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 |
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* http://creativecommons.org/licenses/publicdomain |
5 |
dl |
1.2 |
*/ |
6 |
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|
7 |
tim |
1.1 |
package java.util.concurrent; |
8 |
dl |
1.2 |
import java.util.concurrent.atomic.*; |
9 |
dl |
1.7 |
import java.util.concurrent.locks.*; |
10 |
tim |
1.1 |
import java.util.*; |
11 |
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|
12 |
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/** |
13 |
dholmes |
1.14 |
* An optionally-bounded {@linkplain BlockingQueue blocking queue} based on |
14 |
dholmes |
1.8 |
* linked nodes. |
15 |
|
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* This queue orders elements FIFO (first-in-first-out). |
16 |
tim |
1.12 |
* The <em>head</em> of the queue is that element that has been on the |
17 |
dholmes |
1.8 |
* queue the longest time. |
18 |
|
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* The <em>tail</em> of the queue is that element that has been on the |
19 |
dl |
1.20 |
* queue the shortest time. New elements |
20 |
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* are inserted at the tail of the queue, and the queue retrieval |
21 |
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* operations obtain elements at the head of the queue. |
22 |
dholmes |
1.8 |
* Linked queues typically have higher throughput than array-based queues but |
23 |
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* less predictable performance in most concurrent applications. |
24 |
tim |
1.12 |
* |
25 |
dl |
1.3 |
* <p> The optional capacity bound constructor argument serves as a |
26 |
dholmes |
1.8 |
* way to prevent excessive queue expansion. The capacity, if unspecified, |
27 |
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* is equal to {@link Integer#MAX_VALUE}. Linked nodes are |
28 |
dl |
1.3 |
* dynamically created upon each insertion unless this would bring the |
29 |
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* queue above capacity. |
30 |
dholmes |
1.8 |
* |
31 |
dl |
1.36 |
* <p>This class and its iterator implement all of the |
32 |
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* <em>optional</em> methods of the {@link Collection} and {@link |
33 |
dl |
1.38 |
* Iterator} interfaces. |
34 |
dl |
1.21 |
* |
35 |
dl |
1.34 |
* <p>This class is a member of the |
36 |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
37 |
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* Java Collections Framework</a>. |
38 |
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* |
39 |
dl |
1.6 |
* @since 1.5 |
40 |
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* @author Doug Lea |
41 |
dl |
1.27 |
* @param <E> the type of elements held in this collection |
42 |
tim |
1.12 |
* |
43 |
jsr166 |
1.40 |
*/ |
44 |
dl |
1.2 |
public class LinkedBlockingQueue<E> extends AbstractQueue<E> |
45 |
tim |
1.1 |
implements BlockingQueue<E>, java.io.Serializable { |
46 |
dl |
1.18 |
private static final long serialVersionUID = -6903933977591709194L; |
47 |
tim |
1.1 |
|
48 |
dl |
1.2 |
/* |
49 |
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* A variant of the "two lock queue" algorithm. The putLock gates |
50 |
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* entry to put (and offer), and has an associated condition for |
51 |
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* waiting puts. Similarly for the takeLock. The "count" field |
52 |
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* that they both rely on is maintained as an atomic to avoid |
53 |
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* needing to get both locks in most cases. Also, to minimize need |
54 |
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* for puts to get takeLock and vice-versa, cascading notifies are |
55 |
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* used. When a put notices that it has enabled at least one take, |
56 |
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* it signals taker. That taker in turn signals others if more |
