1 /* |
|
2 * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved. |
|
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
|
4 * |
|
5 * This code is free software; you can redistribute it and/or modify it |
|
6 * under the terms of the GNU General Public License version 2 only, as |
|
7 * published by the Free Software Foundation. Oracle designates this |
|
8 * particular file as subject to the "Classpath" exception as provided |
|
9 * by Oracle in the LICENSE file that accompanied this code. |
|
10 * |
|
11 * This code is distributed in the hope that it will be useful, but WITHOUT |
|
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
|
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
|
14 * version 2 for more details (a copy is included in the LICENSE file that |
|
15 * accompanied this code). |
|
16 * |
|
17 * You should have received a copy of the GNU General Public License version |
|
18 * 2 along with this work; if not, write to the Free Software Foundation, |
|
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
|
20 * |
|
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
|
22 * or visit www.oracle.com if you need additional information or have any |
|
23 * questions. |
|
24 */ |
|
25 |
|
26 package jdk.incubator.http.internal; |
|
27 |
|
28 import java.nio.ByteBuffer; |
|
29 import java.util.ArrayList; |
|
30 import java.util.Collections; |
|
31 import java.util.List; |
|
32 import java.util.ListIterator; |
|
33 import java.util.Objects; |
|
34 import java.util.concurrent.CompletionStage; |
|
35 import java.util.concurrent.Flow; |
|
36 import java.util.concurrent.atomic.AtomicBoolean; |
|
37 import jdk.incubator.http.HttpResponse.BodySubscriber; |
|
38 import jdk.incubator.http.internal.common.Demand; |
|
39 import jdk.incubator.http.internal.common.SequentialScheduler; |
|
40 import jdk.incubator.http.internal.common.Utils; |
|
41 |
|
42 /** |
|
43 * A buffering BodySubscriber. When subscribed, accumulates ( buffers ) a given |
|
44 * amount ( in bytes ) of a publisher's data before pushing it to a downstream |
|
45 * subscriber. |
|
46 */ |
|
47 public class BufferingSubscriber<T> implements BodySubscriber<T> |
|
48 { |
|
49 /** The downstream consumer of the data. */ |
|
50 private final BodySubscriber<T> downstreamSubscriber; |
|
51 /** The amount of data to be accumulate before pushing downstream. */ |
|
52 private final int bufferSize; |
|
53 |
|
54 /** The subscription, created lazily. */ |
|
55 private volatile Flow.Subscription subscription; |
|
56 /** The downstream subscription, created lazily. */ |
|
57 private volatile DownstreamSubscription downstreamSubscription; |
|
58 |
|
59 /** Must be held when accessing the internal buffers. */ |
|
60 private final Object buffersLock = new Object(); |
|
61 /** The internal buffers holding the buffered data. */ |
|
62 private ArrayList<ByteBuffer> internalBuffers; |
|
63 /** The actual accumulated remaining bytes in internalBuffers. */ |
|
64 private int accumulatedBytes; |
|
65 |
|
66 /** Holds the Throwable from upstream's onError. */ |
|
67 private volatile Throwable throwable; |
|
68 |
|
69 /** State of the buffering subscriber: |
|
70 * 1) [UNSUBSCRIBED] when initially created |
|
71 * 2) [ACTIVE] when subscribed and can receive data |
|
72 * 3) [ERROR | CANCELLED | COMPLETE] (terminal state) |
|
73 */ |
|
74 static final int UNSUBSCRIBED = 0x01; |
|
75 static final int ACTIVE = 0x02; |
|
76 static final int ERROR = 0x04; |
|
77 static final int CANCELLED = 0x08; |
|
78 static final int COMPLETE = 0x10; |
|
79 |
|
80 private volatile int state; |
|
81 |
|
82 public BufferingSubscriber(BodySubscriber<T> downstreamSubscriber, |
|
83 int bufferSize) { |
|
84 this.downstreamSubscriber = Objects.requireNonNull(downstreamSubscriber); |
