1 |
dl |
1.2 |
/* |
2 |
|
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
dl |
1.33 |
* Expert Group and released to the public domain, as explained at |
4 |
jsr166 |
1.58 |
* http://creativecommons.org/publicdomain/zero/1.0/ |
5 |
dl |
1.2 |
*/ |
6 |
|
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|
7 |
tim |
1.1 |
package java.util.concurrent; |
8 |
jsr166 |
1.51 |
|
9 |
|
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import java.util.AbstractQueue; |
10 |
|
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import java.util.Collection; |
11 |
|
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import java.util.Iterator; |
12 |
|
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import java.util.NoSuchElementException; |
13 |
dl |
1.74 |
import java.util.Spliterator; |
14 |
dl |
1.75 |
import java.util.Spliterators; |
15 |
jsr166 |
1.89 |
import java.util.concurrent.atomic.AtomicInteger; |
16 |
|
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import java.util.concurrent.locks.Condition; |
17 |
|
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import java.util.concurrent.locks.ReentrantLock; |
18 |
|
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import java.util.function.Consumer; |
19 |
tim |
1.1 |
|
20 |
|
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/** |
21 |
dholmes |
1.14 |
* An optionally-bounded {@linkplain BlockingQueue blocking queue} based on |
22 |
dholmes |
1.8 |
* linked nodes. |
23 |
|
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* This queue orders elements FIFO (first-in-first-out). |
24 |
tim |
1.12 |
* The <em>head</em> of the queue is that element that has been on the |
25 |
dholmes |
1.8 |
* queue the longest time. |
26 |
|
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* The <em>tail</em> of the queue is that element that has been on the |
27 |
dl |
1.20 |
* queue the shortest time. New elements |
28 |
|
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* are inserted at the tail of the queue, and the queue retrieval |
29 |
|
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* operations obtain elements at the head of the queue. |
30 |
dholmes |
1.8 |
* Linked queues typically have higher throughput than array-based queues but |
31 |
|
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* less predictable performance in most concurrent applications. |
32 |
tim |
1.12 |
* |
33 |
jsr166 |
1.70 |
* <p>The optional capacity bound constructor argument serves as a |
34 |
dholmes |
1.8 |
* way to prevent excessive queue expansion. The capacity, if unspecified, |
35 |
|
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* is equal to {@link Integer#MAX_VALUE}. Linked nodes are |
36 |
dl |
1.3 |
* dynamically created upon each insertion unless this would bring the |
37 |
|
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* queue above capacity. |
38 |
dholmes |
1.8 |
* |
39 |
dl |
1.36 |
* <p>This class and its iterator implement all of the |
40 |
|
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* <em>optional</em> methods of the {@link Collection} and {@link |
41 |
dl |
1.38 |
* Iterator} interfaces. |
42 |
dl |
1.21 |
* |
43 |
dl |
1.34 |
* <p>This class is a member of the |
44 |
jsr166 |
1.48 |
* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
45 |
dl |
1.34 |
* Java Collections Framework</a>. |
46 |
|
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* |
47 |
dl |
1.6 |
* @since 1.5 |
48 |
|
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* @author Doug Lea |
49 |
jsr166 |
1.88 |
* @param <E> the type of elements held in this queue |
50 |
jsr166 |
1.40 |
*/ |
51 |
dl |
1.2 |
public class LinkedBlockingQueue<E> extends AbstractQueue<E> |
52 |
tim |
1.1 |
implements BlockingQueue<E>, java.io.Serializable { |
53 |
dl |
1.18 |
private static final long serialVersionUID = -6903933977591709194L; |
54 |
tim |
1.1 |
|
55 |
dl |
1.2 |
/* |
56 |
|
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* A variant of the "two lock queue" algorithm. The putLock gates |
57 |
|
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* entry to put (and offer), and has an associated condition for |
58 |
|
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* waiting puts. Similarly for the takeLock. The "count" field |
59 |
|
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* that they both rely on is maintained as an atomic to avoid |
60 |
|
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* needing to get both locks in most cases. Also, to minimize need |
61 |
|
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* for puts to get takeLock and vice-versa, cascading notifies are |
62 |
|
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* used. When a put notices that it has enabled at least one take, |
63 |
|
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* it signals taker. That taker in turn signals others if more |
64 |
|
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* items have been entered since the signal. And symmetrically for |
65 |
tim |
1.12 |
* takes signalling puts. Operations such as remove(Object) and |
66 |
dl |
1.2 |
* iterators acquire both locks. |
67 |
jsr166 |
1.51 |
* |
68 |
|
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* Visibility between writers and readers is provided as follows: |
69 |
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* |
70 |
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* Whenever an element is enqueued, the putLock is acquired and |
71 |
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* count updated. A subsequent reader guarantees visibility to the |
72 |