57 |
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* items have been entered since the signal. And symmetrically for |
58 |
tim |
1.12 |
* takes signalling puts. Operations such as remove(Object) and |
59 |
dl |
1.2 |
* iterators acquire both locks. |
60 |
dl |
1.38 |
*/ |
61 |
dl |
1.2 |
|
62 |
dl |
1.6 |
/** |
63 |
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* Linked list node class |
64 |
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*/ |
65 |
dl |
1.2 |
static class Node<E> { |
66 |
dl |
1.6 |
/** The item, volatile to ensure barrier separating write and read */ |
67 |
dl |
1.2 |
volatile E item; |
68 |
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Node<E> next; |
69 |
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Node(E x) { item = x; } |
70 |
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} |
71 |
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|
72 |
dl |
1.6 |
/** The capacity bound, or Integer.MAX_VALUE if none */ |
73 |
dl |
1.2 |
private final int capacity; |
74 |
dl |
1.6 |
|
75 |
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/** Current number of elements */ |
76 |
dl |
1.19 |
private final AtomicInteger count = new AtomicInteger(0); |
77 |
dl |
1.2 |
|
78 |
dl |
1.6 |
/** Head of linked list */ |
79 |
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private transient Node<E> head; |
80 |
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|
81 |
dholmes |
1.8 |
/** Tail of linked list */ |
82 |
dl |
1.6 |
private transient Node<E> last; |
83 |
dl |
1.2 |
|
84 |
dl |
1.6 |
/** Lock held by take, poll, etc */ |
85 |
dl |
1.5 |
private final ReentrantLock takeLock = new ReentrantLock(); |
86 |
dl |
1.6 |
|
87 |
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/** Wait queue for waiting takes */ |
88 |
dl |
1.32 |
private final Condition notEmpty = takeLock.newCondition(); |
89 |
dl |
1.2 |
|
90 |
dl |
1.6 |
/** Lock held by put, offer, etc */ |
91 |
dl |
1.5 |
private final ReentrantLock putLock = new ReentrantLock(); |
92 |
dl |
1.6 |
|
93 |
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/** Wait queue for waiting puts */ |
94 |
dl |
1.32 |
private final Condition notFull = putLock.newCondition(); |
95 |
dl |
1.2 |
|
96 |
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/** |
97 |
jsr166 |
1.40 |
* Signals a waiting take. Called only from put/offer (which do not |
98 |
dl |
1.4 |
* otherwise ordinarily lock takeLock.) |
99 |
dl |
1.2 |
*/ |
100 |
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private void signalNotEmpty() { |
101 |
dl |
1.31 |
final ReentrantLock takeLock = this.takeLock; |
102 |
dl |
1.2 |
takeLock.lock(); |
103 |
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try { |
104 |
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notEmpty.signal(); |
105 |
tim |
1.17 |
} finally { |
106 |
dl |
1.2 |
takeLock.unlock(); |
107 |
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} |
108 |
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} |
109 |
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110 |
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/** |
111 |
jsr166 |
1.40 |
* Signals a waiting put. Called only from take/poll. |
112 |
dl |
1.2 |
*/ |
113 |
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private void signalNotFull() { |
114 |
dl |
1.31 |
final ReentrantLock putLock = this.putLock; |
115 |
dl |
1.2 |
putLock.lock(); |
116 |
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try { |
117 |
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notFull.signal(); |
118 |
tim |
1.17 |
} finally { |
119 |
dl |
1.2 |
putLock.unlock(); |
120 |
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} |
121 |
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} |
122 |
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123 |
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/** |
124 |
jsr166 |
1.40 |
* Creates a node and links it at end of queue. |
125 |
dl |
1.6 |
* @param x the item |
126 |
dl |
1.2 |
*/ |
127 |
