| 6 |
|
*/ |
| 7 |
|
|
| 8 |
|
package jsr166e.extra; |
| 9 |
+ |
|
| 10 |
|
import static java.lang.Double.doubleToRawLongBits; |
| 11 |
|
import static java.lang.Double.longBitsToDouble; |
| 11 |
– |
import sun.misc.Unsafe; |
| 12 |
|
|
| 13 |
|
/** |
| 14 |
|
* A {@code double} value that may be updated atomically. See the |
| 15 |
|
* {@link java.util.concurrent.atomic} package specification for |
| 16 |
|
* description of the properties of atomic variables. An {@code |
| 17 |
< |
* AtomicDouble} is used in applications such as atomic summation, and |
| 18 |
< |
* cannot be used as a replacement for a {@link Double}. However, |
| 17 |
> |
* AtomicDouble} is used in applications such as atomic accumulation, |
| 18 |
> |
* and cannot be used as a replacement for a {@link Double}. However, |
| 19 |
|
* this class does extend {@code Number} to allow uniform access by |
| 20 |
|
* tools and utilities that deal with numerically-based classes. |
| 21 |
|
* |
| 22 |
< |
* <p>This class differs from the primitive double {@code ==} operator |
| 23 |
< |
* and from {@link Double#equals} in that it uses purely bitwise |
| 24 |
< |
* equality in methods such as {@link #compareAndSet}, as if |
| 25 |
< |
* implemented by: |
| 22 |
> |
* <p id="bitEquals">This class compares primitive {@code double} |
| 23 |
> |
* values in methods such as {@link #compareAndSet} by comparing their |
| 24 |
> |
* bitwise representation using {@link Double#doubleToRawLongBits}, |
| 25 |
> |
* which differs from both the primitive double {@code ==} operator |
| 26 |
> |
* and from {@link Double#equals}, as if implemented by: |
| 27 |
|
* <pre> {@code |
| 28 |
< |
* boolean bitEquals(double x, double y) { |
| 28 |
> |
* static boolean bitEquals(double x, double y) { |
| 29 |
|
* long xBits = Double.doubleToRawLongBits(x); |
| 30 |
|
* long yBits = Double.doubleToRawLongBits(y); |
| 31 |
|
* return xBits == yBits; |
| 32 |
|
* }}</pre> |
| 33 |
< |
* |
| 34 |
< |
* @since 1.5 |
| 33 |
> |
* |
| 34 |
> |
* @see jsr166e.DoubleAdder |
| 35 |
> |
* @see jsr166e.DoubleMaxUpdater |
| 36 |
> |
* |
| 37 |
|
* @author Doug Lea |
| 38 |
|
* @author Martin Buchholz |
| 39 |
|
*/ |
| 40 |
|
public class AtomicDouble extends Number implements java.io.Serializable { |
| 41 |
< |
private static final long serialVersionUID = 1927816293512124184L; |
| 39 |
< |
|
| 40 |
< |
// setup to use Unsafe.compareAndSwapLong for updates |
| 41 |
< |
private static final Unsafe unsafe = Unsafe.getUnsafe(); |
| 42 |
< |
private static final long valueOffset; |
| 43 |
< |
|
| 44 |
< |
/** |
| 45 |
< |
* Records whether the underlying JVM supports lockless |
| 46 |
< |
* compareAndSwap for longs. While the Unsafe.compareAndSwapLong |
| 47 |
< |
* method works in either case, some constructions should be |
| 48 |
< |
* handled at Java level to avoid locking user-visible locks. |
| 49 |
< |
*/ |
| 50 |
< |
static final boolean VM_SUPPORTS_LONG_CAS = VMSupportsCS8(); |
| 51 |
< |
|
| 52 |
< |
/** |
| 53 |
< |
* Returns whether underlying JVM supports lockless CompareAndSet |
| 54 |
< |
* for longs. Called only once and cached in VM_SUPPORTS_LONG_CAS. |
| 55 |
< |
*/ |
| 56 |
< |
private static boolean VMSupportsCS8() { |
| 57 |
< |
try { |
| 58 |
< |
Class<?> klazz = java.util.concurrent.atomic.AtomicLong.class; |
| 59 |
< |
java.lang.reflect.Method m = |
| 60 |
< |
klazz.getDeclaredMethod("VMSupportsCS8", new Class<?>[0]); |
| 61 |
< |
