1 |
dl |
1.2 |
/* |
2 |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
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* Expert Group and released to the public domain. Use, modify, and |
4 |
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* redistribute this code in any way without acknowledgement. |
5 |
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*/ |
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 |
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* queue the shortest time. |
20 |
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* Linked queues typically have higher throughput than array-based queues but |
21 |
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* less predictable performance in most concurrent applications. |
22 |
tim |
1.12 |
* |
23 |
dl |
1.3 |
* <p> The optional capacity bound constructor argument serves as a |
24 |
dholmes |
1.8 |
* way to prevent excessive queue expansion. The capacity, if unspecified, |
25 |
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* is equal to {@link Integer#MAX_VALUE}. Linked nodes are |
26 |
dl |
1.3 |
* dynamically created upon each insertion unless this would bring the |
27 |
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* queue above capacity. |
28 |
dholmes |
1.8 |
* |
29 |
dl |
1.6 |
* @since 1.5 |
30 |
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* @author Doug Lea |
31 |
tim |
1.12 |
* |
32 |
tim |
1.1 |
**/ |
33 |
dl |
1.2 |
public class LinkedBlockingQueue<E> extends AbstractQueue<E> |
34 |
tim |
1.1 |
implements BlockingQueue<E>, java.io.Serializable { |
35 |
dl |
1.18 |
private static final long serialVersionUID = -6903933977591709194L; |
36 |
tim |
1.1 |
|
37 |
dl |
1.2 |
/* |
38 |
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* A variant of the "two lock queue" algorithm. The putLock gates |
39 |
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* entry to put (and offer), and has an associated condition for |
40 |
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* waiting puts. Similarly for the takeLock. The "count" field |
41 |
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* that they both rely on is maintained as an atomic to avoid |
42 |
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* needing to get both locks in most cases. Also, to minimize need |
43 |
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* for puts to get takeLock and vice-versa, cascading notifies are |
44 |
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* used. When a put notices that it has enabled at least one take, |
45 |
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* it signals taker. That taker in turn signals others if more |
46 |
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* items have been entered since the signal. And symmetrically for |
47 |
tim |
1.12 |
* takes signalling puts. Operations such as remove(Object) and |
48 |
dl |
1.2 |
* iterators acquire both locks. |
49 |
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*/ |
50 |
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|
51 |
dl |
1.6 |
/** |
52 |
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* Linked list node class |
53 |
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*/ |
54 |
dl |
1.2 |
static class Node<E> { |
55 |
dl |
1.6 |
/** The item, volatile to ensure barrier separating write and read */ |
56 |
dl |
1.2 |
volatile E item; |
57 |
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Node<E> next; |
58 |
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Node(E x) { item = x; } |
59 |
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} |
60 |
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|
61 |
dl |
1.6 |
/** The capacity bound, or Integer.MAX_VALUE if none */ |
62 |
dl |
1.2 |
private final int capacity; |
63 |
dl |
1.6 |
|
64 |