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private void insert(E x) { |
128 |
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last = last.next = new Node<E>(x); |
129 |
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} |
130 |
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131 |
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/** |
132 |
jsr166 |
1.40 |
* Removes a node from head of queue, |
133 |
dl |
1.6 |
* @return the node |
134 |
dl |
1.2 |
*/ |
135 |
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private E extract() { |
136 |
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Node<E> first = head.next; |
137 |
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head = first; |
138 |
dl |
1.28 |
E x = first.item; |
139 |
dl |
1.2 |
first.item = null; |
140 |
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return x; |
141 |
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} |
142 |
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|
143 |
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/** |
144 |
tim |
1.12 |
* Lock to prevent both puts and takes. |
145 |
dl |
1.2 |
*/ |
146 |
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private void fullyLock() { |
147 |
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putLock.lock(); |
148 |
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takeLock.lock(); |
149 |
tim |
1.1 |
} |
150 |
dl |
1.2 |
|
151 |
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/** |
152 |
tim |
1.12 |
* Unlock to allow both puts and takes. |
153 |
dl |
1.2 |
*/ |
154 |
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private void fullyUnlock() { |
155 |
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takeLock.unlock(); |
156 |
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putLock.unlock(); |
157 |
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} |
158 |
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|
159 |
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|
160 |
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/** |
161 |
dholmes |
1.13 |
* Creates a <tt>LinkedBlockingQueue</tt> with a capacity of |
162 |
dholmes |
1.8 |
* {@link Integer#MAX_VALUE}. |
163 |
dl |
1.2 |
*/ |
164 |
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public LinkedBlockingQueue() { |
165 |
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this(Integer.MAX_VALUE); |
166 |
|
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} |
167 |
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|
168 |
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/** |
169 |
tim |
1.16 |
* Creates a <tt>LinkedBlockingQueue</tt> with the given (fixed) capacity. |
170 |
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* |
171 |
dholmes |
1.8 |
* @param capacity the capacity of this queue. |
172 |
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* @throws IllegalArgumentException if <tt>capacity</tt> is not greater |
173 |
tim |
1.16 |
* than zero. |
174 |
dl |
1.2 |
*/ |
175 |
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public LinkedBlockingQueue(int capacity) { |
176 |
dholmes |
1.8 |
if (capacity <= 0) throw new IllegalArgumentException(); |
177 |
dl |
1.2 |
this.capacity = capacity; |
178 |
dl |
1.6 |
last = head = new Node<E>(null); |
179 |
dl |
1.2 |
} |
180 |
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|
181 |
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/** |
182 |
dholmes |
1.13 |
* Creates a <tt>LinkedBlockingQueue</tt> with a capacity of |
183 |
dholmes |
1.14 |
* {@link Integer#MAX_VALUE}, initially containing the elements of the |
184 |
tim |
1.12 |
* given collection, |
185 |
dholmes |
1.8 |
* added in traversal order of the collection's iterator. |
186 |
dholmes |
1.9 |
* @param c the collection of elements to initially contain |
187 |
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* @throws NullPointerException if <tt>c</tt> or any element within it |
188 |
jsr166 |
1.40 |
* is <tt>null</tt>. |
189 |
dl |
1.2 |
*/ |
190 |
dholmes |
1.10 |
public LinkedBlockingQueue(Collection<? extends E> c) { |
191 |
dl |
1.2 |
