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- package test.javassist.convert;
-
- import java.util.AbstractQueue;
- import java.util.Collection;
- import java.util.Iterator;
- import java.util.NoSuchElementException;
- import java.util.concurrent.BlockingQueue;
- import java.util.concurrent.TimeUnit;
- import java.util.concurrent.locks.Condition;
- import java.util.concurrent.locks.ReentrantLock;
-
-
- /**
- * A clone of java.util.concurrent.ArrayBlockingQueue as target for testing
- */
- public class InstrumentationTarget<E> extends AbstractQueue<E>
- implements BlockingQueue<E>, java.io.Serializable {
- /**
- * Serialization ID. This class relies on default serialization
- * even for the items array, which is default-serialized, even if
- * it is empty. Otherwise it could not be declared final, which is
- * necessary here.
- */
- private static final long serialVersionUID = -817911632652898426L;
-
- /**
- * The queued items
- */
- final Object[] items;
-
- /**
- * items index for next take, poll, peek or remove
- */
- int takeIndex;
-
- /**
- * items index for next put, offer, or add
- */
- int putIndex;
-
- /**
- * Number of elements in the queue
- */
- int count;
-
- /*
- * Concurrency control uses the classic two-condition algorithm
- * found in any textbook.
- */
-
- /**
- * Main lock guarding all access
- */
- final ReentrantLock lock;
- /**
- * Condition for waiting takes
- */
- private final Condition notEmpty;
- /**
- * Condition for waiting puts
- */
- private final Condition notFull;
-
- // Internal helper methods
-
- /**
- * Circularly increment i.
- */
- final int inc(int i) {
- return (++i == items.length) ? 0 : i;
- }
-
- /**
- * Circularly decrement i.
- */
- final int dec(int i) {
- return ((i == 0) ? items.length : i) - 1;
- }
-
- @SuppressWarnings("unchecked")
- static <E> E cast(Object item) {
- return (E) item;
- }
-
- /**
- * Returns item at index i.
- */
- final E itemAt(int i) {
- return this.<E>cast(items[i]);
- }
-
- /**
- * Throws NullPointerException if argument is null.
- *
- * @param v the element
- */
- private static void checkNotNull(Object v) {
- if (v == null)
- throw new NullPointerException();
- }
-
- /**
- * Inserts element at current put position, advances, and signals.
- * Call only when holding lock.
- */
- private void insert(E x) {
- items[putIndex] = x;
- putIndex = inc(putIndex);
- ++count;
- notEmpty.signal();
- }
-
- /**
- * Extracts element at current take position, advances, and signals.
- * Call only when holding lock.
- */
- private E extract() {
- final Object[] items = this.items;
- E x = this.<E>cast(items[takeIndex]);
- items[takeIndex] = null;
- takeIndex = inc(takeIndex);
- --count;
- notFull.signal();
- return x;
- }
-
- /**
- * Deletes item at position i.
- * Utility for remove and iterator.remove.
- * Call only when holding lock.
- */
- void removeAt(int i) {
- final Object[] items = this.items;
- // if removing front item, just advance
- if (i == takeIndex) {
- items[takeIndex] = null;
- takeIndex = inc(takeIndex);
- } else {
- // slide over all others up through putIndex.
- for (; ; ) {
- int nexti = inc(i);
- if (nexti != putIndex) {
- items[i] = items[nexti];
- i = nexti;
- } else {
- items[i] = null;
- putIndex = i;
- break;
- }
- }
- }
- --count;
- notFull.signal();
- }
-
- /**
- * Creates an {@code Target} with the given (fixed)
- * capacity and default access policy.
- *
- * @param capacity the capacity of this queue
- * @throws IllegalArgumentException if {@code capacity < 1}
- */
- public InstrumentationTarget(int capacity) {
- this(capacity, false);
- }
-
- /**
- * Creates an {@code Target} with the given (fixed)
- * capacity and the specified access policy.
- *
- * @param capacity the capacity of this queue
- * @param fair if {@code true} then queue accesses for threads blocked
- * on insertion or removal, are processed in FIFO order;
- * if {@code false} the access order is unspecified.
- * @throws IllegalArgumentException if {@code capacity < 1}
- */
- public InstrumentationTarget(int capacity, boolean fair) {
- if (capacity <= 0)
- throw new IllegalArgumentException();
- this.items = new Object[capacity];
- lock = new ReentrantLock(fair);
- notEmpty = lock.newCondition();
- notFull = lock.newCondition();
- }
-
- /**
- * Creates an {@code Target} with the given (fixed)
- * capacity, the specified access policy and initially containing the
- * elements of the given collection,
- * added in traversal order of the collection's iterator.
- *
- * @param capacity the capacity of this queue
- * @param fair if {@code true} then queue accesses for threads blocked
- * on insertion or removal, are processed in FIFO order;
- * if {@code false} the access order is unspecified.