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* enqueued Node by either acquiring the putLock (via fullyLock) |
73 |
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* or by acquiring the takeLock, and then reading n = count.get(); |
74 |
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* this gives visibility to the first n items. |
75 |
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* |
76 |
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* To implement weakly consistent iterators, it appears we need to |
77 |
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* keep all Nodes GC-reachable from a predecessor dequeued Node. |
78 |
|
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* That would cause two problems: |
79 |
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* - allow a rogue Iterator to cause unbounded memory retention |
80 |
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* - cause cross-generational linking of old Nodes to new Nodes if |
81 |
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* a Node was tenured while live, which generational GCs have a |
82 |
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* hard time dealing with, causing repeated major collections. |
83 |
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* However, only non-deleted Nodes need to be reachable from |
84 |
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* dequeued Nodes, and reachability does not necessarily have to |
85 |
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* be of the kind understood by the GC. We use the trick of |
86 |
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* linking a Node that has just been dequeued to itself. Such a |
87 |
|
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* self-link implicitly means to advance to head.next. |
88 |
dl |
1.38 |
*/ |
89 |
dl |
1.2 |
|
90 |
dl |
1.6 |
/** |
91 |
jsr166 |
1.97 |
* Linked list node class. |
92 |
dl |
1.6 |
*/ |
93 |
dl |
1.2 |
static class Node<E> { |
94 |
jsr166 |
1.51 |
E item; |
95 |
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|
96 |
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/** |
97 |
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* One of: |
98 |
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* - the real successor Node |
99 |
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* - this Node, meaning the successor is head.next |
100 |
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* - null, meaning there is no successor (this is the last node) |
101 |
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*/ |
102 |
dl |
1.2 |
Node<E> next; |
103 |
jsr166 |
1.51 |
|
104 |
dl |
1.2 |
Node(E x) { item = x; } |
105 |
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} |
106 |
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|
107 |
dl |
1.6 |
/** The capacity bound, or Integer.MAX_VALUE if none */ |
108 |
dl |
1.2 |
private final int capacity; |
109 |
dl |
1.6 |
|
110 |
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/** Current number of elements */ |
111 |
jsr166 |
1.61 |
private final AtomicInteger count = new AtomicInteger(); |
112 |
dl |
1.2 |
|
113 |
jsr166 |
1.51 |
/** |
114 |
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* Head of linked list. |
115 |
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* Invariant: head.item == null |
116 |
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*/ |
117 |
jsr166 |
1.64 |
transient Node<E> head; |
118 |
dl |
1.6 |
|
119 |
jsr166 |
1.51 |
/** |
120 |
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* Tail of linked list. |
121 |
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* Invariant: last.next == null |
122 |
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*/ |
123 |
dl |
1.6 |
private transient Node<E> last; |
124 |
dl |
1.2 |
|
125 |
dl |
1.6 |
/** Lock held by take, poll, etc */ |
126 |
dl |
1.5 |
private final ReentrantLock takeLock = new ReentrantLock(); |
127 |
dl |
1.6 |
|
128 |
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/** Wait queue for waiting takes */ |
129 |
dl |
1.32 |
private final Condition notEmpty = takeLock.newCondition(); |
130 |
dl |
1.2 |
|
131 |
dl |
1.6 |
/** Lock held by put, offer, etc */ |
132 |
dl |
1.5 |
private final ReentrantLock putLock = new ReentrantLock(); |
133 |
dl |
1.6 |
|
134 |
|
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/** Wait queue for waiting puts */ |
135 |
dl |
1.32 |
private final Condition notFull = putLock.newCondition(); |
136 |
dl |
1.2 |
|
137 |
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/** |
138 |
jsr166 |
1.40 |
* Signals a waiting take. Called only from put/offer (which do not |
139 |
dl |
1.4 |
* otherwise ordinarily lock takeLock.) |
140 |
dl |
1.2 |
*/ |
141 |
|
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private void signalNotEmpty() { |
142 |
dl |
1.31 |
final ReentrantLock takeLock = this.takeLock; |
143 |
dl |
1.2 |
takeLock.lock(); |
144 |
|
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try { |
145 |
|
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notEmpty.signal(); |
146 |
tim |
1.17 |
} finally { |
147 |
dl |
1.2 |
takeLock.unlock(); |
148 |
|
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} |
149 |
|
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} |
150 |
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|
151 |
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/** |
152 |
jsr166 |
1.40 |
* Signals a waiting put. Called only from take/poll. |
153 |
dl |
1.2 |
*/ |
154 |
|
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private void signalNotFull() { |
155 |
dl |
1.31 |
final ReentrantLock putLock = this.putLock; |
