/*
* Javolution - Java(TM) Solution for Real-Time and Embedded Systems
* Copyright (C) 2006 - Javolution (http://javolution.org/)
* All rights reserved.
*
* Permission to use, copy, modify, and distribute this software is
* freely granted, provided that this notice is preserved.
*/
package javolution.util;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.lang.UnsupportedOperationException;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Set;
import javolution.lang.Realtime;
import javolution.text.Text;
import javolution.xml.XMLSerializable;
import java.io.IOException;
/**
* <p> This class represents collections which can quickly be iterated over
* (forward or backward) and which an be made {@link #shared() thread-safe}
* and/or {@link #unmodifiable() unmodifiable}.</p>
*
* <p> Fast collections can be iterated over without creating new objects
* and without using {@link #iterator iterators} .
* [code]
* public boolean search(Object item, FastCollection c) {
* for (Record r = c.head(), end = c.tail(); (r = r.getNext()) != end;) {
* if (item.equals(c.valueOf(r))) return true;
* }
* return false;
* }
* [/code]</p>
*
* <p> Fast collections are thread-safe when marked {@link #shared shared}
* (can be read, iterated over or modified concurrently).
* [code]
* public class Foo {
* private static final Collection<Foo> INSTANCES = new FastTable().shared();
* public Foo() {
* INSTANCES.add(this);
* }
* public static void showInstances() {
* for (Foo foo : INSTANCES) { // Iterations are thread-safe even if new Foo instances are added.
* System.out.println(foo);
* }
* }
* }[/code]</p>
*
* <p> Users may provide a read-only view of any {@link FastCollection}
* instance using the {@link #unmodifiable()} method (the view is
* thread-safe if the collection is {@link #shared shared}).
* [code]
* class Foo {
* private static final FastTable<Foo> INSTANCES = new FastTable().shared();
* Foo() {
* INSTANCES.add(this);
* }
* public static Collection<Foo> getInstances() {
* return INSTANCES.unmodifiable(); // Returns a public unmodifiable view over the shared collection.
* }
* }[/code]</p>
*
* <p> Finally, {@link FastCollection} may use custom {@link #getValueComparator
* comparators} for element equality or ordering if the collection is
* ordered (e.g. <code>FastTree</code>).
*
* @author <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
* @version 5.4.5, March 23, 2010
*/
public abstract class FastCollection <E> implements
Collection <E> , XMLSerializable, Realtime {
/**
* Default constructor.
*/
protected FastCollection() {
}
/**
* Returns the number of values in this collection.
*
* @return the number of values.
*/
public abstract int size();
/**
* Returns the head record of this collection; it is the record such as
* <code>head().getNext()</code> holds the first collection value.
*
* @return the head record.
*/
public abstract Record head();
/**
* Returns the tail record of this collection; it is the record such as
* <code>tail().getPrevious()</code> holds the last collection value.
*
* @return the tail record.
*/
public abstract Record tail();
/**
* Returns the collection value for the specified record.
*
* @param record the record whose current value is returned.
* @return the current value.
*/
public abstract E valueOf(Record record);
/**
* Deletes the specified record from this collection.
*
* <p> Implementation must ensure that removing a record from the
* collection does not affect in any way the records preceding
* the record being removed (it might affect the next records though,
* e.g. in a list collection, the indices of the subsequent records
* will change).</p>
*
* @param record the record to be removed.
* @throws UnsupportedOperationException if not supported.
*/
public abstract void delete(Record record);
/**
* Returns the unmodifiable view associated to this collection.
* Attempts to modify the returned collection result in an
* {@link UnsupportedOperationException} being thrown.
*
* @return the unmodifiable view over this collection.
*/
public Collection <E> unmodifiable() {
return new Unmodifiable();
}
/**
* <p> Returns a thread-safe read-write view of this collection.</p>
* <p> The default implementation performs synchronization on read and write.
* Sub-classes may provide more efficient implementation (e.g.
* only synchronizing on writes modifying the internal data structure).</p>
* <p> Having a shared collection does not mean that modifications made
* by onethread are automatically viewed by others thread. Which in practice
* is not an issue. In a well-behaved system, threads need to synchronize
* only at predetermined synchronization points (the fewer the better).</p>
*
* @return a thread-safe collection.
*/
public Collection <E> shared() {
return new Shared();
}
/**
* Returns an iterator over the elements in this collection
* (allocated on the stack when executed in a
* {@link javolution.context.StackContext StackContext}).
*
* @return an iterator over this collection's elements.
