whyred: Import gps from LA.UM.6.2.r2-03600-sdm660.0

gps/utils/LocSharedLock.h

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+/* Copyright (c) 2015, The Linux Foundation. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ *       copyright notice, this list of conditions and the following
+ *       disclaimer in the documentation and/or other materials provided
+ *       with the distribution.
+ *     * Neither the name of The Linux Foundation, nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+ * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
+ * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+#ifndef __LOC_SHARED_LOCK__
+#define __LOC_SHARED_LOCK__
+
+#include <stddef.h>
+#include <cutils/atomic.h>
+#include <pthread.h>
+
+// This is a utility created for use cases such that there are more than
+// one client who need to share the same lock, but it is not predictable
+// which of these clients is to last to go away. This shared lock deletes
+// itself when the last client calls its drop() method. To add a cient,
+// this share lock's share() method has to be called, so that the obj
+// can maintain an accurate client count.
+class LocSharedLock {
+    volatile int32_t mRef;
+    pthread_mutex_t mMutex;
+    inline ~LocSharedLock() { pthread_mutex_destroy(&mMutex); }
+public:
+    // first client to create this LockSharedLock
+    inline LocSharedLock() : mRef(1) { pthread_mutex_init(&mMutex, NULL); }
+    // following client(s) are to *share()* this lock created by the first client
+    inline LocSharedLock* share() { android_atomic_inc(&mRef); return this; }
+    // whe a client no longer needs this shared lock, drop() shall be called.
+    inline void drop() { if (1 == android_atomic_dec(&mRef)) delete this; }
+    // locking the lock to enter critical section
+    inline void lock() { pthread_mutex_lock(&mMutex); }
+    // unlocking the lock to leave the critical section
+    inline void unlock() { pthread_mutex_unlock(&mMutex); }
+};
+
+#endif //__LOC_SHARED_LOCK__