156 |
dl |
1.2 |
putLock.lock(); |
157 |
|
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try { |
158 |
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notFull.signal(); |
159 |
tim |
1.17 |
} finally { |
160 |
dl |
1.2 |
putLock.unlock(); |
161 |
|
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} |
162 |
|
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} |
163 |
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|
164 |
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/** |
165 |
dl |
1.54 |
* Links node at end of queue. |
166 |
jsr166 |
1.51 |
* |
167 |
dl |
1.54 |
* @param node the node |
168 |
dl |
1.2 |
*/ |
169 |
dl |
1.54 |
private void enqueue(Node<E> node) { |
170 |
jsr166 |
1.51 |
// assert putLock.isHeldByCurrentThread(); |
171 |
|
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// assert last.next == null; |
172 |
dl |
1.54 |
last = last.next = node; |
173 |
dl |
1.2 |
} |
174 |
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|
175 |
|
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/** |
176 |
jsr166 |
1.51 |
* Removes a node from head of queue. |
177 |
|
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* |
178 |
dl |
1.6 |
* @return the node |
179 |
dl |
1.2 |
*/ |
180 |
jsr166 |
1.51 |
private E dequeue() { |
181 |
|
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// assert takeLock.isHeldByCurrentThread(); |
182 |
|
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// assert head.item == null; |
183 |
dl |
1.50 |
Node<E> h = head; |
184 |
|
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Node<E> first = h.next; |
185 |
jsr166 |
1.51 |
h.next = h; // help GC |
186 |
dl |
1.2 |
head = first; |
187 |
dl |
1.28 |
E x = first.item; |
188 |
dl |
1.2 |
first.item = null; |
189 |
|
|
return x; |
190 |
|
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} |
191 |
|
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|
192 |
|
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/** |
193 |
jsr166 |
1.71 |
* Locks to prevent both puts and takes. |
194 |
dl |
1.2 |
*/ |
195 |
jsr166 |
1.51 |
void fullyLock() { |
196 |
dl |
1.2 |
putLock.lock(); |
197 |
|
|
takeLock.lock(); |
198 |
tim |
1.1 |
} |
199 |
dl |
1.2 |
|
200 |
|
|
/** |
201 |
jsr166 |
1.71 |
* Unlocks to allow both puts and takes. |
202 |
dl |
1.2 |
*/ |
203 |
jsr166 |
1.51 |
void fullyUnlock() { |
204 |
dl |
1.2 |
takeLock.unlock(); |
205 |
|
|
putLock.unlock(); |
206 |
|
|
} |
207 |
|
|
|
208 |
|
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/** |
209 |
jsr166 |
1.51 |
* Creates a {@code LinkedBlockingQueue} with a capacity of |
210 |
dholmes |
1.8 |
* {@link Integer#MAX_VALUE}. |
211 |
dl |
1.2 |
*/ |
212 |
|
|
public LinkedBlockingQueue() { |
213 |
|
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this(Integer.MAX_VALUE); |
214 |
|
|
} |
215 |
|
|
|
216 |
|
|
/** |
217 |
jsr166 |
1.51 |
* Creates a {@code LinkedBlockingQueue} with the given (fixed) capacity. |
218 |
tim |
1.16 |
* |
219 |
jsr166 |
1.43 |
* @param capacity the capacity of this queue |
220 |
jsr166 |
1.51 |
* @throws IllegalArgumentException if {@code capacity} is not greater |
221 |
jsr166 |
1.43 |
* than zero |
222 |
dl |
1.2 |
*/ |
223 |
|
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public LinkedBlockingQueue(int capacity) { |
224 |
dholmes |
1.8 |
if (capacity <= 0) throw new IllegalArgumentException(); |
225 |
dl |
1.2 |
this.capacity = capacity; |
226 |
dl |
1.6 |
last = head = new Node<E>(null); |
227 |
dl |
1.2 |
} |
228 |
|
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|
229 |
|
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/** |
230 |
jsr166 |
1.51 |
* Creates a {@code LinkedBlockingQueue} with a capacity of |
231 |
dholmes |
1.14 |
* {@link Integer#MAX_VALUE}, initially containing the elements of the |
232 |
tim |
1.12 |
* given collection, |
233 |
dholmes |
1.8 |
* added in traversal order of the collection's iterator. |
234 |
jsr166 |
1.43 |
* |
235 |
dholmes |
1.9 |
* @param c the collection of elements to initially contain |
236 |
jsr166 |
1.43 |
* @throws NullPointerException if the specified collection or any |
237 |
|
|
* of its elements are null |
238 |
dl |
1.2 |
*/ |
239 |
dholmes |
1.10 |
public LinkedBlockingQueue(Collection<? extends E> c) { |
240 |
dl |
1.2 |
this(Integer.MAX_VALUE); |
241 |
jsr166 |
1.51 |
final ReentrantLock putLock = this.putLock; |
242 |
|
|
putLock.lock(); // Never contended, but necessary for visibility |
243 |
|
|
try { |
244 |
|
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int n = 0; |
245 |
|
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for (E e : c) { |
246 |
|
|
if (e == null) |
247 |
|
|
throw new NullPointerException(); |
248 |
|
|
if (n == capacity) |
249 |
|
|
throw new IllegalStateException("Queue full"); |
250 |
dl |
1.54 |
enqueue(new Node<E>(e)); |
251 |
jsr166 |
1.51 |
++n; |
252 |
|
|
} |
253 |
|
|
count.set(n); |
254 |
|
|
} finally { |
255 |
|
|
putLock.unlock(); |
256 |
|
|
} |
257 |
dl |
1.2 |
} |
258 |
|
|
|
259 |
dholmes |
1.8 |
// this doc comment is overridden to remove the reference to collections |
260 |
|
|
// greater in size than Integer.MAX_VALUE |
261 |
tim |
1.12 |
/** |
262 |
dl |
1.20 |
* Returns the number of elements in this queue. |
263 |
|
|
* |
264 |
jsr166 |
1.43 |
* @return the number of elements in this queue |
265 |
dholmes |
1.8 |
*/ |
266 |
dl |
1.2 |
public int size() { |
267 |
|
|
return count.get(); |
268 |
tim |
1.1 |
} |
269 |
dl |
1.2 |
|
270 |
dholmes |
1.8 |
// this doc comment is a modified copy of the inherited doc comment, |
271 |
|
|
// without the reference to unlimited queues. |
272 |
tim |
1.12 |
/** |
273 |
jsr166 |
