/* $Id$ */

/** @file overflowsafe_type.hpp An overflow safe integer-like type. */

#ifndef OVERFLOWSAFE_TYPE_HPP

#define OVERFLOWSAFE_TYPE_HPP

/**

 * Overflow safe template for integers, i.e. integers that will never overflow

 * you multiply the maximum value with 2, or add 2, or substract somethng from

 * the minimum value, etc.

 * @param T     the type these integers are stored with.

 * @param T_MAX the maximum value for the integers.

 * @param T_MIN the minimum value for the integers.

 */

template <class T, T T_MAX, T T_MIN>

class OverflowSafeInt

{

private:

	/** The non-overflow safe backend to store the value in. */

	T m_value;

public:

	OverflowSafeInt() : m_value(0) { }

	OverflowSafeInt(const OverflowSafeInt& other) { this->m_value = other.m_value; }

	OverflowSafeInt(const int64 int_)             { this->m_value = int_; }

	FORCEINLINE OverflowSafeInt& operator = (const OverflowSafeInt& other) { this->m_value = other.m_value; return *this; }

	FORCEINLINE OverflowSafeInt operator - () const { return OverflowSafeInt(-this->m_value); }

	/**

	 * Safe implementation of addition.

	 * @param other the amount to add

	 * @note when the addition would yield more than T_MAX (or less than T_MIN),

	 *       it will be T_MAX (respectively T_MIN).

	 */

	FORCEINLINE OverflowSafeInt& operator += (const OverflowSafeInt& other)

	{

		if ((T_MAX - abs(other.m_value)) < abs(this->m_value) &&

				(this->m_value < 0) == (other.m_value < 0)) {

			this->m_value = (this->m_value < 0) ? T_MIN : T_MAX ;

		} else {

			this->m_value += other.m_value;

		}

		return *this;

	}

	/* Operators for addition and substraction */

	FORCEINLINE OverflowSafeInt  operator +  (const OverflowSafeInt& other) const { OverflowSafeInt result = *this; result += other; return result; }

	FORCEINLINE OverflowSafeInt  operator +  (const int              other) const { OverflowSafeInt result = *this; result += (int64)other; return result; }

	FORCEINLINE OverflowSafeInt  operator +  (const uint             other) const { OverflowSafeInt result = *this; result += (int64)other; return result; }

	FORCEINLINE OverflowSafeInt& operator -= (const OverflowSafeInt& other)       { return *this += (-other); }

	FORCEINLINE OverflowSafeInt  operator -  (const OverflowSafeInt& other) const { OverflowSafeInt result = *this; result -= other; return result; }

	FORCEINLINE OverflowSafeInt  operator -  (const int              other) const { OverflowSafeInt result = *this; result -= (int64)other; return result; }