|
85 this.bufferSize = bufferSize; |
|
86 synchronized (buffersLock) { |
|
87 internalBuffers = new ArrayList<>(); |
|
88 } |
|
89 state = UNSUBSCRIBED; |
|
90 } |
|
91 |
|
92 /** Returns the number of bytes remaining in the given buffers. */ |
|
93 private static final long remaining(List<ByteBuffer> buffers) { |
|
94 return buffers.stream().mapToLong(ByteBuffer::remaining).sum(); |
|
95 } |
|
96 |
|
97 /** |
|
98 * Tells whether, or not, there is at least a sufficient number of bytes |
|
99 * accumulated in the internal buffers. If the subscriber is COMPLETE, and |
|
100 * has some buffered data, then there is always enough ( to pass downstream ). |
|
101 */ |
|
102 private final boolean hasEnoughAccumulatedBytes() { |
|
103 assert Thread.holdsLock(buffersLock); |
|
104 return accumulatedBytes >= bufferSize |
|
105 || (state == COMPLETE && accumulatedBytes > 0); |
|
106 } |
|
107 |
|
108 /** |
|
109 * Returns a new, unmodifiable, List<ByteBuffer> containing exactly the |
|
110 * amount of data as required before pushing downstream. The amount of data |
|
111 * may be less than required ( bufferSize ), in the case where the subscriber |
|
112 * is COMPLETE. |
|
113 */ |
|
114 private List<ByteBuffer> fromInternalBuffers() { |
|
115 assert Thread.holdsLock(buffersLock); |
|
116 int leftToFill = bufferSize; |
|
117 int state = this.state; |
|
118 assert (state == ACTIVE || state == CANCELLED) |
|
119 ? accumulatedBytes >= leftToFill : true; |
|
120 List<ByteBuffer> dsts = new ArrayList<>(); |
|
121 |
|
122 ListIterator<ByteBuffer> itr = internalBuffers.listIterator(); |
|
123 while (itr.hasNext()) { |
|
124 ByteBuffer b = itr.next(); |
|
125 if (b.remaining() <= leftToFill) { |
|
126 itr.remove(); |
|
127 if (b.position() != 0) |
|
128 b = b.slice(); // ensure position = 0 when propagated |
|
129 dsts.add(b); |
|
130 leftToFill -= b.remaining(); |
|
131 accumulatedBytes -= b.remaining(); |
|
132 if (leftToFill == 0) |
|
133 break; |
|
134 } else { |
|
135 int prevLimit = b.limit(); |
|
136 b.limit(b.position() + leftToFill); |
|
137 ByteBuffer slice = b.slice(); |
|
138 dsts.add(slice); |
|
139 b.limit(prevLimit); |
|
140 b.position(b.position() + leftToFill); |
|
141 accumulatedBytes -= leftToFill; |
|
142 leftToFill = 0; |
|
143 break; |
|
144 } |
|
145 } |
|
146 assert (state == ACTIVE || state == CANCELLED) |
|
147 ? leftToFill == 0 : state == COMPLETE; |
|
148 assert (state == ACTIVE || state == CANCELLED) |
|
149 ? remaining(dsts) == bufferSize : state == COMPLETE; |
|
150 assert accumulatedBytes >= 0; |
|
151 assert dsts.stream().noneMatch(b -> b.position() != 0); |
|
152 return Collections.unmodifiableList(dsts); |
|
153 } |
|
154 |
|
155 /** Subscription that is passed to the downstream subscriber. */ |
|
156 private class DownstreamSubscription implements Flow.Subscription { |
|
157 private final AtomicBoolean cancelled = new AtomicBoolean(); // false |
|
158 private final Demand demand = new Demand(); |
|
159 private volatile boolean illegalArg; |
|
160 |
|
161 @Override |
|
162 public void request(long n) { |
|
163 if (cancelled.get() || illegalArg) { |
|
164 return; |
|
165 } |
|
166 if (n <= 0L) { |
|
167 // pass the "bad" value upstream so the Publisher can deal with |
|
168 // it appropriately, i.e. invoke onError |
|
169 illegalArg = true; |
|
170 subscription.request(n); |
|
171 return; |
|
172 } |
|
173 |
|
174 demand.increase(n); |
|
175 |
|
176 pushDemanded(); |
|
177 } |
|
178 |
|
179 private final SequentialScheduler pushDemandedScheduler = |
|
180 new SequentialScheduler(new PushDemandedTask()); |
|
181 |
|
182 void pushDemanded() { |
|
183 if (cancelled.get()) |
|
184 return; |
|
185 pushDemandedScheduler.runOrSchedule(); |
|
186 } |
|
187 |
|