- * @param c the collection of elements to initially contain
- * @throws IllegalArgumentException if {@code capacity} is less than
- * {@code c.size()}, or less than 1.
- * @throws NullPointerException if the specified collection or any
- * of its elements are null
- */
- public InstrumentationTarget(int capacity, boolean fair,
- Collection<? extends E> c) {
- this(capacity, fair);
-
- final ReentrantLock lock = this.lock;
- lock.lock(); // Lock only for visibility, not mutual exclusion
- try {
- int i = 0;
- try {
- for (E e : c) {
- checkNotNull(e);
- items[i++] = e;
- }
- } catch (ArrayIndexOutOfBoundsException ex) {
- throw new IllegalArgumentException();
- }
- count = i;
- putIndex = (i == capacity) ? 0 : i;
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * Inserts the specified element at the tail of this queue if it is
- * possible to do so immediately without exceeding the queue's capacity,
- * returning {@code true} upon success and throwing an
- * {@code IllegalStateException} if this queue is full.
- *
- * @param e the element to add
- * @return {@code true} (as specified by {@link Collection#add})
- * @throws IllegalStateException if this queue is full
- * @throws NullPointerException if the specified element is null
- */
- public boolean add(E e) {
- return super.add(e);
- }
-
- /**
- * Inserts the specified element at the tail of this queue if it is
- * possible to do so immediately without exceeding the queue's capacity,
- * returning {@code true} upon success and {@code false} if this queue
- * is full. This method is generally preferable to method {@link #add},
- * which can fail to insert an element only by throwing an exception.
- *
- * @throws NullPointerException if the specified element is null
- */
- public boolean offer(E e) {
- checkNotNull(e);
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- if (count == items.length)
- return false;
- else {
- insert(e);
- return true;
- }
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * Inserts the specified element at the tail of this queue, waiting
- * for space to become available if the queue is full.
- *
- * @throws InterruptedException {@inheritDoc}
- * @throws NullPointerException {@inheritDoc}
- */
- public void put(E e) throws InterruptedException {
- checkNotNull(e);
- final ReentrantLock lock = this.lock;
- lock.lockInterruptibly();
- try {
- while (count == items.length)
- notFull.await();
- insert(e);
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * Inserts the specified element at the tail of this queue, waiting
- * up to the specified wait time for space to become available if
- * the queue is full.
- *
- * @throws InterruptedException {@inheritDoc}
- * @throws NullPointerException {@inheritDoc}
- */
- public boolean offer(E e, long timeout, TimeUnit unit)
- throws InterruptedException {
-
- checkNotNull(e);
- long nanos = unit.toNanos(timeout);
- final ReentrantLock lock = this.lock;
- lock.lockInterruptibly();
- try {
- while (count == items.length) {
- if (nanos <= 0)
- return false;
- nanos = notFull.awaitNanos(nanos);
- }
- insert(e);
- return true;
- } finally {
- lock.unlock();
- }
- }
-
- public E poll() {
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- return (count == 0) ? null : extract();
- } finally {
- lock.unlock();
- }
- }
-
- public E take() throws InterruptedException {
- final ReentrantLock lock = this.lock;
- lock.lockInterruptibly();
- try {
- while (count == 0)
- notEmpty.await();
- return extract();
- } finally {
- lock.unlock();
- }
- }
-
- public E poll(long timeout, TimeUnit unit) throws InterruptedException {
- long nanos = unit.toNanos(timeout);
- final ReentrantLock lock = this.lock;
- lock.lockInterruptibly();
- try {
- while (count == 0) {
- if (nanos <= 0)
- return null;
- nanos = notEmpty.awaitNanos(nanos);
- }
- return extract();
- } finally {
- lock.unlock();
- }
- }
-
- public E peek() {
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- return (count == 0) ? null : itemAt(takeIndex);
- } finally {
- lock.unlock();
- }
- }
-
- // this doc comment is overridden to remove the reference to collections
- // greater in size than Integer.MAX_VALUE
-
- /**
- * Returns the number of elements in this queue.
- *
- * @return the number of elements in this queue
- */
- public int size() {
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- return count;
- } finally {
- lock.unlock();
- }
- }
-
- // this doc comment is a modified copy of the inherited doc comment,
- // without the reference to unlimited queues.
-
- /**
- * Returns the number of additional elements that this queue can ideally
- * (in the absence of memory or resource constraints) accept without
- * blocking. This is always equal to the initial capacity of this queue
- * less the current {@code size} of this queue.
- *
- * <p>Note that you <em>cannot</em> always tell if an attempt to insert
- * an element will succeed by inspecting {@code remainingCapacity}
- * because it may be the case that another thread is about to
- * insert or remove an element.