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/** Current number of elements */ |
65 |
dl |
1.2 |
private transient final AtomicInteger count = new AtomicInteger(0); |
66 |
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67 |
dl |
1.6 |
/** Head of linked list */ |
68 |
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private transient Node<E> head; |
69 |
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|
70 |
dholmes |
1.8 |
/** Tail of linked list */ |
71 |
dl |
1.6 |
private transient Node<E> last; |
72 |
dl |
1.2 |
|
73 |
dl |
1.6 |
/** Lock held by take, poll, etc */ |
74 |
dl |
1.5 |
private final ReentrantLock takeLock = new ReentrantLock(); |
75 |
dl |
1.6 |
|
76 |
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/** Wait queue for waiting takes */ |
77 |
dl |
1.5 |
private final Condition notEmpty = takeLock.newCondition(); |
78 |
dl |
1.2 |
|
79 |
dl |
1.6 |
/** Lock held by put, offer, etc */ |
80 |
dl |
1.5 |
private final ReentrantLock putLock = new ReentrantLock(); |
81 |
dl |
1.6 |
|
82 |
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/** Wait queue for waiting puts */ |
83 |
dl |
1.5 |
private final Condition notFull = putLock.newCondition(); |
84 |
dl |
1.2 |
|
85 |
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/** |
86 |
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* Signal a waiting take. Called only from put/offer (which do not |
87 |
dl |
1.4 |
* otherwise ordinarily lock takeLock.) |
88 |
dl |
1.2 |
*/ |
89 |
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private void signalNotEmpty() { |
90 |
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takeLock.lock(); |
91 |
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try { |
92 |
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notEmpty.signal(); |
93 |
tim |
1.17 |
} finally { |
94 |
dl |
1.2 |
takeLock.unlock(); |
95 |
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} |
96 |
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} |
97 |
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98 |
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/** |
99 |
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* Signal a waiting put. Called only from take/poll. |
100 |
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*/ |
101 |
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private void signalNotFull() { |
102 |
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putLock.lock(); |
103 |
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try { |
104 |
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notFull.signal(); |
105 |
tim |
1.17 |
} finally { |
106 |
dl |
1.2 |
putLock.unlock(); |
107 |
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} |
108 |
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} |
109 |
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110 |
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/** |
111 |
dholmes |
1.8 |
* Create a node and link it at end of queue |
112 |
dl |
1.6 |
* @param x the item |
113 |
dl |
1.2 |
*/ |
114 |
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private void insert(E x) { |
115 |
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last = last.next = new Node<E>(x); |
116 |
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} |
117 |
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118 |
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/** |
119 |
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* Remove a node from head of queue, |
120 |
dl |
1.6 |
* @return the node |
121 |
dl |
1.2 |
*/ |
122 |
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private E extract() { |
123 |
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Node<E> first = head.next; |
124 |
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head = first; |
125 |
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E x = (E)first.item; |
126 |