1.41 |
* Returns the number of additional elements that this queue can ideally |
274 |
|
|
* (in the absence of memory or resource constraints) accept without |
275 |
dholmes |
1.8 |
* blocking. This is always equal to the initial capacity of this queue |
276 |
jsr166 |
1.51 |
* less the current {@code size} of this queue. |
277 |
jsr166 |
1.41 |
* |
278 |
|
|
* <p>Note that you <em>cannot</em> always tell if an attempt to insert |
279 |
jsr166 |
1.51 |
* an element will succeed by inspecting {@code remainingCapacity} |
280 |
jsr166 |
1.41 |
* because it may be the case that another thread is about to |
281 |
jsr166 |
1.43 |
* insert or remove an element. |
282 |
dholmes |
1.8 |
*/ |
283 |
dl |
1.2 |
public int remainingCapacity() { |
284 |
|
|
return capacity - count.get(); |
285 |
|
|
} |
286 |
|
|
|
287 |
dholmes |
1.22 |
/** |
288 |
jsr166 |
1.44 |
* Inserts the specified element at the tail of this queue, waiting if |
289 |
dholmes |
1.22 |
* necessary for space to become available. |
290 |
jsr166 |
1.43 |
* |
291 |
|
|
* @throws InterruptedException {@inheritDoc} |
292 |
|
|
* @throws NullPointerException {@inheritDoc} |
293 |
dholmes |
1.22 |
*/ |
294 |
jsr166 |
1.42 |
public void put(E e) throws InterruptedException { |
295 |
|
|
if (e == null) throw new NullPointerException(); |
296 |
jsr166 |
1.51 |
// Note: convention in all put/take/etc is to preset local var |
297 |
|
|
// holding count negative to indicate failure unless set. |
298 |
tim |
1.12 |
int c = -1; |
299 |
jsr166 |
1.60 |
Node<E> node = new Node<E>(e); |
300 |
dl |
1.31 |
final ReentrantLock putLock = this.putLock; |
301 |
|
|
final AtomicInteger count = this.count; |
302 |
dl |
1.2 |
putLock.lockInterruptibly(); |
303 |
|
|
try { |
304 |
|
|
/* |
305 |
|
|
* Note that count is used in wait guard even though it is |
306 |
|
|
* not protected by lock. This works because count can |
307 |
|
|
* only decrease at this point (all other puts are shut |
308 |
|
|
* out by lock), and we (or some other waiting put) are |
309 |
jsr166 |
1.51 |
* signalled if it ever changes from capacity. Similarly |
310 |
|
|
* for all other uses of count in other wait guards. |
311 |
dl |
1.2 |
*/ |
312 |
jsr166 |
1.51 |
while (count.get() == capacity) { |
313 |
|
|
notFull.await(); |
314 |
dl |
1.2 |
} |
315 |
dl |
1.54 |
enqueue(node); |
316 |
dl |
1.2 |
c = count.getAndIncrement(); |
317 |
dl |
1.6 |
if (c + 1 < capacity) |
318 |
dl |
1.2 |
notFull.signal(); |
319 |
tim |
1.17 |
} finally { |
320 |
dl |
1.2 |
putLock.unlock(); |
321 |
|
|
} |
322 |
tim |
1.12 |
if (c == 0) |
323 |
dl |
1.2 |
signalNotEmpty(); |
324 |
tim |
1.1 |
} |
325 |
dl |
1.2 |
|
326 |
dholmes |
1.22 |
/** |
327 |
|
|
* Inserts the specified element at the tail of this queue, waiting if |
328 |
|
|
* necessary up to the specified wait time for space to become available. |
329 |
jsr166 |
1.43 |
* |
330 |
jsr166 |
1.51 |
* @return {@code true} if successful, or {@code false} if |
331 |
jsr166 |
1.73 |
* the specified waiting time elapses before space is available |
332 |
jsr166 |
1.43 |
* @throws InterruptedException {@inheritDoc} |
333 |
|
|
* @throws NullPointerException {@inheritDoc} |
334 |
dholmes |
1.22 |
*/ |
335 |
jsr166 |
1.42 |
public boolean offer(E e, long timeout, TimeUnit unit) |
336 |
dholmes |
1.8 |
throws InterruptedException { |
337 |
tim |
1.12 |
|
338 |
jsr166 |
1.42 |
if (e == null) throw new NullPointerException(); |
339 |
dl |
1.2 |
long nanos = unit.toNanos(timeout); |
340 |
|
|
int c = -1; |
341 |
dl |
1.31 |
final ReentrantLock putLock = this.putLock; |
342 |
|
|
final AtomicInteger count = this.count; |
343 |
dholmes |
1.8 |
putLock.lockInterruptibly(); |
344 |
dl |
1.2 |
try { |
345 |
jsr166 |
1.51 |
while (count.get() == capacity) { |
346 |
jsr166 |
1.98 |
if (nanos <= 0L) |
347 |
dl |
1.2 |
return false; |
348 |
jsr166 |
1.51 |
nanos = notFull.awaitNanos(nanos); |
349 |
dl |
1.2 |
} |
350 |
dl |
1.54 |
enqueue(new Node<E>(e)); |
351 |
jsr166 |
1.51 |
c = count.getAndIncrement(); |
352 |
|
|
if (c + 1 < capacity) |
353 |
|
|
notFull.signal(); |
354 |
tim |
1.17 |
} finally { |
355 |
dl |
1.2 |
putLock.unlock(); |
356 |
|
|
} |
357 |
tim |
1.12 |
if (c == 0) |
358 |
dl |
1.2 |
signalNotEmpty(); |
359 |
|
|
return true; |
360 |
tim |
1.1 |
} |
361 |
dl |
1.2 |
|
362 |
dl |
1.23 |
/** |
363 |
jsr166 |
1.44 |
* Inserts the specified element at the tail of this queue if it is |
364 |
|
|
* possible to do so immediately without exceeding the queue's capacity, |
365 |
jsr166 |
1.51 |
* returning {@code true} upon success and {@code false} if this queue |
366 |
jsr166 |
1.44 |
* is full. |
367 |
|
|
* When using a capacity-restricted queue, this method is generally |
368 |
|
|
* preferable to method {@link BlockingQueue#add add}, which can fail to |
369 |
|
|
* insert an element only by throwing an exception. |
370 |
dl |
1.23 |
* |
371 |
jsr166 |
1.43 |
* @throws NullPointerException if the specified element is null |
372 |
dl |
1.23 |
*/ |
373 |
jsr166 |
1.42 |
public boolean offer(E e) { |
374 |
|
|
if (e == null) throw new NullPointerException(); |
375 |
dl |
1.31 |
final AtomicInteger count = this.count; |
376 |
dl |
1.2 |
if (count.get() == capacity) |
377 |
|
|
return false; |
378 |
tim |
1.12 |
int c = -1; |
379 |
jsr166 |
1.60 |
Node<E> node = new Node<E>(e); |
380 |
dl |
1.31 |
final ReentrantLock putLock = this.putLock; |
381 |
dholmes |
1.8 |
putLock.lock(); |
382 |
dl |
1.2 |
try { |
383 |
|
|
if (count.get() < capacity) { |
384 |
dl |
1.54 |
enqueue(node); |
385 |
dl |
1.2 |
c = count.getAndIncrement(); |
386 |
dl |
1.6 |
if (c + 1 < capacity) |
387 |
dl |
1.2 |
notFull.signal(); |
388 |
|
|
} |
389 |
tim |
1.17 |
} finally { |
