michael@0: /*
michael@0:  * Copyright 2010 Google Inc.
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: #ifndef GrTemplates_DEFINED
michael@0: #define GrTemplates_DEFINED
michael@0: 
michael@0: #include "SkTypes.h"
michael@0: 
michael@0: /**
michael@0:  *  Use to cast a ptr to a different type, and maintain strict-aliasing
michael@0:  */
michael@0: template <typename Dst, typename Src> Dst GrTCast(Src src) {
michael@0:     union {
michael@0:         Src src;
michael@0:         Dst dst;
michael@0:     } data;
michael@0:     data.src = src;
michael@0:     return data.dst;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * takes a T*, saves the value it points to,  in and restores the value in the
michael@0:  * destructor
michael@0:  * e.g.:
michael@0:  * {
michael@0:  *      GrAutoTRestore<int*> autoCountRestore;
michael@0:  *      if (useExtra) {
michael@0:  *          autoCountRestore.reset(&fCount);
michael@0:  *          fCount += fExtraCount;
michael@0:  *      }
michael@0:  *      ...
michael@0:  * }  // fCount is restored
michael@0:  */
michael@0: template <typename T> class GrAutoTRestore : public SkNoncopyable {
michael@0: public:
michael@0:     GrAutoTRestore() : fPtr(NULL), fVal() {}
michael@0: 
michael@0:     GrAutoTRestore(T* ptr) {
michael@0:         fPtr = ptr;
michael@0:         if (NULL != ptr) {
michael@0:             fVal = *ptr;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     ~GrAutoTRestore() {
michael@0:         if (NULL != fPtr) {
michael@0:             *fPtr = fVal;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     // restores previously saved value (if any) and saves value for passed T*
michael@0:     void reset(T* ptr) {
michael@0:         if (NULL != fPtr) {
michael@0:             *fPtr = fVal;
michael@0:         }
michael@0:         fPtr = ptr;
michael@0:         fVal = *ptr;
michael@0:     }
michael@0: private:
michael@0:     T* fPtr;
michael@0:     T  fVal;
michael@0: };
michael@0: 
michael@0: #endif