NvFlowReadbackBuffer.h

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// Copyright (c) 2014-2022 NVIDIA Corporation. All rights reserved.
 
#pragma once
 
#include "NvFlowContext.h"
#include "NvFlowArray.h"
 
struct NvFlowReadbackBufferInstance
{
    NvFlowBuffer* buffer = nullptr;
    NvFlowUint64 bufferSizeInBytes = 0llu;
    NvFlowBool32 isActive = NV_FLOW_FALSE;
    NvFlowUint64 completedFrame = ~0llu;
    NvFlowUint64 completedGlobalFrame = ~0llu;
    NvFlowUint64 version = ~0llu;
    NvFlowUint64 validNumBytes = 0llu;
};
 
struct NvFlowReadbackBuffer
{
    NvFlowContextInterface* contextInterface = nullptr;
    NvFlowUint64 versionCounter = 0llu;
 
    NvFlowArray<NvFlowReadbackBufferInstance, 8u> buffers;
    NvFlowArray<NvFlowUint64, 8u> activeBuffers;
};
 
NV_FLOW_INLINE void NvFlowReadbackBuffer_init(NvFlowContextInterface* contextInterface, NvFlowContext* context, NvFlowReadbackBuffer* ptr)
{
    ptr->contextInterface = contextInterface;
}
 
NV_FLOW_INLINE void NvFlowReadbackBuffer_destroy(NvFlowContext* context, NvFlowReadbackBuffer* ptr)
{
    for (NvFlowUint idx = 0u; idx < ptr->buffers.size; idx++)
    {
        if (ptr->buffers[idx].buffer)
        {
            ptr->contextInterface->destroyBuffer(context, ptr->buffers[idx].buffer);
            ptr->buffers[idx].buffer = nullptr;
        }
    }
    ptr->buffers.size = 0u;
}
 
struct NvFlowReadbackBufferCopyRange
{
    NvFlowUint64 offset;
    NvFlowUint64 numBytes;
};
 
NV_FLOW_INLINE void NvFlowReadbackBuffer_copyN(NvFlowContext* context, NvFlowReadbackBuffer* ptr, NvFlowUint64 numBytes, NvFlowBufferTransient* src, const NvFlowReadbackBufferCopyRange* copyRanges, NvFlowUint copyRangeCount, NvFlowUint64* pOutVersion)
{
    // find inactive buffer, create as needed
    NvFlowUint64 bufferIdx = 0u;
    for (; bufferIdx < ptr->buffers.size; bufferIdx++)
    {
        if (!ptr->buffers[bufferIdx].isActive)
        {
            break;
        }
    }
    if (bufferIdx == ptr->buffers.size)
    {
        bufferIdx = ptr->buffers.allocateBack();
    }
    NvFlowReadbackBufferInstance* inst = &ptr->buffers[bufferIdx];
    
    // resize buffer as needed
    if (inst->buffer && inst->bufferSizeInBytes < numBytes)
    {
        ptr->contextInterface->destroyBuffer(context, inst->buffer);
        inst->buffer = nullptr;
        inst->bufferSizeInBytes = 0llu;
    }
    if (!inst->buffer)
    {
        NvFlowBufferDesc bufDesc = {};
        bufDesc.usageFlags = eNvFlowBufferUsage_bufferCopyDst;
        bufDesc.format = eNvFlowFormat_unknown;
        bufDesc.structureStride = 0u;
        bufDesc.sizeInBytes = 65536u;
        while (bufDesc.sizeInBytes < numBytes)
        {
            bufDesc.sizeInBytes *= 2u;
        }
 
        inst->buffer = ptr->contextInterface->createBuffer(context, eNvFlowMemoryType_readback, &bufDesc);
        inst->bufferSizeInBytes = bufDesc.sizeInBytes;
    }
 
    // set active state
    ptr->versionCounter++;
    inst->isActive = NV_FLOW_TRUE;
    inst->completedFrame = ptr->contextInterface->getCurrentFrame(context);
    inst->completedGlobalFrame = ptr->contextInterface->getCurrentGlobalFrame(context);
    inst->version = ptr->versionCounter;
    inst->validNumBytes = numBytes;
    if (pOutVersion)
    {
        *pOutVersion = inst->version;
    }
 
    // copy
    NvFlowBufferTransient* dst = ptr->contextInterface->registerBufferAsTransient(context, inst->buffer);
    for (NvFlowUint copyRangeIdx = 0u; copyRangeIdx < copyRangeCount; copyRangeIdx++)
    {
        NvFlowPassCopyBufferParams copyParams = {};
        copyParams.srcOffset = copyRanges[copyRangeIdx].offset;
        copyParams.dstOffset = copyRanges[copyRangeIdx].offset;
        copyParams.numBytes = copyRanges[copyRangeIdx].numBytes;
        copyParams.src = src;
        copyParams.dst = dst;
 
        copyParams.debugLabel = "ReadbackBufferCopy";
 
        ptr->contextInterface->addPassCopyBuffer(context, &copyParams);
    }
    if (copyRangeCount == 0u)
    {
        NvFlowPassCopyBufferParams copyParams = {};
        copyParams.srcOffset = 0llu;
        copyParams.dstOffset = 0llu;
        copyParams.numBytes = 0llu;
        copyParams.src = src;
        copyParams.dst = dst;
 
        copyParams.debugLabel = "ReadbackBufferCopy";
 
        ptr->contextInterface->addPassCopyBuffer(context, &copyParams);
    }
 
    // push on active queue
    ptr->activeBuffers.pushBack(bufferIdx);
}
 
NV_FLOW_INLINE void NvFlowReadbackBuffer_copy(NvFlowContext* context, NvFlowReadbackBuffer* ptr, NvFlowUint64 numBytes, NvFlowBufferTransient* src, NvFlowUint64* pOutVersion)
{
    NvFlowReadbackBufferCopyRange copyRange = { 0llu, numBytes };
    NvFlowReadbackBuffer_copyN(context, ptr, numBytes, src, &copyRange, 1u, pOutVersion);
}
 
