1 /*
2  * Copyright 2020 Google LLC
3  *
4  * Use of this source code is governed by a BSD-style license that can be
5  * found in the LICENSE file.
6  */
7 
8 #ifndef GrRingBuffer_DEFINED
9 #define GrRingBuffer_DEFINED
10 
11 #include "src/gpu/GrGpuBuffer.h"
12 
13 #include <vector>
14 
15 class GrGpu;
16 
17 /**
18  * A wrapper for a GPU buffer that allocates slices in a continuous ring.
19  *
20  * It's assumed that suballocate and startSubmit are always called in the same thread,
21  * and that finishSubmit could be called in a separate thread.
22  */
23 class GrRingBuffer {
24 public:
GrRingBuffer(GrGpu * gpu,size_t size,size_t alignment,GrGpuBufferType intendedType)25     GrRingBuffer(GrGpu* gpu, size_t size, size_t alignment, GrGpuBufferType intendedType)
26         : fGpu(gpu)
27         , fTotalSize(size)
28         , fAlignment(alignment)
29         , fType(intendedType)
30         , fHead(0)
31         , fTail(0)
32         , fGenID(0) {
33         // We increment fHead and fTail without bound and let overflow handle any wrapping.
34         // Because of this, size needs to be a power of two.
35         SkASSERT(SkIsPow2(size));
36     }
37 
38     struct Slice {
39         GrGpuBuffer* fBuffer;
40         size_t fOffset;
41     };
42     Slice suballocate(size_t size);
43 
44     // Backends should call startSubmit() at submit time
45     void startSubmit(GrGpu*);
46 
size()47     size_t size() const { return fTotalSize; }
48 
49 private:
50     size_t getAllocationOffset(size_t size);
51     struct SubmitData {
52         GrRingBuffer* fOwner;
53         size_t fLastHead;
54         size_t fGenID;
55     };
56     static void FinishSubmit(void*);
57 
58     GrGpu* fGpu;
59     sk_sp<GrGpuBuffer> fCurrentBuffer;
60     std::vector<sk_sp<GrGpuBuffer>> fTrackedBuffers;  // all buffers we've used in this submit
61     size_t fTotalSize;
62     size_t fAlignment;
63     GrGpuBufferType fType;
64     size_t fHead;     // where we start allocating
65     size_t fTail;     // where we start deallocating
66     uint64_t fGenID;  // incremented when createBuffer is called
67 };
68 
69 #endif
70