this(Integer.MAX_VALUE); |
192 |
dl |
1.38 |
for (E e : c) |
193 |
|
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add(e); |
194 |
dl |
1.2 |
} |
195 |
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|
196 |
dholmes |
1.9 |
|
197 |
dholmes |
1.8 |
// this doc comment is overridden to remove the reference to collections |
198 |
|
|
// greater in size than Integer.MAX_VALUE |
199 |
tim |
1.12 |
/** |
200 |
dl |
1.20 |
* Returns the number of elements in this queue. |
201 |
|
|
* |
202 |
|
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* @return the number of elements in this queue. |
203 |
dholmes |
1.8 |
*/ |
204 |
dl |
1.2 |
public int size() { |
205 |
|
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return count.get(); |
206 |
tim |
1.1 |
} |
207 |
dl |
1.2 |
|
208 |
dholmes |
1.8 |
// this doc comment is a modified copy of the inherited doc comment, |
209 |
|
|
// without the reference to unlimited queues. |
210 |
tim |
1.12 |
/** |
211 |
dholmes |
1.13 |
* Returns the number of elements that this queue can ideally (in |
212 |
dholmes |
1.8 |
* the absence of memory or resource constraints) accept without |
213 |
|
|
* blocking. This is always equal to the initial capacity of this queue |
214 |
|
|
* less the current <tt>size</tt> of this queue. |
215 |
|
|
* <p>Note that you <em>cannot</em> always tell if |
216 |
|
|
* an attempt to <tt>add</tt> an element will succeed by |
217 |
|
|
* inspecting <tt>remainingCapacity</tt> because it may be the |
218 |
|
|
* case that a waiting consumer is ready to <tt>take</tt> an |
219 |
|
|
* element out of an otherwise full queue. |
220 |
|
|
*/ |
221 |
dl |
1.2 |
public int remainingCapacity() { |
222 |
|
|
return capacity - count.get(); |
223 |
|
|
} |
224 |
|
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|
225 |
dholmes |
1.22 |
/** |
226 |
|
|
* Adds the specified element to the tail of this queue, waiting if |
227 |
|
|
* necessary for space to become available. |
228 |
dl |
1.23 |
* @param o the element to add |
229 |
|
|
* @throws InterruptedException if interrupted while waiting. |
230 |
dholmes |
1.22 |
* @throws NullPointerException if the specified element is <tt>null</tt>. |
231 |
|
|
*/ |
232 |
dholmes |
1.14 |
public void put(E o) throws InterruptedException { |
233 |
|
|
if (o == null) throw new NullPointerException(); |
234 |
dl |
1.2 |
// Note: convention in all put/take/etc is to preset |
235 |
|
|
// local var holding count negative to indicate failure unless set. |
236 |
tim |
1.12 |
int c = -1; |
237 |
dl |
1.31 |
final ReentrantLock putLock = this.putLock; |
238 |
|
|
final AtomicInteger count = this.count; |
239 |
dl |
1.2 |
putLock.lockInterruptibly(); |
240 |
|
|
try { |
241 |
|
|
/* |
242 |
|
|
* Note that count is used in wait guard even though it is |
243 |
|
|
* not protected by lock. This works because count can |
244 |
|
|
* only decrease at this point (all other puts are shut |
245 |
|
|
* out by lock), and we (or some other waiting put) are |
246 |
|
|
* signalled if it ever changes from |
247 |
|
|
* capacity. Similarly for all other uses of count in |
248 |
|
|
* other wait guards. |
249 |
|
|
*/ |
250 |
|
|
try { |
251 |
tim |
1.12 |
while (count.get() == capacity) |
252 |
dl |
1.2 |
notFull.await(); |
253 |
tim |
1.17 |
} catch (InterruptedException ie) { |
254 |
dl |
1.2 |
notFull.signal(); // propagate to a non-interrupted thread |
255 |
|
|
throw ie; |
256 |
|
|
} |
257 |
dholmes |
1.14 |
insert(o); |
258 |
dl |
1.2 |
c = count.getAndIncrement(); |
259 |
dl |
1.6 |
if (c + 1 < capacity) |
260 |
dl |
1.2 |
notFull.signal(); |
261 |
tim |
1.17 |
} finally { |
262 |
dl |
1.2 |
putLock.unlock(); |
263 |
|
|
} |
264 |
tim |
1.12 |
if (c == 0) |
265 |
dl |
1.2 |
signalNotEmpty(); |
266 |
tim |
1.1 |
} |
267 |
dl |
1.2 |
|
268 |
dholmes |
1.22 |
/** |
269 |
|
|
* Inserts the specified element at the tail of this queue, waiting if |
270 |
|
|
* necessary up to the specified wait time for space to become available. |
271 |
dl |
1.23 |
* @param o the element to add |
272 |
|
|
* @param timeout how long to wait before giving up, in units of |