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first.item = null; |
127 |
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return x; |
128 |
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} |
129 |
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130 |
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/** |
131 |
tim |
1.12 |
* Lock to prevent both puts and takes. |
132 |
dl |
1.2 |
*/ |
133 |
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private void fullyLock() { |
134 |
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putLock.lock(); |
135 |
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takeLock.lock(); |
136 |
tim |
1.1 |
} |
137 |
dl |
1.2 |
|
138 |
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/** |
139 |
tim |
1.12 |
* Unlock to allow both puts and takes. |
140 |
dl |
1.2 |
*/ |
141 |
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private void fullyUnlock() { |
142 |
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takeLock.unlock(); |
143 |
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putLock.unlock(); |
144 |
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} |
145 |
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146 |
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147 |
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/** |
148 |
dholmes |
1.13 |
* Creates a <tt>LinkedBlockingQueue</tt> with a capacity of |
149 |
dholmes |
1.8 |
* {@link Integer#MAX_VALUE}. |
150 |
dl |
1.2 |
*/ |
151 |
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public LinkedBlockingQueue() { |
152 |
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this(Integer.MAX_VALUE); |
153 |
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} |
154 |
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155 |
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/** |
156 |
tim |
1.16 |
* Creates a <tt>LinkedBlockingQueue</tt> with the given (fixed) capacity. |
157 |
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* |
158 |
dholmes |
1.8 |
* @param capacity the capacity of this queue. |
159 |
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* @throws IllegalArgumentException if <tt>capacity</tt> is not greater |
160 |
tim |
1.16 |
* than zero. |
161 |
dl |
1.2 |
*/ |
162 |
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public LinkedBlockingQueue(int capacity) { |
163 |
dholmes |
1.8 |
if (capacity <= 0) throw new IllegalArgumentException(); |
164 |
dl |
1.2 |
this.capacity = capacity; |
165 |
dl |
1.6 |
last = head = new Node<E>(null); |
166 |
dl |
1.2 |
} |
167 |
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|
168 |
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/** |
169 |
dholmes |
1.13 |
* Creates a <tt>LinkedBlockingQueue</tt> with a capacity of |
170 |
dholmes |
1.14 |
* {@link Integer#MAX_VALUE}, initially containing the elements of the |
171 |
tim |
1.12 |
* given collection, |
172 |
dholmes |
1.8 |
* added in traversal order of the collection's iterator. |
173 |
dholmes |
1.9 |
* @param c the collection of elements to initially contain |
174 |
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* @throws NullPointerException if <tt>c</tt> or any element within it |
175 |
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* is <tt>null</tt> |
176 |
dl |
1.2 |
*/ |
177 |
dholmes |
1.10 |
public LinkedBlockingQueue(Collection<? extends E> c) { |
178 |
dl |
1.2 |
this(Integer.MAX_VALUE); |
179 |
tim |
1.12 |
for (Iterator<? extends E> it = c.iterator(); it.hasNext();) |
180 |
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add(it.next()); |
181 |
dl |
1.2 |
} |
182 |
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183 |
dholmes |
1.14 |
// Have to override just to update the javadoc |
184 |
dholmes |
1.9 |
|
185 |
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/** |
186 |
dholmes |
1.14 |
* Adds the specified element to the tail of this queue. |
