added RWLock C++ wrapper

Change-Id: Ia736bf7f6e2c49915a9ab5669551cf89dafa7961

include/utils/threads.h

@@ -295,6 +295,96 @@ typedef Mutex::Autolock AutoMutex;
 
 /*****************************************************************************/
 
+#if defined(HAVE_PTHREADS)
+
+/*
+ * Simple mutex class.  The implementation is system-dependent.
+ *
+ * The mutex must be unlocked by the thread that locked it.  They are not
+ * recursive, i.e. the same thread can't lock it multiple times.
+ */
+class RWLock {
+public:
+    enum {
+        PRIVATE = 0,
+        SHARED = 1
+    };
+
+                RWLock();
+                RWLock(const char* name);
+                RWLock(int type, const char* name = NULL);
+                ~RWLock();
+
+    status_t    readLock();
+    status_t    tryReadLock();
+    status_t    writeLock();
+    status_t    tryWriteLock();
+    void        unlock();
+
+    class AutoRLock {
+    public:
+        inline AutoRLock(RWLock& rwlock) : mLock(rwlock)  { mLock.readLock(); }
+        inline ~AutoRLock() { mLock.unlock(); }
+    private:
+        RWLock& mLock;
+    };
+
+    class AutoWLock {
+    public:
+        inline AutoWLock(RWLock& rwlock) : mLock(rwlock)  { mLock.writeLock(); }
+        inline ~AutoWLock() { mLock.unlock(); }
+    private:
+        RWLock& mLock;
+    };
+
+private:
+    // A RWLock cannot be copied
+                RWLock(const RWLock&);
+   RWLock&      operator = (const RWLock&);
+
+   pthread_rwlock_t mRWLock;
+};
+
+inline RWLock::RWLock() {
+    pthread_rwlock_init(&mRWLock, NULL);
+}
+inline RWLock::RWLock(const char* name) {
+    pthread_rwlock_init(&mRWLock, NULL);
+}
+inline RWLock::RWLock(int type, const char* name) {
+    if (type == SHARED) {
+        pthread_rwlockattr_t attr;
+        pthread_rwlockattr_init(&attr);
+        pthread_rwlockattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
+        pthread_rwlock_init(&mRWLock, &attr);
+        pthread_rwlockattr_destroy(&attr);
+    } else {
+        pthread_rwlock_init(&mRWLock, NULL);
+    }
+}
+inline RWLock::~RWLock() {
+    pthread_rwlock_destroy(&mRWLock);
+}
+inline status_t RWLock::readLock() {
+    return -pthread_rwlock_rdlock(&mRWLock);
+}
+inline status_t RWLock::tryReadLock() {
+    return -pthread_rwlock_tryrdlock(&mRWLock);
+}
+inline status_t RWLock::writeLock() {
+    return -pthread_rwlock_wrlock(&mRWLock);
+}
+inline status_t RWLock::tryWriteLock() {
+    return -pthread_rwlock_trywrlock(&mRWLock);
+}
+inline void RWLock::unlock() {
+    pthread_rwlock_unlock(&mRWLock);
+}
+
+#endif // HAVE_PTHREADS
+
+/*****************************************************************************/
+
 /*
  * Condition variable class.  The implementation is system-dependent.
  *