/*
* Cloud9: A MapReduce Library for Hadoop
*
* Licensed 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.
*/
package tw.org.nchc.tuple;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInput;
import java.io.DataInputStream;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import org.apache.hadoop.io.WritableComparable;
/**
*
* Class that represents a list in Hadoop's data type system. Elements in the
* list must be homogeneous and must implement Hadoop's WritableComparable
* interface. This class, combined with {@link Tuple}, allows the user to
* define arbitrarily complex data structures.
*
*
* @see Tuple
* @param
* type of list element
*/
public class ListWritable implements WritableComparable, Iterable, List {
private List mList;
private Class> listElementClass;
/**
* Creates a ListWritable object.
*/
public ListWritable() {
mList = new ArrayList();
}
/**
* Appends the specified element to the end of this list.
*
* @param e
* element to be appended to this list
*/
public boolean add(E e) {
if (mList.size() == 0)
listElementClass = e.getClass();
else if (!e.getClass().equals(listElementClass))
throw new IllegalArgumentException("Cannot add element of type " + e.getClass().getCanonicalName() + " to list of type " + listElementClass.getCanonicalName());
return mList.add(e);
}
/**
* Returns the element at the specified position in this list
*
* @param index
* index of the element to return
* @return the element at the specified position in this list
*/
public E get(int index) {
if (index < 0 || index >= mList.size()) {
throw new IndexOutOfBoundsException();
}
return mList.get(index);
}
/**
* Removes all elements from this list.
*/
public void clear() {
mList.clear();
}
/**
* Replaces the element at the specified position in this list with the
* specified element.
*
* @param index
* index of the element to replace
* @param element
* element to be stored at the specified position
*/
public E set(int index, E element) {
if(mList.size() > 0 && !element.getClass().equals(listElementClass)) {
throw new IllegalArgumentException("Cannot add element of type " + element.getClass().getCanonicalName() + " to list of type " + listElementClass.getCanonicalName());
}
return mList.set(index, element);
}
/**
* Returns the number of elements in this list.
*
* @return the number of elements in this list
*/
public int size() {
return mList.size();
}
/**
* Deserializes the Tuple.
*
* @param in
* source for raw byte representation
*/
@SuppressWarnings("unchecked")
public void readFields(DataInput in) throws IOException {
mList.clear();
int numFields = in.readInt();
String className = in.readUTF();
E obj;
try {
Class c = Class.forName(className);
listElementClass = c;
for (int i = 0; i < numFields; i++) {
obj = (E) c.newInstance();
int sz = in.readInt();
byte[] bytes = new byte[sz];
in.readFully(bytes);
obj.readFields(new DataInputStream(new ByteArrayInputStream(bytes)));
this.add(obj);
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
}
}
/**
* Serializes this Tuple.
*
* @param out
* where to write the raw byte representation
*/
public void write(DataOutput out) throws IOException {
out.writeInt(mList.size());
if (mList.size() > 0)
out.writeUTF(listElementClass.getCanonicalName());
else
out.writeUTF(WritableComparable.class.getCanonicalName());
for (int i = 0; i < mList.size(); i++) {
if (mList.get(i) == null) {
throw new IOException("Cannot serialize null fields!");
}
ByteArrayOutputStream bytesOut = new ByteArrayOutputStream();
DataOutputStream dataOut = new DataOutputStream(bytesOut);
mList.get(i).write(dataOut);
out.writeInt(bytesOut.size());
out.write(bytesOut.toByteArray());
}
}
/**
* Generates human-readable String representation of this Tuple.
*
* @return human-readable String representation of this Tuple
*/
public String toString() {
StringBuffer sb = new StringBuffer();
sb.append("[");
for (int i = 0; i < this.size(); i++) {
if (i != 0)
sb.append(", ");
sb.append(this.get(i));
}
sb.append("]");
return sb.toString();
}
/**
*
* Defines a natural sort order for the ListWritable class. Following
* standard convention, this method returns a value less than zero, a value
* greater than zero, or zero if this ListWritable should be sorted before,
* sorted after, or is equal to obj. The sort order is
* defined as follows:
*
*
*
*
Each element in the list is compared sequentially from first to
* last.
*
Lists are sorted with respect to the natural order of the current
* list element under consideration, by calling its compareTo
* method.
*
If the current list elements are equal, the next set of elements are
* considered.
*
If all compared elements are equal, but lists are different lengths,
* the shorter list is sorted first.
*
If all list elements are equal and the lists are equal in length,
* then the lists are considered equal
*
*
* @return a value less than zero, a value greater than zero, or zero if
* this Tuple should be sorted before, sorted after, or is equal to
* obj.
*/
public int compareTo(Object obj) {
ListWritable> that = (ListWritable>) obj;
// iterate through the fields
for (int i = 0; i < this.size(); i++) {
// sort shorter list first
if (i >= that.size())
return 1;
@SuppressWarnings("unchecked")
Comparable