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/*
* Copyright (C) 2002-2022 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 PACKAGE;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.function.Consumer;
import it.unimi.dsi.fastutil.SafeMath;
/** A class providing static methods and objects that do useful things with type-specific iterators.
*
* @see Iterator
*/
public final class BIG_LIST_ITERATORS {
private BIG_LIST_ITERATORS() {}
/** A class returning no elements and a type-specific big list iterator interface.
*
* This class may be useful to implement your own in case you subclass
* a type-specific iterator.
*/
public static class EmptyBigListIterator KEY_GENERIC implements KEY_BIG_LIST_ITERATOR KEY_GENERIC, java.io.Serializable, Cloneable {
private static final long serialVersionUID = -7046029254386353129L;
protected EmptyBigListIterator() {}
@Override
public boolean hasNext() { return false; }
@Override
public boolean hasPrevious() { return false; }
@Override
public KEY_GENERIC_TYPE NEXT_KEY() { throw new NoSuchElementException(); }
@Override
public KEY_GENERIC_TYPE PREV_KEY() { throw new NoSuchElementException(); }
@Override
public long nextIndex() { return 0; }
@Override
public long previousIndex() { return -1; }
@Override
public long skip(long n) { return 0; }
@Override
public long back(long n) { return 0; }
@Override
public Object clone() { return EMPTY_BIG_LIST_ITERATOR; }
#if KEYS_PRIMITIVE
@Override
public void forEachRemaining(final METHOD_ARG_KEY_CONSUMER action) { }
#endif
DEPRECATED_IF_KEYS_PRIMITIVE
@Override
public void forEachRemaining(final Consumer action) { }
private Object readResolve() { return EMPTY_BIG_LIST_ITERATOR; }
}
/** An empty iterator (immutable). It is serializable and cloneable.
*
*
The class of this objects represent an abstract empty iterator
* that can iterate as a type-specific (list) iterator.
*/
SUPPRESS_WARNINGS_KEY_RAWTYPES
public static final EmptyBigListIterator EMPTY_BIG_LIST_ITERATOR = new EmptyBigListIterator();
/** An iterator returning a single element. */
private static class SingletonBigListIterator KEY_GENERIC implements KEY_BIG_LIST_ITERATOR KEY_GENERIC {
private final KEY_GENERIC_TYPE element;
private int curr;
public SingletonBigListIterator(final KEY_GENERIC_TYPE element) {
this.element = element;
}
@Override
public boolean hasNext() { return curr == 0; }
@Override
public boolean hasPrevious() { return curr == 1; }
@Override
public KEY_GENERIC_TYPE NEXT_KEY() {
if (! hasNext()) throw new NoSuchElementException();
curr = 1;
return element;
}
@Override
public KEY_GENERIC_TYPE PREV_KEY() {
if (! hasPrevious()) throw new NoSuchElementException();
curr = 0;
return element;
}
@Override
#if KEYS_PRIMITIVE
public void forEachRemaining(final METHOD_ARG_KEY_CONSUMER action) {
#else // ! KEY_PRIMITIVE == KEY_REFERENCE
public void forEachRemaining(final Consumer action) {
#endif
Objects.requireNonNull(action);
if (curr == 0) {
action.accept(element);
curr = 1;
}
}
@Override
public long nextIndex() {
return curr;
}
@Override
public long previousIndex() {
return curr - 1;
}
@Override
public long back(long n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
if (n == 0 || curr < 1) return 0;
curr = 1;
return 1;
}
@Override
public long skip(long n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
if (n == 0 || curr > 0) return 0;
curr = 0;
return 1;
}
}
/** Returns an iterator that iterates just over the given element.
*
* @param element the only element to be returned by a type-specific list iterator.
* @return an iterator that iterates just over {@code element}.
*/
public static KEY_GENERIC KEY_BIG_LIST_ITERATOR KEY_GENERIC singleton(final KEY_GENERIC_TYPE element) {
return new SingletonBigListIterator KEY_GENERIC_DIAMOND(element);
}
/** An unmodifiable wrapper class for big list iterators. */
public static class UnmodifiableBigListIterator KEY_GENERIC implements KEY_BIG_LIST_ITERATOR KEY_GENERIC {
protected final KEY_BIG_LIST_ITERATOR KEY_EXTENDS_GENERIC i;
public UnmodifiableBigListIterator(final KEY_BIG_LIST_ITERATOR KEY_EXTENDS_GENERIC i) {
this.i = i;
}
@Override
public boolean hasNext() { return i.hasNext(); }
@Override
public boolean hasPrevious() { return i.hasPrevious(); }
@Override
public KEY_GENERIC_TYPE NEXT_KEY() { return i.NEXT_KEY(); }
@Override
public KEY_GENERIC_TYPE PREV_KEY() { return i.PREV_KEY(); }
@Override
public long nextIndex() { return i.nextIndex(); }
@Override
public long previousIndex() { return i.previousIndex(); }
#if KEYS_PRIMITIVE
@Override
public void forEachRemaining(final METHOD_ARG_KEY_CONSUMER action) {
i.forEachRemaining(action);
}
#endif
DEPRECATED_IF_KEYS_PRIMITIVE
@Override
public void forEachRemaining(final Consumer action) {
i.forEachRemaining(action);
}
}
/** Returns an unmodifiable list iterator backed by the specified list iterator.
