1 /* 2 * Copyright (c) 2008-2013 Apple Inc. All rights reserved. 3 * 4 * @APPLE_APACHE_LICENSE_HEADER_START@ 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 * 18 * @APPLE_APACHE_LICENSE_HEADER_END@ 19 */ 20 21 #ifndef __DISPATCH_SEMAPHORE__ 22 #define __DISPATCH_SEMAPHORE__ 23 24 #ifndef __DISPATCH_INDIRECT__ 25 #error "Please #include <dispatch/dispatch.h> instead of this file directly." 26 #include <dispatch/base.h> // for HeaderDoc 27 #endif 28 29 /*! 30 * @typedef dispatch_semaphore_t 31 * 32 * @abstract 33 * A counting semaphore. 34 */ 35 DISPATCH_DECL(dispatch_semaphore); 36 37 __BEGIN_DECLS 38 39 /*! 40 * @function dispatch_semaphore_create 41 * 42 * @abstract 43 * Creates new counting semaphore with an initial value. 44 * 45 * @discussion 46 * Passing zero for the value is useful for when two threads need to reconcile 47 * the completion of a particular event. Passing a value greather than zero is 48 * useful for managing a finite pool of resources, where the pool size is equal 49 * to the value. 50 * 51 * @param value 52 * The starting value for the semaphore. Passing a value less than zero will 53 * cause NULL to be returned. 54 * 55 * @result 56 * The newly created semaphore, or NULL on failure. 57 */ 58 __OSX_AVAILABLE_STARTING(__MAC_10_6,__IPHONE_4_0) 59 DISPATCH_EXPORT DISPATCH_MALLOC DISPATCH_RETURNS_RETAINED DISPATCH_WARN_RESULT 60 DISPATCH_NOTHROW 61 dispatch_semaphore_t 62 dispatch_semaphore_create(long value); 63 64 /*! 65 * @function dispatch_semaphore_wait 66 * 67 * @abstract 68 * Wait (decrement) for a semaphore. 69 * 70 * @discussion 71 * Decrement the counting semaphore. If the resulting value is less than zero, 72 * this function waits for a signal to occur before returning. 73 * 74 * @param dsema 75 * The semaphore. The result of passing NULL in this parameter is undefined. 76 * 77 * @param timeout 78 * When to timeout (see dispatch_time). As a convenience, there are the 79 * DISPATCH_TIME_NOW and DISPATCH_TIME_FOREVER constants. 80 * 81 * @result 82 * Returns zero on success, or non-zero if the timeout occurred. 83 */ 84 __OSX_AVAILABLE_STARTING(__MAC_10_6,__IPHONE_4_0) 85 DISPATCH_EXPORT DISPATCH_NONNULL_ALL DISPATCH_NOTHROW 86 long 87 dispatch_semaphore_wait(dispatch_semaphore_t dsema, dispatch_time_t timeout); 88 89 /*! 90 * @function dispatch_semaphore_signal 91 * 92 * @abstract 93 * Signal (increment) a semaphore. 94 * 95 * @discussion 96 * Increment the counting semaphore. If the previous value was less than zero, 97 * this function wakes a waiting thread before returning. 98 * 99 * @param dsema The counting semaphore. 100 * The result of passing NULL in this parameter is undefined. 101 * 102 * @result 103 * This function returns non-zero if a thread is woken. Otherwise, zero is 104 * returned. 105 */ 106 __OSX_AVAILABLE_STARTING(__MAC_10_6,__IPHONE_4_0) 107 DISPATCH_EXPORT DISPATCH_NONNULL_ALL DISPATCH_NOTHROW 108 long 109 dispatch_semaphore_signal(dispatch_semaphore_t dsema); 110 111 __END_DECLS 112 113 #endif /* __DISPATCH_SEMAPHORE__ */ 114