nexttoward.c revision 25c28e83beb90e7c80452a7c818c5e6f73a07dc8
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * CDDL HEADER START
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * The contents of this file are subject to the terms of the
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Common Development and Distribution License (the "License").
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * You may not use this file except in compliance with the License.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Use is subject to license terms.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * nexttoward(x, y) delivers the next representable number after x
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * in the direction of y. If x and y are both zero, the result is
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * zero with the same sign as y. If either x or y is NaN, the result
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * If x != y and the result is infinite, overflow is raised; if
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * x != y and the result is subnormal or zero, underflow is raised.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * (This is wrong, but it's what C99 apparently wants.)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis unsigned i[2];
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis 0x00100000, 0,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis 0x7fe00000, 0,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtisextern enum fcc_type _Q_cmp(const long double *, const long double *);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis__nexttoward(double x, long double y) {
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis unsigned i[2];
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis unsigned i[4];
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis long double q;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis volatile double dummy;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * It would be somewhat more efficient to check for NaN and
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * zero operands before converting x to long double and then
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * to code the comparison in line rather than calling _Q_cmp.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * However, since this code probably won't get used much,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * I'm opting in favor of simplicity instead.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* check for each of four possible orderings */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis if (hx == 0) { /* x is zero; return zero with y's sign */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis } else if ((int)xx.i[0] >= 0) { /* x is positive */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis } else if ((int)xx.i[0] >= 0) { /* x is positive */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* raise exceptions as needed */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis unsigned i[2];
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis 0, 0x00100000,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis 0, 0x7fe00000,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis__nexttoward(double x, long double y) {
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis unsigned i[2];
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis volatile double dummy;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* check for each of four possible orderings */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return ((double) (lx + y));
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return ((double) y);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis } else if ((int)xx.i[1] >= 0) { /* x is positive */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis if (++xx.i[0] == 0)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis if (xx.i[0]-- == 0)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis } else if ((int)xx.i[1] >= 0) { /* x is positive */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis if (xx.i[0]-- == 0)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis if (++xx.i[0] == 0)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* raise exceptions as needed */