*
* @param i the list iterator to be wrapped in an unmodifiable list iterator.
* @return an unmodifiable view of the specified list iterator.
*/
public static KEY_GENERIC KEY_BIG_LIST_ITERATOR KEY_GENERIC unmodifiable(final KEY_BIG_LIST_ITERATOR KEY_EXTENDS_GENERIC i) { return new UnmodifiableBigListIterator KEY_GENERIC_DIAMOND(i); }
/** A class exposing a list iterator as a big-list iterator.. */
public static class BigListIteratorListIterator KEY_GENERIC implements KEY_BIG_LIST_ITERATOR KEY_GENERIC {
protected final KEY_LIST_ITERATOR KEY_GENERIC i;
protected BigListIteratorListIterator(final KEY_LIST_ITERATOR KEY_GENERIC i) {
this.i = i;
}
private int intDisplacement(long n) {
if (n < Integer.MIN_VALUE || n > Integer.MAX_VALUE) throw new IndexOutOfBoundsException("This big iterator is restricted to 32-bit displacements");
return (int)n;
}
@Override
public void set(KEY_GENERIC_TYPE ok) { i.set(ok); }
@Override
public void add(KEY_GENERIC_TYPE ok) { i.add(ok); }
@Override
public int back(int n) { return i.back(n); }
@Override
public long back(long n) { return i.back(intDisplacement(n)); }
@Override
public void remove() { i.remove(); }
@Override
public int skip(int n) { return i.skip(n); }
@Override
public long skip(long n) { return i.skip(intDisplacement(n)); }
@Override
public boolean hasNext() { return i.hasNext(); }
@Override
public boolean hasPrevious() { return i.hasPrevious(); }
@Override
public KEY_GENERIC_TYPE NEXT_KEY() { return i.NEXT_KEY(); }
@Override
public KEY_GENERIC_TYPE PREV_KEY() { return i.PREV_KEY(); }
@Override
public long nextIndex() { return i.nextIndex(); }
@Override
public long previousIndex() { return i.previousIndex(); }
#if KEYS_PRIMITIVE
@Override
public void forEachRemaining(final METHOD_ARG_KEY_CONSUMER action) {
i.forEachRemaining(action);
}
#endif
DEPRECATED_IF_KEYS_PRIMITIVE
@Override
public void forEachRemaining(final Consumer action) {
i.forEachRemaining(action);
}
}
/** Returns a big-list iterator backed by the specified list iterator.
*
* @param i the list iterator to adapted to the big-list-iterator interface.
* @return a big-list iterator backed by the specified list iterator.
*/
public static KEY_GENERIC KEY_BIG_LIST_ITERATOR KEY_GENERIC asBigListIterator(final KEY_LIST_ITERATOR KEY_GENERIC i) { return new BigListIteratorListIterator KEY_GENERIC_DIAMOND(i); }
/**
* A skeletal implementation for an iterator backed by an index based data store. High performance
* concrete implementations (like the main Iterator of BigArrayBigList) generally should avoid using this
* and just implement the interface directly, but should be decent for less
* performance critical implementations.
*
*
As the abstract methods in this class are used in inner loops, it is generally a
* good idea to override the class as {@code final} as to encourage the JVM to inline
* them (or alternatively, override the abstract methods as final).
*/
public static abstract class AbstractIndexBasedBigIterator KEY_GENERIC extends KEY_ABSTRACT_ITERATOR KEY_GENERIC {
/** The minimum pos can be, and is the logical start of the "range".
* Usually set to the initialPos unless it is a ListIterator, in which case it can vary.
*
* There isn't any way for a range to shift its beginning like the end can (through {@link #remove}),
* so this is final.
*/
protected final long minPos;
/** The current position index, the index of the item to be returned after the next call to {@link #next()}.
*
*
This value will be between {@code minPos} and {@link #getMaxPos()} (exclusive) (on a best effort, so concurrent
* structural modifications outside this iterator may cause this to be violated, but that usually invalidates
* iterators anyways). Thus {@code pos} being {@code minPos + 2} would mean {@link #next()}
* was called twice and the next call will return the third element of this iterator.
*/
protected long pos;
/** The last returned index by a call to {@link #next} or, if a list-iterator, {@link java.util.ListIterator#previous().
*
* Is {@code -1} if no such call has occurred or a mutation has occurred through this iterator and no
* advancement has been done.
