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/*
* Copyright (C) 2002-2017 Sebastiano Vigna
*
* 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 it.unimi.dsi.fastutil.objects;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.RandomAccess;
import java.util.NoSuchElementException;
/**
* A type-specific array-based list; provides some additional methods that use
* polymorphism to avoid (un)boxing.
*
*
* This class implements a lightweight, fast, open, optimized, reuse-oriented
* version of array-based lists. Instances of this class represent a list with
* an array that is enlarged as needed when new entries are created (by doubling
* the current length), but is never made smaller (even on a
* {@link #clear()}). A family of {@linkplain #trim() trimming methods} lets you
* control the size of the backing array; this is particularly useful if you
* reuse instances of this class. Range checks are equivalent to those of
* {@link java.util}'s classes, but they are delayed as much as possible.
*
*
* The backing array is exposed by the {@link #elements()} method. If an
* instance of this class was created {@linkplain #wrap(Object[],int) by
* wrapping}, backing-array reallocations will be performed using reflection, so
* that {@link #elements()} can return an array of the same type of the original
* array: the comments about efficiency made in
* {@link it.unimi.dsi.fastutil.objects.ObjectArrays} apply here. Moreover, you
* must take into consideration that assignment to an array not of type
* {@code Object[]} is slower due to type checking.
*
*
* This class implements the bulk methods {@code removeElements()},
* {@code addElements()} and {@code getElements()} using high-performance system
* calls (e.g., {@link System#arraycopy(Object,int,Object,int,int)
* System.arraycopy()} instead of expensive loops.
*
* @see java.util.ArrayList
*/
public class ReferenceArrayList extends AbstractReferenceList
implements
RandomAccess,
Cloneable,
java.io.Serializable {
private static final long serialVersionUID = -7046029254386353131L;
/** The initial default capacity of an array list. */
public static final int DEFAULT_INITIAL_CAPACITY = 10;
/**
* Whether the backing array was passed to {@code wrap()}. In this case, we must
* reallocate with the same type of array.
*/
protected final boolean wrapped;
/** The backing array. */
protected transient K a[];
/**
* The current actual size of the list (never greater than the backing-array
* length).
*/
protected int size;
/**
* Creates a new array list using a given array.
*
*
* This constructor is only meant to be used by the wrapping methods.
*
* @param a
* the array that will be used to back this array list.
*/
protected ReferenceArrayList(final K a[], @SuppressWarnings("unused") boolean dummy) {
this.a = a;
this.wrapped = true;
}
/**
* Creates a new array list with given capacity.
*
* @param capacity
* the initial capacity of the array list (may be 0).
*/
@SuppressWarnings("unchecked")
public ReferenceArrayList(final int capacity) {
if (capacity < 0)
throw new IllegalArgumentException("Initial capacity (" + capacity + ") is negative");
if (capacity == 0)
a = (K[]) ObjectArrays.EMPTY_ARRAY;
else
a = (K[]) new Object[capacity];
wrapped = false;
}
/** Creates a new array list with {@link #DEFAULT_INITIAL_CAPACITY} capacity. */
@SuppressWarnings("unchecked")
public ReferenceArrayList() {
a = (K[]) ObjectArrays.DEFAULT_EMPTY_ARRAY; // We delay allocation
wrapped = false;
}
/**
* Creates a new array list and fills it with a given collection.
*
* @param c
* a collection that will be used to fill the array list.
*/
public ReferenceArrayList(final Collection c) {
this(c.size());
size = ObjectIterators.unwrap(c.iterator(), a);
}
/**
* Creates a new array list and fills it with a given type-specific collection.
*
* @param c
* a type-specific collection that will be used to fill the array
* list.
*/
public ReferenceArrayList(final ReferenceCollection c) {
this(c.size());
size = ObjectIterators.unwrap(c.iterator(), a);
}
/**
* Creates a new array list and fills it with a given type-specific list.
*
* @param l
* a type-specific list that will be used to fill the array list.
*/
public ReferenceArrayList(final ReferenceList l) {
this(l.size());
l.getElements(0, a, 0, size = l.size());
}
/**
* Creates a new array list and fills it with the elements of a given array.
*
* @param a
* an array whose elements will be used to fill the array list.
*/
public ReferenceArrayList(final K a[]) {
this(a, 0, a.length);
}
/**
* Creates a new array list and fills it with the elements of a given array.
*
* @param a
* an array whose elements will be used to fill the array list.
* @param offset
* the first element to use.
* @param length
* the number of elements to use.
*/
public ReferenceArrayList(final K a[], final int offset, final int length) {
this(length);
System.arraycopy(a, offset, this.a, 0, length);
size = length;
}
/**
* Creates a new array list and fills it with the elements returned by an
* iterator..
*
* @param i
* an iterator whose returned elements will fill the array list.
*/
public ReferenceArrayList(final Iterator i) {
this();
while (i.hasNext())
this.add((i.next()));
}
/**
* Creates a new array list and fills it with the elements returned by a
* type-specific iterator..
*
* @param i
* a type-specific iterator whose returned elements will fill the
* array list.
