cosmopolitan/third_party/gdtoa/sum.c

/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8   -*-│
│ vi: set noet ft=c ts=8 sw=8 fenc=utf-8                                   :vi │
╚──────────────────────────────────────────────────────────────────────────────╝
│                                                                              │
│  The author of this software is David M. Gay.                                │
│  Please send bug reports to David M. Gay <dmg@acm.org>                       │
│                          or Justine Tunney <jtunney@gmail.com>               │
│                                                                              │
│  Copyright (C) 1998, 1999 by Lucent Technologies                             │
│  All Rights Reserved                                                         │
│                                                                              │
│  Permission to use, copy, modify, and distribute this software and           │
│  its documentation for any purpose and without fee is hereby                 │
│  granted, provided that the above copyright notice appear in all             │
│  copies and that both that the copyright notice and this                     │
│  permission notice and warranty disclaimer appear in supporting              │
│  documentation, and that the name of Lucent or any of its entities           │
│  not be used in advertising or publicity pertaining to                       │
│  distribution of the software without specific, written prior                │
│  permission.                                                                 │
│                                                                              │
│  LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,               │
│  INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.            │
│  IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY           │
│  SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES                   │
│  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER             │
│  IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,              │
│  ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF              │
│  THIS SOFTWARE.                                                              │
│                                                                              │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "third_party/gdtoa/gdtoa.internal.h"

Bigint *
__gdtoa_sum(Bigint *a, Bigint *b, ThInfo **PTI)
{
	Bigint *c;
	ULong carry, *xc, *xa, *xb, *xe, y;
	ULong z;
	if (a->wds < b->wds) {
		c = b; b = a; a = c;
	}
	c = __gdtoa_Balloc(a->k, PTI);
	c->wds = a->wds;
	carry = 0;
	xa = a->x;
	xb = b->x;
	xc = c->x;
	xe = xc + b->wds;
	do {
		y = (*xa & 0xffff) + (*xb & 0xffff) + carry;
		carry = (y & 0x10000) >> 16;
		z = (*xa++ >> 16) + (*xb++ >> 16) + carry;
		carry = (z & 0x10000) >> 16;
		Storeinc(xc, z, y);
	}
	while(xc < xe);
	xe += a->wds - b->wds;
	while(xc < xe) {
		y = (*xa & 0xffff) + carry;
		carry = (y & 0x10000) >> 16;
		z = (*xa++ >> 16) + carry;
		carry = (z & 0x10000) >> 16;
		Storeinc(xc, z, y);
	}
	if (carry) {
		if (c->wds == c->maxwds) {
			b = __gdtoa_Balloc(c->k + 1, PTI);
			Bcopy(b, c);
			__gdtoa_Bfree(c, PTI);
			c = b;
		}
		c->x[c->wds++] = 1;
	}
	return c;
}