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/*
* Copyright (C) 2002-2023 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.Spliterator;
import java.util.List;
import static it.unimi.dsi.fastutil.Size64.sizeOf;
/**
* A type-specific {@link List}; provides some additional methods that use polymorphism to avoid
* (un)boxing.
*
*
* Additionally, this interface strengthens {@link #iterator()}, {@link #listIterator()},
* {@link #listIterator(int)} and {@link #subList(int,int)}. The former had been already
* strengthened upstream, but unfortunately {@link List} re-specifies it.
*
*
* This interface specifies reference equality semantics (members will be compared equal with
* {@code ==} instead of {@link Object#equals(Object) equals}), which may result in breaks in
* contract if attempted to be used with non reference-equality semantics based {@link List}s. For
* example, a {@code aReferenceList.equals(aObjectList)} may return different a different result
* then {@code aObjectList.equals(aReferenceList)}, in violation of {@link Object#equals equals}'s
* contract requiring it being symmetric.
*
*
* Besides polymorphic methods, this interfaces specifies methods to copy into an array or remove
* contiguous sublists. Although the abstract implementation of this interface provides simple,
* one-by-one implementations of these methods, it is expected that concrete implementation override
* them with optimized versions.
*
* @see List
*/
public interface ReferenceList extends List, ReferenceCollection {
/**
* Returns a type-specific iterator on the elements of this list.
*
* @apiNote This specification strengthens the one given in {@link List#iterator()}. It would not be
* normally necessary, but {@link java.lang.Iterable#iterator()} is bizarrily re-specified
* in {@link List}.
*
* Also, this is generally the only {@code iterator} method subclasses should override.
*
* @return an iterator on the elements of this list.
*/
@Override
ObjectListIterator iterator();
/**
* Returns a type-specific spliterator on the elements of this list.
*
*
* List spliterators must report at least {@link Spliterator#SIZED} and {@link Spliterator#ORDERED}.
*
*
* See {@link java.util.List#spliterator()} for more documentation on the requirements of the
* returned spliterator.
*
* @apiNote This specification strengthens the one given in
* {@link java.util.Collection#spliterator()}, which was already strengthened in the
* corresponding type-specific class, but was weakened by the fact that this interface
* extends {@link List}.
*
* Also, this is generally the only {@code spliterator} method subclasses should override.
*
* @implSpec The default implementation returns a late-binding spliterator (see {@link Spliterator}
* for documentation on what binding policies mean).
*
* - For {@link java.util.RandomAccess RandomAccess} lists, this will return a
* spliterator that calls the type-specific {@link #get(int)} method on the appropriate
* indexes.
* - Otherwise, the spliterator returned will wrap this instance's type specific
* {@link #iterator}.
*
*
* In either case, the spliterator reports {@link Spliterator#SIZED},
* {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
*
* @implNote As the non-{@linkplain java.util.RandomAccess RandomAccess} case is based on the
* iterator, and {@link java.util.Iterator} is an inherently linear API, the returned
* spliterator will yield limited performance gains when run in parallel contexts, as the
* returned spliterator's {@link Spliterator#trySplit() trySplit()} will have linear
* runtime.
*
* For {@link java.util.RandomAccess RandomAccess} lists, the parallel performance should
* be reasonable assuming {@link #get(int)} is truly constant time like
* {@link java.util.RandomAccess RandomAccess} suggests.
*
* @return {@inheritDoc}
* @since 8.5.0
*/
@Override
default ObjectSpliterator spliterator() {
if (this instanceof java.util.RandomAccess) {
return new AbstractReferenceList.IndexBasedSpliterator<>(this, 0);
} else {
return ObjectSpliterators.asSpliterator(iterator(), sizeOf(this), ObjectSpliterators.LIST_SPLITERATOR_CHARACTERISTICS);
}
}
/**
* Returns a type-specific list iterator on the list.
*
* @see List#listIterator()
*/
@Override
ObjectListIterator listIterator();
/**
* Returns a type-specific list iterator on the list starting at a given index.
*
* @see List#listIterator(int)
*/
@Override
ObjectListIterator listIterator(int index);
/**
* Returns a type-specific view of the portion of this list from the index {@code from}, inclusive,
* to the index {@code to}, exclusive.
*
* @apiNote This specification strengthens the one given in {@link List#subList(int,int)}.
*
* @see List#subList(int,int)
*/
@Override
ReferenceList subList(int from, int to);
/**
* Sets the size of this list.
*
*
* If the specified size is smaller than the current size, the last elements are discarded.
* Otherwise, they are filled with 0/{@code null}/{@code false}.
*
* @param size the new size.
*/
void size(int size);
/**
* Copies (hopefully quickly) elements of this type-specific list into the given array.
*
* @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.
*/
void getElements(int from, Object a[], int offset, int length);
/**
* Removes (hopefully quickly) elements of this type-specific list.
*
* @param from the start index (inclusive).
* @param to the end index (exclusive).
*/
void removeElements(int from, int to);
/**
* Add (hopefully quickly) elements to this type-specific list.
*
* @param index the index at which to add elements.
* @param a the array containing the elements.
*/
void addElements(int index, K a[]);
/**
* Add (hopefully quickly) elements to this type-specific list.
*
* @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.
*/
void addElements(int index, K a[], int offset, int length);
/**
* Set (hopefully quickly) elements to match the array given.
*
* @param a the array containing the elements.
* @since 8.3.0
*/
default void setElements(K a[]) {
setElements(0, a);
}
/**
* Set (hopefully quickly) elements to match the array given.
*
* @param index the index at which to start setting elements.