m.setAccessible(true); |
| 62 |
< |
return (Boolean) m.invoke(new Class<?>[0]); |
| 63 |
< |
} catch (Throwable t) { throw new Error(t); } |
| 64 |
< |
} |
| 41 |
> |
private static final long serialVersionUID = -8405198993435143622L; |
| 42 |
|
|
| 43 |
< |
static { |
| 67 |
< |
try { |
| 68 |
< |
valueOffset = unsafe.objectFieldOffset |
| 69 |
< |
(AtomicDouble.class.getDeclaredField("value")); |
| 70 |
< |
} catch (Exception ex) { throw new Error(ex); } |
| 71 |
< |
} |
| 72 |
< |
|
| 73 |
< |
private volatile long value; |
| 43 |
> |
private transient volatile long value; |
| 44 |
|
|
| 45 |
|
/** |
| 46 |
< |
* Creates a new AtomicDouble with the given initial value. |
| 46 |
> |
* Creates a new {@code AtomicDouble} with the given initial value. |
| 47 |
|
* |
| 48 |
|
* @param initialValue the initial value |
| 49 |
|
*/ |
| 52 |
|
} |
| 53 |
|
|
| 54 |
|
/** |
| 55 |
< |
* Creates a new AtomicDouble with initial value {@code 0.0}. |
| 55 |
> |
* Creates a new {@code AtomicDouble} with initial value {@code 0.0}. |
| 56 |
|
*/ |
| 57 |
< |
public AtomicDouble() { this(0.0); } |
| 57 |
> |
public AtomicDouble() { |
| 58 |
> |
// assert doubleToRawLongBits(0.0) == 0L; |
| 59 |
> |
} |
| 60 |
|
|
| 61 |
|
/** |
| 62 |
|
* Gets the current value. |
| 73 |
|
* @param newValue the new value |
| 74 |
|
*/ |
| 75 |
|
public final void set(double newValue) { |
| 76 |
< |
value = doubleToRawLongBits(newValue); |
| 76 |
> |
long next = doubleToRawLongBits(newValue); |
| 77 |
> |
value = next; |
| 78 |
|
} |
| 79 |
|
|
| 80 |
|
/** |
| 81 |
|
* Eventually sets to the given value. |
| 82 |
|
* |
| 83 |
|
* @param newValue the new value |
| 111 |
– |
* @since 1.6 |
| 84 |
|
*/ |
| 85 |
|
public final void lazySet(double newValue) { |
| 86 |
< |
unsafe.putOrderedLong(this, valueOffset, doubleToRawLongBits(newValue)); |
| 86 |
> |
long next = doubleToRawLongBits(newValue); |
| 87 |
> |
unsafe.putOrderedLong(this, valueOffset, next); |
| 88 |
|
} |
| 89 |
|
|
| 90 |
|
/** |
| 94 |
|
* @return the previous value |
| 95 |
|
*/ |
| 96 |
|
public final double getAndSet(double newValue) { |
| 97 |
< |
long newBits = doubleToRawLongBits(newValue); |
| 97 |
> |
long next = doubleToRawLongBits(newValue); |
| 98 |
|
while (true) { |
| 99 |
< |
long currentBits = value; |
| 100 |
< |
if (unsafe.compareAndSwapLong(this, valueOffset, |
| 101 |
< |
currentBits, newBits)) |
| 129 |
< |
return longBitsToDouble(currentBits); |
| 99 |
> |
long current = value; |
| 100 |
> |
if (unsafe.compareAndSwapLong(this, valueOffset, current, next)) |
| 101 |
> |
return longBitsToDouble(current); |
| 102 |
|
} |
| 103 |
|
} |
| 104 |
|
|
| 105 |
|
/** |
| 106 |
|
* Atomically sets the value to the given updated value |
| 107 |
< |
* if the current value {@code ==} the expected value. |
| 107 |
> |
* if the current value is <a href="#bitEquals">bitwise equal</a> |
| 108 |
> |
* to the expected value. |
| 109 |
|
* |
| 110 |
|
* @param expect the expected value |
| 111 |
|
* @param update the new value |
| 112 |
< |
* @return true if successful. False return indicates that |
| 113 |
< |
* the actual value was not equal to the expected value. |
| 112 |
> |
* @return {@code true} if successful. False return indicates that |
| 113 |
> |
* the actual value was not bitwise equal to the expected value. |
| 114 |
|
*/ |
| 115 |
|
public final boolean compareAndSet(double expect, double update) { |
| 116 |
|