188 class PushDemandedTask extends SequentialScheduler.CompleteRestartableTask { |
|
189 @Override |
|
190 public void run() { |
|
191 try { |
|
192 Throwable t = throwable; |
|
193 if (t != null) { |
|
194 pushDemandedScheduler.stop(); // stop the demand scheduler |
|
195 downstreamSubscriber.onError(t); |
|
196 return; |
|
197 } |
|
198 |
|
199 while (true) { |
|
200 List<ByteBuffer> item; |
|
201 synchronized (buffersLock) { |
|
202 if (cancelled.get()) |
|
203 return; |
|
204 if (!hasEnoughAccumulatedBytes()) |
|
205 break; |
|
206 if (!demand.tryDecrement()) |
|
207 break; |
|
208 item = fromInternalBuffers(); |
|
209 } |
|
210 assert item != null; |
|
211 |
|
212 downstreamSubscriber.onNext(item); |
|
213 } |
|
214 if (cancelled.get()) |
|
215 return; |
|
216 |
|
217 // complete only if all data consumed |
|
218 boolean complete; |
|
219 synchronized (buffersLock) { |
|
220 complete = state == COMPLETE && internalBuffers.isEmpty(); |
|
221 } |
|
222 if (complete) { |
|
223 assert internalBuffers.isEmpty(); |
|
224 pushDemandedScheduler.stop(); // stop the demand scheduler |
|
225 downstreamSubscriber.onComplete(); |
|
226 return; |
|
227 } |
|
228 } catch (Throwable t) { |
|
229 cancel(); // cancel if there is any error |
|
230 throw t; |
|
231 } |
|
232 |
|
233 boolean requestMore = false; |
|
234 synchronized (buffersLock) { |
|
235 if (!hasEnoughAccumulatedBytes() && !demand.isFulfilled()) { |
|
236 // request more upstream data |
|
237 requestMore = true; |
|
238 } |
|
239 } |
|
240 if (requestMore) |
|
241 subscription.request(1); |
|
242 } |
|
243 } |
|
244 |
|
245 @Override |
|
246 public void cancel() { |
|
247 if (cancelled.compareAndExchange(false, true)) |
|
248 return; // already cancelled |
|
249 |
|
250 state = CANCELLED; // set CANCELLED state of upstream subscriber |
|
251 subscription.cancel(); // cancel upstream subscription |
|
252 pushDemandedScheduler.stop(); // stop the demand scheduler |
|
253 } |
|
254 } |
|
255 |
|
256 @Override |
|
257 public void onSubscribe(Flow.Subscription subscription) { |
|
258 Objects.requireNonNull(subscription); |
|
259 if (this.subscription != null) { |
|
260 subscription.cancel(); |
|
261 return; |
|
262 } |
|
263 |
|
264 int s = this.state; |
|
265 assert s == UNSUBSCRIBED; |
|
266 state = ACTIVE; |
|
267 this.subscription = subscription; |
|
268 downstreamSubscription = new DownstreamSubscription(); |
|
269 downstreamSubscriber.onSubscribe(downstreamSubscription); |
|
270 } |
|
271 |
|
272 @Override |
|
273 public void onNext(List<ByteBuffer> item) { |
|
274 Objects.requireNonNull(item); |
|
275 |
|
276 int s = state; |
|
277 if (s == CANCELLED) |
|
278 return; |
|
279 |
|
280 if (s != ACTIVE) |
|
281 throw new InternalError("onNext on inactive subscriber"); |
|
282 |
|
283 synchronized (buffersLock) { |
|
284 internalBuffers.addAll(item); |
|
285 accumulatedBytes += remaining(item); |
|
286 } |
|
287 |
|
288 downstreamSubscription.pushDemanded(); |
|
289 } |
|
290 |
|
291 @Override |
|
292 public void onError(Throwable incomingThrowable) { |
|
293 Objects.requireNonNull(incomingThrowable); |
|
294 int s = state; |
|
295 assert s == ACTIVE : "Expected ACTIVE, got:" + s; |
|
296 state = ERROR; |
|
297 Throwable t = this.throwable; |
|
298 assert t == null : "Expected null, got:" + t; |
|
299 this.throwable = incomingThrowable; |
|
300 downstreamSubscription.pushDemanded(); |
|
301 } |
|
302 |
|
303 @Override |
|
304 public void onComplete() { |
|
305 int s = state; |
|
306 assert s == ACTIVE : "Expected ACTIVE, got:" + s; |
|
307 state = COMPLETE; |
|
308 downstreamSubscription.pushDemanded(); |
|
309 } |
|
310 |
|
311 @Override |
|
312 public CompletionStage<T> getBody() { |
|
313 return downstreamSubscriber.getBody(); |
|
314 } |
|
315 } |
|