*/
public Iterator <E> iterator() {
return FastIterator.valueOf(this);
}
/**
* Returns the value comparator for this collection (default
* {@link FastComparator#DEFAULT}).
*
* @return the comparator to use for value equality (or ordering if
* the collection is ordered)
*/
public FastComparator <? super E> getValueComparator() {
return FastComparator.DEFAULT;
}
/**
* Appends the specified value to the end of this collection
* (optional operation).
*
* <p>Note: This default implementation always throws
* <code>UnsupportedOperationException</code>.</p>
*
* @param value the value to be appended to this collection.
* @return <code>true</code> (as per the general contract of the
* <code>Collection.add</code> method).
* @throws UnsupportedOperationException if not supported.
*/
public boolean add( E value) {
throw new UnsupportedOperationException();
}
/**
* Removes the first occurrence in this collection of the specified value
* (optional operation).
*
* @param value the value to be removed from this collection.
* @return <code>true</code> if this collection contained the specified
* value; <code>false</code> otherwise.
* @throws UnsupportedOperationException if not supported.
*/
public boolean remove(Object value) {
final FastComparator valueComp = this.getValueComparator();
for (Record r = head(), end = tail(); (r = r.getNext()) != end;) {
if (valueComp.areEqual(value, valueOf(r))) {
delete(r);
return true;
}
}
return false;
}
/**
* Removes all of the values from this collection (optional operation).
*
* @throws UnsupportedOperationException if not supported.
*/
public void clear() {
// Removes last record until empty.
for (Record head = head(), r = tail().getPrevious(); r != head; r = r.getPrevious()) {
delete(r);
}
}
/**
* Indicates if this collection is empty.
*
* @return <code>true</code> if this collection contains no value;
* <code>false</code> otherwise.
*/
public final boolean isEmpty() {
return size() == 0;
}
/**
* Indicates if this collection contains the specified value.
*
* @param value the value whose presence in this collection
* is to be tested.
* @return <code>true</code> if this collection contains the specified
* value;<code>false</code> otherwise.
*/
public boolean contains(Object value) {
final FastComparator valueComp = this.getValueComparator();
for (Record r = head(), end = tail(); (r = r.getNext()) != end;) {
if (valueComp.areEqual(value, valueOf(r)))
return true;
}
return false;
}
/**
* Appends all of the values in the specified collection to the end of
* this collection, in the order that they are returned by the specified
* collection's iterator.
*
* @param c collection whose values are to be added to this collection.
* @return <code>true</code> if this collection changed as a result of
* the call; <code>false</code> otherwise.
*/
public boolean addAll(Collection <? extends E> c) {
boolean modified = false;
Iterator <? extends E> itr = c.iterator();
while (itr.hasNext()) {
if (add(itr.next())) {
modified = true;
}
}
return modified;
}
/**
* Indicates if this collection contains all of the values of the
* specified collection.
*
* @param c collection to be checked for containment in this collection.
* @return <code>true</code> if this collection contains all of the values
* of the specified collection; <code>false</code> otherwise.
*/
public boolean containsAll(Collection <?> c) {
Iterator <?> itr = c.iterator();
while (itr.hasNext()) {
if (!contains(itr.next()))
return false;
}
return true;
}
/**
* Removes from this collection all the values that are contained in the
* specified collection.
*
* @param c collection that defines which values will be removed from
* this collection.
* @return <code>true</code> if this collection changed as a result of
* the call; <code>false</code> otherwise.
*/
public boolean removeAll(Collection <?> c) {
boolean modified = false;
// Iterates from the tail and remove the record if present in c.
for (Record head = head(), r = tail().getPrevious(), previous; r != head; r = previous) {
previous = r.getPrevious(); // Saves previous.
if (FastCollection.contains(c, valueOf(r), this.getValueComparator())) {
delete(r);
modified = true;
}
}
return modified;
}
private static boolean contains(Collection c, Object obj, FastComparator cmp) {
if ((c instanceof FastCollection)
&& ((FastCollection) c).getValueComparator().equals(cmp))
return c.contains(obj); // Direct is ok (same value comparator).
Iterator <?> itr = c.iterator();
while (itr.hasNext()) {
if (cmp.areEqual(obj, itr.next()))
return true;
}
return false;
}
/**
* Retains only the values in this collection that are contained in the
* specified collection.
*
* @param c collection that defines which values this set will retain.
* @return <code>true</code> if this collection changed as a result of
* the call; <code>false</code> otherwise.