273 |
|
|
* <tt>unit</tt> |
274 |
|
|
* @param unit a <tt>TimeUnit</tt> determining how to interpret the |
275 |
|
|
* <tt>timeout</tt> parameter |
276 |
|
|
* @return <tt>true</tt> if successful, or <tt>false</tt> if |
277 |
|
|
* the specified waiting time elapses before space is available. |
278 |
|
|
* @throws InterruptedException if interrupted while waiting. |
279 |
dholmes |
1.22 |
* @throws NullPointerException if the specified element is <tt>null</tt>. |
280 |
|
|
*/ |
281 |
dholmes |
1.14 |
public boolean offer(E o, long timeout, TimeUnit unit) |
282 |
dholmes |
1.8 |
throws InterruptedException { |
283 |
tim |
1.12 |
|
284 |
dholmes |
1.14 |
if (o == null) throw new NullPointerException(); |
285 |
dl |
1.2 |
long nanos = unit.toNanos(timeout); |
286 |
|
|
int c = -1; |
287 |
dl |
1.31 |
final ReentrantLock putLock = this.putLock; |
288 |
|
|
final AtomicInteger count = this.count; |
289 |
dholmes |
1.8 |
putLock.lockInterruptibly(); |
290 |
dl |
1.2 |
try { |
291 |
|
|
for (;;) { |
292 |
|
|
if (count.get() < capacity) { |
293 |
dholmes |
1.14 |
insert(o); |
294 |
dl |
1.2 |
c = count.getAndIncrement(); |
295 |
dl |
1.6 |
if (c + 1 < capacity) |
296 |
dl |
1.2 |
notFull.signal(); |
297 |
|
|
break; |
298 |
|
|
} |
299 |
|
|
if (nanos <= 0) |
300 |
|
|
return false; |
301 |
|
|
try { |
302 |
|
|
nanos = notFull.awaitNanos(nanos); |
303 |
tim |
1.17 |
} catch (InterruptedException ie) { |
304 |
dl |
1.2 |
notFull.signal(); // propagate to a non-interrupted thread |
305 |
|
|
throw ie; |
306 |
|
|
} |
307 |
|
|
} |
308 |
tim |
1.17 |
} finally { |
309 |
dl |
1.2 |
putLock.unlock(); |
310 |
|
|
} |
311 |
tim |
1.12 |
if (c == 0) |
312 |
dl |
1.2 |
signalNotEmpty(); |
313 |
|
|
return true; |
314 |
tim |
1.1 |
} |
315 |
dl |
1.2 |
|
316 |
dl |
1.23 |
/** |
317 |
|
|
* Inserts the specified element at the tail of this queue if possible, |
318 |
|
|
* returning immediately if this queue is full. |
319 |
|
|
* |
320 |
|
|
* @param o the element to add. |
321 |
|
|
* @return <tt>true</tt> if it was possible to add the element to |
322 |
|
|
* this queue, else <tt>false</tt> |
323 |
jsr166 |
1.40 |
* @throws NullPointerException if the specified element is <tt>null</tt>. |
324 |
dl |
1.23 |
*/ |
325 |
dholmes |
1.14 |
public boolean offer(E o) { |
326 |
|
|
if (o == null) throw new NullPointerException(); |
327 |
dl |
1.31 |
final AtomicInteger count = this.count; |
328 |
dl |
1.2 |
if (count.get() == capacity) |
329 |
|
|
return false; |
330 |
tim |
1.12 |
int c = -1; |
331 |
dl |
1.31 |
final ReentrantLock putLock = this.putLock; |
332 |
dholmes |
1.8 |
putLock.lock(); |
333 |
dl |
1.2 |
try { |
334 |
|
|
if (count.get() < capacity) { |
335 |
dholmes |
1.14 |
insert(o); |
336 |
dl |
1.2 |
c = count.getAndIncrement(); |
337 |
dl |
1.6 |
if (c + 1 < capacity) |
338 |
dl |
1.2 |
notFull.signal(); |
339 |
|
|
} |
340 |
tim |
1.17 |
} finally { |
341 |
dl |
1.2 |
putLock.unlock(); |
342 |
|
|
} |
343 |
tim |
1.12 |
if (c == 0) |
344 |
dl |
1.2 |
signalNotEmpty(); |
345 |
|
|
return c >= 0; |
346 |
tim |
1.1 |
} |
347 |
dl |
1.2 |
|
348 |
|
|
|
349 |
|
|
public E take() throws InterruptedException { |
350 |
|
|
E x; |
351 |
|
|
int c = -1; |
352 |
dl |
1.31 |
final AtomicInteger count = this.count; |
353 |
|
|
final ReentrantLock takeLock = this.takeLock; |
354 |
dl |
1.2 |
takeLock.lockInterruptibly(); |
355 |
|
|
try { |
356 |
|
|
try { |
357 |
tim |
1.12 |
while (count.get() == 0) |
358 |
dl |
1.2 |
notEmpty.await(); |
359 |
tim |
1.17 |
} catch (InterruptedException ie) { |
360 |
dl |
1.2 |
notEmpty.signal(); // propagate to a non-interrupted thread |
361 |
|
|
throw ie; |
362 |
|
|
} |
363 |
|
|
|
364 |
|
|
x = extract(); |
365 |
|
|
c = count.getAndDecrement(); |
366 |
|
|
if (c > 1) |
367 |
|
|
notEmpty.signal(); |
368 |
tim |
1.17 |
} finally { |
369 |
dl |
1.2 |
takeLock.unlock(); |
370 |
|
|
} |
371 |
tim |
1.12 |
if (c == capacity) |
372 |
dl |
1.2 |
signalNotFull(); |
373 |
|
|
return x; |
374 |
|
|
} |
375 |
|
|
|
376 |
|
|
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
377 |
|
|
E x = null; |
378 |
|
|
