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1 
2 /*
3  * Copyright 2010 Google Inc.
4  *
5  * Use of this source code is governed by a BSD-style license that can be
6  * found in the LICENSE file.
7  */
8 
9 
10 #ifndef GrTemplates_DEFINED
11 #define GrTemplates_DEFINED
12 
13 #include "GrNoncopyable.h"
14 
15 /**
16  *  Use to cast a ptr to a different type, and maintain strict-aliasing
17  */
GrTCast(Src src)18 template <typename Dst, typename Src> Dst GrTCast(Src src) {
19     union {
20         Src src;
21         Dst dst;
22     } data;
23     data.src = src;
24     return data.dst;
25 }
26 
27 /**
28  * saves value of T* in and restores in destructor
29  * e.g.:
30  * {
31  *      GrAutoTPtrValueRestore<int*> autoCountRestore;
32  *      if (useExtra) {
33  *          autoCountRestore.save(&fCount);
34  *          fCount += fExtraCount;
35  *      }
36  *      ...
37  * }  // fCount is restored
38  */
39 template <typename T> class GrAutoTPtrValueRestore : public GrNoncopyable {
40 public:
GrAutoTPtrValueRestore()41     GrAutoTPtrValueRestore() : fPtr(NULL), fVal() {}
42 
GrAutoTPtrValueRestore(T * ptr)43     GrAutoTPtrValueRestore(T* ptr) {
44         fPtr = ptr;
45         if (NULL != ptr) {
46             fVal = *ptr;
47         }
48     }
49 
~GrAutoTPtrValueRestore()50     ~GrAutoTPtrValueRestore() {
51         if (NULL != fPtr) {
52             *fPtr = fVal;
53         }
54     }
55 
56     // restores previously saved value (if any) and saves value for passed T*
save(T * ptr)57     void save(T* ptr) {
58         if (NULL != fPtr) {
59             *fPtr = fVal;
60         }
61         fPtr = ptr;
62         fVal = *ptr;
63     }
64 private:
65     T* fPtr;
66     T  fVal;
67 };
68 
69 #endif
70