luni/src/main/java/java/util/concurrent/atomic/AtomicLong.java - platform/libcore - Git at Google

 /*
  * 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.util.function.LongBinaryOperator;
 import java.util.function.LongUnaryOperator;

 /**
  * A {@code long} value that may be updated atomically.  See the
  * {@link java.util.concurrent.atomic} package specification for
  * description of the properties of atomic variables. An
  * {@code AtomicLong} is used in applications such as atomically
  * incremented sequence numbers, and cannot be used as a replacement
  * for a {@link java.lang.Long}. However, this class does extend
  * {@code Number} to allow uniform access by tools and utilities that
  * deal with numerically-based classes.
  *
  * @since 1.5
  * @author Doug Lea
  */
 public class AtomicLong extends Number implements java.io.Serializable {
     private static final long serialVersionUID = 1927816293512124184L;

     private static final sun.misc.Unsafe U = sun.misc.Unsafe.getUnsafe();
     private static final long VALUE;

     /**
      * Records whether the underlying JVM supports lockless
      * compareAndSwap for longs. While the Unsafe.compareAndSwapLong
      * method works in either case, some constructions should be
      * handled at Java level to avoid locking user-visible locks.
      */
     static final boolean VM_SUPPORTS_LONG_CAS = VMSupportsCS8();

     /**
      * Returns whether underlying JVM supports lockless CompareAndSet
      * for longs. Called only once and cached in VM_SUPPORTS_LONG_CAS.
      */
     private static native boolean VMSupportsCS8();

     static {
         try {
             VALUE = U.objectFieldOffset
                 (AtomicLong.class.getDeclaredField("value"));
         } catch (ReflectiveOperationException e) {
             throw new Error(e);
         }
     }

     private volatile long value;

     /**
      * Creates a new AtomicLong with the given initial value.
      *
      * @param initialValue the initial value
      */
     public AtomicLong(long initialValue) {
         value = initialValue;
     }

     /**
      * Creates a new AtomicLong with initial value {@code 0}.
      */
     public AtomicLong() {
     }

     /**
      * Gets the current value.
      *
      * @return the current value
      */
     public final long get() {
         return value;
     }

     /**
      * Sets to the given value.
      *
      * @param newValue the new value
      */
     public final void set(long newValue) {
         // Use putLongVolatile instead of ordinary volatile store when
         // using compareAndSwapLong, for sake of some 32bit systems.
         U.putLongVolatile(this, VALUE, newValue);
     }

     /**
      * Eventually sets to the given value.
      *
      * @param newValue the new value
      * @since 1.6
      */
     public final void lazySet(long newValue) {
         U.putOrderedLong(this, VALUE, newValue);
     }

     /**
      * Atomically sets to the given value and returns the old value.
      *
      * @param newValue the new value
      * @return the previous value
      */
     public final long getAndSet(long newValue) {
         return U.getAndSetLong(this, VALUE, newValue);
     }

     /**
      * Atomically sets the value to the given updated value
      * if the current value {@code ==} the expected value.
      *
      * @param expect the expected value
      * @param update 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(long expect, long update) {
         return U.compareAndSwapLong(this, VALUE, expect, update);
     }

     /**
      * Atomically sets the value to the given updated value
      * if the current value {@code ==} the expected value.
      *
      * <p><a href="package-summary.html#weakCompareAndSet">May fail
      * spuriously and does not provide ordering guarantees</a>, so is
      * only rarely an appropriate alternative to {@code compareAndSet}.
      *
      * @param expect the expected value
      * @param update the new value
      * @return {@code true} if successful
      */
     public final boolean weakCompareAndSet(long expect, long update) {
         return U.compareAndSwapLong(this, VALUE, expect, update);
     }

     /**
      * Atomically increments by one the current value.
      *
      * @return the previous value
      */
     public final long getAndIncrement() {
         return U.getAndAddLong(this, VALUE, 1L);
     }

