dev.miku.r2dbc.mysql.util.InternalArrays Maven / Gradle / Ivy
/*
* Copyright 2018-2020 the original author or authors.
*
* 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 dev.miku.r2dbc.mysql.util;
import java.util.AbstractList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.RandomAccess;
import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.function.UnaryOperator;
import static dev.miku.r2dbc.mysql.util.AssertUtils.requireNonNull;
/**
* An utility with constants of arrays for reduce temporary objects and
* ensure immutability, do NOT use it outer than {@literal r2dbc-mysql}.
*/
public final class InternalArrays {
public static final byte[] EMPTY_BYTES = {};
public static final String[] EMPTY_STRINGS = {};
/**
* Wrap an array to an immutable {@link List} without deep copy.
*
* WARNING: make sure {@code a} will not be changed by other one.
*
* @param a the array which want to be wrapped.
* @param the type for elements of {@code a}.
* @return read only {@link List}.
*/
@SuppressWarnings("varargs")
@SafeVarargs
public static List asImmutableList(E... a) {
requireNonNull(a, "array must not be null");
switch (a.length) {
case 0:
return Collections.emptyList();
case 1:
return Collections.singletonList(a[0]);
default:
return new ArrList<>(a);
}
}
/**
* Convert an array to an immutable {@link List} with array copy.
* It will copy array but will not clone each element.
*
* @param a the array which want to be converted.
* @param the type for elements of {@code a}.
* @return read only {@link List}.
*/
@SuppressWarnings("varargs")
@SafeVarargs
public static List toImmutableList(E... a) {
requireNonNull(a, "array must not be null");
switch (a.length) {
case 0:
return Collections.emptyList();
case 1:
return Collections.singletonList(a[0]);
default:
return new ArrList<>(Arrays.copyOf(a, a.length));
}
}
/**
* Wrap an array to a read only {@link Iterator}.
*
* WARNING: make sure {@code a} will not be changed by other one.
*
* @param a the array which want to be wrapped.
* @param the type for elements of {@code a}.
* @return read only {@link Iterator}.
*/
@SuppressWarnings("varargs")
@SafeVarargs
public static Iterator asIterator(E... a) {
requireNonNull(a, "array must not be null");
if (a.length == 0) {
return Collections.emptyIterator();
}
return new ArrItr<>(0, a);
}
private InternalArrays() {
}
}
final class ArrItr implements ListIterator, Iterator {
private int i;
private final E[] a;
ArrItr(int i, E[] a) {
this.i = i;
this.a = a;
}
@Override
public boolean hasNext() {
return i < a.length;
}
@Override
public E next() {
if (i >= a.length) {
throw new NoSuchElementException();
}
return a[i++];
}
@Override
public boolean hasPrevious() {
return i > 0;
}
@Override
public E previous() {
if (i <= 0) {
throw new NoSuchElementException();
}
return a[--i];
}
public int nextIndex() {
return i;
}
public int previousIndex() {
return i - 1;
}
@Override
public void forEachRemaining(Consumer action) {
Objects.requireNonNull(action);
while (i < a.length) {
action.accept(a[i++]);
}
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
@Override
public void set(E e) {
throw new UnsupportedOperationException();
}
@Override
public void add(E e) {
throw new UnsupportedOperationException();
}
}
final class ArrList extends AbstractList implements List, RandomAccess {
private final E[] a;
ArrList(E[] a) {
this.a = a;
}
@Override
public E get(int index) {
return a[index];
}
@Override
public int size() {
return a.length;
}
@Override
public boolean isEmpty() {
return a.length == 0;
}
@Override
public Iterator iterator() {
return new ArrItr<>(0, a);
}
@Override
public ListIterator listIterator(int index) {
if (index < 0 || index > a.length) {
throw new IndexOutOfBoundsException();
}
return new ArrItr<>(index, a);
}
@Override
public Spliterator spliterator() {
return Arrays.spliterator(a);
}
@Override
public void forEach(Consumer action) {
Objects.requireNonNull(action);
for (E t : a) {
action.accept(t);
}
}
@Override
public Object[] toArray() {
return Arrays.copyOf(a, a.length);
}
@SuppressWarnings("unchecked")
@Override
public T[] toArray(T[] a) {
T[] source = (T[]) this.a;
if (a.length < source.length) {
// Make a new array of a's runtime type, but my contents:
return (T[]) Arrays.copyOf(source, source.length, a.getClass());
}
System.arraycopy(source, 0, a, 0, this.a.length);
if (a.length > source.length) {
a[source.length] = null;
}
return a;
}
@Override
public boolean addAll(int index, Collection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeIf(Predicate filter) {
throw new UnsupportedOperationException();
}
@Override
public void replaceAll(UnaryOperator operator) {
throw new UnsupportedOperationException();
}
@Override
public void sort(Comparator c) {
throw new UnsupportedOperationException();
}
@Override
public void clear() {
throw new UnsupportedOperationException();
}
@Override
public boolean remove(Object o) {
throw new UnsupportedOperationException();
}
@Override
public boolean addAll(Collection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeAll(Collection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean retainAll(Collection c) {
throw new UnsupportedOperationException();
}
}