return unsafe.compareAndSwapLong(this, valueOffset, |
| 120 |
|
|
| 121 |
|
/** |
| 122 |
|
* Atomically sets the value to the given updated value |
| 123 |
< |
* if the current value {@code ==} the expected value. |
| 123 |
> |
* if the current value is <a href="#bitEquals">bitwise equal</a> |
| 124 |
> |
* to the expected value. |
| 125 |
|
* |
| 126 |
< |
* <p>May <a href="package-summary.html#Spurious">fail spuriously</a> |
| 127 |
< |
* and does not provide ordering guarantees, so is only rarely an |
| 128 |
< |
* appropriate alternative to {@code compareAndSet}. |
| 126 |
> |
* <p><a |
| 127 |
> |
* href="http://download.oracle.com/javase/7/docs/api/java/util/concurrent/atomic/package-summary.html#Spurious"> |
| 128 |
> |
* May fail spuriously and does not provide ordering guarantees</a>, |
| 129 |
> |
* so is only rarely an appropriate alternative to {@code compareAndSet}. |
| 130 |
|
* |
| 131 |
|
* @param expect the expected value |
| 132 |
|
* @param update the new value |
| 133 |
< |
* @return true if successful. |
| 133 |
> |
* @return {@code true} if successful |
| 134 |
|
*/ |
| 135 |
|
public final boolean weakCompareAndSet(double expect, double update) { |
| 136 |
|
return compareAndSet(expect, update); |
| 144 |
|
*/ |
| 145 |
|
public final double getAndAdd(double delta) { |
| 146 |
|
while (true) { |
| 147 |
< |
long currentBits = value; |
| 148 |
< |
long nextBits = doubleToRawLongBits(longBitsToDouble(currentBits) + delta); |
| 149 |
< |
if (unsafe.compareAndSwapLong(this, valueOffset, |
| 150 |
< |
currentBits, nextBits)) |
| 151 |
< |
return longBitsToDouble(currentBits); |
| 147 |
> |
long current = value; |
| 148 |
> |
double currentVal = longBitsToDouble(current); |
| 149 |
> |
double nextVal = currentVal + delta; |
| 150 |
> |
long next = doubleToRawLongBits(nextVal); |
| 151 |
> |
if (unsafe.compareAndSwapLong(this, valueOffset, current, next)) |
| 152 |
> |
return currentVal; |
| 153 |
|
} |
| 154 |
|
} |
| 155 |
|
|
| 160 |
|
* @return the updated value |
| 161 |
|
*/ |
| 162 |
|
public final double addAndGet(double delta) { |
| 163 |
< |
for (;;) { |
| 164 |
< |
double current = get(); |
| 165 |
< |
double next = current + delta; |
| 166 |
< |
if (compareAndSet(current, next)) |
| 167 |
< |
return next; |
| 163 |
> |
while (true) { |
| 164 |
> |
long current = value; |
| 165 |
> |
double currentVal = longBitsToDouble(current); |
| 166 |
> |
double nextVal = currentVal + delta; |
| 167 |
> |
long next = doubleToRawLongBits(nextVal); |
| 168 |
> |
if (unsafe.compareAndSwapLong(this, valueOffset, current, next)) |
| 169 |
> |
return nextVal; |
| 170 |
|
} |
| 171 |
|
} |
| 172 |
|
|
| 173 |
|
/** |
| 174 |
|
* Returns the String representation of the current value. |
| 175 |
< |
* @return the String representation of the current value. |
| 175 |
> |
* @return the String representation of the current value |
| 176 |
|
*/ |
| 177 |
|
public String toString() { |
| 178 |
|
return Double.toString(get()); |
| 179 |
|
} |
| 180 |
|
|
| 203 |
– |
|
| 181 |
|
/** |
| 182 |
|
* Returns the value of this {@code AtomicDouble} as an {@code int} |
| 183 |
|
* after a narrowing primitive conversion. |
| 184 |
|
*/ |
| 185 |
|
public int intValue() { |
| 186 |
< |
return (int)get(); |
| 186 |
> |
return (int) get(); |
| 187 |
|
} |
| 188 |
|
|
| 189 |
|
/** |
| 190 |
< |
* Returns the value of this {@code AtomicDouble} as a {@code long}. |
| 190 |
> |
