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#include <math.h>
#include "GPUDataBuffer.h"
namespace GPU
{
// 修改buffer数据要绑定到这个目标上，其他情况下用GetHandle()绑定到其他目标
// GL_COPY_READ_BUFFER
static const GLenum kBufferTarget = GL_COPY_WRITE_BUFFER;
DataBuffer::DataBuffer()
{
glGenBuffers(1, &m_Handle);
m_Size = 0;
}
DataBuffer::~DataBuffer()
{
glDeleteBuffers(1, &m_Handle);
}
void DataBuffer::Restore(int size, GLenum usage)
{
RestoreWithData(size, usage, 0);
}
void DataBuffer::RestoreWithData(int size, GLenum usage, const void* data)
{
glBindBuffer(kBufferTarget, m_Handle);
glBufferData(kBufferTarget, size, data, usage);
glBindBuffer(kBufferTarget, 0);
m_Size = size;
m_Usage = usage;
}
// glBufferSubData
// glMapBuffer
// glMapBufferRange (best one)
void DataBuffer::Upload(int offset, int size, const void* data)
{
glBindBuffer(kBufferTarget, m_Handle);
glBufferSubData(kBufferTarget, offset, size, data);
glBindBuffer(kBufferTarget, 0);
}
void* DataBuffer::Map(uint32 access)
{
glBindBuffer(kBufferTarget, m_Handle);
void* ptr = glMapBuffer(kBufferTarget, access);
glBindBuffer(kBufferTarget, 0);
return ptr;
}
void* DataBuffer::MapRange(int offset, int size, uint32 access)
{
glBindBuffer(kBufferTarget, m_Handle);
void* ptr = glMapBufferRange(kBufferTarget, offset, size, access);
glBindBuffer(kBufferTarget, 0);
return ptr;
}
void DataBuffer::FlushMapedRange(int offset, int size)
{
glBindBuffer(kBufferTarget, m_Handle);
glFlushMappedBufferRange(kBufferTarget, offset, size);
glBindBuffer(kBufferTarget, 0);
}
void DataBuffer::UnMap()
{
glBindBuffer(kBufferTarget, m_Handle);
glUnmapBuffer(kBufferTarget);
glBindBuffer(kBufferTarget, 0);
}
void DataBuffer::Orphan()
{
glBindBuffer(kBufferTarget, m_Handle);
glBufferData(kBufferTarget, 0, 0, GL_STREAM_DRAW);
glBindBuffer(kBufferTarget, 0);
}
//---------------------------------------------------------------------------------------
static bool IsBufferPoolCreated = false;
BufferPool::BufferPool()
:m_LiveBuffers()
{
Assert(!IsBufferPoolCreated);
IsBufferPoolCreated = true;
}
BufferPool::~BufferPool()
{
}
static const float kBufferAllocateWeight = 10.0f; //! Default weight for buffer allocation from scratch.
static const float kBufferSizeWeightFactor = 1.f / 8096.f; //!< Weight factor for size difference.
static const float kBufferUsageDiffWeight = 8.f; //!< Weight factor for usage difference.
static int ComputeBufferWeight(DataBuffer* buffer, int desiredSize, GLenum desiredUsage)
{
const int bufferSize = buffer->GetSize();
const GLenum bufferUsage = buffer->GetUsage();
if (bufferSize == 0)
return kBufferAllocateWeight;
const int sizeDiff = std::abs(bufferSize - desiredSize);
return float(sizeDiff)*kBufferSizeWeightFactor + ((bufferUsage != desiredUsage) ? kBufferUsageDiffWeight : 0.f);
}
DataBuffer* BufferPool::ClaimBuffer(int size, GLenum usage)
{
const float maxWeight = kBufferAllocateWeight;
const int maxCandidates = 5; // Number of potential candidates to consider actually.
const int sizeClass = GetSizeClass(size);
int numCandidates = 0; // Number of potential candidates considered
int bestBufferNdx = -1;
float bestWeight = std::numeric_limits<float>::infinity();
for (int idx = 0; idx < m_LiveBuffers[sizeClass].size(); ++idx)
{
DataBuffer* buffer = m_LiveBuffers[sizeClass][idx];
const float weight = ComputeBufferWeight(buffer, size, usage);
if (weight < maxWeight && weight < bestWeight)
{
bestWeight = weight;
bestBufferNdx = idx;
++numCandidates;
}
if (numCandidates >= maxCandidates)
break; // Do not try other buffers, sorry.
}
if (bestBufferNdx >= 0)
{
DataBuffer* selectedBuffer = m_LiveBuffers[sizeClass][bestBufferNdx];
if (bestBufferNdx + 1 != m_LiveBuffers[sizeClass].size())
std::swap(m_LiveBuffers[sizeClass][bestBufferNdx], m_LiveBuffers[sizeClass].back());
m_LiveBuffers[sizeClass].pop_back();
return selectedBuffer;
}
else
return new DataBuffer();
}
void BufferPool::ReleaseBuffer(DataBuffer* buffer)
{
InsertToLive(buffer);
}
void BufferPool::OnEndFrame()
{
UpdatePendingBuffersArray();
}
void BufferPool::UpdatePendingBuffersArray()
{
}
void BufferPool::InsertToLive(DataBuffer* buffer)
{
const int bufferSize = buffer->GetSize();
const int sizeClass = GetSizeClass(bufferSize);
m_LiveBuffers[sizeClass].push_back(buffer);
}
uint BufferPool::GetSizeClass(uint bufferSize)
{
for (int idx = 0; idx < kSizeClassCount; ++idx)
{
if (bufferSize < GetSizeClassLimit(idx))
return idx;
}
Assert(false);
return 0;
}
DataBuffer* ClaimBuffer(int size, GLenum usage)
{
return BufferPool::Instance()->ClaimBuffer(size, usage);
}
void ReleaseBuffer(DataBuffer* buffer)
{
BufferPool::Instance()->ReleaseBuffer(buffer);
}
int BufferPool::GetSizeClassLimit(int classNdx)
{
// (0, 2^10] 2^11 2^12 2^13 2^14 2^15 INT_MAX
return classNdx + 1 < kSizeClassCount ? (1 << (classNdx*kSizeClassStepLog2 + kSizeClassBaseLog2)) : INT_MAX;
}
}
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