*/
public ReferenceArrayList(final ObjectIterator i) {
this();
while (i.hasNext())
this.add(i.next());
}
/**
* Returns the backing array of this list.
*
*
* If this array list was created by wrapping a given array, it is guaranteed
* that the type of the returned array will be the same. Otherwise, the returned
* array will be of type {@link Object Object[]} (in spite of the declared
* return type).
*
*
* Warning: This behaviour may cause (unfathomable) run-time
* errors if a method expects an array actually of type {@code K[]}, but this
* methods returns an array of type {@link Object Object[]}.
*
* @return the backing array.
*/
public K[] elements() {
return a;
}
/**
* Wraps a given array into an array list of given size.
*
*
* Note it is guaranteed that the type of the array returned by
* {@link #elements()} will be the same (see the comments in the class
* documentation).
*
* @param a
* an array to wrap.
* @param length
* the length of the resulting array list.
* @return a new array list of the given size, wrapping the given array.
*/
public static ReferenceArrayList wrap(final K a[], final int length) {
if (length > a.length)
throw new IllegalArgumentException(
"The specified length (" + length + ") is greater than the array size (" + a.length + ")");
final ReferenceArrayList l = new ReferenceArrayList<>(a, false);
l.size = length;
return l;
}
/**
* Wraps a given array into an array list.
*
*
* Note it is guaranteed that the type of the array returned by
* {@link #elements()} will be the same (see the comments in the class
* documentation).
*
* @param a
* an array to wrap.
* @return a new array list wrapping the given array.
*/
public static ReferenceArrayList wrap(final K a[]) {
return wrap(a, a.length);
}
/**
* Ensures that this array list can contain the given number of entries without
* resizing.
*
* @param capacity
* the new minimum capacity for this array list.
*/
@SuppressWarnings("unchecked")
public void ensureCapacity(final int capacity) {
if (capacity <= a.length || (a == ObjectArrays.DEFAULT_EMPTY_ARRAY && capacity <= DEFAULT_INITIAL_CAPACITY))
return;
if (wrapped)
a = ObjectArrays.ensureCapacity(a, capacity, size);
else {
if (capacity > a.length) {
final Object t[] = new Object[capacity];
System.arraycopy(a, 0, t, 0, size);
a = (K[]) t;
}
}
assert size <= a.length;
}
/**
* Grows this array list, ensuring that it can contain the given number of
* entries without resizing, and in case increasing the current capacity at
* least by a factor of 50%.
*
* @param capacity
* the new minimum capacity for this array list.
*/
@SuppressWarnings("unchecked")
private void grow(int capacity) {
if (capacity <= a.length)
return;
if (a != ObjectArrays.DEFAULT_EMPTY_ARRAY)
capacity = (int) Math.max(
Math.min((long) a.length + (a.length >> 1), it.unimi.dsi.fastutil.Arrays.MAX_ARRAY_SIZE), capacity);
else if (capacity < DEFAULT_INITIAL_CAPACITY)
capacity = DEFAULT_INITIAL_CAPACITY;
if (wrapped)
a = ObjectArrays.forceCapacity(a, capacity, size);
else {
final Object t[] = new Object[capacity];
System.arraycopy(a, 0, t, 0, size);
a = (K[]) t;
}
assert size <= a.length;
}
@Override
public void add(final int index, final K k) {
ensureIndex(index);
grow(size + 1);
if (index != size)
System.arraycopy(a, index, a, index + 1, size - index);
a[index] = k;
size++;
assert size <= a.length;
}
@Override
public boolean add(final K k) {
grow(size + 1);
a[size++] = k;
assert size <= a.length;
return true;
}
@Override
public K get(final int index) {
if (index >= size)
throw new IndexOutOfBoundsException(
"Index (" + index + ") is greater than or equal to list size (" + size + ")");
return a[index];
}
@Override
public int indexOf(final Object k) {
for (int i = 0; i < size; i++)
if (((k) == (a[i])))
return i;
return -1;
}
@Override
public int lastIndexOf(final Object k) {
for (int i = size; i-- != 0;)
if (((k) == (a[i])))
return i;
return -1;
}
@Override
public K remove(final int index) {
if (index >= size)
throw new IndexOutOfBoundsException(
"Index (" + index + ") is greater than or equal to list size (" + size + ")");
final K old = a[index];
size--;
if (index != size)
System.arraycopy(a, index + 1, a, index, size - index);
a[size] = null;
assert size <= a.length;
return old;
}
@Override
public boolean remove(final Object k) {
int index = indexOf(k);
if (index == -1)
return false;
remove(index);
assert size <= a.length;
return true;
}
@Override
public K set(final int index, final K k) {
if (index >= size)
throw new IndexOutOfBoundsException(
"Index (" + index + ") is greater than or equal to list size (" + size + ")");
K old = a[index];
a[index] = k;
return old;
}
@Override
public void clear() {
Arrays.fill(a, 0, size, null);
size = 0;
assert size <= a.length;
}
@Override
public int size() {
return size;
}
@Override
public void size(final int size) {
if (size > a.length)
a = ObjectArrays.forceCapacity(a, size, this.size);
if (size > this.size)
Arrays.fill(a, this.size, size, (null));
else
Arrays.fill(a, size, this.size, (null));
this.size = size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
/**
* Trims this array list so that the capacity is equal to the size.