390 |
dl |
1.2 |
putLock.unlock(); |
391 |
|
|
} |
392 |
tim |
1.12 |
if (c == 0) |
393 |
dl |
1.2 |
signalNotEmpty(); |
394 |
|
|
return c >= 0; |
395 |
tim |
1.1 |
} |
396 |
dl |
1.2 |
|
397 |
|
|
public E take() throws InterruptedException { |
398 |
|
|
E x; |
399 |
|
|
int c = -1; |
400 |
dl |
1.31 |
final AtomicInteger count = this.count; |
401 |
|
|
final ReentrantLock takeLock = this.takeLock; |
402 |
dl |
1.2 |
takeLock.lockInterruptibly(); |
403 |
|
|
try { |
404 |
jsr166 |
1.51 |
while (count.get() == 0) { |
405 |
|
|
notEmpty.await(); |
406 |
dl |
1.2 |
} |
407 |
jsr166 |
1.51 |
x = dequeue(); |
408 |
dl |
1.2 |
c = count.getAndDecrement(); |
409 |
|
|
if (c > 1) |
410 |
|
|
notEmpty.signal(); |
411 |
tim |
1.17 |
} finally { |
412 |
dl |
1.2 |
takeLock.unlock(); |
413 |
|
|
} |
414 |
tim |
1.12 |
if (c == capacity) |
415 |
dl |
1.2 |
signalNotFull(); |
416 |
|
|
return x; |
417 |
|
|
} |
418 |
|
|
|
419 |
|
|
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
420 |
|
|
E x = null; |
421 |
|
|
int c = -1; |
422 |
dholmes |
1.8 |
long nanos = unit.toNanos(timeout); |
423 |
dl |
1.31 |
final AtomicInteger count = this.count; |
424 |
|
|
final ReentrantLock takeLock = this.takeLock; |
425 |
dl |
1.2 |
takeLock.lockInterruptibly(); |
426 |
|
|
try { |
427 |
jsr166 |
1.51 |
while (count.get() == 0) { |
428 |
jsr166 |
1.98 |
if (nanos <= 0L) |
429 |
dl |
1.2 |
return null; |
430 |
jsr166 |
1.51 |
nanos = notEmpty.awaitNanos(nanos); |
431 |
dl |
1.2 |
} |
432 |
jsr166 |
1.51 |
x = dequeue(); |
433 |
|
|
c = count.getAndDecrement(); |
434 |
|
|
if (c > 1) |
435 |
|
|
notEmpty.signal(); |
436 |
tim |
1.17 |
} finally { |
437 |
dl |
1.2 |
takeLock.unlock(); |
438 |
|
|
} |
439 |
tim |
1.12 |
if (c == capacity) |
440 |
dl |
1.2 |
signalNotFull(); |
441 |
|
|
return x; |
442 |
|
|
} |
443 |
|
|
|
444 |
|
|
public E poll() { |
445 |
dl |
1.31 |
final AtomicInteger count = this.count; |
446 |
dl |
1.2 |
if (count.get() == 0) |
447 |
|
|
return null; |
448 |
|
|
E x = null; |
449 |
tim |
1.12 |
int c = -1; |
450 |
dl |
1.31 |
final ReentrantLock takeLock = this.takeLock; |
451 |
dl |
1.30 |
takeLock.lock(); |
452 |
dl |
1.2 |
try { |
453 |
|
|
if (count.get() > 0) { |
454 |
jsr166 |
1.51 |
x = dequeue(); |
455 |
dl |
1.2 |
c = count.getAndDecrement(); |
456 |
|
|
if (c > 1) |
457 |
|
|
notEmpty.signal(); |
458 |
|
|
} |
459 |
tim |
1.17 |
} finally { |
460 |
dl |
1.2 |
takeLock.unlock(); |
461 |
|
|
} |
462 |
tim |
1.12 |
if (c == capacity) |
463 |
dl |
1.2 |
signalNotFull(); |
464 |
|
|
return x; |
465 |
tim |
1.1 |
} |
466 |
dl |
1.2 |
|
467 |
|
|
public E peek() { |
468 |
|
|
if (count.get() == 0) |
469 |
|
|
return null; |
470 |
dl |
1.31 |
final ReentrantLock takeLock = this.takeLock; |
471 |
dholmes |
1.8 |
takeLock.lock(); |
472 |
dl |
1.2 |
try { |
473 |
jsr166 |
1.96 |
return (count.get() > 0) ? head.next.item : null; |
474 |
tim |
1.17 |
} finally { |
475 |
dl |
1.2 |
takeLock.unlock(); |
476 |
|
|
} |
477 |
tim |
1.1 |
} |
478 |
|
|
|
479 |
dl |
1.35 |
/** |
480 |
jsr166 |
1.51 |
* Unlinks interior Node p with predecessor trail. |
481 |
|
|
*/ |
482 |
|
|
void unlink(Node<E> p, Node<E> trail) { |
483 |
jsr166 |
1.100 |
// assert putLock.isHeldByCurrentThread(); |
484 |
|
|
// assert takeLock.isHeldByCurrentThread(); |
485 |
jsr166 |
1.51 |
// p.next is not changed, to allow iterators that are |
486 |
|
|
// traversing p to maintain their weak-consistency guarantee. |
487 |
|
|
p.item = null; |
488 |
|
|
trail.next = p.next; |
489 |
|
|
if (last == p) |
490 |
|
|
last = trail; |
491 |
|
|
if (count.getAndDecrement() == capacity) |
492 |
|
|
notFull.signal(); |
493 |
|
|
} |
494 |
|
|
|
495 |
|
|
/** |
496 |
jsr166 |
1.44 |
* Removes a single instance of the specified element from this queue, |
497 |
jsr166 |
1.51 |
* if it is present. More formally, removes an element {@code e} such |
498 |
|
|
* that {@code o.equals(e)}, if this queue contains one or more such |
499 |
jsr166 |
1.44 |
* elements. |
500 |
jsr166 |
1.51 |
* Returns {@code true} if this queue contained the specified element |
501 |
jsr166 |
1.44 |
* (or equivalently, if this queue changed as a result of the call). |
502 |
|
|
* |
503 |
|
|
* @param o element to be removed from this queue, if present |
504 |
jsr166 |
1.51 |
* @return {@code true} if this queue changed as a result of the call |
505 |
dl |
1.35 |
*/ |
506 |
dholmes |
1.9 |
public boolean remove(Object o) { |
507 |
|
|
if (o == null) return false; |
508 |
dl |
1.2 |
fullyLock(); |
509 |
|
|
try { |
510 |
jsr166 |
1.51 |
for (Node<E> trail = head, p = trail.next; |
511 |
|
|
p != null; |
512 |
|
|
trail = p, p = p.next) { |
513 |
dholmes |
1.9 |
if (o.equals(p.item)) { |
514 |
jsr166 |
1.51 |
unlink(p, trail); |
515 |
|
|
return true; |
516 |
dl |
1.2 |
} |
517 |
|
|
} |
518 |
jsr166 |
1.51 |
return false; |
519 |
tim |
1.17 |
} finally { |
520 |
dl |
1.2 |
fullyUnlock(); |
521 |
|
|
} |
522 |
tim |
1.1 |
} |
523 |
dl |
1.2 |
|
524 |
jsr166 |
1.43 |
/** |
525 |
jsr166 |
1.56 |
* Returns {@code true} if this queue contains the specified element. |
526 |
|
|
* More formally, returns {@code true} if and only if this queue contains |
527 |
|
|
* at least one element {@code e} such that {@code o.equals(e)}. |
528 |
|
|
* |
529 |
|
|
* @param o object to be checked for containment in this queue |
530 |
|
|
* @return {@code true} if this queue contains the specified element |
531 |
|
|
*/ |
532 |
|
|
public boolean contains(Object o) { |
533 |
|
|
if (o == null) return false; |
534 |
|
|
fullyLock(); |
535 |
|
|
try { |
536 |
|
|
for (Node<E> p = head.next; p != null; p = p.next) |
537 |
|
|
if (o.equals(p.item)) |
538 |
|
|
return true; |
539 |
|
|
