| /* |
| * Copyright 2020 Google LLC |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "src/gpu/GrRingBuffer.h" |
| |
| // Get offset into buffer that has enough space for size |
| // Returns fTotalSize if no space |
| size_t GrRingBuffer::getAllocationOffset(size_t size) { |
| // capture current state locally (because fTail could be overwritten by the completion handler) |
| size_t head, tail; |
| SkAutoSpinlock lock(fMutex); |
| head = fHead; |
| tail = fTail; |
| |
| // The head and tail indices increment without bound, wrapping with overflow, |
| // so we need to mod them down to the actual bounds of the allocation to determine |
| // which blocks are available. |
| size_t modHead = head & (fTotalSize - 1); |
| size_t modTail = tail & (fTotalSize - 1); |
| |
| bool full = (head != tail && modHead == modTail); |
| |
| if (full) { |
| return fTotalSize; |
| } |
| |
| // case 1: free space lies at the beginning and/or the end of the buffer |
| if (modHead >= modTail) { |
| // check for room at the end |
| if (fTotalSize - modHead < size) { |
| // no room at the end, check the beginning |
| if (modTail < size) { |
| // no room at the beginning |
| return fTotalSize; |
| } |
| // we are going to allocate from the beginning, adjust head to '0' position |
| head += fTotalSize - modHead; |
| modHead = 0; |
| } |
| // case 2: free space lies in the middle of the buffer, check for room there |
| } else if (modTail - modHead < size) { |
| // no room in the middle |
| return fTotalSize; |
| } |
| |
| fHead = GrAlignTo(head + size, fAlignment); |
| return modHead; |
| } |
| |
| GrRingBuffer::Slice GrRingBuffer::suballocate(size_t size) { |
| size_t offset = this->getAllocationOffset(size); |
| if (offset < fTotalSize) { |
| return { fBuffer, offset }; |
| } |
| |
| // Try to grow allocation (old allocation will age out). |
| fTotalSize *= 2; |
| fBuffer = this->createBuffer(fTotalSize); |
| SkASSERT(fBuffer); |
| SkAutoSpinlock lock(fMutex); |
| fHead = 0; |
| fTail = 0; |
| fGenID++; |
| offset = this->getAllocationOffset(size); |
| SkASSERT(offset < fTotalSize); |
| return { fBuffer, offset }; |
| } |
| |
| // used when current command buffer/command list is submitted |
| GrRingBuffer::SubmitData GrRingBuffer::startSubmit() { |
| SubmitData submitData; |
| SkAutoSpinlock lock(fMutex); |
| submitData.fBuffer = fBuffer; |
| submitData.fLastHead = fHead; |
| submitData.fGenID = fGenID; |
| return submitData; |
| } |
| |
| // used when current command buffer/command list is completed |
| void GrRingBuffer::finishSubmit(const GrRingBuffer::SubmitData& submitData) { |
| SkAutoSpinlock lock(fMutex); |
| if (submitData.fGenID == fGenID) { |
| fTail = submitData.fLastHead; |
| } |
| } |