- */
- public int remainingCapacity() {
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- return items.length - count;
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * Removes a single instance of the specified element from this queue,
- * if it is present. More formally, removes an element {@code e} such
- * that {@code o.equals(e)}, if this queue contains one or more such
- * elements.
- * Returns {@code true} if this queue contained the specified element
- * (or equivalently, if this queue changed as a result of the call).
- *
- * <p>Removal of interior elements in circular array based queues
- * is an intrinsically slow and disruptive operation, so should
- * be undertaken only in exceptional circumstances, ideally
- * only when the queue is known not to be accessible by other
- * threads.
- *
- * @param o element to be removed from this queue, if present
- * @return {@code true} if this queue changed as a result of the call
- */
- public boolean remove(Object o) {
- if (o == null) return false;
- final Object[] items = this.items;
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- for (int i = takeIndex, k = count; k > 0; i = inc(i), k--) {
- if (o.equals(items[i])) {
- removeAt(i);
- return true;
- }
- }
- return false;
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * Returns {@code true} if this queue contains the specified element.
- * More formally, returns {@code true} if and only if this queue contains
- * at least one element {@code e} such that {@code o.equals(e)}.
- *
- * @param o object to be checked for containment in this queue
- * @return {@code true} if this queue contains the specified element
- */
- public boolean contains(Object o) {
- if (o == null) return false;
- final Object[] items = this.items;
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- for (int i = takeIndex, k = count; k > 0; i = inc(i), k--)
- if (o.equals(items[i]))
- return true;
- return false;
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * Returns an array containing all of the elements in this queue, in
- * proper sequence.
- *
- * <p>The returned array will be "safe" in that no references to it are
- * maintained by this queue. (In other words, this method must allocate
- * a new array). The caller is thus free to modify the returned array.
- *
- * <p>This method acts as bridge between array-based and collection-based
- * APIs.
- *
- * @return an array containing all of the elements in this queue
- */
- public Object[] toArray() {
- final Object[] items = this.items;
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- final int count = this.count;
- Object[] a = new Object[count];
- for (int i = takeIndex, k = 0; k < count; i = inc(i), k++)
- a[k] = items[i];
- return a;
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * Returns an array containing all of the elements in this queue, in
- * proper sequence; the runtime type of the returned array is that of
- * the specified array. If the queue fits in the specified array, it
- * is returned therein. Otherwise, a new array is allocated with the
- * runtime type of the specified array and the size of this queue.
- *
- * <p>If this queue fits in the specified array with room to spare
- * (i.e., the array has more elements than this queue), the element in
- * the array immediately following the end of the queue is set to
- * {@code null}.
- *
- * <p>Like the {@link #toArray()} method, this method acts as bridge between
- * array-based and collection-based APIs. Further, this method allows
- * precise control over the runtime type of the output array, and may,
- * under certain circumstances, be used to save allocation costs.
- *
- * <p>Suppose {@code x} is a queue known to contain only strings.
- * The following code can be used to dump the queue into a newly
- * allocated array of {@code String}:
- *
- * <pre>
- * String[] y = x.toArray(new String[0]);</pre>
- * <p>
- * Note that {@code toArray(new Object[0])} is identical in function to
- * {@code toArray()}.
- *
- * @param a the array into which the elements of the queue are to
- * be stored, if it is big enough; otherwise, a new array of the
- * same runtime type is allocated for this purpose
- * @return an array containing all of the elements in this queue
- * @throws ArrayStoreException if the runtime type of the specified array
- * is not a supertype of the runtime type of every element in
- * this queue
- * @throws NullPointerException if the specified array is null
- */
- @SuppressWarnings("unchecked")
- public <T> T[] toArray(T[] a) {
- final Object[] items = this.items;
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- final int count = this.count;
- final int len = a.length;
- if (len < count)
- a = (T[]) java.lang.reflect.Array.newInstance(
- a.getClass().getComponentType(), count);
- for (int i = takeIndex, k = 0; k < count; i = inc(i), k++)
- a[k] = (T) items[i];
- if (len > count)
- a[count] = null;
- return a;
- } finally {
- lock.unlock();
- }
- }
-
- public String toString() {
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- int k = count;
- if (k == 0)
- return "[]";
-
- StringBuilder sb = new StringBuilder();
- sb.append('[');
- for (int i = takeIndex; ; i = inc(i)) {
- Object e = items[i];
- sb.append(e == this ? "(this Collection)" : e);
- if (--k == 0)
- return sb.append(']').toString();
- sb.append(',').append(' ');
- }
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * Atomically removes all of the elements from this queue.
- * The queue will be empty after this call returns.
