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      1 /*
      2  * Copyright (C) 2010 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 A_LOOPER_H_
     18 
     19 #define A_LOOPER_H_
     20 
     21 #include <media/stagefright/foundation/ABase.h>
     22 #include <media/stagefright/foundation/AString.h>
     23 #include <utils/Errors.h>
     24 #include <utils/KeyedVector.h>
     25 #include <utils/List.h>
     26 #include <utils/RefBase.h>
     27 #include <utils/threads.h>
     28 
     29 namespace android {
     30 
     31 struct AHandler;
     32 struct AMessage;
     33 struct AReplyToken;
     34 
     35 struct ALooper : public RefBase {
     36     typedef int32_t event_id;
     37     typedef int32_t handler_id;
     38 
     39     ALooper();
     40 
     41     // Takes effect in a subsequent call to start().
     42     void setName(const char *name);
     43 
     44     handler_id registerHandler(const sp<AHandler> &handler);
     45     void unregisterHandler(handler_id handlerID);
     46 
     47     status_t start(
     48             bool runOnCallingThread = false,
     49             bool canCallJava = false,
     50             int32_t priority = PRIORITY_DEFAULT
     51             );
     52 
     53     status_t stop();
     54 
     55     static int64_t GetNowUs();
     56 
     57     const char *getName() const {
     58         return mName.c_str();
     59     }
     60 
     61 protected:
     62     virtual ~ALooper();
     63 
     64 private:
     65     friend struct AMessage;       // post()
     66 
     67     struct Event {
     68         int64_t mWhenUs;
     69         sp<AMessage> mMessage;
     70     };
     71 
     72     Mutex mLock;
     73     Condition mQueueChangedCondition;
     74 
     75     AString mName;
     76 
     77     List<Event> mEventQueue;
     78 
     79     struct LooperThread;
     80     sp<LooperThread> mThread;
     81     bool mRunningLocally;
     82 
     83     // use a separate lock for reply handling, as it is always on another thread
     84     // use a central lock, however, to avoid creating a mutex for each reply
     85     Mutex mRepliesLock;
     86     Condition mRepliesCondition;
     87 
     88     // START --- methods used only by AMessage
     89 
     90     // posts a message on this looper with the given timeout
     91     void post(const sp<AMessage> &msg, int64_t delayUs);
     92 
     93     // creates a reply token to be used with this looper
     94     sp<AReplyToken> createReplyToken();
     95     // waits for a response for the reply token.  If status is OK, the response
     96     // is stored into the supplied variable.  Otherwise, it is unchanged.
     97     status_t awaitResponse(const sp<AReplyToken> &replyToken, sp<AMessage> *response);
     98     // posts a reply for a reply token.  If the reply could be successfully posted,
     99     // it returns OK. Otherwise, it returns an error value.
    100     status_t postReply(const sp<AReplyToken> &replyToken, const sp<AMessage> &msg);
    101 
    102     // END --- methods used only by AMessage
    103 
    104     bool loop();
    105 
    106     DISALLOW_EVIL_CONSTRUCTORS(ALooper);
    107 };
    108 
    109 } // namespace android
    110 
    111 #endif  // A_LOOPER_H_
    112