diff options
Diffstat (limited to 'yolean/src/main/java/com/yahoo/yolean/concurrent/Memoized.java')
| -rw-r--r-- | yolean/src/main/java/com/yahoo/yolean/concurrent/Memoized.java | 64 |
1 files changed, 0 insertions, 64 deletions
diff --git a/yolean/src/main/java/com/yahoo/yolean/concurrent/Memoized.java b/yolean/src/main/java/com/yahoo/yolean/concurrent/Memoized.java deleted file mode 100644 index e8660504a8a..00000000000 --- a/yolean/src/main/java/com/yahoo/yolean/concurrent/Memoized.java +++ /dev/null @@ -1,64 +0,0 @@ -package com.yahoo.yolean.concurrent; - -import java.util.function.Supplier; - -import static java.util.Objects.requireNonNull; - -/** - * Wraps a lazily initialised resource which needs to be shut down. - * The wrapped supplier may not return {@code null}, and should be retryable on failure. - * If it throws, it will be retried if {@link #get} is retried. A supplier that fails to - * clean up partial state on failure may cause a resource leak. - * - * @author jonmv - */ -public class Memoized<T, E extends Exception> implements Supplier<T>, AutoCloseable { - - /** Provides a tighter bound on the thrown exception type. */ - @FunctionalInterface - public interface Closer<T, E extends Exception> { void close(T t) throws E; } - - private final Object monitor = new Object(); - private final Closer<T, E> closer; - private volatile T wrapped; - private Supplier<T> factory; - - public Memoized(Supplier<T> factory, Closer<T, E> closer) { - this.factory = requireNonNull(factory); - this.closer = requireNonNull(closer); - } - - public static <T extends AutoCloseable> Memoized<T, ?> of(Supplier<T> factory) { - return new Memoized<>(factory, AutoCloseable::close); - } - - @Override - public T get() { - // Double-checked locking: try the variable, and if not initialized, try to initialize it. - if (wrapped == null) synchronized (monitor) { - // Ensure the factory is called only once, by clearing it once successfully called. - if (factory != null) wrapped = requireNonNull(factory.get()); - factory = null; - - // If we found the factory, we won the initialization race, and return normally; otherwise - // if wrapped is non-null, we lost the race, wrapped was set by the winner, and we return; otherwise - // we tried to initialise because wrapped was cleared by closing this, and we fail. - if (wrapped == null) throw new IllegalStateException("already closed"); - } - return wrapped; - } - - @Override - public void close() throws E { - // Alter state only when synchronized with calls to get(). - synchronized (monitor) { - // Ensure we only try to close the generated resource once, by clearing it after picking it up here. - T maybe = wrapped; - wrapped = null; - // Clear the factory, to signal this has been closed. - factory = null; - if (maybe != null) closer.close(maybe); - } - } - -}
\ No newline at end of file |