     /**
      * Atomically decrements by one the current value.
      *
      * @return the previous value
      */
     public final long getAndDecrement() {
         return U.getAndAddLong(this, VALUE, -1L);
     }

     /**
      * Atomically adds the given value to the current value.
      *
      * @param delta the value to add
      * @return the previous value
      */
     public final long getAndAdd(long delta) {
         return U.getAndAddLong(this, VALUE, delta);
     }

     /**
      * Atomically increments by one the current value.
      *
      * @return the updated value
      */
     public final long incrementAndGet() {
         return U.getAndAddLong(this, VALUE, 1L) + 1L;
     }

     /**
      * Atomically decrements by one the current value.
      *
      * @return the updated value
      */
     public final long decrementAndGet() {
         return U.getAndAddLong(this, VALUE, -1L) - 1L;
     }

     /**
      * Atomically adds the given value to the current value.
      *
      * @param delta the value to add
      * @return the updated value
      */
     public final long addAndGet(long delta) {
         return U.getAndAddLong(this, VALUE, delta) + delta;
     }

     /**
      * Atomically updates the current value 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 updateFunction a side-effect-free function
      * @return the previous value
      * @since 1.8
      */
     public final long getAndUpdate(LongUnaryOperator updateFunction) {
         long prev, next;
         do {
             prev = get();
             next = updateFunction.applyAsLong(prev);
         } while (!compareAndSet(prev, next));
         return prev;
     }

     /**
      * Atomically updates the current value 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 updateFunction a side-effect-free function
      * @return the updated value
      * @since 1.8
      */
     public final long updateAndGet(LongUnaryOperator updateFunction) {
         long prev, next;
         do {
             prev = get();
             next = updateFunction.applyAsLong(prev);
         } while (!compareAndSet(prev, next));
         return next;
     }

     /**
      * Atomically updates the current value 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 as its first argument,
      * and the given update as the second argument.
      *
      * @param x the update value
      * @param accumulatorFunction a side-effect-free function of two arguments
      * @return the previous value
      * @since 1.8
      */
     public final long getAndAccumulate(long x,
                                        LongBinaryOperator accumulatorFunction) {
         long prev, next;
         do {
             prev = get();
             next = accumulatorFunction.applyAsLong(prev, x);
         } while (!compareAndSet(prev, next));
         return prev;
     }

     /**
      * Atomically updates the current value 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 as its first argument,
      * and the given update as the second argument.
      *
      * @param x the update value
      * @param accumulatorFunction a side-effect-free function of two arguments
      * @return the updated value
      * @since 1.8
      */
     public final long accumulateAndGet(long x,
                                        LongBinaryOperator accumulatorFunction) {
         long prev, next;
         do {
             prev = get();
             next = accumulatorFunction.applyAsLong(prev, x);
         } while (!compareAndSet(prev, next));
         return next;
     }

     /**
      * Returns the String representation of the current value.
      * @return the String representation of the current value
      */
     public String toString() {
         return Long.toString(get());
     }

     /**
      * Returns the value of this {@code AtomicLong} as an {@code int}
      * after a narrowing primitive conversion.
      * @jls 5.1.3 Narrowing Primitive Conversions
      */
     public int intValue() {
         return (int)get();
     }

     /**
      * Returns the value of this {@code AtomicLong} as a {@code long}.
      * Equivalent to {@link #get()}.
      */
     public long longValue() {
         return get();
     }

     /**
      * Returns the value of this {@code AtomicLong} as a {@code float}
      * after a widening primitive conversion.
      * @jls 5.1.2 Widening Primitive Conversions
      */
     public float floatValue() {
         return (float)get();
     }

     /**
      * Returns the value of this {@code AtomicLong} as a {@code double}
      * after a widening primitive conversion.
      * @jls 5.1.2 Widening Primitive Conversions
      */
     public double doubleValue() {
         return (double)get();
     }