187 |
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* @return <tt>true</tt> (as per the general contract of |
188 |
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* <tt>Collection.add</tt>). |
189 |
dholmes |
1.9 |
* @throws IllegalStateException {@inheritDoc} |
190 |
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* @throws NullPointerException {@inheritDoc} |
191 |
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*/ |
192 |
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public boolean add(E o) { |
193 |
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return super.add(o); |
194 |
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} |
195 |
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196 |
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/** |
197 |
dholmes |
1.14 |
* Adds all of the elements in the specified collection to this queue. |
198 |
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* The behavior of this operation is undefined if |
199 |
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* the specified collection is modified while the operation is in |
200 |
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* progress. (This implies that the behavior of this call is undefined if |
201 |
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* the specified collection is this queue, and this queue is nonempty.) |
202 |
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* <p> |
203 |
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* This implementation iterates over the specified collection, and adds |
204 |
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* each object returned by the iterator to this queue's tail, in turn. |
205 |
dholmes |
1.9 |
* @throws IllegalStateException {@inheritDoc} |
206 |
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* @throws NullPointerException {@inheritDoc} |
207 |
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*/ |
208 |
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public boolean addAll(Collection<? extends E> c) { |
209 |
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return super.addAll(c); |
210 |
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} |
211 |
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|
212 |
dholmes |
1.8 |
// this doc comment is overridden to remove the reference to collections |
213 |
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// greater in size than Integer.MAX_VALUE |
214 |
tim |
1.12 |
/** |
215 |
dholmes |
1.13 |
* Returns the number of elements in this collection. |
216 |
dholmes |
1.8 |
*/ |
217 |
dl |
1.2 |
public int size() { |
218 |
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return count.get(); |
219 |
tim |
1.1 |
} |
220 |
dl |
1.2 |
|
221 |
dholmes |
1.8 |
// this doc comment is a modified copy of the inherited doc comment, |
222 |
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// without the reference to unlimited queues. |
223 |
tim |
1.12 |
/** |
224 |
dholmes |
1.13 |
* Returns the number of elements that this queue can ideally (in |
225 |
dholmes |
1.8 |
* the absence of memory or resource constraints) accept without |
226 |
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* blocking. This is always equal to the initial capacity of this queue |
227 |
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* less the current <tt>size</tt> of this queue. |
228 |
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* <p>Note that you <em>cannot</em> always tell if |
229 |
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* an attempt to <tt>add</tt> an element will succeed by |
230 |
|
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* inspecting <tt>remainingCapacity</tt> because it may be the |
231 |
|
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* case that a waiting consumer is ready to <tt>take</tt> an |
