1 /* 2 * Copyright (c) 2015, 2016, 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 */ 24 package java.net.http; 25 26 import java.util.concurrent.Semaphore; 27 28 /** 29 * Connection or stream blocking flow control window. 30 */ 31 class WindowControl { 32 33 final Semaphore window; 34 35 WindowControl() { 36 this(0); 37 } 38 39 WindowControl(int intialPermits) { 40 this.window = new Semaphore(intialPermits); 41 } 42 43 void update(int permits) { 44 /* TODO 45 RFC-7540 says: 46 A sender MUST NOT allow a flow-control window to exceed 2^31-1 47 octets. If a sender receives a WINDOW_UPDATE that causes a flow- 48 control window to exceed this maximum, it MUST terminate either the 49 stream or the connection, as appropriate. For streams, the sender 50 sends a RST_STREAM with an error code of FLOW_CONTROL_ERROR; for the 51 connection, a GOAWAY frame with an error code of FLOW_CONTROL_ERROR 52 is sent. 53 */ 54 if (permits > 0) { 55 window.release(permits); 56 } 57 } 58 59 void acquire(int permits) throws InterruptedException { 60 if (permits > 0) { 61 window.acquire(permits); 62 } 63 } 64 65 int available() { 66 return window.availablePermits(); 67 } 68 }