1 /*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 *
11 * From: @(#)s_floor.c 5.1 93/09/24
12 */
13
14 /*
15 * truncl(x)
16 * Return x rounded toward 0 to integral value
17 * Method:
18 * Bit twiddling.
19 * Exception:
20 * Inexact flag raised if x not equal to truncl(x).
21 */
22
23
24
25
26 #ifdef LDBL_IMPLICIT_NBIT
27 #define MANH_SIZE (EXT_FRACHBITS + 1)
28 #else
29 #define MANH_SIZE EXT_FRACHBITS
30 #endif
31
32 static const long double huge = 1.0e300L;
33 static const float zero[] = { 0.0, -0.0 };
34
35 long double
truncl(long double x)36 truncl(long double x)
37 {
38 int e, es;
39 uint32_t ix0, ix1;
40
41 GET_LDOUBLE_WORDS(es,ix0,ix1,x);
42 e = (es&0x7fff) - LDBL_MAX_EXP + 1;
43
44 if (e < MANH_SIZE - 1) {
45 if (e < 0) { /* raise inexact if x != 0 */
46 if (huge + x > 0.0L)
47 return ((long double)zero[(es&0x8000)!=0]);
48 } else {
49 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
50 if (((ix0 & m) | ix1) == 0)
51 return (x); /* x is integral */
52 if (huge + x > 0.0L) { /* raise inexact flag */
53 ix0 &= ~m;
54 ix1 = 0;
55 }
56 }
57 } else if (e < LDBL_MANT_DIG - 1) {
58 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
59 if ((ix1 & m) == 0)
60 return (x); /* x is integral */
61 if (huge + x > 0.0L) /* raise inexact flag */
62 ix1 &= ~m;
63 }
64 SET_LDOUBLE_WORDS(x,es,ix0,ix1);
65 return (x);
66 }
67