232 |
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* element out of an otherwise full queue. |
233 |
|
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*/ |
234 |
dl |
1.2 |
public int remainingCapacity() { |
235 |
|
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return capacity - count.get(); |
236 |
|
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} |
237 |
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|
238 |
dholmes |
1.8 |
/** |
239 |
dholmes |
1.13 |
* Adds the specified element to the tail of this queue, waiting if |
240 |
dholmes |
1.8 |
* necessary for space to become available. |
241 |
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* @throws NullPointerException {@inheritDoc} |
242 |
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*/ |
243 |
dholmes |
1.14 |
public void put(E o) throws InterruptedException { |
244 |
|
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if (o == null) throw new NullPointerException(); |
245 |
dl |
1.2 |
// Note: convention in all put/take/etc is to preset |
246 |
|
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// local var holding count negative to indicate failure unless set. |
247 |
tim |
1.12 |
int c = -1; |
248 |
dl |
1.2 |
putLock.lockInterruptibly(); |
249 |
|
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try { |
250 |
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/* |
251 |
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* Note that count is used in wait guard even though it is |
252 |
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* not protected by lock. This works because count can |
253 |
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* only decrease at this point (all other puts are shut |
254 |
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* out by lock), and we (or some other waiting put) are |
255 |
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* signalled if it ever changes from |
256 |
|
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* capacity. Similarly for all other uses of count in |
257 |
|
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* other wait guards. |
258 |
|
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*/ |
259 |
|
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try { |
260 |
tim |
1.12 |
while (count.get() == capacity) |
261 |
dl |
1.2 |
notFull.await(); |
262 |
tim |
1.17 |
} catch (InterruptedException ie) { |
263 |
dl |
1.2 |
notFull.signal(); // propagate to a non-interrupted thread |
264 |
|
|
throw ie; |
265 |
|
|
} |
266 |
dholmes |
1.14 |
insert(o); |
267 |
dl |
1.2 |
c = count.getAndIncrement(); |
268 |
dl |
1.6 |
if (c + 1 < capacity) |
269 |
dl |
1.2 |
notFull.signal(); |
270 |
tim |
1.17 |
} finally { |
271 |
dl |
1.2 |
putLock.unlock(); |
272 |
|
|
} |
273 |
tim |
1.12 |
if (c == 0) |
274 |
dl |
1.2 |
signalNotEmpty(); |
275 |
tim |
1.1 |
} |
276 |
dl |
1.2 |
|
277 |
dholmes |
1.8 |
/** |
278 |
dholmes |
1.13 |
* Adds the specified element to the tail of this queue, waiting if |
279 |
dholmes |
1.8 |
* necessary up to the specified wait time for space to become available. |
280 |
|
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* @throws NullPointerException {@inheritDoc} |
281 |
|
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*/ |
282 |
dholmes |
1.14 |
public boolean offer(E o, long timeout, TimeUnit unit) |
283 |
dholmes |
1.8 |
throws InterruptedException { |
284 |
tim |
1.12 |
|
285 |
dholmes |
1.14 |
if (o == null) throw new NullPointerException(); |
286 |
dl |
1.2 |
long nanos = unit.toNanos(timeout); |
287 |
|
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int c = -1; |
288 |
dholmes |
1.8 |
putLock.lockInterruptibly(); |
289 |
dl |
1.2 |
try { |
290 |
|
|
for (;;) { |
291 |
|
|
if (count.get() < capacity) { |
292 |
dholmes |
1.14 |
insert(o); |
293 |
dl |
1.2 |
c = count.getAndIncrement(); |
294 |
