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      1 /*
      2  * Copyright (C) 2007 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef _LIBS_UTILS_RWLOCK_H
     18 #define _LIBS_UTILS_RWLOCK_H
     19 
     20 #include <stdint.h>
     21 #include <sys/types.h>
     22 
     23 #if defined(HAVE_PTHREADS)
     24 # include <pthread.h>
     25 #endif
     26 
     27 #include <utils/Errors.h>
     28 #include <utils/ThreadDefs.h>
     29 
     30 // ---------------------------------------------------------------------------
     31 namespace android {
     32 // ---------------------------------------------------------------------------
     33 
     34 #if defined(HAVE_PTHREADS)
     35 
     36 /*
     37  * Simple mutex class.  The implementation is system-dependent.
     38  *
     39  * The mutex must be unlocked by the thread that locked it.  They are not
     40  * recursive, i.e. the same thread can't lock it multiple times.
     41  */
     42 class RWLock {
     43 public:
     44     enum {
     45         PRIVATE = 0,
     46         SHARED = 1
     47     };
     48 
     49                 RWLock();
     50                 RWLock(const char* name);
     51                 RWLock(int type, const char* name = NULL);
     52                 ~RWLock();
     53 
     54     status_t    readLock();
     55     status_t    tryReadLock();
     56     status_t    writeLock();
     57     status_t    tryWriteLock();
     58     void        unlock();
     59 
     60     class AutoRLock {
     61     public:
     62         inline AutoRLock(RWLock& rwlock) : mLock(rwlock)  { mLock.readLock(); }
     63         inline ~AutoRLock() { mLock.unlock(); }
     64     private:
     65         RWLock& mLock;
     66     };
     67 
     68     class AutoWLock {
     69     public:
     70         inline AutoWLock(RWLock& rwlock) : mLock(rwlock)  { mLock.writeLock(); }
     71         inline ~AutoWLock() { mLock.unlock(); }
     72     private:
     73         RWLock& mLock;
     74     };
     75 
     76 private:
     77     // A RWLock cannot be copied
     78                 RWLock(const RWLock&);
     79    RWLock&      operator = (const RWLock&);
     80 
     81    pthread_rwlock_t mRWLock;
     82 };
     83 
     84 inline RWLock::RWLock() {
     85     pthread_rwlock_init(&mRWLock, NULL);
     86 }
     87 inline RWLock::RWLock(__attribute__((unused)) const char* name) {
     88     pthread_rwlock_init(&mRWLock, NULL);
     89 }
     90 inline RWLock::RWLock(int type, __attribute__((unused)) const char* name) {
     91     if (type == SHARED) {
     92         pthread_rwlockattr_t attr;
     93         pthread_rwlockattr_init(&attr);
     94         pthread_rwlockattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
     95         pthread_rwlock_init(&mRWLock, &attr);
     96         pthread_rwlockattr_destroy(&attr);
     97     } else {
     98         pthread_rwlock_init(&mRWLock, NULL);
     99     }
    100 }
    101 inline RWLock::~RWLock() {
    102     pthread_rwlock_destroy(&mRWLock);
    103 }
    104 inline status_t RWLock::readLock() {
    105     return -pthread_rwlock_rdlock(&mRWLock);
    106 }
    107 inline status_t RWLock::tryReadLock() {
    108     return -pthread_rwlock_tryrdlock(&mRWLock);
    109 }
    110 inline status_t RWLock::writeLock() {
    111     return -pthread_rwlock_wrlock(&mRWLock);
    112 }
    113 inline status_t RWLock::tryWriteLock() {
    114     return -pthread_rwlock_trywrlock(&mRWLock);
    115 }
    116 inline void RWLock::unlock() {
    117     pthread_rwlock_unlock(&mRWLock);
    118 }
    119 
    120 #endif // HAVE_PTHREADS
    121 
    122 // ---------------------------------------------------------------------------
    123 }; // namespace android
    124 // ---------------------------------------------------------------------------
    125 
    126 #endif // _LIBS_UTILS_RWLOCK_H
    127