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      1 
      2 /*
      3  * Copyright 2015 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 GrTransferBuffer_DEFINED
     11 #define GrTransferBuffer_DEFINED
     12 
     13 #include "GrGpuResource.h"
     14 
     15 class GrTransferBuffer : public GrGpuResource {
     16 public:
     17     /**
     18     * Maps the buffer to be written by the CPU.
     19     *
     20     * The previous content of the buffer is invalidated. It is an error
     21     * to transfer to or from the buffer while it is mapped. It is an error to
     22     * call map on an already mapped buffer. Must be matched by an unmap() call.
     23     * Currently only one map at a time is supported (no nesting of map/unmap).
     24     *
     25     * Note that buffer mapping does not go through GrContext and therefore is
     26     * not serialized with other operations.
     27     *
     28     * @return a pointer to the data or nullptr if the map fails.
     29     */
     30     void* map() { return (fMapPtr = this->onMap()); }
     31 
     32     /**
     33     * Unmaps the buffer.
     34     *
     35     * The pointer returned by the previous map call will no longer be valid.
     36     */
     37     void unmap() {
     38         SkASSERT(fMapPtr);
     39         this->onUnmap();
     40         fMapPtr = nullptr;
     41     }
     42 
     43     /**
     44     * Returns the same ptr that map() returned at time of map or nullptr if the
     45     * is not mapped.
     46     *
     47     * @return ptr to mapped buffer data or nullptr if buffer is not mapped.
     48     */
     49     void* mapPtr() const { return fMapPtr; }
     50 
     51     /**
     52     Queries whether the buffer has been mapped.
     53 
     54     @return true if the buffer is mapped, false otherwise.
     55     */
     56     bool isMapped() const { return SkToBool(fMapPtr); }
     57 
     58 protected:
     59     GrTransferBuffer(GrGpu* gpu, size_t gpuMemorySize)
     60         : INHERITED(gpu, kUncached_LifeCycle)
     61         , fGpuMemorySize(gpuMemorySize) {
     62     }
     63 
     64 private:
     65     virtual size_t onGpuMemorySize() const { return fGpuMemorySize; }
     66 
     67     virtual void* onMap() = 0;
     68     virtual void  onUnmap() = 0;
     69 
     70     void*    fMapPtr;
     71     size_t   fGpuMemorySize;
     72 
     73     typedef GrGpuResource INHERITED;
     74 };
     75 
     76 #endif
     77