dl |
1.6 |
if (c + 1 < capacity) |
295 |
dl |
1.2 |
notFull.signal(); |
296 |
|
|
break; |
297 |
|
|
} |
298 |
|
|
if (nanos <= 0) |
299 |
|
|
return false; |
300 |
|
|
try { |
301 |
|
|
nanos = notFull.awaitNanos(nanos); |
302 |
tim |
1.17 |
} catch (InterruptedException ie) { |
303 |
dl |
1.2 |
notFull.signal(); // propagate to a non-interrupted thread |
304 |
|
|
throw ie; |
305 |
|
|
} |
306 |
|
|
} |
307 |
tim |
1.17 |
} finally { |
308 |
dl |
1.2 |
putLock.unlock(); |
309 |
|
|
} |
310 |
tim |
1.12 |
if (c == 0) |
311 |
dl |
1.2 |
signalNotEmpty(); |
312 |
|
|
return true; |
313 |
tim |
1.1 |
} |
314 |
dl |
1.2 |
|
315 |
tim |
1.12 |
/** |
316 |
dholmes |
1.13 |
* Adds the specified element to the tail of this queue if possible, |
317 |
dholmes |
1.8 |
* returning immediately if this queue is full. |
318 |
|
|
* |
319 |
|
|
* @throws NullPointerException {@inheritDoc} |
320 |
|
|
*/ |
321 |
dholmes |
1.14 |
public boolean offer(E o) { |
322 |
|
|
if (o == null) throw new NullPointerException(); |
323 |
dl |
1.2 |
if (count.get() == capacity) |
324 |
|
|
return false; |
325 |
tim |
1.12 |
int c = -1; |
326 |
dholmes |
1.8 |
putLock.lock(); |
327 |
dl |
1.2 |
try { |
328 |
|
|
if (count.get() < capacity) { |
329 |
dholmes |
1.14 |
insert(o); |
330 |
dl |
1.2 |
c = count.getAndIncrement(); |
331 |
dl |
1.6 |
if (c + 1 < capacity) |
332 |
dl |
1.2 |
notFull.signal(); |
333 |
|
|
} |
334 |
tim |
1.17 |
} finally { |
335 |
dl |
1.2 |
putLock.unlock(); |
336 |
|
|
} |
337 |
tim |
1.12 |
if (c == 0) |
338 |
dl |
1.2 |
signalNotEmpty(); |
339 |
|
|
return c >= 0; |
340 |
tim |
1.1 |
} |
341 |
dl |
1.2 |
|
342 |
|
|
|
343 |
|
|
public E take() throws InterruptedException { |
344 |
|
|
E x; |
345 |
|
|
int c = -1; |
346 |
|
|
takeLock.lockInterruptibly(); |
347 |
|
|
try { |
348 |
|
|
try { |
349 |
tim |
1.12 |
while (count.get() == 0) |
350 |
dl |
1.2 |
notEmpty.await(); |
351 |
tim |
1.17 |
} catch (InterruptedException ie) { |
352 |
dl |
1.2 |
notEmpty.signal(); // propagate to a non-interrupted thread |
353 |
|
|
throw ie; |
354 |
|
|
} |
355 |
|
|
|
356 |
|
|
x = extract(); |
357 |
|
|
c = count.getAndDecrement(); |
358 |
|
|
if (c > 1) |
359 |
|
|
notEmpty.signal(); |
360 |
tim |
1.17 |
} finally { |
361 |
dl |
1.2 |
takeLock.unlock(); |
362 |
|
|
} |
363 |
tim |
1.12 |
if (c == capacity) |
364 |
dl |
1.2 |
signalNotFull(); |
365 |
|
|
return x; |
366 |
|
|
} |
367 |
|
|
|
368 |
|
|
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
369 |
|
|
E x = null; |
370 |
|
|
int c = -1; |
371 |
dholmes |
1.8 |
long nanos = unit.toNanos(timeout); |
372 |
dl |
1.2 |
takeLock.lockInterruptibly(); |
373 |
|
|
try { |
374 |
|
|
for (;;) { |
375 |
|
|
if (count.get() > 0) { |
376 |
|
|
x = extract(); |
377 |
|
|
c = count.getAndDecrement(); |
378 |
|
|
if (c > 1) |
379 |
|
|
notEmpty.signal(); |
380 |
|
|
break; |
381 |
|
|
} |
382 |
|
|
if (nanos <= 0) |
383 |
|
|
return null; |
384 |
|
|
try { |
385 |
|
|
nanos = notEmpty.awaitNanos(nanos); |
386 |
tim |
1.17 |
} catch (InterruptedException ie) { |
387 |
dl |
1.2 |
notEmpty.signal(); // propagate to a non-interrupted thread |
388 |
|
|
throw ie; |
389 |
|
|
} |
390 |
|
|
} |
391 |
tim |
1.17 |
} finally { |
392 |
dl |
1.2 |
takeLock.unlock(); |
393 |
|
|
} |
394 |
tim |
1.12 |
if (c == capacity) |
395 |
dl |
1.2 |
signalNotFull(); |
396 |
|
|
return x; |
397 |
|
|
} |
398 |
|
|
|
399 |
|
|
public E poll() { |
400 |
|
|
if (count.get() == 0) |
401 |
|
|
return null; |
402 |
|
|
E x = null; |
403 |
tim |
1.12 |
int c = -1; |
404 |
dl |
1.2 |
takeLock.tryLock(); |
405 |
|
|
try { |
406 |
|
|
if (count.get() > 0) { |
407 |
|
|
x = extract(); |
408 |
|
|
c = count.getAndDecrement(); |
409 |
|
|
if (c > 1) |
410 |
|
|
notEmpty.signal(); |
411 |
|
|
} |
412 |
tim |
1.17 |
} finally { |
413 |
dl |
1.2 |
takeLock.unlock(); |
414 |
|
|
} |
415 |
tim |
1.12 |
if (c == capacity) |
416 |
dl |
1.2 |
