cadd.c

来自「SecuDe是一个由安全应用程序接口组成,对验证机制、证件处理、PEM、X.40」· C语言 代码 · 共 47 行

/*
 *  SecuDE Release 4.1 (GMD)
 */
/********************************************************************
 * Copyright (C) 1991, GMD. All rights reserved.                    *
 *                                                                  *
 *                                                                  *
 *                         NOTICE                                   *
 *                                                                  *
 *    Acquisition, use, and distribution of this module             *
 *    and related materials are subject to restrictions             *
 *    mentioned in each volume of the documentation.                *
 *                                                                  *
 ********************************************************************/

/*	addition/subtraktion mit carry
 *
 *	cadd(A,B,A+B,carry) RETURNS carry
 */

#include	"arithmetic.h"


int 
_cadd(opa, opb, opa_b, carry)
	L_NUMBER        opa, opb;
	register L_NUMBER *opa_b, carry;
{
	register L_NUMBER zulu = opb + carry;
	register L_NUMBER sum;

	/*
	 * NOTE: optimized to achieve best result for subtraktion of small
	 * int
	 */

	if (zulu) {		/* means no carry at all */
		sum = opa + zulu;
		zulu |= opa;
		*opa_b = sum;
		return (zulu > sum);
	} else {		/* propagate carry */
		*opa_b = opa;
		return carry;
	}
}