/*
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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/*
 *
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 *
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

package java.util.concurrent.atomic;

import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.function.BinaryOperator;
import java.util.function.UnaryOperator;

/**
 * An array of object references in which elements may be updated
 * atomically. See the {@link VarHandle} specification for
 * descriptions of the properties of atomic accesses.
 * @since 1.5
 * @author Doug Lea
 * @param <E> The base class of elements held in this array
 */
public class AtomicReferenceArray<E> implements java.io.Serializable {
 private static final long serialVersionUID = -6209656149925076980L;
 private static final VarHandle AA
 = MethodHandles.arrayElementVarHandle(Object[].class);
 private final Object[] array; // must have exact type Object[]

 /**
 * Creates a new AtomicReferenceArray of the given length, with all
 * elements initially null.
 *
 * @param length the length of the array
 */
 public AtomicReferenceArray(int length) {
 array = new Object[length];
 }

 /**
 * Creates a new AtomicReferenceArray with the same length as, and
 * all elements copied from, the given array.
 *
 * @param array the array to copy elements from
 * @throws NullPointerException if array is null
 */
 public AtomicReferenceArray(E[] array) {
 // Visibility guaranteed by final field guarantees
 this.array = Arrays.copyOf(array, array.length, Object[].class);
 }

 /**
 * Returns the length of the array.
 *
 * @return the length of the array
 */
 public final int length() {
 return array.length;
 }

 /**
 * Returns the current value of the element at index {@code i},
 * with memory effects as specified by {@link VarHandle#getVolatile}.
 *
 * @param i the index
 * @return the current value
 */
 @SuppressWarnings("unchecked")
 public final E get(int i) {
 return (E)AA.getVolatile(array, i);
 }

 /**
 * Sets the element at index {@code i} to {@code newValue},
 * with memory effects as specified by {@link VarHandle#setVolatile}.
 *
 * @param i the index
 * @param newValue the new value
 */
 public final void set(int i, E newValue) {
 AA.setVolatile(array, i, newValue);
 }

 /**
 * Sets the element at index {@code i} to {@code newValue},
 * with memory effects as specified by {@link VarHandle#setRelease}.
 *
 * @param i the index
 * @param newValue the new value
 * @since 1.6
 */
 public final void lazySet(int i, E newValue) {
 AA.setRelease(array, i, newValue);
 }

 /**
 * Atomically sets the element at index {@code i} to {@code
 * newValue} and returns the old value,
 * with memory effects as specified by {@link VarHandle#getAndSet}.
 *
 * @param i the index
 * @param newValue the new value
 * @return the previous value
 */
 @SuppressWarnings("unchecked")
 public final E getAndSet(int i, E newValue) {
 return (E)AA.getAndSet(array, i, newValue);
 }

 /**
 * Atomically sets the element at index {@code i} to {@code newValue}
 * if the element's current value {@code == expectedValue},
 * with memory effects as specified by {@link VarHandle#compareAndSet}.
 *
 * @param i the index
 * @param expectedValue the expected value
 * @param newValue the new value
 * @return {@code true} if successful. False return indicates that
 * the actual value was not equal to the expected value.
 */
 public final boolean compareAndSet(int i, E expectedValue, E newValue) {
 return AA.compareAndSet(array, i, expectedValue, newValue);
 }

 /**
 * Possibly atomically sets the element at index {@code i} to
 * {@code newValue} if the element's current value {@code == expectedValue},
 * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
 *
 * @deprecated This method has plain memory effects but the method
 * name implies volatile memory effects (see methods such as
 * {@link #compareAndExchange} and {@link #compareAndSet}). To avoid
 * confusion over plain or volatile memory effects it is recommended that
 * the method {@link #weakCompareAndSetPlain} be used instead.
 *
 * @param i the index
 * @param expectedValue the expected value
 * @param newValue the new value
 * @return {@code true} if successful
 * @see #weakCompareAndSetPlain
 */
 @Deprecated(since="9")
 public final boolean weakCompareAndSet(int i, E expectedValue, E newValue) {
 return AA.weakCompareAndSetPlain(array, i, expectedValue, newValue);
 }

 /**
 * Possibly atomically sets the element at index {@code i} to
 * {@code newValue} if the element's current value {@code == expectedValue},
 * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
 *
 * @param i the index
 * @param expectedValue the expected value
 * @param newValue the new value
 * @return {@code true} if successful
 * @since 9
 */
 public final boolean weakCompareAndSetPlain(int i, E expectedValue, E newValue) {
 return AA.weakCompareAndSetPlain(array, i, expectedValue, newValue);
 }

 /**
 * Atomically updates (with memory effects as specified by {@link
 * VarHandle#compareAndSet}) the element at index {@code i} with
 * the results of applying the given function, returning the
 * previous value. The function should be side-effect-free, since
 * it may be re-applied when attempted updates fail due to
 * contention among threads.
 *
 * @param i the index
 * @param updateFunction a side-effect-free function
 * @return the previous value
 * @since 1.8
 */
 public final E getAndUpdate(int i, UnaryOperator<E> updateFunction) {
 E prev = get(i), next = null;
 for (boolean haveNext = false;;) {
 if (!haveNext)
 next = updateFunction.apply(prev);
 if (weakCompareAndSetVolatile(i, prev, next))
 return prev;
 haveNext = (prev == (prev = get(i)));
 }
 }