*
* @see java.util.ArrayList#trimToSize()
*/
public void trim() {
trim(0);
}
/**
* Trims the backing array if it is too large.
*
* If the current array length is smaller than or equal to {@code n}, this
* method does nothing. Otherwise, it trims the array length to the maximum
* between {@code n} and {@link #size()}.
*
*
* This method is useful when reusing lists. {@linkplain #clear() Clearing a
* list} leaves the array length untouched. If you are reusing a list many
* times, you can call this method with a typical size to avoid keeping around a
* very large array just because of a few large transient lists.
*
* @param n
* the threshold for the trimming.
*/
@SuppressWarnings("unchecked")
public void trim(final int n) {
// TODO: use Arrays.trim() and preserve type only if necessary
if (n >= a.length || size == a.length)
return;
final K t[] = (K[]) new Object[Math.max(n, size)];
System.arraycopy(a, 0, t, 0, size);
a = t;
assert size <= a.length;
}
/**
* Copies element of this type-specific list into the given array using
* optimized system calls.
*
* @param from
* the start index (inclusive).
* @param a
* the destination array.
* @param offset
* the offset into the destination array where to store the first
* element copied.
* @param length
* the number of elements to be copied.
*/
@Override
public void getElements(final int from, final Object[] a, final int offset, final int length) {
ObjectArrays.ensureOffsetLength(a, offset, length);
System.arraycopy(this.a, from, a, offset, length);
}
/**
* Removes elements of this type-specific list using optimized system calls.
*
* @param from
* the start index (inclusive).
* @param to
* the end index (exclusive).
*/
@Override
public void removeElements(final int from, final int to) {
it.unimi.dsi.fastutil.Arrays.ensureFromTo(size, from, to);
System.arraycopy(a, to, a, from, size - to);
size -= (to - from);
int i = to - from;
while (i-- != 0)
a[size + i] = null;
}
/**
* Adds elements to this type-specific list using optimized system calls.
*
* @param index
* the index at which to add elements.
* @param a
* the array containing the elements.
* @param offset
* the offset of the first element to add.
* @param length
* the number of elements to add.
*/
@Override
public void addElements(final int index, final K a[], final int offset, final int length) {
ensureIndex(index);
ObjectArrays.ensureOffsetLength(a, offset, length);
grow(size + length);
System.arraycopy(this.a, index, this.a, index + length, size - index);
System.arraycopy(a, offset, this.a, index, length);
size += length;
}
@Override
public boolean removeAll(final Collection c) {
final Object[] a = this.a;
int j = 0;
for (int i = 0; i < size; i++)
if (!c.contains((a[i])))
a[j++] = a[i];
Arrays.fill(a, j, size, null);
final boolean modified = size != j;
size = j;
return modified;
}
@Override
public ObjectListIterator listIterator(final int index) {
ensureIndex(index);
return new ObjectListIterator() {
int pos = index, last = -1;
@Override
public boolean hasNext() {
return pos < size;
}
@Override
public boolean hasPrevious() {
return pos > 0;
}
@Override
public K next() {
if (!hasNext())
throw new NoSuchElementException();
return a[last = pos++];
}
@Override
public K previous() {
if (!hasPrevious())
throw new NoSuchElementException();
return a[last = --pos];
}
@Override
public int nextIndex() {
return pos;
}
@Override
public int previousIndex() {
return pos - 1;
}
@Override
public void add(K k) {
ReferenceArrayList.this.add(pos++, k);
last = -1;
}
@Override
public void set(K k) {
if (last == -1)
throw new IllegalStateException();
ReferenceArrayList.this.set(last, k);
}
@Override
public void remove() {
if (last == -1)
throw new IllegalStateException();
ReferenceArrayList.this.remove(last);
/*
* If the last operation was a next(), we are removing an element *before* us,
* and we must decrease pos correspondingly.
*/
if (last < pos)
pos--;
last = -1;
}
};
}
@Override
public ReferenceArrayList clone() {
ReferenceArrayList c = new ReferenceArrayList<>(size);
System.arraycopy(a, 0, c.a, 0, size);
c.size = size;
return c;
}
/**
* Compares this type-specific array list to another one.
*
*
* This method exists only for sake of efficiency. The implementation inherited
* from the abstract implementation would already work.
*
* @param l
* a type-specific array list.
* @return true if the argument contains the same elements of this type-specific
* array list.
*/
public boolean equals(final ReferenceArrayList l) {
if (l == this)
return true;
int s = size();
if (s != l.size())
return false;
final K[] a1 = a;
final K[] a2 = l.a;
while (s-- != 0)
if (a1[s] != a2[s])
return false;
return true;
}
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
s.defaultWriteObject();
for (int i = 0; i < size; i++)
s.writeObject(a[i]);
}
@SuppressWarnings("unchecked")
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
a = (K[]) new Object[size];
for (int i = 0; i < size; i++)
a[i] = (K) s.readObject();
}
}