return false; |
540 |
|
|
} finally { |
541 |
|
|
fullyUnlock(); |
542 |
|
|
} |
543 |
|
|
} |
544 |
|
|
|
545 |
|
|
/** |
546 |
jsr166 |
1.43 |
* Returns an array containing all of the elements in this queue, in |
547 |
|
|
* proper sequence. |
548 |
|
|
* |
549 |
|
|
* <p>The returned array will be "safe" in that no references to it are |
550 |
|
|
* maintained by this queue. (In other words, this method must allocate |
551 |
|
|
* a new array). The caller is thus free to modify the returned array. |
552 |
jsr166 |
1.45 |
* |
553 |
jsr166 |
1.43 |
* <p>This method acts as bridge between array-based and collection-based |
554 |
|
|
* APIs. |
555 |
|
|
* |
556 |
|
|
* @return an array containing all of the elements in this queue |
557 |
|
|
*/ |
558 |
dl |
1.2 |
public Object[] toArray() { |
559 |
|
|
fullyLock(); |
560 |
|
|
try { |
561 |
|
|
int size = count.get(); |
562 |
tim |
1.12 |
Object[] a = new Object[size]; |
563 |
dl |
1.2 |
int k = 0; |
564 |
tim |
1.12 |
for (Node<E> p = head.next; p != null; p = p.next) |
565 |
dl |
1.2 |
a[k++] = p.item; |
566 |
|
|
return a; |
567 |
tim |
1.17 |
} finally { |
568 |
dl |
1.2 |
fullyUnlock(); |
569 |
|
|
} |
570 |
tim |
1.1 |
} |
571 |
dl |
1.2 |
|
572 |
jsr166 |
1.43 |
/** |
573 |
|
|
* Returns an array containing all of the elements in this queue, in |
574 |
|
|
* proper sequence; the runtime type of the returned array is that of |
575 |
|
|
* the specified array. If the queue fits in the specified array, it |
576 |
|
|
* is returned therein. Otherwise, a new array is allocated with the |
577 |
|
|
* runtime type of the specified array and the size of this queue. |
578 |
|
|
* |
579 |
|
|
* <p>If this queue fits in the specified array with room to spare |
580 |
|
|
* (i.e., the array has more elements than this queue), the element in |
581 |
|
|
* the array immediately following the end of the queue is set to |
582 |
jsr166 |
1.51 |
* {@code null}. |
583 |
jsr166 |
1.43 |
* |
584 |
|
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
585 |
|
|
* array-based and collection-based APIs. Further, this method allows |
586 |
|
|
* precise control over the runtime type of the output array, and may, |
587 |
|
|
* under certain circumstances, be used to save allocation costs. |
588 |
|
|
* |
589 |
jsr166 |
1.51 |
* <p>Suppose {@code x} is a queue known to contain only strings. |
590 |
jsr166 |
1.43 |
* The following code can be used to dump the queue into a newly |
591 |
jsr166 |
1.51 |
* allocated array of {@code String}: |
592 |
jsr166 |
1.43 |
* |
593 |
jsr166 |
1.92 |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
594 |
jsr166 |
1.43 |
* |
595 |
jsr166 |
1.51 |
* Note that {@code toArray(new Object[0])} is identical in function to |
596 |
|
|
* {@code toArray()}. |
597 |
jsr166 |
1.43 |
* |
598 |
|
|
* @param a the array into which the elements of the queue are to |
599 |
|
|
* be stored, if it is big enough; otherwise, a new array of the |
600 |
|
|
* same runtime type is allocated for this purpose |
601 |
|
|
* @return an array containing all of the elements in this queue |
602 |
|
|
* @throws ArrayStoreException if the runtime type of the specified array |
603 |
|
|
* is not a supertype of the runtime type of every element in |
604 |
|
|
* this queue |
605 |
|
|
* @throws NullPointerException if the specified array is null |
606 |
|
|
*/ |
607 |
jsr166 |
1.51 |
@SuppressWarnings("unchecked") |
608 |
dl |
1.2 |
public <T> T[] toArray(T[] a) { |
609 |
|
|
fullyLock(); |
610 |
|
|
try { |
611 |
|
|
int size = count.get(); |
612 |
|
|
if (a.length < size) |
613 |
dl |
1.4 |
a = (T[])java.lang.reflect.Array.newInstance |
614 |
|
|
(a.getClass().getComponentType(), size); |
615 |
tim |
1.12 |
|
616 |
dl |
1.2 |
int k = 0; |
617 |
jsr166 |
1.51 |
for (Node<E> p = head.next; p != null; p = p.next) |
618 |
dl |
1.2 |
a[k++] = (T)p.item; |
619 |
jsr166 |
1.47 |
if (a.length > k) |
620 |
|
|
a[k] = null; |
621 |
dl |
1.2 |
return a; |
622 |
tim |
1.17 |
} finally { |
623 |
dl |
1.2 |
fullyUnlock(); |
624 |
|
|
} |
625 |
tim |
1.1 |
} |
626 |
dl |
1.2 |
|
627 |
|
|
public String toString() { |
628 |
jsr166 |
1.94 |
return Helpers.collectionToString(this); |
629 |
tim |
1.1 |
} |
630 |
dl |
1.2 |
|
631 |
dl |
1.35 |
/** |
632 |
|
|
* Atomically removes all of the elements from this queue. |
633 |
|
|
* The queue will be empty after this call returns. |
634 |
|
|
*/ |
635 |
dl |
1.24 |
public void clear() { |
636 |
|
|
fullyLock(); |
637 |
|
|
try { |
638 |
jsr166 |
1.51 |
for (Node<E> p, h = head; (p = h.next) != null; h = p) { |
639 |
|
|
h.next = h; |
640 |
|
|
p.item = null; |
641 |
|
|
} |
642 |
|
|
head = last; |
643 |
|
|
// assert head.item == null && head.next == null; |
644 |
dl |
1.24 |
if (count.getAndSet(0) == capacity) |
645 |
jsr166 |
1.51 |
notFull.signal(); |
646 |
dl |
1.24 |
} finally { |
647 |
|
|
fullyUnlock(); |
648 |
|
|
} |
649 |
|
|
} |
650 |
|
|
|
651 |
jsr166 |
1.43 |
/** |
652 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
653 |
|
|
* @throws ClassCastException {@inheritDoc} |
654 |
|
|
* @throws NullPointerException {@inheritDoc} |
655 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
656 |
|
|
*/ |
657 |
dl |
1.24 |
public int drainTo(Collection<? super E> c) { |
658 |
jsr166 |
1.51 |
return drainTo(c, Integer.MAX_VALUE); |
659 |
dl |
1.24 |
} |
660 |
jsr166 |
1.40 |
|
661 |
jsr166 |
1.43 |
/** |
662 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
663 |
|
|
* @throws ClassCastException {@inheritDoc} |
664 |
|
|
* @throws NullPointerException {@inheritDoc} |
665 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
666 |
|
|
*/ |
667 |
dl |
1.24 |
public int drainTo(Collection<? super E> c, int maxElements) { |