int c = -1; |
379 |
dholmes |
1.8 |
long nanos = unit.toNanos(timeout); |
380 |
dl |
1.31 |
final AtomicInteger count = this.count; |
381 |
|
|
final ReentrantLock takeLock = this.takeLock; |
382 |
dl |
1.2 |
takeLock.lockInterruptibly(); |
383 |
|
|
try { |
384 |
|
|
for (;;) { |
385 |
|
|
if (count.get() > 0) { |
386 |
|
|
x = extract(); |
387 |
|
|
c = count.getAndDecrement(); |
388 |
|
|
if (c > 1) |
389 |
|
|
notEmpty.signal(); |
390 |
|
|
break; |
391 |
|
|
} |
392 |
|
|
if (nanos <= 0) |
393 |
|
|
return null; |
394 |
|
|
try { |
395 |
|
|
nanos = notEmpty.awaitNanos(nanos); |
396 |
tim |
1.17 |
} catch (InterruptedException ie) { |
397 |
dl |
1.2 |
notEmpty.signal(); // propagate to a non-interrupted thread |
398 |
|
|
throw ie; |
399 |
|
|
} |
400 |
|
|
} |
401 |
tim |
1.17 |
} finally { |
402 |
dl |
1.2 |
takeLock.unlock(); |
403 |
|
|
} |
404 |
tim |
1.12 |
if (c == capacity) |
405 |
dl |
1.2 |
signalNotFull(); |
406 |
|
|
return x; |
407 |
|
|
} |
408 |
|
|
|
409 |
|
|
public E poll() { |
410 |
dl |
1.31 |
final AtomicInteger count = this.count; |
411 |
dl |
1.2 |
if (count.get() == 0) |
412 |
|
|
return null; |
413 |
|
|
E x = null; |
414 |
tim |
1.12 |
int c = -1; |
415 |
dl |
1.31 |
final ReentrantLock takeLock = this.takeLock; |
416 |
dl |
1.30 |
takeLock.lock(); |
417 |
dl |
1.2 |
try { |
418 |
|
|
if (count.get() > 0) { |
419 |
|
|
x = extract(); |
420 |
|
|
c = count.getAndDecrement(); |
421 |
|
|
if (c > 1) |
422 |
|
|
notEmpty.signal(); |
423 |
|
|
} |
424 |
tim |
1.17 |
} finally { |
425 |
dl |
1.2 |
takeLock.unlock(); |
426 |
|
|
} |
427 |
tim |
1.12 |
if (c == capacity) |
428 |
dl |
1.2 |
signalNotFull(); |
429 |
|
|
return x; |
430 |
tim |
1.1 |
} |
431 |
dl |
1.2 |
|
432 |
|
|
|
433 |
|
|
public E peek() { |
434 |
|
|
if (count.get() == 0) |
435 |
|
|
return null; |
436 |
dl |
1.31 |
final ReentrantLock takeLock = this.takeLock; |
437 |
dholmes |
1.8 |
takeLock.lock(); |
438 |
dl |
1.2 |
try { |
439 |
|
|
Node<E> first = head.next; |
440 |
|
|
if (first == null) |
441 |
|
|
return null; |
442 |
|
|
else |
443 |
|
|
return first.item; |
444 |
tim |
1.17 |
} finally { |
445 |
dl |
1.2 |
takeLock.unlock(); |
446 |
|
|
} |
447 |
tim |
1.1 |
} |
448 |
|
|
|
449 |
dl |
1.35 |
/** |
450 |
|
|
* Removes a single instance of the specified element from this |
451 |
dl |
1.36 |
* queue, if it is present. |
452 |
dl |
1.35 |
*/ |
453 |
dholmes |
1.9 |
public boolean remove(Object o) { |
454 |
|
|
if (o == null) return false; |
455 |
dl |
1.2 |
boolean removed = false; |
456 |
|
|
fullyLock(); |
457 |
|
|
try { |
458 |
|
|
Node<E> trail = head; |
459 |
|
|
Node<E> p = head.next; |
460 |
|
|
while (p != null) { |
461 |
dholmes |
1.9 |
if (o.equals(p.item)) { |
462 |
dl |
1.2 |
removed = true; |
463 |
|
|
break; |
464 |
|
|
} |
465 |
|
|
trail = p; |
466 |
|
|
p = p.next; |
467 |
|
|
} |
468 |
|
|
if (removed) { |
469 |
|
|
p.item = null; |
470 |
|
|
trail.next = p.next; |
471 |
dl |
1.39 |
if (last == p) |
472 |
|
|
last = trail; |
473 |
dl |
1.2 |
if (count.getAndDecrement() == capacity) |
474 |
|
|
notFull.signalAll(); |
475 |
|
|
} |
476 |
tim |
1.17 |
} finally { |
477 |
dl |
1.2 |
fullyUnlock(); |
478 |
|
|
} |
479 |
|
|
return removed; |
480 |
tim |
1.1 |
} |
481 |
dl |
1.2 |
|
482 |
|
|
public Object[] toArray() { |
483 |
|
|
fullyLock(); |
484 |
|
|
try { |
485 |
|
|
int size = count.get(); |
486 |
tim |
1.12 |
Object[] a = new Object[size]; |
487 |
dl |
1.2 |
int k = 0; |
488 |
tim |
1.12 |
for (Node<E> p = head.next; p != null; p = p.next) |
489 |
dl |
1.2 |
a[k++] = p.item; |
490 |
|
|
return a; |
491 |
tim |
1.17 |
} finally { |
492 |
dl |
1.2 |
fullyUnlock(); |
493 |
|
|
} |
494 |
tim |
1.1 |
} |
495 |
dl |
1.2 |
|
496 |
|
|
public <T> T[] toArray(T[] a) { |
497 |
|
|
fullyLock(); |
498 |
|
|
try { |
499 |
|
|
int size = count.get(); |
500 |
|
|
if (a.length < size) |
501 |
dl |
1.4 |
a = (T[])java.lang.reflect.Array.newInstance |
502 |
|
|
(a.getClass().getComponentType(), size); |
503 |
tim |
1.12 |
|
504 |
dl |
1.2 |
int k = 0; |
505 |
tim |
1.12 |
for (Node p = head.next; p != null; p = p.next) |
506 |
