code>long</tcodet> values are
* read or written.
*
* <p>Example usage (1).
* <code><pre>
* // create a long array
*
* long[] array = {1234567890l, 123456789012345l};
*
* // create a byte array output stream
*
* ByteArrayOutputStream output = new ByteArrayOutputStream();
*
* // write array to the output stream
*
* LongArrayConverter.DEFAULT_INSTANCE.write(new DataOutputStream(output), array);
*
* // create a byte array input stream on the output stream
*
* ByteArrayInputStream input = new ByteArrayInputStream(output.toByteArray());
*
* // reset the array
*
* array = null;
*
* // read array from the input stream
*
* array = LongArrayConverter.DEFAULT_INSTANCE.read(new DataInputStream(input));
*
* // print the array
*
* for (long l : array)
* System.out.println(l);
*
* // close the streams after use
*
* input.close();
* output.close();
* </pre></code></p>
*
* @see DataInput
* @see DataOutput
* @see IOException
*/
public class LongArrayConverter extends Converter<long[]> {
/**
* This instance can be used for getting a default instance of a long array
* converter. It is similar to the <i>Singleton Design Pattern</i> (for
* further details see Creational Patterns, Prototype in <i>Design
* Patterns: Elements of Reusable Object-Oriented Software</i> by Erich
* Gamma, Richard Helm, Ralph Johnson, and John Vlissides) except that
* there are no mechanisms to avoid the creation of other instances of a
* long array converter.
*/
public static final LongArrayConverter DEFAULT_INSTANCE = new LongArrayConverter();
/**
* Determines the length of the conversion of a long array.
*
* @param withLengthInfo has to be <code>true</code> iff the length info of
* the array has to be stored.
* @param length the length of the array to be stored.
* @return the length of the conversion of a long array.
*/
public static int getSizeForArray(boolean withLengthInfo, int length) {
return (withLengthInfo ? 4 : 0) + 8*length;
}
/**
* Determines the length of the array. If it is <code>-1</code>, then the
* size information is also serialized.
*/
protected int arraySize;
/**
* Constructors a LongArrayConverter which not necessarily
* serializes/deserializes the length of the array.
*
* @param arraySize if <code>-1</code> then the size is not
* serialized/deserialized. Else this int value represents the
* number of elements which are serialized/deserialized.
*/
public LongArrayConverter(int arraySize) {
this.arraySize = arraySize;
}
/**
* Sole constructor. (For invocation by subclass constructors, typically
* implicit.)
*/
public LongArrayConverter() {
this(-1);
}
/**
* Reads an array of <code>long</code> values from the specified data input
* and returns the restored <code>long</code> array.
*
* <p>When the specified <code>long</code> array is <code>null</code> this
* implementation returns a new array of <code>long</code> values,
* otherwise the size of the specified long array has to be sufficient.</p>
*
* @param dataInput the stream to read the <code>long</code> array from.
* @param object the <code>long</code> array to be restored.
* @return the read array of <code>long</code> values.
* @throws IOException if I/O errors occur.
*/
@Override
public long[] read(DataInput dataInput, long[] object) throws IOException {
int length = arraySize;
if (length == -1)
length = dataInput.readInt();
if (object == null)
object = new long[length];
for (int i = 0; i < object.length; i++)
object[i] = dataInput.readLong();
return object;
}
/**
* Writes the specified array of <code>long</code> values to the specified
* data output.
*
* <p>This implementation first writes the length of the array to the data
* output. Thereafter the <code>long</code> values are written.</p>
*
* @param dataOutput the stream to write the <code>long</code> array to.
* @param object the <code>long</code> array that should be written to the
* data output.
* @throws IOException includes any I/O exceptions that may occur.
*/
@Override
public void write(DataOutput dataOutput, long[] object) throws IOException {
int len = arraySize;
if (arraySize == -1){
dataOutput.writeInt(object.length);
len = object.length;
}
for (int i = 0; i < len; i++)
dataOutput.writeLong(object[i]);
}
/**
* Determines the size of the long array in bytes.
*
* @param object the long array.
* @return the size of the long array in bytes.
* @see xxl.core.io.converters.SizeConverter#getSerializedSize(java.lang.Object)
*/
public int getSerializedSize(long[] object) {
return arraySize==-1 ?
getSizeForArray(true, object.length) :
getSizeForArray(false, arraySize);
}
}