1/****************************************************************
 2
 3The author of this software is David M. Gay.
 4
 5Copyright (C) 1998, 1999 by Lucent Technologies
 6All Rights Reserved
 7
 8Permission to use, copy, modify, and distribute this software and
 9its documentation for any purpose and without fee is hereby
10granted, provided that the above copyright notice appear in all
11copies and that both that the copyright notice and this
12permission notice and warranty disclaimer appear in supporting
13documentation, and that the name of Lucent or any of its entities
14not be used in advertising or publicity pertaining to
15distribution of the software without specific, written prior
16permission.
17
18LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
19INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
20IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY
21SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
22WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
23IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
24ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
25THIS SOFTWARE.
26
27****************************************************************/
28
29/* Please send bug reports to David M. Gay (dmg at acm dot org,
30 * with " at " changed at "@" and " dot " changed to ".").	*/
31
32#include "gdtoaimp.h"
33
34double ulp (dbl_union *x)
35{
36	Long L;
37	union _dbl_union a;
38
39	L = (word0(x) & Exp_mask) - (P-1)*Exp_msk1;
40#ifndef Sudden_Underflow
41	if (L > 0) {
42#endif
43		word0(&a) = L;
44		word1(&a) = 0;
45#ifndef Sudden_Underflow
46	}
47	else {
48		L = -L >> Exp_shift;
49		if (L < Exp_shift) {
50			word0(&a) = 0x80000 >> L;
51			word1(&a) = 0;
52		}
53		else {
54			word0(&a) = 0;
55			L -= Exp_shift;
56			word1(&a) = L >= 31 ? 1 : 1 << (31 - L);
57		}
58	}
59#endif
60	return dval(&a);
61}