haiku/headers/private/kernel/util/FixedWidthPointer.h

/*
 * Copyright 2012, Alex Smith, alex@alex-smith.me.uk.
 * Distributed under the terms of the MIT License.
 */
#ifndef KERNEL_UTIL_FIXED_WIDTH_POINTER_H
#define KERNEL_UTIL_FIXED_WIDTH_POINTER_H


#include <SupportDefs.h>


/*!
	\class FixedWidthPointer
	\brief Pointer class with fixed size (64-bit) storage.

	This class is a pointer-like class that uses a fixed size 64-bit storage.
	This is used to make kernel_args compatible (i.e. the same size) for both
	32-bit and 64-bit kernels.
*/
template<typename Type>
class FixedWidthPointer {
public:
	operator Type*() const
	{
		return (Type *)(addr_t)fValue;
	}

	operator addr_t() const
	{
		return (addr_t)fValue;
	}

	Type &operator*() const
	{
		return *(Type *)*this;
	}

	Type *operator->() const
	{
		return *this;
	}

	FixedWidthPointer &operator=(const FixedWidthPointer &p)
	{
		fValue = p.fValue;
		return *this;
	}

	FixedWidthPointer &operator=(Type *p)
	{
		fValue = (addr_t)p;
		return *this;
	}

	/*!
		Get the 64-bit pointer value.
		\return Pointer address.
	*/
	uint64 Get() const
	{
		return fValue;
	}

	/*!
		Set the 64-bit pointer value.
		\param addr New address for the pointer.
	*/
	void SetTo(uint64 addr)
	{
		fValue = addr;
	}
private:
	uint64 fValue;
} _PACKED;


// Specialization for void pointers, can be converted to another pointer type.
template<>
class FixedWidthPointer<void> {
public:
	operator void*() const
	{
		return (void *)(addr_t)fValue;
	}

	template<typename OtherType>
	operator OtherType*() const
	{
		return (OtherType *)(addr_t)fValue;
	}

	operator addr_t() const
	{
		return (addr_t)fValue;
	}

	FixedWidthPointer &operator=(const FixedWidthPointer &p)
	{
		fValue = p.fValue;
		return *this;
	}

	FixedWidthPointer &operator=(void *p)
	{
		fValue = (addr_t)p;
		return *this;
	}

	uint64 Get() const
	{
		return fValue;
	}

	void SetTo(uint64 addr)
	{
		fValue = addr;
	}
private:
	uint64 fValue;
} _PACKED;


#endif	/* KERNEL_UTIL_FIXED_WIDTH_POINTER_H */