*/
public boolean retainAll(Collection <?> c) {
boolean modified = false;
// Iterates from the tail and remove the record if not present in c.
for (Record head = head(), r = tail().getPrevious(), previous; r != head; r = previous) {
previous = r.getPrevious(); // Saves previous.
if (!FastCollection.contains(c, valueOf(r), this.getValueComparator())) {
delete(r);
modified = true;
}
}
return modified;
}
/**
* Returns a new array allocated on the heap containing all of the values
* in this collection in proper sequence.
* <p> Note: To avoid heap allocation {@link #toArray(Object[])} is
* recommended.</p>
* @return <code>toArray(new Object[size()])</code>
*/
public Object[] toArray() {
return toArray(new Object[size()]);
}
/**
* Fills the specified array with the values of this collection in
* the proper sequence.
*
* <p> Note: Unlike standard Collection, this method does not try to resize
* the array using reflection (which might not be supported) if
* the array is too small. UnsupportedOperationException is raised
* if the specified array is too small for this collection.</p>
*
* @param array the array into which the values of this collection
* are to be stored.
* @return the specified array.
* @throws UnsupportedOperationException if <code>array.length < size()</code>
*/
public <T> T [] toArray( T [] array) {
int size = size();
if (array.length < size)
throw new UnsupportedOperationException(
"Destination array too small");
if (array.length > size) {
array[size] = null; // As per Collection contract.
}
int i = 0;
Object[] arrayView = array;
for (Record r = head(), end = tail(); (r = r.getNext()) != end;) {
arrayView[i++] = valueOf(r);
}
return array;
}
/**
* Returns the textual representation of this collection.
*
* @return this collection textual representation.
*/
public Text toText() {
// We use Text concatenation instead of TextBuilder to avoid copying
// the text representation of the record values (unknown length).
Text text = Text.valueOf("{");
for (Record r = head(), end = tail(); (r = r.getNext()) != end;) {
text = text.plus(valueOf(r));
if (r.getNext() != end) {
text = text.plus(", ");
}
}
return text.plus("}");
}
/**
* Returns the <code>String</code> representation of this
* {@link FastCollection}.
*
* @return <code>toText().toString()</code>
*/
public final String toString() {
return toText().toString();
}
/**
* Compares the specified object with this collection for equality.
* The default behavior is to consider two collections equal if they
* hold the same values and have the same iterative order if any of
* the collections is an ordered collection ({@link List} instances).
* Equality comparisons are performed using this collection
* {@link #getValueComparator value comparator}.
*
* @param obj the object to be compared for equality with this collection
* @return <code>true</code> if the specified object is a collection with
* the same content and iteration order when necessary;
* <code>false</code> otherwise.
*/
public boolean equals(Object obj) {
if (this instanceof List)
return (obj instanceof List) ? equalsOrder((List) obj) : false;
if (obj instanceof List)
return false; // 'this' is not a list but obj is!
if (!(obj instanceof Collection))
return false; // Can only compare collections.
Collection that = (Collection) obj;
return (this == that) || ((this.size() == that.size()) && containsAll(that));
}
private boolean equalsOrder(List that) {
if (that == this)
return true;
if (this.size() != that.size())
return false;
Iterator thatIterator = that.iterator();
final FastComparator comp = this.getValueComparator();
for (Record r = head(), end = tail(); (r = r.getNext()) != end;) {
Object o1 = valueOf(r);
Object o2 = thatIterator.next();
if (!comp.areEqual(o1, o2))
return false;
}
return true;
}
/**
* Returns the hash code for this collection. For non-ordered collection
* the hashcode of this collection is the sum of the hashcode of its
* values.
* @return the hash code for this collection.
*/
public int hashCode() {
if (this instanceof List)
return hashCodeList();
final FastComparator valueComp = this.getValueComparator();
int hash = 0;
for (Record r = head(), end = tail(); (r = r.getNext()) != end;) {
hash += valueComp.hashCodeOf(valueOf(r));
}
return hash;
}
private int hashCodeList() {
final FastComparator comp = this.getValueComparator();
int h = 1;
for (Record r = head(), end = tail(); (r = r.getNext()) != end;) {
h = 31 * h + comp.hashCodeOf(valueOf(r));
}
return h;
}
/**
* This interface represents the collection records which can directly be
* iterated over.
*/
public interface Record {
/**
* Returns the record before this one.
*
* @return the previous record.
*/
public Record getPrevious();
/**
* Returns the record after this one.
*
* @return the next record.
*/
public Record getNext();
}
/**
* This inner class represents an unmodifiable view over the collection.
