~kris/9p

9hist

ref: 150ca26a9045f63dd57e8c7f1ac4d2b66b18ee2d 9hist/bitsy/fpimem.c -rw-r--r-- 2.2 KiB
150ca26a — David du Colombier Plan 9 from Bell Labs 2002-01-25 24 years ago 
                                                                                
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136

#include "fpi.h"

/*
 * the following routines depend on memory format, not the machine
 */

void
fpis2i(Internal *i, void *v)
{
	Single *s = v;

	i->s = (*s & 0x80000000) ? 1: 0;
	if((*s & ~0x80000000) == 0){
		SetZero(i);
		return;
	}
	i->e = ((*s>>23) & 0x00FF) - SingleExpBias + ExpBias;
	i->h = (*s & 0x007FFFFF)<<(1+NGuardBits);
	i->l = 0;
	if(i->e)
		i->h |= HiddenBit;
	else
		i->e++;
}

void
fpid2i(Internal *i, void *v)
{
	Double *d = v;

	i->s = (d->h & 0x80000000) ? 1: 0;
	i->e = (d->h>>20) & 0x07FF;
	i->h = ((d->h & 0x000FFFFF)<<(4+NGuardBits))|((d->l>>25) & 0x7F);
	i->l = (d->l & 0x01FFFFFF)<<NGuardBits;
	if(i->e)
		i->h |= HiddenBit;
	else
		i->e++;
}

void
fpiw2i(Internal *i, void *v)
{
	Word w, word = *(Word*)v;
	short e;

	if(word < 0){
		i->s = 1;
		word = -word;
	}
	else
		i->s = 0;
	if(word == 0){
		SetZero(i);
		return;
	}
	if(word > 0){
		for (e = 0, w = word; w; w >>= 1, e++)
			;
	} else
		e = 32;
	if(e > FractBits){
		i->h = word>>(e - FractBits);
		i->l = (word & ((1<<(e - FractBits)) - 1))<<(2*FractBits - e);
	}
	else {
		i->h = word<<(FractBits - e);
		i->l = 0;
	}
	i->e = (e - 1) + ExpBias;
}

void
fpii2s(void *v, Internal *i)
{
	short e;
	Single *s = (Single*)v;

	fpiround(i);
	if(i->h & HiddenBit)
		i->h &= ~HiddenBit;
	else
		i->e--;
	*s = i->s ? 0x80000000: 0;
	e = i->e;
	if(e < ExpBias){
		if(e <= (ExpBias - SingleExpBias))
			return;
		e = SingleExpBias - (ExpBias - e);
	}
	else  if(e >= (ExpBias + (SingleExpMax-SingleExpBias))){
		*s |= SingleExpMax<<23;
		return;
	}
	else
		e = SingleExpBias + (e - ExpBias);
	*s |= (e<<23)|(i->h>>(1+NGuardBits));
}

void
fpii2d(void *v, Internal *i)
{
	Double *d = (Double*)v;

	fpiround(i);
	if(i->h & HiddenBit)
		i->h &= ~HiddenBit;
	else
		i->e--;
	i->l = ((i->h & GuardMask)<<25)|(i->l>>NGuardBits);
	i->h >>= NGuardBits;
	d->h = i->s ? 0x80000000: 0;
	d->h |= (i->e<<20)|((i->h & 0x00FFFFFF)>>4);
	d->l = (i->h<<28)|i->l;
}

void
fpii2w(Word *word, Internal *i)
{
	Word w;
	short e;

	fpiround(i);
	e = (i->e - ExpBias) + 1;
	if(e <= 0)
		w = 0;
	else if(e > 31)
		w = 0x7FFFFFFF;
	else if(e > FractBits)
		w = (i->h<<(e - FractBits))|(i->l>>(2*FractBits - e));
	else
		w = i->h>>(FractBits-e);
	if(i->s)
		w = -w;
	*word = w;
}