dl |
1.2 |
a[k++] = (T)p.item; |
507 |
|
|
return a; |
508 |
tim |
1.17 |
} finally { |
509 |
dl |
1.2 |
fullyUnlock(); |
510 |
|
|
} |
511 |
tim |
1.1 |
} |
512 |
dl |
1.2 |
|
513 |
|
|
public String toString() { |
514 |
|
|
fullyLock(); |
515 |
|
|
try { |
516 |
|
|
return super.toString(); |
517 |
tim |
1.17 |
} finally { |
518 |
dl |
1.2 |
fullyUnlock(); |
519 |
|
|
} |
520 |
tim |
1.1 |
} |
521 |
dl |
1.2 |
|
522 |
dl |
1.35 |
/** |
523 |
|
|
* Atomically removes all of the elements from this queue. |
524 |
|
|
* The queue will be empty after this call returns. |
525 |
|
|
*/ |
526 |
dl |
1.24 |
public void clear() { |
527 |
|
|
fullyLock(); |
528 |
|
|
try { |
529 |
|
|
head.next = null; |
530 |
dl |
1.38 |
assert head.item == null; |
531 |
|
|
last = head; |
532 |
dl |
1.24 |
if (count.getAndSet(0) == capacity) |
533 |
|
|
notFull.signalAll(); |
534 |
|
|
} finally { |
535 |
|
|
fullyUnlock(); |
536 |
|
|
} |
537 |
|
|
} |
538 |
|
|
|
539 |
|
|
public int drainTo(Collection<? super E> c) { |
540 |
|
|
if (c == null) |
541 |
|
|
throw new NullPointerException(); |
542 |
|
|
if (c == this) |
543 |
|
|
throw new IllegalArgumentException(); |
544 |
|
|
Node first; |
545 |
|
|
fullyLock(); |
546 |
|
|
try { |
547 |
|
|
first = head.next; |
548 |
|
|
head.next = null; |
549 |
dl |
1.38 |
assert head.item == null; |
550 |
|
|
last = head; |
551 |
dl |
1.24 |
if (count.getAndSet(0) == capacity) |
552 |
|
|
notFull.signalAll(); |
553 |
|
|
} finally { |
554 |
|
|
fullyUnlock(); |
555 |
|
|
} |
556 |
|
|
// Transfer the elements outside of locks |
557 |
|
|
int n = 0; |
558 |
dl |
1.29 |
for (Node<E> p = first; p != null; p = p.next) { |
559 |
|
|
c.add(p.item); |
560 |
dl |
1.24 |
p.item = null; |
561 |
|
|
++n; |
562 |
|
|
} |
563 |
|
|
return n; |
564 |
|
|
} |
565 |
jsr166 |
1.40 |
|
566 |
dl |
1.24 |
public int drainTo(Collection<? super E> c, int maxElements) { |
567 |
|
|
if (c == null) |
568 |
|
|
throw new NullPointerException(); |
569 |
|
|
if (c == this) |
570 |
|
|
throw new IllegalArgumentException(); |
571 |
|
|
fullyLock(); |
572 |
|
|
try { |
573 |
|
|
int n = 0; |
574 |
dl |
1.29 |
Node<E> p = head.next; |
575 |
dl |
1.24 |
while (p != null && n < maxElements) { |
576 |
dl |
1.29 |
c.add(p.item); |
577 |
dl |
1.24 |
p.item = null; |
578 |
|
|
p = p.next; |
579 |
|
|
++n; |
580 |
|
|
} |
581 |
|
|
if (n != 0) { |
582 |
|
|
head.next = p; |
583 |
dl |
1.38 |
assert head.item == null; |
584 |
|
|
if (p == null) |
585 |
|
|
last = head; |
586 |
dl |
1.24 |
if (count.getAndAdd(-n) == capacity) |
587 |
|
|
notFull.signalAll(); |
588 |
|
|
} |
589 |
|
|
return n; |
590 |
|
|
} finally { |
591 |
|
|
fullyUnlock(); |
592 |
|
|
} |
593 |
|
|
} |
594 |
|
|
|
595 |
dholmes |
1.14 |
/** |
596 |
|
|
* Returns an iterator over the elements in this queue in proper sequence. |
597 |
dl |
1.15 |
* The returned <tt>Iterator</tt> is a "weakly consistent" iterator that |
598 |
jsr166 |
1.40 |
* will never throw {@link ConcurrentModificationException}, |
599 |
dl |
1.15 |
* and guarantees to traverse elements as they existed upon |
600 |
|
|
* construction of the iterator, and may (but is not guaranteed to) |
601 |
|
|
* reflect any modifications subsequent to construction. |
602 |
dholmes |
1.14 |
* |
603 |
|
|
* @return an iterator over the elements in this queue in proper sequence. |
604 |
|
|
*/ |
605 |
dl |
1.2 |
public Iterator<E> iterator() { |
606 |
|
|
return new Itr(); |
607 |
tim |
1.1 |
} |
608 |
dl |
1.2 |
|
609 |
|
|
private class Itr implements Iterator<E> { |
610 |
tim |
1.12 |
/* |
611 |
dl |
1.4 |
* Basic weak-consistent iterator. At all times hold the next |
612 |
|
|
* item to hand out so that if hasNext() reports true, we will |
613 |
|
|
* still have it to return even if lost race with a take etc. |
614 |
|
|
*/ |
615 |
dl |
1.31 |
private Node<E> current; |
616 |
|
|
private Node<E> lastRet; |
617 |
|
|
private E currentElement; |
618 |
tim |
1.12 |
|
619 |
dl |
1.2 |
Itr() { |
620 |
dl |
1.31 |
final ReentrantLock putLock = LinkedBlockingQueue.this.putLock; |
621 |
|
|
final ReentrantLock takeLock = LinkedBlockingQueue.this.takeLock; |