 }
	/*
	* 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.util.function.LongBinaryOperator;
	import java.util.function.LongUnaryOperator;

	/**
	* A {@code long} value that may be updated atomically. See the
	* {@link java.util.concurrent.atomic} package specification for
	* description of the properties of atomic variables. An
	* {@code AtomicLong} is used in applications such as atomically
	* incremented sequence numbers, and cannot be used as a replacement
	* for a {@link java.lang.Long}. However, this class does extend
	* {@code Number} to allow uniform access by tools and utilities that
	* deal with numerically-based classes.
	*
	* @since 1.5
	* @author Doug Lea
	*/
	public class AtomicLong extends Number implements java.io.Serializable {
	private static final long serialVersionUID = 1927816293512124184L;

	private static final sun.misc.Unsafe U = sun.misc.Unsafe.getUnsafe();
	private static final long VALUE;

	/**
	* Records whether the underlying JVM supports lockless
	* compareAndSwap for longs. While the Unsafe.compareAndSwapLong
	* method works in either case, some constructions should be
	* handled at Java level to avoid locking user-visible locks.
	*/
	static final boolean VM_SUPPORTS_LONG_CAS = VMSupportsCS8();

	/**
	* Returns whether underlying JVM supports lockless CompareAndSet
	* for longs. Called only once and cached in VM_SUPPORTS_LONG_CAS.
	*/
	private static native boolean VMSupportsCS8();

	static {
	try {
	VALUE = U.objectFieldOffset
	(AtomicLong.class.getDeclaredField("value"));
	} catch (ReflectiveOperationException e) {
	throw new Error(e);
	}
	}

	private volatile long value;

	/**
	* Creates a new AtomicLong with the given initial value.
	*
	* @param initialValue the initial value
	*/
	public AtomicLong(long initialValue) {
	value = initialValue;
	}

	/**
	* Creates a new AtomicLong with initial value {@code 0}.
	*/
	public AtomicLong() {
	}

	/**
	* Gets the current value.
	*
	* @return the current value
	*/
	public final long get() {
	return value;
	}

	/**
	* Sets to the given value.
	*
	* @param newValue the new value
	*/
	public final void set(long newValue) {
	// Use putLongVolatile instead of ordinary volatile store when
	// using compareAndSwapLong, for sake of some 32bit systems.
	U.putLongVolatile(this, VALUE, newValue);
	}

	/**
	* Eventually sets to the given value.
	*
	* @param newValue the new value
	* @since 1.6
	*/
	public final void lazySet(long newValue) {
	U.putOrderedLong(this, VALUE, newValue);
	}

	/**
	* Atomically sets to the given value and returns the old value.
	*
	* @param newValue the new value
	* @return the previous value
	*/
	public final long getAndSet(long newValue) {
	return U.getAndSetLong(this, VALUE, newValue);
	}

	/**
	* Atomically sets the value to the given updated value
	* if the current value {@code ==} the expected value.
	*
	* @param expect the expected value
	* @param update 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(long expect, long update) {
	return U.compareAndSwapLong(this, VALUE, expect, update);
	}

	/**
	* Atomically sets the value to the given updated value
	* if the current value {@code ==} the expected value.
	*
	* <p><a href="package-summary.html#weakCompareAndSet">May fail
	* spuriously and does not provide ordering guarantees</a>, so is
	* only rarely an appropriate alternative to {@code compareAndSet}.
	*
	* @param expect the expected value
	* @param update the new value
	* @return {@code true} if successful
	*/
	public final boolean weakCompareAndSet(long expect, long update) {
	return U.compareAndSwapLong(this, VALUE, expect, update);
	}

	/**
	* Atomically increments by one the current value.
	*
	* @return the previous value
	*/
	public final long getAndIncrement() {
	return U.getAndAddLong(this, VALUE, 1L);
	}