* @param a the array containing the elements.
* @since 8.3.0
*/
default void setElements(int index, K a[]) {
setElements(index, a, 0, a.length);
}
/**
* Set (hopefully quickly) elements to match the array given.
*
* Sets each in this list to the corresponding elements in the array, as if by
*
*
* ListIterator iter = listIterator(index);
* int i = 0;
* while (i < length) {
* iter.next();
* iter.set(a[offset + i++]);
* }
*
*
* However, the exact implementation may be more efficient, taking into account whether random
* access is faster or not, or at the discretion of subclasses, abuse internals.
*
* @param index the index at which to start setting 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.
* @since 8.3.0
*/
default void setElements(int index, K a[], int offset, int length) {
// We can't use AbstractList#ensureIndex, sadly.
if (index < 0) throw new IndexOutOfBoundsException("Index (" + index + ") is negative");
if (index > size()) throw new IndexOutOfBoundsException("Index (" + index + ") is greater than list size (" + (size()) + ")");
ObjectArrays.ensureOffsetLength(a, offset, length);
if (index + length > size()) throw new IndexOutOfBoundsException("End index (" + (index + length) + ") is greater than list size (" + size() + ")");
ObjectListIterator iter = listIterator(index);
int i = 0;
while (i < length) {
iter.next();
iter.set(a[offset + i++]);
}
}
/**
* Inserts all of the elements in the specified type-specific list into this type-specific list at
* the specified position (optional operation).
*
* @apiNote This method exists only for the sake of efficiency: override are expected to use
* {@link #getElements}/{@link #addElements}.
* @implSpec This method delegates to the one accepting a collection, but it might be implemented
* more efficiently.
* @see List#addAll(int,Collection)
*/
default boolean addAll(int index, ReferenceList l) {
return addAll(index, (ReferenceCollection)l);
}
/**
* Appends all of the elements in the specified type-specific list to the end of this type-specific
* list (optional operation).
*
* @implSpec This method delegates to the index-based version, passing {@link #size()} as first
* argument.
* @see List#addAll(Collection)
*/
default boolean addAll(ReferenceList l) {
return addAll(size(), l);
}
/**
* Returns an immutable empty list.
*
* @return an immutable empty list.
*/
public static ReferenceList of() {
// Returning ImmutableList.EMPTY instead of LISTS.EMPTY_LIST to make dimorphic call site.
// See https://github.com/vigna/fastutil/issues/183
return ReferenceImmutableList.of();
}
/**
* Returns an immutable list with the element given.
*
* @param e the element that the returned list will contain.
* @return an immutable list containing {@code e}.
*/
public static ReferenceList of(final K e) {
return ReferenceLists.singleton(e);
}
/**
* Returns an immutable list with the elements given.
*
* @param e0 the first element.
* @param e1 the second element.
* @return an immutable list containing {@code e0} and {@code e1}.
*/
public static ReferenceList of(final K e0, final K e1) {
return ReferenceImmutableList.of(e0, e1);
}
/**
* Returns an immutable list with the elements given.
*
* @param e0 the first element.
* @param e1 the second element.
* @param e2 the third element.
* @return an immutable list containing {@code e0}, {@code e1}, and {@code e2}.
*/
public static ReferenceList of(final K e0, final K e1, final K e2) {
return ReferenceImmutableList.of(e0, e1, e2);
}
/**
* Returns an immutable list with the elements given.
*
*
* Note that this method does not perform a defensive copy.
*
* @param a a list of elements that will be used to initialize the immutable list.
* @return an immutable list containing the elements of {@code a}.
*/
@SuppressWarnings("unchecked")
@SafeVarargs
public static ReferenceList of(final K... a) {
switch (a.length) {
case 0:
return of();
case 1:
return of(a[0]);
// Add cases of 2 and 3 if we ever have special logic for those.
default:
// fall through
}
return ReferenceImmutableList.of(a);
}
/**
* Sorts this list using a sort assured to be stable.
*
*
* Pass {@code null} to sort using natural ordering.
*
*
* Unless a subclass specifies otherwise, the results of the method if the list is concurrently
* modified during the sort are unspecified.
*
* @implSpec The default implementation dumps the elements into an array using {@link #toArray()},
* sorts the array, then replaces all elements using the {@link #setElements} function.
*
* @since 8.5.0
*/
@Override
@SuppressWarnings("unchecked")
default void sort(final java.util.Comparator comparator) {
K[] elements = (K[])toArray();
// Current stableSort implementation delegates to java.util.Arrays.sort for reference types,
// so we aren't losing out on JDK's optimized Timsort.
if (comparator == null) {
ObjectArrays.stableSort(elements);
} else {
ObjectArrays.stableSort(elements, comparator);
}
setElements(elements);
}
/**
* Sorts this list using a sort not assured to be stable. This differs from
* {@link List#sort(java.util.Comparator)} in that the results are not assured to be stable, but may
* be a bit faster.
*
*
* Pass {@code null} to sort using natural ordering.
*
*
* Unless a subclass specifies otherwise, the results of the method if the list is concurrently
* modified during the sort are unspecified.
*
* @implSpec The default implementation dumps the elements into an array using {@link #toArray()},
* sorts the array, then replaces all elements using the {@link #setElements} function.
*
* @since 8.3.0
*/
@SuppressWarnings("unchecked")
default void unstableSort(final java.util.Comparator comparator) {
K[] elements = (K[])toArray();
if (comparator == null) {
ObjectArrays.unstableSort(elements);
} else {
ObjectArrays.unstableSort(elements, comparator);
}
setElements(elements);
}
}