signalNotFull(); |
417 |
|
|
return x; |
418 |
tim |
1.1 |
} |
419 |
dl |
1.2 |
|
420 |
|
|
|
421 |
|
|
public E peek() { |
422 |
|
|
if (count.get() == 0) |
423 |
|
|
return null; |
424 |
dholmes |
1.8 |
takeLock.lock(); |
425 |
dl |
1.2 |
try { |
426 |
|
|
Node<E> first = head.next; |
427 |
|
|
if (first == null) |
428 |
|
|
return null; |
429 |
|
|
else |
430 |
|
|
return first.item; |
431 |
tim |
1.17 |
} finally { |
432 |
dl |
1.2 |
takeLock.unlock(); |
433 |
|
|
} |
434 |
tim |
1.1 |
} |
435 |
|
|
|
436 |
dholmes |
1.14 |
/** |
437 |
|
|
* Removes a single instance of the specified element from this |
438 |
|
|
* queue, if it is present. More formally, |
439 |
|
|
* removes an element <tt>e</tt> such that <tt>(o==null ? e==null : |
440 |
|
|
* o.equals(e))</tt>, if the queue contains one or more such |
441 |
|
|
* elements. Returns <tt>true</tt> if the queue contained the |
442 |
|
|
* specified element (or equivalently, if the queue changed as a |
443 |
|
|
* result of the call). |
444 |
|
|
* |
445 |
|
|
*/ |
446 |
dholmes |
1.9 |
public boolean remove(Object o) { |
447 |
|
|
if (o == null) return false; |
448 |
dl |
1.2 |
boolean removed = false; |
449 |
|
|
fullyLock(); |
450 |
|
|
try { |
451 |
|
|
Node<E> trail = head; |
452 |
|
|
Node<E> p = head.next; |
453 |
|
|
while (p != null) { |
454 |
dholmes |
1.9 |
if (o.equals(p.item)) { |
455 |
dl |
1.2 |
removed = true; |
456 |
|
|
break; |
457 |
|
|
} |
458 |
|
|
trail = p; |
459 |
|
|
p = p.next; |
460 |
|
|
} |
461 |
|
|
if (removed) { |
462 |
|
|
p.item = null; |
463 |
|
|
trail.next = p.next; |
464 |
|
|
if (count.getAndDecrement() == capacity) |
465 |
|
|
notFull.signalAll(); |
466 |
|
|
} |
467 |
tim |
1.17 |
} finally { |
468 |
dl |
1.2 |
fullyUnlock(); |
469 |
|
|
} |
470 |
|
|
return removed; |
471 |
tim |
1.1 |
} |
472 |
dl |
1.2 |
|
473 |
|
|
public Object[] toArray() { |
474 |
|
|
fullyLock(); |
475 |
|
|
try { |
476 |
|
|
int size = count.get(); |
477 |
tim |
1.12 |
Object[] a = new Object[size]; |
478 |
dl |
1.2 |
int k = 0; |
479 |
tim |
1.12 |
for (Node<E> p = head.next; p != null; p = p.next) |
480 |
dl |
1.2 |
a[k++] = p.item; |
481 |
|
|
return a; |
482 |
tim |
1.17 |
} finally { |
483 |
dl |
1.2 |
fullyUnlock(); |
484 |
|
|
} |
485 |
tim |
1.1 |
} |
486 |
dl |
1.2 |
|
487 |
|
|
public <T> T[] toArray(T[] a) { |
488 |
|
|
fullyLock(); |
489 |
|
|
try { |
490 |
|
|
int size = count.get(); |
491 |
|
|
if (a.length < size) |
492 |
dl |
1.4 |
a = (T[])java.lang.reflect.Array.newInstance |
493 |
|
|
(a.getClass().getComponentType(), size); |
494 |
tim |
1.12 |
|
495 |
dl |
1.2 |
int k = 0; |
496 |
tim |
1.12 |
for (Node p = head.next; p != null; p = p.next) |
497 |
dl |
1.2 |
a[k++] = (T)p.item; |
498 |
|
|
return a; |
499 |
tim |
1.17 |
} finally { |
500 |
dl |
1.2 |
fullyUnlock(); |
501 |
|
|
} |
502 |
tim |
1.1 |
} |
503 |
dl |
1.2 |
|
504 |
|
|
public String toString() { |
505 |
|
|
fullyLock(); |
506 |
|
|
try { |
507 |
|
|
return super.toString(); |
508 |
tim |
1.17 |
} finally { |
509 |
dl |
1.2 |
fullyUnlock(); |
510 |
|
|
} |
511 |
tim |
1.1 |
} |
512 |
dl |
1.2 |
|
513 |
dholmes |
1.14 |
/** |
514 |
|
|
* Returns an iterator over the elements in this queue in proper sequence. |
515 |
dl |
1.15 |
* The returned <tt>Iterator</tt> is a "weakly consistent" iterator that |
516 |
|
|
* will never throw {@link java.util.ConcurrentModificationException}, |
517 |
|
|
* and guarantees to traverse elements as they existed upon |
518 |
|
|
* construction of the iterator, and may (but is not guaranteed to) |
519 |
|
|
* reflect any modifications subsequent to construction. |
520 |
dholmes |
1.14 |
* |
521 |
|
|
* @return an iterator over the elements in this queue in proper sequence. |
522 |
|
|
*/ |
523 |
dl |
1.2 |
public Iterator<E> iterator() { |
524 |
|
|
return new Itr(); |
525 |
tim |
1.1 |
} |
526 |
dl |
1.2 |
|
527 |
|
|
private class Itr implements Iterator<E> { |
