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
12 /*
13 * modf(double x, double *iptr)
14 * return fraction part of x, and return x's integral part in *iptr.
15 * Method:
16 * Bit twiddling.
17 *
18 * Exception:
19 * No exception.
20 */
21
22 #include <sys/types.h>
23 #include <machine/endian.h>
24 #include <math.h>
25
26 /* Bit fiddling routines copied from msun/src/math_private.h,v 1.15 */
27
28 #if BYTE_ORDER == BIG_ENDIAN
29
30 typedef union
31 {
32 double value;
33 struct
34 {
35 u_int32_t msw;
36 u_int32_t lsw;
37 } parts;
38 } ieee_double_shape_type;
39
40 #endif
41
42 #if BYTE_ORDER == LITTLE_ENDIAN
43
44 typedef union
45 {
46 double value;
47 struct
48 {
49 u_int32_t lsw;
50 u_int32_t msw;
51 } parts;
52 } ieee_double_shape_type;
53
54 #endif
55
56 /* Get two 32 bit ints from a double. */
57
58 #define EXTRACT_WORDS(ix0,ix1,d) \
59 do { \
60 ieee_double_shape_type ew_u; \
61 ew_u.value = (d); \
62 (ix0) = ew_u.parts.msw; \
63 (ix1) = ew_u.parts.lsw; \
64 } while (0)
65
66 /* Get the more significant 32 bit int from a double. */
67
68 #define GET_HIGH_WORD(i,d) \
69 do { \
70 ieee_double_shape_type gh_u; \
71 gh_u.value = (d); \
72 (i) = gh_u.parts.msw; \
73 } while (0)
74
75 /* Set a double from two 32 bit ints. */
76
77 #define INSERT_WORDS(d,ix0,ix1) \
78 do { \
79 ieee_double_shape_type iw_u; \
80 iw_u.parts.msw = (ix0); \
81 iw_u.parts.lsw = (ix1); \
82 (d) = iw_u.value; \
83 } while (0)
84
85 static const double one = 1.0;
86
87 double
modf(double x,double * iptr)88 modf(double x, double *iptr)
89 {
90 int32_t i0,i1,j0;
91 u_int32_t i;
92 EXTRACT_WORDS(i0,i1,x);
93 j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */
94 if(j0<20) { /* integer part in high x */
95 if(j0<0) { /* |x|<1 */
96 INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */
97 return x;
98 } else {
99 i = (0x000fffff)>>j0;
100 if(((i0&i)|i1)==0) { /* x is integral */
101 u_int32_t high;
102 *iptr = x;
103 GET_HIGH_WORD(high,x);
104 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
105 return x;
106 } else {
107 INSERT_WORDS(*iptr,i0&(~i),0);
108 return x - *iptr;
109 }
110 }
111 } else if (j0>51) { /* no fraction part */
112 u_int32_t high;
113 if (j0 == 0x400) { /* inf/NaN */
114 *iptr = x;
115 return 0.0 / x;
116 }
117 *iptr = x*one;
118 GET_HIGH_WORD(high,x);
119 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
120 return x;
121 } else { /* fraction part in low x */
122 i = ((u_int32_t)(0xffffffff))>>(j0-20);
123 if((i1&i)==0) { /* x is integral */
124 u_int32_t high;
125 *iptr = x;
126 GET_HIGH_WORD(high,x);
127 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
128 return x;
129 } else {
130 INSERT_WORDS(*iptr,i0,i1&(~i));
131 return x - *iptr;
132 }
133 }
134 }
135