~kris/9p

9hist

ref: fafda80b74a110ccc2637b27fcf392784f284d25 9hist/ss/div.c -rw-r--r-- 1.8 KiB
fafda80b — David du Colombier Plan 9 from Bell Labs 1991-02-01 35 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

#include <u.h>

#define	W	32

ulong
_udiv(ulong dividend, ulong divisor)
{
	long R;		/* partial remainder */
	ulong Q;	/* partial quotient */
	int iter;
	ulong logQ, m;

	m = (1<<(W-1))+1;
	if(dividend < m)
		m = dividend;
	for(logQ=0; logQ<W; logQ++)
		if((divisor<<logQ) >= m)
			break;

	R = dividend;
	Q = 0;
	for(iter=logQ; iter>=0; iter--){
		if(R >= 0){
			R -= divisor<<iter;
			Q += 1<<iter;
		}else{
			R += divisor<<iter;
			Q -= 1<<iter;
		}
	}
	if(R < 0)
		Q--;
	return Q;
}

ulong
_urem(ulong dividend, ulong divisor)
{
	long R;		/* partial remainder */
	int iter;
	ulong logQ, m;

	m = (1<<(W-1))+1;
	if(dividend < m)
		m = dividend;
	for(logQ=0; logQ<W; logQ++)
		if((divisor<<logQ) >= m)
			break;

	R = dividend;
	for(iter=logQ; iter>=0; iter--){
		if(R >= 0)
			R -= divisor<<iter;
		else
			R += divisor<<iter;
	}
	if(R < 0)
		R += divisor;
	return R;
}

ulong
_div(long dividend, long divisor)
{
	if(dividend>=0 && divisor>=0)
		return _udiv(dividend, divisor);
	if(dividend<0 && divisor<0)
		return _udiv(-dividend, -divisor);
	if(dividend < 0)
		return -_udiv(-dividend, divisor);
	return -_udiv(dividend, -divisor);
}

ulong
_rem(long dividend, long divisor)
{
	if(dividend>=0 && divisor>=0)
		return _urem(dividend, divisor);
	if(dividend<0 && divisor<0)
		return _urem(-dividend, -divisor);
	if(dividend < 0)
		return -_urem(-dividend, divisor);
	return -_urem(dividend, -divisor);
}

long
_asmul(long *a, long b)
{
	long c;

	c = *a * b;
	*a = c;
	return c;
}

long
_asdiv(long *a, long b)
{
	long c;

	c = *a / b;
	*a = c;
	return c;
}

long
_asrem(long *a, long b)
{
	long c;

	c = *a % b;
	*a = c;
	return c;
}

ulong
_asudiv(ulong *a, ulong b)
{
	ulong c;

	c = *a / b;
	*a = c;
	return c;
}

ulong
_asurem(ulong *a, ulong b)
{
	ulong c;

	c = *a % b;
	*a = c;
	return c;
}