	/**
	* Atomically decrements by one the current value.
	*
	* @return the previous value
	*/
	public final long getAndDecrement() {
	return U.getAndAddLong(this, VALUE, -1L);
	}

	/**
	* Atomically adds the given value to the current value.
	*
	* @param delta the value to add
	* @return the previous value
	*/
	public final long getAndAdd(long delta) {
	return U.getAndAddLong(this, VALUE, delta);
	}

	/**
	* Atomically increments by one the current value.
	*
	* @return the updated value
	*/
	public final long incrementAndGet() {
	return U.getAndAddLong(this, VALUE, 1L) + 1L;
	}

	/**
	* Atomically decrements by one the current value.
	*
	* @return the updated value
	*/
	public final long decrementAndGet() {
	return U.getAndAddLong(this, VALUE, -1L) - 1L;
	}

	/**
	* Atomically adds the given value to the current value.
	*
	* @param delta the value to add
	* @return the updated value
	*/
	public final long addAndGet(long delta) {
	return U.getAndAddLong(this, VALUE, delta) + delta;
	}

	/**
	* Atomically updates the current value 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 updateFunction a side-effect-free function
	* @return the previous value
	* @since 1.8
	*/
	public final long getAndUpdate(LongUnaryOperator updateFunction) {
	long prev, next;
	do {
	prev = get();
	next = updateFunction.applyAsLong(prev);
	} while (!compareAndSet(prev, next));
	return prev;
	}

	/**
	* Atomically updates the current value 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 updateFunction a side-effect-free function
	* @return the updated value
	* @since 1.8
	*/
	public final long updateAndGet(LongUnaryOperator updateFunction) {
	long prev, next;
	do {
	prev = get();
	next = updateFunction.applyAsLong(prev);
	} while (!compareAndSet(prev, next));
	return next;
	}

	/**
	* Atomically updates the current value 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 as its first argument,
	* and the given update as the second argument.
	*
	* @param x the update value
	* @param accumulatorFunction a side-effect-free function of two arguments
	* @return the previous value
	* @since 1.8
	*/
	public final long getAndAccumulate(long x,
	LongBinaryOperator accumulatorFunction) {
	long prev, next;
	do {
	prev = get();
	next = accumulatorFunction.applyAsLong(prev, x);
	} while (!compareAndSet(prev, next));
	return prev;
	}

	/**
	* Atomically updates the current value 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 as its first argument,
	* and the given update as the second argument.
	*
	* @param x the update value
	* @param accumulatorFunction a side-effect-free function of two arguments
	* @return the updated value
	* @since 1.8
	*/
	public final long accumulateAndGet(long x,
	LongBinaryOperator accumulatorFunction) {
	long prev, next;
	do {
	prev = get();
	next = accumulatorFunction.applyAsLong(prev, x);
	} while (!compareAndSet(prev, next));
	return next;
	}

	/**
	* Returns the String representation of the current value.
	* @return the String representation of the current value
	*/
	public String toString() {
	return Long.toString(get());
	}

	/**
	* Returns the value of this {@code AtomicLong} as an {@code int}
	* after a narrowing primitive conversion.
	* @jls 5.1.3 Narrowing Primitive Conversions
	*/
	public int intValue() {
	return (int)get();
	}

	/**
	* Returns the value of this {@code AtomicLong} as a {@code long}.
	* Equivalent to {@link #get()}.
	*/
	public long longValue() {
	return get();
	}

	/**
	* Returns the value of this {@code AtomicLong} as a {@code float}
	* after a widening primitive conversion.
	* @jls 5.1.2 Widening Primitive Conversions
	*/
	public float floatValue() {
	return (float)get();
	}

	/**
	* Returns the value of this {@code AtomicLong} as a {@code double}
	* after a widening primitive conversion.
	* @jls 5.1.2 Widening Primitive Conversions
	*/
	public double doubleValue() {
	return (double)get();
	}

	}