NV_FLOW_INLINE void NvFlowReadbackBuffer_flush(NvFlowContext* context, NvFlowReadbackBuffer* ptr)
{
    // flush queue
    NvFlowUint completedCount = 0u;
    NvFlowUint64 lastFenceCompleted = ptr->contextInterface->getLastFrameCompleted(context);
    for (NvFlowUint activeBufferIdx = 0u; activeBufferIdx < ptr->activeBuffers.size; activeBufferIdx++)
    {
        if (ptr->buffers[ptr->activeBuffers[activeBufferIdx]].completedFrame > lastFenceCompleted)
        {
            break;
        }
        completedCount++;
    }
    NvFlowUint popCount = completedCount >= 2u ? completedCount - 1u : 0u;
    if (popCount > 0u)
    {
        for (NvFlowUint activeBufferIdx = 0u; activeBufferIdx < popCount; activeBufferIdx++)
        {
            ptr->buffers[ptr->activeBuffers[activeBufferIdx]].isActive = NV_FLOW_FALSE;
        }
        // compact
        for (NvFlowUint activeBufferIdx = popCount; activeBufferIdx < ptr->activeBuffers.size; activeBufferIdx++)
        {
            ptr->activeBuffers[activeBufferIdx - popCount] = ptr->activeBuffers[activeBufferIdx];
        }
        ptr->activeBuffers.size = ptr->activeBuffers.size - popCount;
    }
}
 
NV_FLOW_INLINE NvFlowUint NvFlowReadbackBuffer_getActiveCount(NvFlowContext* context, NvFlowReadbackBuffer* ptr)
{
    return (NvFlowUint)ptr->activeBuffers.size;
}
 
NV_FLOW_INLINE NvFlowUint64 NvFlowReadbackBuffer_getCompletedGlobalFrame(NvFlowContext* context, NvFlowReadbackBuffer* ptr, NvFlowUint activeIdx)
{
    if (activeIdx < ptr->activeBuffers.size)
    {
        return ptr->buffers[ptr->activeBuffers[activeIdx]].completedGlobalFrame;
    }
    return ~0llu;
}
 
NV_FLOW_INLINE void* NvFlowReadbackBuffer_map(NvFlowContext* context, NvFlowReadbackBuffer* ptr, NvFlowUint activeIdx, NvFlowUint64* pOutVersion, NvFlowUint64* pNumBytes)
{
    if (activeIdx > ptr->activeBuffers.size)
    {
        if (pOutVersion)
        {
            *pOutVersion = 0llu;
        }
        if (pNumBytes)
        {
            *pNumBytes = 0llu;
        }
        return nullptr;
    }
 
    NvFlowReadbackBufferInstance* inst = &ptr->buffers[ptr->activeBuffers[activeIdx]];
    if (pOutVersion)
    {
        *pOutVersion = inst->version;
    }
    if (pNumBytes)
    {
        *pNumBytes = inst->validNumBytes;
    }
    return ptr->contextInterface->mapBuffer(context, inst->buffer);
}
 
NV_FLOW_INLINE void* NvFlowReadbackBuffer_mapLatest(NvFlowContext* context, NvFlowReadbackBuffer* ptr, NvFlowUint64* pOutVersion, NvFlowUint64* pNumBytes)
{
    NvFlowReadbackBuffer_flush(context, ptr);
 
    NvFlowUint64 lastFenceCompleted = ptr->contextInterface->getLastFrameCompleted(context);
    bool shouldMap = true;
    if (ptr->activeBuffers.size > 0u)
    {
        if (ptr->buffers[ptr->activeBuffers[0u]].completedFrame > lastFenceCompleted)
        {
            shouldMap = false;
        }
    }
    else if (ptr->buffers[ptr->activeBuffers[0u]].completedFrame > lastFenceCompleted)
    {
        shouldMap = false;
    }
    if (!shouldMap)
    {
        if (pOutVersion)
        {
            *pOutVersion = 0llu;
        }
        if (pNumBytes)
        {
            *pNumBytes = 0llu;
        }
        return nullptr;
    }
 
    return NvFlowReadbackBuffer_map(context, ptr, 0u, pOutVersion, pNumBytes);
}
 
NV_FLOW_INLINE void NvFlowReadbackBuffer_unmap(NvFlowContext* context, NvFlowReadbackBuffer* ptr, NvFlowUint activeIdx)
{
    if (activeIdx < ptr->activeBuffers.size)
    {
        NvFlowReadbackBufferInstance* inst = &ptr->buffers[ptr->activeBuffers[activeIdx]];
        ptr->contextInterface->unmapBuffer(context, inst->buffer);
    }
}
 
NV_FLOW_INLINE void NvFlowReadbackBuffer_unmapLatest(NvFlowContext* context, NvFlowReadbackBuffer* ptr)
{
    NvFlowReadbackBuffer_unmap(context, ptr, 0u);
}