622 |
|
|
putLock.lock(); |
623 |
|
|
takeLock.lock(); |
624 |
dl |
1.2 |
try { |
625 |
|
|
current = head.next; |
626 |
dl |
1.4 |
if (current != null) |
627 |
|
|
currentElement = current.item; |
628 |
tim |
1.17 |
} finally { |
629 |
dl |
1.31 |
takeLock.unlock(); |
630 |
|
|
putLock.unlock(); |
631 |
dl |
1.2 |
} |
632 |
|
|
} |
633 |
tim |
1.12 |
|
634 |
|
|
public boolean hasNext() { |
635 |
dl |
1.2 |
return current != null; |
636 |
|
|
} |
637 |
|
|
|
638 |
tim |
1.12 |
public E next() { |
639 |
dl |
1.31 |
final ReentrantLock putLock = LinkedBlockingQueue.this.putLock; |
640 |
|
|
final ReentrantLock takeLock = LinkedBlockingQueue.this.takeLock; |
641 |
|
|
putLock.lock(); |
642 |
|
|
takeLock.lock(); |
643 |
dl |
1.2 |
try { |
644 |
|
|
if (current == null) |
645 |
|
|
throw new NoSuchElementException(); |
646 |
dl |
1.4 |
E x = currentElement; |
647 |
dl |
1.2 |
lastRet = current; |
648 |
|
|
current = current.next; |
649 |
dl |
1.4 |
if (current != null) |
650 |
|
|
currentElement = current.item; |
651 |
dl |
1.2 |
return x; |
652 |
tim |
1.17 |
} finally { |
653 |
dl |
1.31 |
takeLock.unlock(); |
654 |
|
|
putLock.unlock(); |
655 |
dl |
1.2 |
} |
656 |
|
|
} |
657 |
|
|
|
658 |
tim |
1.12 |
public void remove() { |
659 |
dl |
1.2 |
if (lastRet == null) |
660 |
tim |
1.12 |
throw new IllegalStateException(); |
661 |
dl |
1.31 |
final ReentrantLock putLock = LinkedBlockingQueue.this.putLock; |
662 |
|
|
final ReentrantLock takeLock = LinkedBlockingQueue.this.takeLock; |
663 |
|
|
putLock.lock(); |
664 |
|
|
takeLock.lock(); |
665 |
dl |
1.2 |
try { |
666 |
|
|
Node<E> node = lastRet; |
667 |
|
|
lastRet = null; |
668 |
|
|
Node<E> trail = head; |
669 |
|
|
Node<E> p = head.next; |
670 |
|
|
while (p != null && p != node) { |
671 |
|
|
trail = p; |
672 |
|
|
p = p.next; |
673 |
|
|
} |
674 |
|
|
if (p == node) { |
675 |
|
|
p.item = null; |
676 |
|
|
trail.next = p.next; |
677 |
dl |
1.39 |
if (last == p) |
678 |
|
|
last = trail; |
679 |
dl |
1.2 |
int c = count.getAndDecrement(); |
680 |
|
|
if (c == capacity) |
681 |
|
|
notFull.signalAll(); |
682 |
|
|
} |
683 |
tim |
1.17 |
} finally { |
684 |
dl |
1.31 |
takeLock.unlock(); |
685 |
|
|
putLock.unlock(); |
686 |
dl |
1.2 |
} |
687 |
|
|
} |
688 |
tim |
1.1 |
} |
689 |
dl |
1.2 |
|
690 |
|
|
/** |
691 |
|
|
* Save the state to a stream (that is, serialize it). |
692 |
|
|
* |
693 |
|
|
* @serialData The capacity is emitted (int), followed by all of |
694 |
|
|
* its elements (each an <tt>Object</tt>) in the proper order, |
695 |
|
|
* followed by a null |
696 |
dl |
1.6 |
* @param s the stream |
697 |
dl |
1.2 |
*/ |
698 |
|
|
private void writeObject(java.io.ObjectOutputStream s) |
699 |
|
|
throws java.io.IOException { |
700 |
|
|
|
701 |
tim |
1.12 |
fullyLock(); |
702 |
dl |
1.2 |
try { |
703 |
|
|
// Write out any hidden stuff, plus capacity |
704 |
|
|
s.defaultWriteObject(); |
705 |
|
|
|
706 |
|
|
// Write out all elements in the proper order. |
707 |
tim |
1.12 |
for (Node<E> p = head.next; p != null; p = p.next) |
708 |
dl |
1.2 |
s.writeObject(p.item); |
709 |
|
|
|
710 |
|
|
// Use trailing null as sentinel |
711 |
|
|
s.writeObject(null); |
712 |
tim |
1.17 |
} finally { |
713 |
dl |
1.2 |
fullyUnlock(); |
714 |
|
|
} |
715 |
tim |
1.1 |
} |
716 |
|
|
|
717 |
dl |
1.2 |
/** |
718 |
dholmes |
1.8 |
* Reconstitute this queue instance from a stream (that is, |
719 |
dl |
1.2 |
* deserialize it). |
720 |
dl |
1.6 |
* @param s the stream |
721 |
dl |
1.2 |
*/ |
722 |
|
|
private void readObject(java.io.ObjectInputStream s) |
723 |
|
|
throws java.io.IOException, ClassNotFoundException { |
724 |
tim |
1.12 |
// Read in capacity, and any hidden stuff |
725 |
|
|
s.defaultReadObject(); |
726 |
dl |
1.2 |
|
727 |
dl |
1.19 |
count.set(0); |
728 |
|
|
last = head = new Node<E>(null); |
729 |
|
|
|
730 |
dl |
1.6 |
// Read in all elements and place in queue |
731 |
dl |
1.2 |
for (;;) { |
732 |
|
|
E item = (E)s.readObject(); |
733 |
|
|
if (item == null) |
734 |
|
|
break; |
735 |
|
|
add(item); |
736 |
|
|
} |
737 |
tim |
1.1 |
} |
738 |
|
|
} |