* Returns the value of this {@code AtomicDouble} as a {@code long} |
| 191 |
> |
* after a narrowing primitive conversion. |
| 192 |
|
*/ |
| 193 |
|
public long longValue() { |
| 194 |
< |
return (long)get(); |
| 194 |
> |
return (long) get(); |
| 195 |
|
} |
| 196 |
|
|
| 197 |
|
/** |
| 198 |
|
* Returns the value of this {@code AtomicDouble} as a {@code float} |
| 199 |
< |
* after a widening primitive conversion. |
| 199 |
> |
* after a narrowing primitive conversion. |
| 200 |
|
*/ |
| 201 |
|
public float floatValue() { |
| 202 |
< |
return (float)get(); |
| 202 |
> |
return (float) get(); |
| 203 |
|
} |
| 204 |
|
|
| 205 |
|
/** |
| 206 |
< |
* Returns the value of this {@code AtomicDouble} as a {@code double} |
| 229 |
< |
* after a widening primitive conversion. |
| 206 |
> |
* Returns the value of this {@code AtomicDouble} as a {@code double}. |
| 207 |
|
*/ |
| 208 |
|
public double doubleValue() { |
| 209 |
|
return get(); |
| 210 |
|
} |
| 211 |
|
|
| 212 |
+ |
/** |
| 213 |
+ |
* Saves the state to a stream (that is, serializes it). |
| 214 |
+ |
* |
| 215 |
+ |
* @serialData The current value is emitted (a {@code double}). |
| 216 |
+ |
*/ |
| 217 |
+ |
private void writeObject(java.io.ObjectOutputStream s) |
| 218 |
+ |
throws java.io.IOException { |
| 219 |
+ |
s.defaultWriteObject(); |
| 220 |
+ |
|
| 221 |
+ |
s.writeDouble(get()); |
| 222 |
+ |
} |
| 223 |
+ |
|
| 224 |
+ |
/** |
| 225 |
+ |
* Reconstitutes the instance from a stream (that is, deserializes it). |
| 226 |
+ |
*/ |
| 227 |
+ |
private void readObject(java.io.ObjectInputStream s) |
| 228 |
+ |
throws java.io.IOException, ClassNotFoundException { |
| 229 |
+ |
s.defaultReadObject(); |
| 230 |
+ |
|
| 231 |
+ |
set(s.readDouble()); |
| 232 |
+ |
} |
| 233 |
+ |
|
| 234 |
+ |
// Unsafe mechanics |
| 235 |
+ |
private static final sun.misc.Unsafe unsafe = getUnsafe(); |
| 236 |
+ |
private static final long valueOffset; |
| 237 |
+ |
|
| 238 |
+ |
static { |
| 239 |
+ |
try { |
| 240 |
+ |
valueOffset = unsafe.objectFieldOffset |
| 241 |
+ |
(AtomicDouble.class.getDeclaredField("value")); |
| 242 |
+ |
} catch (Exception ex) { throw new Error(ex); } |
| 243 |
+ |
} |
| 244 |
+ |
|
| 245 |
+ |
/** |
| 246 |
+ |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
| 247 |
+ |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
| 248 |
+ |
* into a jdk. |
| 249 |
+ |
* |
| 250 |
+ |
* @return a sun.misc.Unsafe |
| 251 |
+ |
*/ |
| 252 |
+ |
private static sun.misc.Unsafe getUnsafe() { |
| 253 |
+ |
try { |
| 254 |
+ |
return sun.misc.Unsafe.getUnsafe(); |
| 255 |
+ |
} catch (SecurityException tryReflectionInstead) {} |
| 256 |
+ |
try { |
| 257 |
+ |
return java.security.AccessController.doPrivileged |
| 258 |
+ |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
| 259 |
+ |
public sun.misc.Unsafe run() throws Exception { |
| 260 |
+ |
Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class; |
| 261 |
+ |
for (java.lang.reflect.Field f : k.getDeclaredFields()) { |
| 262 |
+ |
f.setAccessible(true); |
| 263 |
+ |
Object x = f.get(null); |
| 264 |
+ |
if (k.isInstance(x)) |
| 265 |
+ |
return k.cast(x); |
| 266 |
+ |
} |
| 267 |
+ |
throw new NoSuchFieldError("the Unsafe"); |
| 268 |
+ |
}}); |
| 269 |
+ |
} catch (java.security.PrivilegedActionException e) { |
| 270 |
+ |
throw new RuntimeException("Could not initialize intrinsics", |
| 271 |
+ |
e.getCause()); |
| 272 |
+ |
} |
| 273 |
+ |
} |
| 274 |
|
} |