668 |
|
|
if (c == null) |
669 |
|
|
throw new NullPointerException(); |
670 |
|
|
if (c == this) |
671 |
|
|
throw new IllegalArgumentException(); |
672 |
jsr166 |
1.63 |
if (maxElements <= 0) |
673 |
|
|
return 0; |
674 |
jsr166 |
1.51 |
boolean signalNotFull = false; |
675 |
|
|
final ReentrantLock takeLock = this.takeLock; |
676 |
|
|
takeLock.lock(); |
677 |
dl |
1.24 |
try { |
678 |
jsr166 |
1.51 |
int n = Math.min(maxElements, count.get()); |
679 |
|
|
// count.get provides visibility to first n Nodes |
680 |
|
|
Node<E> h = head; |
681 |
|
|
int i = 0; |
682 |
|
|
try { |
683 |
|
|
while (i < n) { |
684 |
|
|
Node<E> p = h.next; |
685 |
|
|
c.add(p.item); |
686 |
|
|
p.item = null; |
687 |
|
|
h.next = h; |
688 |
|
|
h = p; |
689 |
|
|
++i; |
690 |
|
|
} |
691 |
|
|
return n; |
692 |
|
|
} finally { |
693 |
|
|
// Restore invariants even if c.add() threw |
694 |
|
|
if (i > 0) { |
695 |
|
|
// assert h.item == null; |
696 |
|
|
head = h; |
697 |
|
|
signalNotFull = (count.getAndAdd(-i) == capacity); |
698 |
|
|
} |
699 |
dl |
1.24 |
} |
700 |
|
|
} finally { |
701 |
jsr166 |
1.51 |
takeLock.unlock(); |
702 |
|
|
if (signalNotFull) |
703 |
|
|
signalNotFull(); |
704 |
dl |
1.24 |
} |
705 |
|
|
} |
706 |
|
|
|
707 |
dholmes |
1.14 |
/** |
708 |
|
|
* Returns an iterator over the elements in this queue in proper sequence. |
709 |
jsr166 |
1.57 |
* The elements will be returned in order from first (head) to last (tail). |
710 |
|
|
* |
711 |
jsr166 |
1.87 |
* <p>The returned iterator is |
712 |
|
|
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>. |
713 |
dholmes |
1.14 |
* |
714 |
jsr166 |
1.43 |
* @return an iterator over the elements in this queue in proper sequence |
715 |
dholmes |
1.14 |
*/ |
716 |
dl |
1.2 |
public Iterator<E> iterator() { |
717 |
jsr166 |
1.59 |
return new Itr(); |
718 |
tim |
1.1 |
} |
719 |
dl |
1.2 |
|
720 |
|
|
private class Itr implements Iterator<E> { |
721 |
tim |
1.12 |
/* |
722 |
jsr166 |
1.51 |
* Basic weakly-consistent iterator. At all times hold the next |
723 |
dl |
1.4 |
* item to hand out so that if hasNext() reports true, we will |
724 |
|
|
* still have it to return even if lost race with a take etc. |
725 |
|
|
*/ |
726 |
jsr166 |
1.72 |
|
727 |
dl |
1.31 |
private Node<E> current; |
728 |
|
|
private Node<E> lastRet; |
729 |
|
|
private E currentElement; |
730 |
tim |
1.12 |
|
731 |
dl |
1.2 |
Itr() { |
732 |
jsr166 |
1.51 |
fullyLock(); |
733 |
dl |
1.2 |
try { |
734 |
jsr166 |
1.100 |
if ((current = head.next) != null) |
735 |
dl |
1.4 |
currentElement = current.item; |
736 |
tim |
1.17 |
} finally { |
737 |
jsr166 |
1.51 |
fullyUnlock(); |
738 |
dl |
1.2 |
} |
739 |
|
|
} |
740 |
tim |
1.12 |
|
741 |
|
|
public boolean hasNext() { |
742 |
dl |
1.2 |
return current != null; |
743 |
|
|
} |
744 |
|
|
|
745 |
tim |
1.12 |
public E next() { |
746 |
jsr166 |
1.100 |
if (current == null) |
747 |
|
|
throw new NoSuchElementException(); |
748 |
jsr166 |
1.51 |
fullyLock(); |
749 |
dl |
1.2 |
try { |
750 |
|
|
lastRet = current; |
751 |
jsr166 |
1.91 |
E item = null; |
752 |
|
|
// Unlike other traversal methods, iterators must handle both: |
753 |
|
|
// - dequeued nodes (p.next == p) |
754 |
|
|
// - (possibly multiple) interior removed nodes (p.item == null) |
755 |
|
|
for (Node<E> p = current, q;; p = q) { |
756 |
|
|
if ((q = p.next) == p) |
757 |
|
|
q = head.next; |
758 |
|
|
if (q == null || (item = q.item) != null) { |
759 |
|
|
current = q; |
760 |
|
|
E x = currentElement; |
761 |
|
|
currentElement = item; |
762 |
|
|
return x; |
763 |
|
|
} |
764 |
|
|
} |
765 |
tim |
1.17 |
} finally { |
766 |
jsr166 |
1.51 |
fullyUnlock(); |
767 |
dl |
1.2 |
} |
768 |
|
|
} |
769 |
|
|
|
770 |
tim |
1.12 |
public void remove() { |
771 |
dl |
1.2 |
if (lastRet == null) |
772 |
tim |
1.12 |
throw new IllegalStateException(); |
773 |
jsr166 |
1.51 |
fullyLock(); |
774 |
dl |
1.2 |
try { |
775 |
|
|
Node<E> node = lastRet; |
776 |
|
|
lastRet = null; |
777 |
jsr166 |
1.51 |
for (Node<E> trail = head, p = trail.next; |
778 |
|
|
p != null; |
779 |
|
|
trail = p, p = p.next) { |
780 |
|
|
if (p == node) { |
781 |
|
|
unlink(p, trail); |
782 |
|
|
break; |
783 |
|
|
} |
784 |
dl |
1.2 |
} |
785 |
tim |
1.17 |
} finally { |
786 |
jsr166 |
1.51 |
fullyUnlock(); |
787 |
dl |
1.2 |
} |
788 |
|
|
} |
789 |
tim |
1.1 |
} |
790 |
dl |
1.2 |
|
791 |
jsr166 |
1.100 |
/** |
792 |
|
|
* A customized variant of Spliterators.IteratorSpliterator. |
793 |
|
|
* Keep this class in sync with (very similar) LBDSpliterator. |
794 |
|
|
*/ |
795 |
|
|
private final class LBQSpliterator implements Spliterator<E> { |
796 |
dl |
1.80 |
static final int MAX_BATCH = 1 << 25; // max batch array size; |
797 |
dl |
1.74 |
Node<E> current; // current node; null until initialized |
798 |
|
|
int batch; // batch size for splits |
799 |
|
|
boolean exhausted; // true when no more nodes |
800 |
jsr166 |
1.100 |
long est = size(); // size estimate |
801 |
jsr166 |
1.99 |
|
802 |
jsr166 |
1.100 |
LBQSpliterator() {} |
803 |
|
|
|
804 |
|
|
private Node<E> succ(Node<E> p) { |
805 |
|
|
return (p == (p = p.next)) ? head.next : p; |
806 |
|
|
} |
807 |
dl |
1.74 |
|
808 |
|
|
public long estimateSize() { return est; } |
809 |
|
|
|
810 |
|
|
public Spliterator<E> trySplit() { |
811 |
dl |
1.80 |
Node<E> h; |
812 |
|
|
int b = batch; |
813 |
|
|
int n = (b <= 0) ? 1 : (b >= MAX_BATCH) ? MAX_BATCH : b + 1; |
814 |
jsr166 |
1.78 |
if (!exhausted && |
815 |
jsr166 |
1.100 |
((h = current) != null || (h = head.next) != null) |
816 |
|
|
&& h.next != null) { |
817 |
dl |
1.83 |
Object[] a = new Object[n]; |
818 |
dl |
1.74 |
int i = 0; |
819 |
|
|
Node<E> p = current; |
820 |
