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      1 /*
      2     Copyright 2010 Google Inc.
      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 
     18 #ifndef GrRefCnt_DEFINED
     19 #define GrRefCnt_DEFINED
     20 
     21 #include "GrTypes.h"
     22 #include "GrNoncopyable.h"
     23 
     24 /**
     25  *  Base class for reference counting. When an object is first instantiated,
     26  *  its reference count is 1. If the object may be null, use GrSafeRef() and
     27  *  GrSafeUnref().
     28  *
     29  *  It is an error (though only checked for in the debug build) to call unref()
     30  *  such that the reference count becomes 0.
     31  */
     32 class GR_API GrRefCnt : GrNoncopyable {
     33 public:
     34             GrRefCnt() : fRefCnt(1) {}
     35     virtual ~GrRefCnt() {
     36         GrAssert(1 == fRefCnt);
     37 #if GR_DEBUG
     38         fRefCnt = 0;    // force validate() to trigger if called afterwards
     39 #endif
     40     }
     41 
     42     int32_t refcnt() const { return fRefCnt; }
     43 
     44     void ref() const {
     45         GrAssert(fRefCnt > 0);
     46         ++fRefCnt;
     47     }
     48 
     49     void unref() const {
     50         GrAssert(fRefCnt > 0);
     51         if (1 == fRefCnt) {
     52             delete this;
     53         } else {
     54             --fRefCnt;
     55         }
     56     }
     57 
     58 #if GR_DEBUG
     59     void validate() const {
     60         GrAssert(fRefCnt > 0);
     61     }
     62 #else
     63     void validate() const {}
     64 #endif
     65 
     66 private:
     67     mutable int32_t fRefCnt;
     68 };
     69 
     70 ///////////////////////////////////////////////////////////////////////////////
     71 
     72 /**
     73  *  Call with instance/subclass of GrRefCnt. This does nothing if obj is null,
     74  *  but otherwise it calls ref().
     75  */
     76 static inline void GrSafeRef(const GrRefCnt* obj) {
     77     if (obj) {
     78         obj->ref();
     79     }
     80 }
     81 
     82 /**
     83  *  Call with instance/subclass of GrRefCnt. This does nothing if obj is null,
     84  *  but otherwise it calls unref().
     85  */
     86 static inline void GrSafeUnref(const GrRefCnt* obj) {
     87     if (obj) {
     88         obj->unref();
     89     }
     90 }
     91 
     92 /**
     93  *  Assigns src to dst, checking for NULLs in each, and correctly incrementing
     94  *  the reference count of src, and decrementing the reference count of dst
     95  */
     96 template<typename T>
     97 static inline void GrSafeAssign(T*& dst, T* src) {
     98     if (src) {
     99         src->ref();
    100     }
    101     if (dst) {
    102         dst->unref();
    103     }
    104     dst = src;
    105 }
    106 
    107 template<typename T>
    108 static inline void GrSafeSetNull(T*& obj) {
    109     if (NULL != obj) {
    110         obj->unref();
    111         obj = NULL;
    112     }
    113 }
    114 
    115 ///////////////////////////////////////////////////////////////////////////////
    116 
    117 class GrAutoRef : GrNoncopyable {
    118 public:
    119     GrAutoRef(GrRefCnt* obj) : fObj(obj) { GrSafeRef(obj); }
    120     ~GrAutoRef() { GrSafeUnref(fObj); }
    121 private:
    122     GrRefCnt* fObj;
    123 };
    124 
    125 class GrAutoUnref : GrNoncopyable {
    126 public:
    127     GrAutoUnref(GrRefCnt* obj) : fObj(obj) {}
    128     ~GrAutoUnref() { GrSafeUnref(fObj); }
    129 private:
    130     GrRefCnt* fObj;
    131 };
    132 
    133 #endif
    134 
    135