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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 #include <media/stagefright/foundation/AHierarchicalStateMachine.h>
     18 
     19 #include <media/stagefright/foundation/ADebug.h>
     20 #include <media/stagefright/foundation/AMessage.h>
     21 #include <utils/Vector.h>
     22 
     23 namespace android {
     24 
     25 AState::AState(const sp<AState> &parentState)
     26     : mParentState(parentState) {
     27 }
     28 
     29 AState::~AState() {
     30 }
     31 
     32 sp<AState> AState::parentState() {
     33     return mParentState;
     34 }
     35 
     36 void AState::stateEntered() {
     37 }
     38 
     39 void AState::stateExited() {
     40 }
     41 
     42 ////////////////////////////////////////////////////////////////////////////////
     43 
     44 AHierarchicalStateMachine::AHierarchicalStateMachine() {
     45 }
     46 
     47 AHierarchicalStateMachine::~AHierarchicalStateMachine() {
     48 }
     49 
     50 void AHierarchicalStateMachine::onMessageReceived(const sp<AMessage> &msg) {
     51     sp<AState> save = mState;
     52 
     53     sp<AState> cur = mState;
     54     while (cur != NULL && !cur->onMessageReceived(msg)) {
     55         // If you claim not to have handled the message you shouldn't
     56         // have called setState...
     57         CHECK(save == mState);
     58 
     59         cur = cur->parentState();
     60     }
     61 
     62     if (cur != NULL) {
     63         return;
     64     }
     65 
     66     ALOGW("Warning message %s unhandled in root state.",
     67          msg->debugString().c_str());
     68 }
     69 
     70 void AHierarchicalStateMachine::changeState(const sp<AState> &state) {
     71     if (state == mState) {
     72         // Quick exit for the easy case.
     73         return;
     74     }
     75 
     76     Vector<sp<AState> > A;
     77     sp<AState> cur = mState;
     78     for (;;) {
     79         A.push(cur);
     80         if (cur == NULL) {
     81             break;
     82         }
     83         cur = cur->parentState();
     84     }
     85 
     86     Vector<sp<AState> > B;
     87     cur = state;
     88     for (;;) {
     89         B.push(cur);
     90         if (cur == NULL) {
     91             break;
     92         }
     93         cur = cur->parentState();
     94     }
     95 
     96     // Remove the common tail.
     97     while (A.size() > 0 && B.size() > 0 && A.top() == B.top()) {
     98         A.pop();
     99         B.pop();
    100     }
    101 
    102     mState = state;
    103 
    104     for (size_t i = 0; i < A.size(); ++i) {
    105         A.editItemAt(i)->stateExited();
    106     }
    107 
    108     for (size_t i = B.size(); i-- > 0;) {
    109         B.editItemAt(i)->stateEntered();
    110     }
    111 }
    112 
    113 }  // namespace android
    114