1 // Copyright (C) 2014 The Android Open Source Project
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 
15 #include "emugl/common/smart_ptr.h"
16 
17 #ifdef _WIN32
18 #define WIN32_LEAN_AND_MEAN
19 #include <windows.h>
20 #endif
21 
22 namespace emugl {
23 
24 // Thread-safe atomic reference-counting type.
25 class RefCount {
26 public:
RefCount()27     RefCount() : mCount(1) {}
~RefCount()28     ~RefCount() {}
29 
30     // Technically not thread-safe, use only for testing.
count() const31     int count() const { return (int)mCount; }
32 
increment()33     void increment() {
34 #ifdef _WIN32
35         InterlockedIncrement(&mCount);
36 #else
37         __sync_fetch_and_add(&mCount, 1);
38 #endif
39     }
40 
decrement()41     bool decrement() {
42 #ifdef _WIN32
43         return InterlockedDecrement(&mCount) == 0;
44 #else
45         return __sync_add_and_fetch(&mCount, -1) == 0;
46 #endif
47     }
48 
49 private:
50 #ifdef _WIN32
51     LONG mCount;
52 #else
53     int mCount;
54 #endif
55 };
56 
57 
58 // SmartPtrBase implementation.
59 
SmartPtrBase(void * ptr)60 SmartPtrBase::SmartPtrBase(void* ptr) : mPtr(ptr), mRefCount(NULL) {
61     if (mPtr)
62         mRefCount = new RefCount();
63 }
64 
65 
SmartPtrBase(const SmartPtrBase & other)66 SmartPtrBase::SmartPtrBase(const SmartPtrBase& other)
67         : mPtr(other.mPtr), mRefCount(other.mRefCount) {
68     if (mRefCount)
69         mRefCount->increment();
70 }
71 
72 
getRefCount() const73 int SmartPtrBase::getRefCount() const {
74     return mRefCount ? mRefCount->count() : 0;
75 }
76 
77 
addRef()78 void SmartPtrBase::addRef() {
79     if (mRefCount)
80         mRefCount->increment();
81 }
82 
83 
copyFrom(const SmartPtrBase & other)84 void* SmartPtrBase::copyFrom(const SmartPtrBase& other) {
85     void* old_ptr = release();
86 
87     mPtr = other.mPtr;
88     mRefCount = other.mRefCount;
89     if (mRefCount)
90         mRefCount->increment();
91 
92     return old_ptr;
93 }
94 
95 
release()96 void* SmartPtrBase::release() {
97     void* old_ptr = mPtr;
98     RefCount* old_refcount = mRefCount;
99 
100     if (old_refcount) {
101         mPtr = NULL;
102         mRefCount = NULL;
103 
104         if (old_refcount->decrement()) {
105           delete old_refcount;
106           return old_ptr;
107         }
108     }
109 
110     return NULL;
111 }
112 
113 }  // namespace emugl
114