/**
* 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.
*/
package org.apache.hadoop.mapred.join;
import java.io.DataOutput;
import java.io.DataInput;
import java.io.IOException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableUtils;
/**
* Writable type storing multiple {@link org.apache.hadoop.io.Writable}s.
*
* This is *not* a general-purpose tuple type. In almost all cases, users are
* encouraged to implement their own serializable types, which can perform
* better validation and provide more efficient encodings than this class is
* capable. TupleWritable relies on the join framework for type safety and
* assumes its instances will rarely be persisted, assumptions not only
* incompatible with, but contrary to the general case.
*
* @see org.apache.hadoop.io.Writable
*/
public class TupleWritable implements Writable, Iterable<Writable> {
private long written;
private Writable[] values;
/**
* Create an empty tuple with no allocated storage for writables.
*/
public TupleWritable() { }
/**
* Initialize tuple with storage; unknown whether any of them contain
* "written" values.
*/
public TupleWritable(Writable[] vals) {
written = 0L;
values = vals;
}
/**
* Return true if tuple has an element at the position provided.
*/
public boolean has(int i) {
return 0 != ((1L << i) & written);
}
/**
* Get ith Writable from Tuple.
*/
public Writable get(int i) {
return values[i];
}
/**
* The number of children in this Tuple.
*/
public int size() {
return values.length;
}
/**
* {@inheritDoc}
*/
public boolean equals(Object other) {
if (other instanceof TupleWritable) {
TupleWritable that = (TupleWritable)other;
if (this.size() != that.size() || this.written != that.written) {
return false;
}
for (int i = 0; i < values.length; ++i) {
if (!has(i)) continue;
if (!values[i].equals(that.get(i))) {
return false;
}
}
return true;
}
return false;
}
public int hashCode() {
assert false : "hashCode not designed";
return (int)written;
}
/**
* Return an iterator over the elements in this tuple.
* Note that this doesn't flatten the tuple; one may receive tuples
* from this iterator.
*/
public Iterator<Writable> iterator() {
final TupleWritable t = this;
return new Iterator<Writable>() {
long i = written;
long last = 0L;
public boolean hasNext() {
return 0L != i;
}
public Writable next() {
last = Long.lowestOneBit(i);
if (0 == last)
throw new NoSuchElementException();
i ^= last;
// numberOfTrailingZeros rtn 64 if lsb set
return t.get(Long.numberOfTrailingZeros(last) % 64);
}
public void remove() {
t.written ^= last;
if (t.has(Long.numberOfTrailingZeros(last))) {
throw new IllegalStateException("Attempt to remove non-existent val");
}
}
};
}
/**
* Convert Tuple to String as in the following.
* <tt>[<child1>,<child2>,...,<childn>]</tt>
*/
public String toString() {
StringBuffer buf = new StringBuffer("[");
for (int i = 0; i < values.length; ++i) {
buf.append(has(i) ? values[i].toString() : "");
buf.append(",");
}
if (values.length != 0)
buf.setCharAt(buf.length() - 1, ']');
else
buf.append(']');
return buf.toString();
}
// Writable
/** Writes each Writable to <code>out</code>.
* TupleWritable format:
* {@code
* <count><type1><type2>...<typen><obj1><obj2>...<objn>
* }
*/
public void write(DataOutput out) throws IOException {
WritableUtils.writeVInt(out, values.length);
WritableUtils.writeVLong(out, written);
for (int i = 0; i < values.length; ++i) {
Text.writeString(out, values[i].getClass().getName());
}
for (int i = 0; i < values.length; ++i) {
if (has(i)) {
values[i].write(out);
}
}
}
/**
* {@inheritDoc}
*/
@SuppressWarnings("unchecked") // No static typeinfo on Tuples
public void readFields(DataInput in) throws IOException {
int card = WritableUtils.readVInt(in);
values = new Writable[card];
written = WritableUtils.readVLong(in);
Class<? extends Writable>[] cls = new Class[card];
try {
for (int i = 0; i < card; ++i) {
cls[i] = Class.forName(Text.readString(in)).asSubclass(Writable.class);
}
for (int i = 0; i < card; ++i) {
values[i] = cls[i].newInstance();
if (has(i)) {
values[i].readFields(in);
}
}
} catch (ClassNotFoundException e) {
throw (IOException)new IOException("Failed tuple init").initCause(e);
} catch (IllegalAccessException e) {
throw (IOException)new IOException("Failed tuple init").initCause(e);
} catch (InstantiationException e) {
throw (IOException)new IOException("Failed tuple init").initCause(e);
}
}
/**
* Record that the tuple contains an element at the position provided.
*/
void setWritten(int i) {
written |= 1L << i;
}
/**
* Record that the tuple does not contain an element at the position
* provided.
*/
void clearWritten(int i) {
written &= -1 ^ (1L << i);
}
/**
* Clear any record of which writables have been written to, without
* releasing storage.
*/
void clearWritten() {
written = 0L;
}
}