 /**
 * Atomically updates (with memory effects as specified by {@link
 * VarHandle#compareAndSet}) the element at index {@code i} with
 * the results of applying the given function, returning the
 * updated value. The function should be side-effect-free, since it
 * may be re-applied when attempted updates fail due to contention
 * among threads.
 *
 * @param i the index
 * @param updateFunction a side-effect-free function
 * @return the updated value
 * @since 1.8
 */
 public final E updateAndGet(int i, UnaryOperator<E> updateFunction) {
 E prev = get(i), next = null;
 for (boolean haveNext = false;;) {
 if (!haveNext)
 next = updateFunction.apply(prev);
 if (weakCompareAndSetVolatile(i, prev, next))
 return next;
 haveNext = (prev == (prev = get(i)));
 }
 }

 /**
 * Atomically updates (with memory effects as specified by {@link
 * VarHandle#compareAndSet}) the element at index {@code i} with
 * the results of applying the given function to the current and
 * given values, returning the previous value. The function should
 * be side-effect-free, since it may be re-applied when attempted
 * updates fail due to contention among threads. The function is
 * applied with the current value of the element at index {@code i}
 * as its first argument, and the given update as the second
 * argument.
 *
 * @param i the index
 * @param x the update value
 * @param accumulatorFunction a side-effect-free function of two arguments
 * @return the previous value
 * @since 1.8
 */
 public final E getAndAccumulate(int i, E x,
 BinaryOperator<E> accumulatorFunction) {
 E prev = get(i), next = null;
 for (boolean haveNext = false;;) {
 if (!haveNext)
 next = accumulatorFunction.apply(prev, x);
 if (weakCompareAndSetVolatile(i, prev, next))
 return prev;
 haveNext = (prev == (prev = get(i)));
 }
 }

 /**
 * Atomically updates (with memory effects as specified by {@link
 * VarHandle#compareAndSet}) the element at index {@code i} with
 * the results of applying the given function to the current and
 * given values, returning the updated value. The function should
 * be side-effect-free, since it may be re-applied when attempted
 * updates fail due to contention among threads. The function is
 * applied with the current value of the element at index {@code i}
 * as its first argument, and the given update as the second
 * argument.
 *
 * @param i the index
 * @param x the update value
 * @param accumulatorFunction a side-effect-free function of two arguments
 * @return the updated value
 * @since 1.8
 */
 public final E accumulateAndGet(int i, E x,
 BinaryOperator<E> accumulatorFunction) {
 E prev = get(i), next = null;
 for (boolean haveNext = false;;) {
 if (!haveNext)
 next = accumulatorFunction.apply(prev, x);
 if (weakCompareAndSetVolatile(i, prev, next))
 return next;
 haveNext = (prev == (prev = get(i)));
 }
 }

 /**
 * Returns the String representation of the current values of array.
 * @return the String representation of the current values of array
 */
 public String toString() {
 int iMax = array.length - 1;
 if (iMax == -1)
 return "[]";

 StringBuilder b = new StringBuilder();
 b.append('[');
 for (int i = 0; ; i++) {
 b.append(get(i));
 if (i == iMax)
 return b.append(']').toString();
 b.append(',').append(' ');
 }
 }

 /**
 * Reconstitutes the instance from a stream (that is, deserializes it).
 * @param s the stream
 * @throws ClassNotFoundException if the class of a serialized object
 * could not be found
 * @throws java.io.IOException if an I/O error occurs
 */
 private void readObject(java.io.ObjectInputStream s)
 throws java.io.IOException, ClassNotFoundException {
 // Note: This must be changed if any additional fields are defined
 Object a = s.readFields().get("array", null);
 if (a == null || !a.getClass().isArray())
 throw new java.io.InvalidObjectException("Not array type");
 if (a.getClass() != Object[].class)
 a = Arrays.copyOf((Object[])a, Array.getLength(a), Object[].class);
 Field arrayField = java.security.AccessController.doPrivileged(
 (java.security.PrivilegedAction<Field>) () -> {
 try {
 Field f = AtomicReferenceArray.class
 .getDeclaredField("array");
 f.setAccessible(true);
 return f;
 } catch (ReflectiveOperationException e) {
 throw new Error(e);
 }});
 try {
 arrayField.set(this, a);
 } catch (IllegalAccessException e) {
 throw new Error(e);
 }
 }

 // jdk9

 /**
 * Returns the current value of the element at index {@code i},
 * with memory semantics of reading as if the variable was declared
 * non-{@code volatile}.
 *
 * @param i the index
 * @return the value
 * @since 9
 */
 public final E getPlain(int i) {
 return (E)AA.get(array, i);
 }