jsr166 |
1.99 |
fullyLock(); |
821 |
dl |
1.74 |
try { |
822 |
jsr166 |
1.100 |
if (p != null || (p = head.next) != null) |
823 |
|
|
for (; p != null && i < n; p = succ(p)) |
824 |
dl |
1.74 |
if ((a[i] = p.item) != null) |
825 |
jsr166 |
1.100 |
i++; |
826 |
dl |
1.74 |
} finally { |
827 |
jsr166 |
1.99 |
fullyUnlock(); |
828 |
dl |
1.74 |
} |
829 |
|
|
if ((current = p) == null) { |
830 |
|
|
est = 0L; |
831 |
|
|
exhausted = true; |
832 |
|
|
} |
833 |
dl |
1.77 |
else if ((est -= i) < 0L) |
834 |
|
|
est = 0L; |
835 |
dl |
1.80 |
if (i > 0) { |
836 |
|
|
batch = i; |
837 |
|
|
return Spliterators.spliterator |
838 |
jsr166 |
1.95 |
(a, 0, i, (Spliterator.ORDERED | |
839 |
|
|
Spliterator.NONNULL | |
840 |
|
|
Spliterator.CONCURRENT)); |
841 |
dl |
1.80 |
} |
842 |
dl |
1.74 |
} |
843 |
|
|
return null; |
844 |
|
|
} |
845 |
|
|
|
846 |
dl |
1.81 |
public void forEachRemaining(Consumer<? super E> action) { |
847 |
dl |
1.74 |
if (action == null) throw new NullPointerException(); |
848 |
|
|
if (!exhausted) { |
849 |
|
|
exhausted = true; |
850 |
|
|
Node<E> p = current; |
851 |
jsr166 |
1.100 |
current = null; |
852 |
dl |
1.74 |
do { |
853 |
|
|
E e = null; |
854 |
jsr166 |
1.99 |
fullyLock(); |
855 |
dl |
1.74 |
try { |
856 |
jsr166 |
1.100 |
if (p != null || (p = head.next) != null) |
857 |
|
|
do { |
858 |
|
|
e = p.item; |
859 |
|
|
p = succ(p); |
860 |
|
|
} while (e == null && p != null); |
861 |
dl |
1.74 |
} finally { |
862 |
jsr166 |
1.99 |
fullyUnlock(); |
863 |
dl |
1.74 |
} |
864 |
|
|
if (e != null) |
865 |
|
|
action.accept(e); |
866 |
|
|
} while (p != null); |
867 |
|
|
} |
868 |
|
|
} |
869 |
|
|
|
870 |
|
|
public boolean tryAdvance(Consumer<? super E> action) { |
871 |
|
|
if (action == null) throw new NullPointerException(); |
872 |
|
|
if (!exhausted) { |
873 |
jsr166 |
1.100 |
Node<E> p = current; |
874 |
dl |
1.74 |
E e = null; |
875 |
jsr166 |
1.99 |
fullyLock(); |
876 |
dl |
1.74 |
try { |
877 |
jsr166 |
1.100 |
if (p != null || (p = head.next) != null) |
878 |
|
|
do { |
879 |
|
|
e = p.item; |
880 |
|
|
p = succ(p); |
881 |
|
|
} while (e == null && p != null); |
882 |
dl |
1.74 |
} finally { |
883 |
jsr166 |
1.99 |
fullyUnlock(); |
884 |
dl |
1.74 |
} |
885 |
jsr166 |
1.100 |
exhausted = ((current = p) == null); |
886 |
dl |
1.74 |
if (e != null) { |
887 |
|
|
action.accept(e); |
888 |
|
|
return true; |
889 |
|
|
} |
890 |
|
|
} |
891 |
|
|
return false; |
892 |
|
|
} |
893 |
|
|
|
894 |
|
|
public int characteristics() { |
895 |
jsr166 |
1.100 |
return (Spliterator.ORDERED | |
896 |
|
|
Spliterator.NONNULL | |
897 |
|
|
Spliterator.CONCURRENT); |
898 |
dl |
1.74 |
} |
899 |
|
|
} |
900 |
|
|
|
901 |
jsr166 |
1.86 |
/** |
902 |
|
|
* Returns a {@link Spliterator} over the elements in this queue. |
903 |
|
|
* |
904 |
jsr166 |
1.87 |
* <p>The returned spliterator is |
905 |
|
|
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>. |
906 |
|
|
* |
907 |
jsr166 |
1.86 |
* <p>The {@code Spliterator} reports {@link Spliterator#CONCURRENT}, |
908 |
|
|
* {@link Spliterator#ORDERED}, and {@link Spliterator#NONNULL}. |
909 |
|
|
* |
910 |
|
|
* @implNote |
911 |
|
|
* The {@code Spliterator} implements {@code trySplit} to permit limited |
912 |
|
|
* parallelism. |
913 |
|
|
* |
914 |
|
|
* @return a {@code Spliterator} over the elements in this queue |
915 |
|
|
* @since 1.8 |
916 |
|
|
*/ |
917 |
dl |
1.76 |
public Spliterator<E> spliterator() { |
918 |
jsr166 |
1.99 |
return new LBQSpliterator(); |
919 |
dl |
1.74 |
} |
920 |
|
|
|
921 |
dl |
1.2 |
/** |
922 |
jsr166 |
1.68 |
* Saves this queue to a stream (that is, serializes it). |
923 |
dl |
1.2 |
* |
924 |
jsr166 |
1.84 |
* @param s the stream |
925 |
jsr166 |
1.85 |
* @throws java.io.IOException if an I/O error occurs |
926 |
dl |
1.2 |
* @serialData The capacity is emitted (int), followed by all of |
927 |
jsr166 |
1.51 |
* its elements (each an {@code Object}) in the proper order, |
928 |
dl |
1.2 |
* followed by a null |
929 |
|
|
*/ |
930 |
|
|
private void writeObject(java.io.ObjectOutputStream s) |
931 |
|
|
throws java.io.IOException { |
932 |
|
|
|
933 |
tim |
1.12 |
fullyLock(); |
934 |
dl |
1.2 |
try { |
935 |
|
|
// Write out any hidden stuff, plus capacity |
936 |
|
|
s.defaultWriteObject(); |
937 |
|
|
|
938 |
|
|
// Write out all elements in the proper order. |
939 |
tim |
1.12 |
for (Node<E> p = head.next; p != null; p = p.next) |
940 |
dl |
1.2 |
s.writeObject(p.item); |
941 |
|
|
|
942 |
|
|
// Use trailing null as sentinel |
943 |
|
|
s.writeObject(null); |
944 |
tim |
1.17 |
} finally { |
945 |
dl |
1.2 |
fullyUnlock(); |
946 |
|
|
} |
947 |
tim |
1.1 |
} |
948 |
|
|
|
949 |
dl |
1.2 |
/** |
950 |
jsr166 |
1.65 |
* Reconstitutes this queue from a stream (that is, deserializes it). |
951 |
jsr166 |
1.84 |
* @param s the stream |
952 |
jsr166 |
1.85 |
* @throws ClassNotFoundException if the class of a serialized object |
953 |
|
|
* could not be found |
954 |
|
|
* @throws java.io.IOException if an I/O error occurs |
955 |
dl |
1.2 |
*/ |
956 |
|
|
private void readObject(java.io.ObjectInputStream s) |
957 |
|
|
throws java.io.IOException, ClassNotFoundException { |
958 |
tim |
1.12 |
// Read in capacity, and any hidden stuff |
959 |
|
|
s.defaultReadObject(); |
960 |
dl |
1.2 |
|
961 |
dl |
1.19 |
count.set(0); |
962 |
|
|
last = head = new Node<E>(null); |
963 |
|
|
|
964 |
dl |
1.6 |
// Read in all elements and place in queue |
965 |
dl |
1.2 |
for (;;) { |
966 |
jsr166 |
1.51 |
@SuppressWarnings("unchecked") |
967 |
dl |
1.2 |
E item = (E)s.readObject(); |
968 |
|
|
if (item == null) |
969 |
|
|
break; |
970 |
|
|
add(item); |
971 |
|
|
} |
972 |
tim |
1.1 |
} |
973 |
|
|
} |