*/
class Unmodifiable extends FastCollection implements List, Set {
// Implements abstract method.
public int size() {
return FastCollection.this.size();
}
// Implements abstract method.
public Record head() {
return FastCollection.this.head();
}
// Implements abstract method.
public Record tail() {
return FastCollection.this.tail();
}
// Implements abstract method.
public Object valueOf(Record record) {
return FastCollection.this.valueOf(record);
}
// Forwards...
public boolean contains(Object value) {
return (FastCollection.this).contains(value);
}
// Forwards...
public boolean containsAll(Collection c) {
return (FastCollection.this).containsAll(c);
}
// Forwards...
public FastComparator getValueComparator() {
return FastCollection.this.getValueComparator();
}
// Disallows...
public boolean add(Object obj) {
throw new UnsupportedOperationException("Unmodifiable");
}
// Disallows...
public void delete(Record node) {
throw new UnsupportedOperationException("Unmodifiable");
}
//////////////////////////////////////////
// List interface supplementary methods //
//////////////////////////////////////////
public boolean addAll(int index, Collection c) {
throw new UnsupportedOperationException("Unmodifiable");
}
public Object get(int index) {
return ((List) FastCollection.this).get(index);
}
public Object set(int index, Object element) {
throw new UnsupportedOperationException("Unmodifiable");
}
public void add(int index, Object element) {
throw new UnsupportedOperationException("Unmodifiable");
}
public Object remove(int index) {
throw new UnsupportedOperationException("Unmodifiable");
}
public int indexOf(Object o) {
return ((List) FastCollection.this).indexOf(o);
}
public int lastIndexOf(Object o) {
return ((List) FastCollection.this).lastIndexOf(o);
}
public ListIterator listIterator() {
throw new UnsupportedOperationException(
"List iterator not supported for unmodifiable collection");
}
public ListIterator listIterator(int index) {
throw new UnsupportedOperationException(
"List iterator not supported for unmodifiable collection");
}
public List subList(int fromIndex, int toIndex) {
throw new UnsupportedOperationException(
"Sub-List not supported for unmodifiable collection");
}
}
/**
* This inner class represents a thread safe view (read-write) over the
* collection.
*/
private class Shared implements Collection , Serializable {
public synchronized int size() {
return FastCollection.this.size();
}
public synchronized boolean isEmpty() {
return FastCollection.this.isEmpty();
}
public synchronized boolean contains(Object o) {
return FastCollection.this.contains(o);
}
public synchronized Object[] toArray() {
return FastCollection.this.toArray();
}
public synchronized Object[] toArray(Object[] a) {
return FastCollection.this.toArray(a);
}
public synchronized Iterator iterator() {
if (FastCollection.this instanceof List)
return new ListArrayIterator(FastCollection.this.toArray());
return new CollectionArrayIterator(FastCollection.this.toArray());
}
public synchronized boolean add(Object e) {
return ((FastCollection)FastCollection.this).add(e);
}
public synchronized boolean remove(Object o) {
return FastCollection.this.remove(o);
}
public synchronized boolean containsAll(Collection c) {
return FastCollection.this.containsAll(c);
}
public synchronized boolean addAll(Collection c) {
return FastCollection.this.addAll(c);
}
public synchronized boolean removeAll(Collection c) {
return FastCollection.this.removeAll(c);
}
public synchronized boolean retainAll(Collection c) {
return FastCollection.this.retainAll(c);
}
public synchronized void clear() {
FastCollection.this.clear();
}
public synchronized String toString() {
return FastCollection.this.toString();
}
private synchronized void writeObject(ObjectOutputStream s) throws IOException {
s.defaultWriteObject();
}
private class ListArrayIterator implements Iterator {
private final Object[] _elements;
private int _index;
private int _removed;
public ListArrayIterator(Object[] elements) {
_elements = elements;
}
public boolean hasNext() {
return _index < _elements.length;
}
public Object next() {
return _elements[_index++];
}
public void remove() {
if (_index == 0)
throw new java.lang.IllegalStateException();
Object removed = _elements[_index - 1];
if (removed == NULL) // Double removed.
throw new java.lang.IllegalStateException();
_elements[_index - 1] = NULL;
_removed++;
synchronized (FastCollection.Shared.this) {
((List) FastCollection.this).remove(_index - _removed);
}
}
}
private class CollectionArrayIterator implements Iterator {
private final Object[] _elements;
private int _index;
private Object _next;
public CollectionArrayIterator(Object[] elements) {
_elements = elements;
}
public boolean hasNext() {
return _index < _elements.length;
}
public Object next() {
return _next = _elements[_index++];
}
public void remove() {
if (_next == null)
throw new java.lang.IllegalStateException();
FastCollection.Shared.this.remove(_next);
_next = null;
}
}
}
private static final Object NULL = new Object();
}