physxCAPI/physxCDLL/include/foundation/PxAlloca.h

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#ifndef PX_ALLOCA_H
#define PX_ALLOCA_H

#include "foundation/PxTempAllocator.h"

#if !PX_DOXYGEN
namespace physx
{
#endif
template <typename T, typename Alloc = PxTempAllocator>
class PxScopedPointer : private Alloc
{
  public:
	~PxScopedPointer()
	{
		if(mOwned)
			Alloc::deallocate(mPointer);
	}

	operator T*() const
	{
		return mPointer;
	}

	T* mPointer;
	bool mOwned;
};

#if !PX_DOXYGEN
} // namespace physx
#endif

  // Don't use inline for alloca !!!
#if PX_WINDOWS_FAMILY
#include <malloc.h>
#define PxAlloca(x) _alloca(x)
#elif PX_LINUX
#include <malloc.h>
#define PxAlloca(x) alloca(x)
#elif PX_APPLE_FAMILY
#include <alloca.h>
#define PxAlloca(x) alloca(x)
#elif PX_SWITCH
#include <malloc.h>
#define PxAlloca(x) alloca(x)
#endif

#define PxAllocaAligned(x, alignment) ((size_t(PxAlloca(x + alignment)) + (alignment - 1)) & ~size_t(alignment - 1))

/*! Stack allocation for \c count instances of \c type. Falling back to temp allocator if using more than 1kB. */
#define PX_ALLOCA(var, type, count)                                                                                    \
	physx::PxScopedPointer<type> var;                                                                            \
	{                                                                                                                  \
		uint32_t size = sizeof(type) * (count);                                                                        \
		var.mOwned = size > 1024;                                                                                      \
		if(var.mOwned)                                                                                                 \
			var.mPointer = reinterpret_cast<type*>(physx::PxTempAllocator().allocate(size, __FILE__, __LINE__)); \
		else                                                                                                           \
			var.mPointer = reinterpret_cast<type*>(PxAlloca(size));                                                    \
	}
#endif