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25 
26 package jdk.internal.net.http;
27 
28 import jdk.internal.net.http.common.FlowTube;
29 import jdk.internal.net.http.common.Logger;
30 import jdk.internal.net.http.frame.SettingsFrame;
31 import jdk.internal.net.http.frame.WindowUpdateFrame;
32 import jdk.internal.net.http.common.Utils;
33 import java.util.concurrent.atomic.AtomicInteger;
34 
35 abstract class WindowUpdateSender {
36 
37     final Logger debug =
38             Utils.getDebugLogger(this::dbgString, Utils.DEBUG);
39 
40     final int limit;
41     final Http2Connection connection;
42     final AtomicInteger received = new AtomicInteger(0);
43 
WindowUpdateSender(Http2Connection connection)44     WindowUpdateSender(Http2Connection connection) {
45         this(connection, connection.clientSettings.getParameter(SettingsFrame.INITIAL_WINDOW_SIZE));
46     }
47 
WindowUpdateSender(Http2Connection connection, int initWindowSize)48     WindowUpdateSender(Http2Connection connection, int initWindowSize) {
49         this(connection, connection.getMaxReceiveFrameSize(), initWindowSize);
50     }
51 
WindowUpdateSender(Http2Connection connection, int maxFrameSize, int initWindowSize)52     WindowUpdateSender(Http2Connection connection, int maxFrameSize, int initWindowSize) {
53         this.connection = connection;
54         int v0 = Math.max(0, initWindowSize - maxFrameSize);
55         int v1 = (initWindowSize + (maxFrameSize - 1)) / maxFrameSize;
56         v1 = v1 * maxFrameSize / 2;
57         // send WindowUpdate heuristic:
58         // - we got data near half of window size
59         //   or
60         // - remaining window size reached max frame size.
61         limit = Math.min(v0, v1);
62         if (debug.on())
63             debug.log("maxFrameSize=%d, initWindowSize=%d, limit=%d",
64                       maxFrameSize, initWindowSize, limit);
65     }
66 
getStreamId()67     abstract int getStreamId();
68 
update(int delta)69     void update(int delta) {
70         int rcv = received.addAndGet(delta);
71         if (debug.on()) debug.log("update: %d, received: %d, limit: %d", delta, rcv, limit);
72         if (rcv > limit) {
73             synchronized (this) {
74                 int tosend = received.get();
75                 if( tosend > limit) {
76                     received.getAndAdd(-tosend);
77                     sendWindowUpdate(tosend);
78                 }
79             }
80         }
81     }
82 
sendWindowUpdate(int delta)83     void sendWindowUpdate(int delta) {
84         if (debug.on()) debug.log("sending window update: %d", delta);
85         connection.sendUnorderedFrame(new WindowUpdateFrame(getStreamId(), delta));
86     }
87 
88     volatile String dbgString;
dbgString()89     String dbgString() {
90         String dbg = dbgString;
91         if (dbg != null) return dbg;
92         FlowTube tube = connection.connection.getConnectionFlow();
93         if (tube == null) {
94             return "WindowUpdateSender(stream: " + getStreamId() + ")";
95         } else {
96             int streamId = getStreamId();
97             dbg = connection.dbgString() + ":WindowUpdateSender(stream: " + streamId + ")";
98             return streamId == 0 ? dbg : (dbgString = dbg);
99         }
100     }
101 
102 }
103