528 |
tim |
1.12 |
/* |
529 |
dl |
1.4 |
* Basic weak-consistent iterator. At all times hold the next |
530 |
|
|
* item to hand out so that if hasNext() reports true, we will |
531 |
|
|
* still have it to return even if lost race with a take etc. |
532 |
|
|
*/ |
533 |
dl |
1.2 |
Node<E> current; |
534 |
|
|
Node<E> lastRet; |
535 |
dl |
1.4 |
E currentElement; |
536 |
tim |
1.12 |
|
537 |
dl |
1.2 |
Itr() { |
538 |
|
|
fullyLock(); |
539 |
|
|
try { |
540 |
|
|
current = head.next; |
541 |
dl |
1.4 |
if (current != null) |
542 |
|
|
currentElement = current.item; |
543 |
tim |
1.17 |
} finally { |
544 |
dl |
1.2 |
fullyUnlock(); |
545 |
|
|
} |
546 |
|
|
} |
547 |
tim |
1.12 |
|
548 |
|
|
public boolean hasNext() { |
549 |
dl |
1.2 |
return current != null; |
550 |
|
|
} |
551 |
|
|
|
552 |
tim |
1.12 |
public E next() { |
553 |
dl |
1.2 |
fullyLock(); |
554 |
|
|
try { |
555 |
|
|
if (current == null) |
556 |
|
|
throw new NoSuchElementException(); |
557 |
dl |
1.4 |
E x = currentElement; |
558 |
dl |
1.2 |
lastRet = current; |
559 |
|
|
current = current.next; |
560 |
dl |
1.4 |
if (current != null) |
561 |
|
|
currentElement = current.item; |
562 |
dl |
1.2 |
return x; |
563 |
tim |
1.17 |
} finally { |
564 |
dl |
1.2 |
fullyUnlock(); |
565 |
|
|
} |
566 |
tim |
1.12 |
|
567 |
dl |
1.2 |
} |
568 |
|
|
|
569 |
tim |
1.12 |
public void remove() { |
570 |
dl |
1.2 |
if (lastRet == null) |
571 |
tim |
1.12 |
throw new IllegalStateException(); |
572 |
dl |
1.2 |
fullyLock(); |
573 |
|
|
try { |
574 |
|
|
Node<E> node = lastRet; |
575 |
|
|
lastRet = null; |
576 |
|
|
Node<E> trail = head; |
577 |
|
|
Node<E> p = head.next; |
578 |
|
|
while (p != null && p != node) { |
579 |
|
|
trail = p; |
580 |
|
|
p = p.next; |
581 |
|
|
} |
582 |
|
|
if (p == node) { |
583 |
|
|
p.item = null; |
584 |
|
|
trail.next = p.next; |
585 |
|
|
int c = count.getAndDecrement(); |
586 |
|
|
if (c == capacity) |
587 |
|
|
notFull.signalAll(); |
588 |
|
|
} |
589 |
tim |
1.17 |
} finally { |
590 |
dl |
1.2 |
fullyUnlock(); |
591 |
|
|
} |
592 |
|
|
} |
593 |
tim |
1.1 |
} |
594 |
dl |
1.2 |
|
595 |
|
|
/** |
596 |
|
|
* Save the state to a stream (that is, serialize it). |
597 |
|
|
* |
598 |
|
|
* @serialData The capacity is emitted (int), followed by all of |
599 |
|
|
* its elements (each an <tt>Object</tt>) in the proper order, |
600 |
|
|
* followed by a null |
601 |
dl |
1.6 |
* @param s the stream |
602 |
dl |
1.2 |
*/ |
603 |
|
|
private void writeObject(java.io.ObjectOutputStream s) |
604 |
|
|
throws java.io.IOException { |
605 |
|
|
|
606 |
tim |
1.12 |
fullyLock(); |
607 |
dl |
1.2 |
try { |
608 |
|
|
// Write out any hidden stuff, plus capacity |
609 |
|
|
s.defaultWriteObject(); |
610 |
|
|
|
611 |
|
|
// Write out all elements in the proper order. |
612 |
tim |
1.12 |
for (Node<E> p = head.next; p != null; p = p.next) |
613 |
dl |
1.2 |
s.writeObject(p.item); |
614 |
|
|
|
615 |
|
|
// Use trailing null as sentinel |
616 |
|
|
s.writeObject(null); |
617 |
tim |
1.17 |
} finally { |
618 |
dl |
1.2 |
fullyUnlock(); |
619 |
|
|
} |
620 |
tim |
1.1 |
} |
621 |
|
|
|
622 |
dl |
1.2 |
/** |
623 |
dholmes |
1.8 |
* Reconstitute this queue instance from a stream (that is, |
624 |
dl |
1.2 |
* deserialize it). |
625 |
dl |
1.6 |
* @param s the stream |
626 |
dl |
1.2 |
*/ |
627 |
|
|
private void readObject(java.io.ObjectInputStream s) |
628 |
|
|
throws java.io.IOException, ClassNotFoundException { |
629 |
tim |
1.12 |
// Read in capacity, and any hidden stuff |
630 |
|
|
s.defaultReadObject(); |
631 |
dl |
1.2 |
|
632 |
dl |
1.6 |
// Read in all elements and place in queue |
633 |
dl |
1.2 |
for (;;) { |
634 |
|
|
E item = (E)s.readObject(); |
635 |
|
|
if (item == null) |
636 |
|
|
break; |
637 |
|
|
add(item); |
638 |
|
|
} |
639 |
tim |
1.1 |
} |
640 |
|
|
} |
641 |
dholmes |
1.8 |
|
642 |
|
|
|
643 |
|
|
|
644 |
|
|
|
645 |
tim |
1.1 |
|