1 // 2 // Copyright 2005 The Android Open Source Project 3 // 4 // Inter-process semaphore. 5 // 6 // These are meant for IPC, not thread management. The Mutex and Condition 7 // classes are much lighter weight. 8 // 9 #ifndef __LIBS_SEMAPHORE_H 10 #define __LIBS_SEMAPHORE_H 11 12 #ifdef HAVE_ANDROID_OS 13 #error DO NOT USE THIS FILE IN THE DEVICE BUILD 14 #endif 15 16 namespace android { 17 18 /* 19 * Platform-independent semaphore class. 20 * 21 * Each object holds a single semaphore. 22 * 23 * The "key" is usually the process ID of the process that created the 24 * semaphore (following POSIX semantics). See the comments in shmem.h. 25 */ 26 class Semaphore { 27 public: 28 Semaphore(void); 29 virtual ~Semaphore(void); 30 31 /* 32 * Create a new semaphore, with the specified initial value. The 33 * value indicates the number of resources available. 34 */ 35 bool create(int key, int initialValue, bool deleteExisting); 36 37 /* 38 * Attach to an existing semaphore. 39 */ 40 bool attach(int key); 41 42 /* 43 * Acquire or release the semaphore. 44 */ 45 void acquire(void); 46 void release(void); 47 bool tryAcquire(void); // take a timeout? 48 49 private: 50 bool adjust(int adj, bool wait); 51 52 unsigned long mHandle; // semid(int) or HANDLE 53 bool mCreator; 54 int mKey; 55 }; 56 57 }; // namespace android 58 59 #endif // __LIBS_SEMAPHORE_H 60