*/
protected long lastReturned;
protected AbstractIndexBasedBigIterator(long minPos, long initialPos) {
this.minPos = minPos;
this.pos = initialPos;
}
// When you implement these, you should probably declare them final to encourage the JVM to inline them.
/** Get the item corresponding to the given index location.
*
*
Do not advance {@link #pos} in this method; the default {@code next} method takes care of this.
*
*
The {@code location} given will be between {@code minPos} and {@link #getMaxPos()} (exclusive).
* Thus, a {@code location} of {@code minPos + 2} would mean {@link #next()} was called twice
* and this method should return what the next call to {@link #next()} should return.
*/
protected abstract KEY_GENERIC_TYPE get(long location);
/** Remove the item at the given index.
*
*
Do not modify {@link #pos} in this method; the default {@code #remove()} method takes care of this.
*
*
This method should also do what is needed to track the change to the {@link #getMaxPos}.
* Usually this is accomplished by having this method call the parent {@link Collection}'s appropriate remove
* method, and having {@link #getMaxPos} track the parent collection's {@code size64()}.
*/
protected abstract void remove(long location);
/** The maximum pos can be, and is the logical end of the "range".
*
*
If pos is equal to the return of this method, this means the last element has been returned and the next call to {@link #next()} will throw.
*
*
Usually set return the parent collection's {@code size64()}, but does not have to be
* (for example, sublists and subranges).
*/
protected abstract long getMaxPos();
@Override
public boolean hasNext() { return pos < getMaxPos(); }
@Override
public KEY_GENERIC_TYPE NEXT_KEY() { if (! hasNext()) throw new NoSuchElementException(); return get(lastReturned = pos++); }
@Override
public void remove() {
if (lastReturned == -1) throw new IllegalStateException();
remove(lastReturned);
/* If the last operation was a next(), we are removing an element *before* us, and we must decrease pos correspondingly. */
if (lastReturned < pos) pos--;
lastReturned = -1;
}
@Override
public void forEachRemaining(final METHOD_ARG_KEY_CONSUMER action) {
while(pos < getMaxPos()) {
action.accept(get(lastReturned = pos++));
}
}
public long skip(long n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
final long max = getMaxPos();
final long remaining = max - pos;
if (n < remaining) {
pos += n;
} else {
n = remaining;
pos = max;
}
lastReturned = pos - 1;
return n;
}
@Override
public int skip(int n) {
return SafeMath.safeLongToInt(skip((long) n));
}
}
/**
* A skeletal implementation for a list-iterator backed by an index based data store. High performance
* concrete implementations (like the main ListIterator of ArrayList) generally should avoid using this
* and just implement the interface directly, but should be decent for less
* performance critical implementations.
*
*
As the abstract methods in this class are used in inner loops, it is generally a
* good idea to override the class as {@code final} as to encourage the JVM to inline
* them (or alternatively, override the abstract methods as final).
*/
public static abstract class AbstractIndexBasedBigListIterator KEY_GENERIC extends AbstractIndexBasedBigIterator KEY_GENERIC implements KEY_BIG_LIST_ITERATOR KEY_GENERIC {
protected AbstractIndexBasedBigListIterator(long minPos, long initialPos) {
super(minPos, initialPos);
}
// When you implement these, you should probably declare them final to encourage the JVM to inline them.
/** Add the given item at the given index.
*
*
This method should also do what is needed to track the change to the {@link #getMaxPos}.
* Usually this is accomplished by having this method call the parent {@link Collection}'s appropriate add
* method, and having {@link #getMaxPos} track the parent {@linkplain Collection#size() collection's size}.
*
*
Do not modify {@link #pos} in this method; the default {@code #add()} method takes care of this.
*
*
See {@link #pos} and {@link #get(int)} for discussion on what the location means.
*/
protected abstract void add(long location, KEY_GENERIC_TYPE k);
/** Sets the given item at the given index.
*
*
See {@link #pos} and {@link #get(int)} for discussion on what the location means.
*/
protected abstract void set(long location, KEY_GENERIC_TYPE k);
@Override
public boolean hasPrevious() { return pos > minPos; }
@Override
public KEY_GENERIC_TYPE PREV_KEY() { if (! hasPrevious()) throw new NoSuchElementException(); return get(lastReturned = --pos); }
@Override
public long nextIndex() { return pos; }
@Override
public long previousIndex() { return pos - 1; }
@Override
public void add(final KEY_GENERIC_TYPE k) {
add(pos++, k);
lastReturned = -1;
}
@Override
public void set(final KEY_GENERIC_TYPE k) {
if (lastReturned == -1) throw new IllegalStateException();
set(lastReturned, k);
}
// TODO since this method doesn't depend on the type at all, should it be "hoisted" into a
// non type-specific superclass in it.unimi.dsi.fastutil?
@Override
public long back(long n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
final long remaining = pos - minPos;
if (n < remaining) {
pos -= n;
} else {
n = remaining;
pos = minPos;
}
lastReturned = pos;
return n;
}
}
}