 /**
 * Sets the element at index {@code i} to {@code newValue},
 * with memory semantics of setting as if the variable was
 * declared non-{@code volatile} and non-{@code final}.
 *
 * @param i the index
 * @param newValue the new value
 * @since 9
 */
 public final void setPlain(int i, E newValue) {
 AA.set(array, i, newValue);
 }

 /**
 * Returns the current value of the element at index {@code i},
 * with memory effects as specified by {@link VarHandle#getOpaque}.
 *
 * @param i the index
 * @return the value
 * @since 9
 */
 public final E getOpaque(int i) {
 return (E)AA.getOpaque(array, i);
 }

 /**
 * Sets the element at index {@code i} to {@code newValue},
 * with memory effects as specified by {@link VarHandle#setOpaque}.
 *
 * @param i the index
 * @param newValue the new value
 * @since 9
 */
 public final void setOpaque(int i, E newValue) {
 AA.setOpaque(array, i, newValue);
 }

 /**
 * Returns the current value of the element at index {@code i},
 * with memory effects as specified by {@link VarHandle#getAcquire}.
 *
 * @param i the index
 * @return the value
 * @since 9
 */
 public final E getAcquire(int i) {
 return (E)AA.getAcquire(array, i);
 }

 /**
 * Sets the element at index {@code i} to {@code newValue},
 * with memory effects as specified by {@link VarHandle#setRelease}.
 *
 * @param i the index
 * @param newValue the new value
 * @since 9
 */
 public final void setRelease(int i, E newValue) {
 AA.setRelease(array, i, newValue);
 }

 /**
 * Atomically sets the element at index {@code i} to {@code newValue}
 * if the element's current value, referred to as the <em>witness
 * value</em>, {@code == expectedValue},
 * with memory effects as specified by
 * {@link VarHandle#compareAndExchange}.
 *
 * @param i the index
 * @param expectedValue the expected value
 * @param newValue the new value
 * @return the witness value, which will be the same as the
 * expected value if successful
 * @since 9
 */
 public final E compareAndExchange(int i, E expectedValue, E newValue) {
 return (E)AA.compareAndExchange(array, i, expectedValue, newValue);
 }

 /**
 * Atomically sets the element at index {@code i} to {@code newValue}
 * if the element's current value, referred to as the <em>witness
 * value</em>, {@code == expectedValue},
 * with memory effects as specified by
 * {@link VarHandle#compareAndExchangeAcquire}.
 *
 * @param i the index
 * @param expectedValue the expected value
 * @param newValue the new value
 * @return the witness value, which will be the same as the
 * expected value if successful
 * @since 9
 */
 public final E compareAndExchangeAcquire(int i, E expectedValue, E newValue) {
 return (E)AA.compareAndExchangeAcquire(array, i, expectedValue, newValue);
 }

 /**
 * Atomically sets the element at index {@code i} to {@code newValue}
 * if the element's current value, referred to as the <em>witness
 * value</em>, {@code == expectedValue},
 * with memory effects as specified by
 * {@link VarHandle#compareAndExchangeRelease}.
 *
 * @param i the index
 * @param expectedValue the expected value
 * @param newValue the new value
 * @return the witness value, which will be the same as the
 * expected value if successful
 * @since 9
 */
 public final E compareAndExchangeRelease(int i, E expectedValue, E newValue) {
 return (E)AA.compareAndExchangeRelease(array, i, expectedValue, newValue);
 }

 /**
 * Possibly atomically sets the element at index {@code i} to
 * {@code newValue} if the element's current value {@code == expectedValue},
 * with memory effects as specified by
 * {@link VarHandle#weakCompareAndSet}.
 *
 * @param i the index
 * @param expectedValue the expected value
 * @param newValue the new value
 * @return {@code true} if successful
 * @since 9
 */
 public final boolean weakCompareAndSetVolatile(int i, E expectedValue, E newValue) {
 return AA.weakCompareAndSet(array, i, expectedValue, newValue);
 }

 /**
 * Possibly atomically sets the element at index {@code i} to
 * {@code newValue} if the element's current value {@code == expectedValue},
 * with memory effects as specified by
 * {@link VarHandle#weakCompareAndSetAcquire}.
 *
 * @param i the index
 * @param expectedValue the expected value
 * @param newValue the new value
 * @return {@code true} if successful
 * @since 9
 */
 public final boolean weakCompareAndSetAcquire(int i, E expectedValue, E newValue) {
 return AA.weakCompareAndSetAcquire(array, i, expectedValue, newValue);
 }

 /**
 * Possibly atomically sets the element at index {@code i} to
 * {@code newValue} if the element's current value {@code == expectedValue},
 * with memory effects as specified by
 * {@link VarHandle#weakCompareAndSetRelease}.
 *
 * @param i the index
 * @param expectedValue the expected value
 * @param newValue the new value
 * @return {@code true} if successful
 * @since 9
 */
 public final boolean weakCompareAndSetRelease(int i, E expectedValue, E newValue) {
 return AA.weakCompareAndSetRelease(array, i, expectedValue, newValue);
 }

}