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#include "src/gpu/GrRingBuffer.h"
9
10#include "src/gpu/GrContextPriv.h"
11#include "src/gpu/GrGpu.h"
12#include "src/gpu/GrResourceProvider.h"
13
14// Get offset into buffer that has enough space for size
15// Returns fTotalSize if no space
16size_t GrRingBuffer::getAllocationOffset(size_t size) {
17 // capture current state locally (because fTail could be overwritten by the completion handler)
18 size_t head, tail;
19 head = fHead;
20 tail = fTail;
21
22 // The head and tail indices increment without bound, wrapping with overflow,
23 // so we need to mod them down to the actual bounds of the allocation to determine
24 // which blocks are available.
25 size_t modHead = head & (fTotalSize - 1);
26 size_t modTail = tail & (fTotalSize - 1);
27
28 bool full = (head != tail && modHead == modTail);
29
30 if (full) {
31 return fTotalSize;
32 }
33
34 // case 1: free space lies at the beginning and/or the end of the buffer
35 if (modHead >= modTail) {
36 // check for room at the end
37 if (fTotalSize - modHead < size) {
38 // no room at the end, check the beginning
39 if (modTail < size) {
40 // no room at the beginning
41 return fTotalSize;
42 }
43 // we are going to allocate from the beginning, adjust head to '0' position
44 head += fTotalSize - modHead;
45 modHead = 0;
46 }
47 // case 2: free space lies in the middle of the buffer, check for room there
48 } else if (modTail - modHead < size) {
49 // no room in the middle
50 return fTotalSize;
51 }
52
53 fHead = GrAlignTo(head + size, fAlignment);
54 return modHead;
55}
56
57GrRingBuffer::Slice GrRingBuffer::suballocate(size_t size) {
58 if (fCurrentBuffer) {
59 size_t offset = this->getAllocationOffset(size);
60 if (offset < fTotalSize) {
61 return { fCurrentBuffer.get(), offset };
62 }
63
64 // Try to grow allocation (old allocation will age out).
65 fTotalSize *= 2;
66 }
67
68 GrResourceProvider* resourceProvider = fGpu->getContext()->priv().resourceProvider();
69 fCurrentBuffer = resourceProvider->createBuffer(fTotalSize, fType, kDynamic_GrAccessPattern);
70
71 SkASSERT(fCurrentBuffer);
72 fTrackedBuffers.push_back(fCurrentBuffer);
73 fHead = 0;
74 fTail = 0;
75 fGenID++;
76 size_t offset = this->getAllocationOffset(size);
77 SkASSERT(offset < fTotalSize);
78 return { fCurrentBuffer.get(), offset };
79}
80
81// used when current command buffer/command list is submitted
82void GrRingBuffer::startSubmit(GrGpu* gpu) {
83 for (unsigned int i = 0; i < fTrackedBuffers.size(); ++i) {
84 gpu->takeOwnershipOfBuffer(std::move(fTrackedBuffers[i]));
85 }
86 fTrackedBuffers.clear();
87 // add current buffer to be tracked for next submit
88 fTrackedBuffers.push_back(fCurrentBuffer);
89
90 SubmitData* submitData = new SubmitData();
91 submitData->fOwner = this;
92 submitData->fLastHead = fHead;
93 submitData->fGenID = fGenID;
94 gpu->addFinishedProc(FinishSubmit, submitData);
95}
96
97// used when current command buffer/command list is completed
98void GrRingBuffer::FinishSubmit(void* finishedContext) {
99 GrRingBuffer::SubmitData* submitData = (GrRingBuffer::SubmitData*)finishedContext;
100 if (submitData && submitData->fOwner && submitData->fGenID == submitData->fOwner->fGenID) {
101 submitData->fOwner->fTail = submitData->fLastHead;
102 submitData->fOwner = nullptr;
103 }
104 delete submitData;
105}
106