jdk.util.concurrent.atomic.AtomicReferenceFieldUpdater — clojure-interop/java.util.concurrent 1.0.5

A reflection-based utility that enables atomic updates to designated volatile reference fields of designated classes. This class is designed for use in atomic data structures in which several reference fields of the same node are independently subject to atomic updates. For example, a tree node might be declared as

class Node { private volatile Node left, right;

private static final AtomicReferenceFieldUpdater<Node, Node> leftUpdater = AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "left"); private static AtomicReferenceFieldUpdater<Node, Node> rightUpdater = AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "right");

Node getLeft() { return left; } boolean compareAndSetLeft(Node expect, Node update) { return leftUpdater.compareAndSet(this, expect, update); } // ... and so on }

Note that the guarantees of the compareAndSet method in this class are weaker than in other atomic classes. Because this class cannot ensure that all uses of the field are appropriate for purposes of atomic access, it can guarantee atomicity only with respect to other invocations of compareAndSet and set on the same updater.

*new-updater clj

(*new-updater tclass vclass field-name)

Creates and returns an updater for objects with the given field. The Class arguments are needed to check that reflective types and generic types match.

tclass - the class of the objects holding the field - java.lang.Class vclass - the class of the field - java.lang.Class field-name - the name of the field to be updated - java.lang.String

returns: the updater - <U,W> java.util.concurrent.atomic.AtomicReferenceFieldUpdater<U,W>

throws: java.lang.ClassCastException - if the field is of the wrong type

accumulate-and-get clj

(accumulate-and-get this obj x accumulator-function)

Atomically updates the field of the given object managed by this updater 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.

obj - An object whose field to get and set - T x - the update value - V accumulator-function - a side-effect-free function of two arguments - java.util.function.BinaryOperator

returns: the updated value - V

compare-and-set clj

(compare-and-set this obj expect update)

Atomically sets the field of the given object managed by this updater to the given updated value if the current value == the expected value. This method is guaranteed to be atomic with respect to other calls to compareAndSet and set, but not necessarily with respect to other changes in the field.

obj - An object whose field to conditionally set - T expect - the expected value - V update - the new value - V

returns: true if successful - boolean

get clj

(get this obj)

Gets the current value held in the field of the given object managed by this updater.

obj - An object whose field to get - T

returns: the current value - V

get-and-accumulate clj

(get-and-accumulate this obj x accumulator-function)

Atomically updates the field of the given object managed by this updater 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.

obj - An object whose field to get and set - T x - the update value - V accumulator-function - a side-effect-free function of two arguments - java.util.function.BinaryOperator

returns: the previous value - V

get-and-set clj

(get-and-set this obj new-value)

Atomically sets the field of the given object managed by this updater to the given value and returns the old value.

obj - An object whose field to get and set - T new-value - the new value - V

returns: the previous value - V

get-and-update clj

(get-and-update this obj update-function)

Atomically updates the field of the given object managed by this updater 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.

obj - An object whose field to get and set - T update-function - a side-effect-free function - java.util.function.UnaryOperator

returns: the previous value - V

lazy-set clj

(lazy-set this obj new-value)

Eventually sets the field of the given object managed by this updater to the given updated value.

obj - An object whose field to set - T new-value - the new value - V

set clj

(set this obj new-value)

Sets the field of the given object managed by this updater to the given updated value. This operation is guaranteed to act as a volatile store with respect to subsequent invocations of compareAndSet.

obj - An object whose field to set - T new-value - the new value - V

update-and-get clj

(update-and-get this obj update-function)

Atomically updates the field of the given object managed by this updater 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.

obj - An object whose field to get and set - T update-function - a side-effect-free function - java.util.function.UnaryOperator

returns: the updated value - V

weak-compare-and-set clj

(weak-compare-and-set this obj expect update)

Atomically sets the field of the given object managed by this updater to the given updated value if the current value == the expected value. This method is guaranteed to be atomic with respect to other calls to compareAndSet and set, but not necessarily with respect to other changes in the field.

May fail spuriously and does not provide ordering guarantees, so is only rarely an appropriate alternative to compareAndSet.

obj - An object whose field to conditionally set - T expect - the expected value - V update - the new value - V

returns: true if successful - boolean