- */
- public void clear() {
- final Object[] items = this.items;
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- for (int i = takeIndex, k = count; k > 0; i = inc(i), k--)
- items[i] = null;
- count = 0;
- putIndex = 0;
- takeIndex = 0;
- notFull.signalAll();
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * @throws UnsupportedOperationException {@inheritDoc}
- * @throws ClassCastException {@inheritDoc}
- * @throws NullPointerException {@inheritDoc}
- * @throws IllegalArgumentException {@inheritDoc}
- */
- public int drainTo(Collection<? super E> c) {
- checkNotNull(c);
- if (c == this)
- throw new IllegalArgumentException();
- final Object[] items = this.items;
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- int i = takeIndex;
- int n = 0;
- int max = count;
- while (n < max) {
- c.add(this.<E>cast(items[i]));
- items[i] = null;
- i = inc(i);
- ++n;
- }
- if (n > 0) {
- count = 0;
- putIndex = 0;
- takeIndex = 0;
- notFull.signalAll();
- }
- return n;
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * @throws UnsupportedOperationException {@inheritDoc}
- * @throws ClassCastException {@inheritDoc}
- * @throws NullPointerException {@inheritDoc}
- * @throws IllegalArgumentException {@inheritDoc}
- */
- public int drainTo(Collection<? super E> c, int maxElements) {
- checkNotNull(c);
- if (c == this)
- throw new IllegalArgumentException();
- if (maxElements <= 0)
- return 0;
- final Object[] items = this.items;
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
- int i = takeIndex;
- int n = 0;
- int max = (maxElements < count) ? maxElements : count;
- while (n < max) {
- c.add(this.<E>cast(items[i]));
- items[i] = null;
- i = inc(i);
- ++n;
- }
- if (n > 0) {
- count -= n;
- takeIndex = i;
- notFull.signalAll();
- }
- return n;
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * Returns an iterator over the elements in this queue in proper sequence.
- * The elements will be returned in order from first (head) to last (tail).
- *
- * <p>The returned {@code Iterator} is a "weakly consistent" iterator that
- * will never throw {@link java.util.ConcurrentModificationException
- * ConcurrentModificationException},
- * and guarantees to traverse elements as they existed upon
- * construction of the iterator, and may (but is not guaranteed to)
- * reflect any modifications subsequent to construction.
- *
- * @return an iterator over the elements in this queue in proper sequence
- */
- public Iterator<E> iterator() {
- return new Itr();
- }
-
- /**
- * Iterator for Target. To maintain weak consistency
- * with respect to puts and takes, we (1) read ahead one slot, so
- * as to not report hasNext true but then not have an element to
- * return -- however we later recheck this slot to use the most
- * current value; (2) ensure that each array slot is traversed at
- * most once (by tracking "remaining" elements); (3) skip over
- * null slots, which can occur if takes race ahead of iterators.
- * However, for circular array-based queues, we cannot rely on any
- * well established definition of what it means to be weakly
- * consistent with respect to interior removes since these may
- * require slot overwrites in the process of sliding elements to
- * cover gaps. So we settle for resiliency, operating on
- * established apparent nexts, which may miss some elements that
- * have moved between calls to next.
- */
- private class Itr implements Iterator<E> {
- private int remaining; // Number of elements yet to be returned
- private int nextIndex; // Index of element to be returned by next
- private E nextItem; // Element to be returned by next call to next
- private E lastItem; // Element returned by last call to next
- private int lastRet; // Index of last element returned, or -1 if none
-
- Itr() {
- final ReentrantLock lock = InstrumentationTarget.this.lock;
- lock.lock();
- try {
- lastRet = -1;
- if ((remaining = count) > 0)
- nextItem = itemAt(nextIndex = takeIndex);
- } finally {
- lock.unlock();
- }
- }
-
- public boolean hasNext() {
- return remaining > 0;
- }
-
- public E next() {
- final ReentrantLock lock = InstrumentationTarget.this.lock;
- lock.lock();
- try {
- if (remaining <= 0)
- throw new NoSuchElementException();
- lastRet = nextIndex;
- E x = itemAt(nextIndex); // check for fresher value
- if (x == null) {
- x = nextItem; // we are forced to report old value
- lastItem = null; // but ensure remove fails
- } else
- lastItem = x;
- while (--remaining > 0 && // skip over nulls
- (nextItem = itemAt(nextIndex = inc(nextIndex))) == null)
- ;
- return x;
- } finally {
- lock.unlock();
- }
- }
-
- public void remove() {
- final ReentrantLock lock = InstrumentationTarget.this.lock;
- lock.lock();
- try {
- int i = lastRet;
- if (i == -1)
- throw new IllegalStateException();
- lastRet = -1;
- E x = lastItem;
- lastItem = null;
- // only remove if item still at index
- if (x != null && x == items[i]) {
- boolean removingHead = (i == takeIndex);
- removeAt(i);
- if (!removingHead)
- nextIndex = dec(nextIndex);
- }
- } finally {
- lock.unlock();
- }
- }
- }
-
- }
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