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// Copyright (C) 2008-2012 NVIDIA Corporation.
// Copyright (C) 2019 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
#ifndef QSSGPERFRAMEALLOCATOR_H
#define QSSGPERFRAMEALLOCATOR_H
//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
#include <QtQuick3DRuntimeRender/private/qtquick3druntimerenderglobal_p.h>
QT_BEGIN_NAMESPACE
class QSSGPerFrameAllocator
{
struct FastAllocator
{
struct Slab;
enum : size_t {
ChunkSize = 8192*2,
Alignment = sizeof(void *),
SlabSize = ChunkSize - sizeof(Slab *),
MaxAlloc = ChunkSize/2 // don't go all the way up to SlabSize, or we'd almost always get a big hole
};
struct Slab {
Slab() = default;
Slab(Slab *previous)
{
previous->next = this;
}
Slab *next = nullptr;
quint8 data[SlabSize];
};
Q_STATIC_ASSERT(sizeof(Slab) == ChunkSize);
Q_STATIC_ASSERT(alignof(Slab) == Alignment);
Slab *first = nullptr;
Slab *current = nullptr;
size_t offset = 0;
FastAllocator()
{
first = current = new Slab;
}
~FastAllocator()
{
Slab *s = first;
while (s) {
Slab *n = s->next;
delete s;
s = n;
}
}
void *allocate(size_t size)
{
size = (size + Alignment - 1) & ~(Alignment - 1);
Q_ASSERT(size <= SlabSize);
Q_ASSERT(!(offset % Alignment));
size_t amountLeftInSlab = SlabSize - offset;
if (size > amountLeftInSlab) {
if (current->next)
current = current->next;
else
current = new Slab(current);
offset = 0;
}
quint8 *data = current->data + offset;
offset += size;
return data;
}
// only reset, so we can re-use the memory
void reset() { current = first; offset = 0; }
};
struct LargeAllocator
{
struct Slab {
Slab *next = nullptr;
};
Slab *current = nullptr;
LargeAllocator() {}
// Automatically deallocates everything that hasn't already been deallocated.
~LargeAllocator() { deallocateAll(); }
void deallocateAll()
{
while (current) {
Slab *n = current->next;
::free(current);
current = n;
}
current = nullptr;
}
void *allocate(size_t size)
{
quint8 *mem = reinterpret_cast<quint8 *>(::malloc(sizeof(Slab) + size));
Slab *s = reinterpret_cast<Slab *>(mem);
s->next = current;
current = s;
return mem + sizeof(Slab);
}
};
FastAllocator m_fastAllocator;
LargeAllocator m_largeAllocator;
public:
QSSGPerFrameAllocator() {}
inline void *allocate(size_t size)
{
if (size < FastAllocator::MaxAlloc)
return m_fastAllocator.allocate(size);
return m_largeAllocator.allocate(size);
}
void reset()
{
m_fastAllocator.reset();
m_largeAllocator.deallocateAll();
}
};
QT_END_NAMESPACE
#endif // QSSGPERFRAMEALLOCATOR_H
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