Line data Source code
1 : /*
2 : * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
3 : *
4 : * Based on former do_div() implementation from asm-parisc/div64.h:
5 : * Copyright (C) 1999 Hewlett-Packard Co
6 : * Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
7 : *
8 : *
9 : * Generic C version of 64bit/32bit division and modulo, with
10 : * 64bit result and 32bit remainder.
11 : *
12 : * The fast case for (n>>32 == 0) is handled inline by do_div().
13 : *
14 : * Code generated for this function might be very inefficient
15 : * for some CPUs. __div64_32() can be overridden by linking arch-specific
16 : * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S.
17 : */
18 :
19 : #include <linux/export.h>
20 : #include <linux/kernel.h>
21 : #include <linux/math64.h>
22 :
23 : /* Not needed on 64bit architectures */
24 : #if BITS_PER_LONG == 32
25 :
26 0 : uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
27 : {
28 0 : uint64_t rem = *n;
29 0 : uint64_t b = base;
30 : uint64_t res, d = 1;
31 0 : uint32_t high = rem >> 32;
32 :
33 : /* Reduce the thing a bit first */
34 : res = 0;
35 0 : if (high >= base) {
36 0 : high /= base;
37 0 : res = (uint64_t) high << 32;
38 0 : rem -= (uint64_t) (high*base) << 32;
39 : }
40 :
41 0 : while ((int64_t)b > 0 && b < rem) {
42 0 : b = b+b;
43 0 : d = d+d;
44 : }
45 :
46 : do {
47 0 : if (rem >= b) {
48 0 : rem -= b;
49 0 : res += d;
50 : }
51 0 : b >>= 1;
52 0 : d >>= 1;
53 0 : } while (d);
54 :
55 0 : *n = res;
56 0 : return rem;
57 : }
58 :
59 : EXPORT_SYMBOL(__div64_32);
60 :
61 : #ifndef div_s64_rem
62 235951 : s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
63 : {
64 : u64 quotient;
65 :
66 235951 : if (dividend < 0) {
67 1 : quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
68 1 : *remainder = -*remainder;
69 1 : if (divisor > 0)
70 1 : quotient = -quotient;
71 : } else {
72 235950 : quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
73 235950 : if (divisor < 0)
74 0 : quotient = -quotient;
75 : }
76 235951 : return quotient;
77 : }
78 : EXPORT_SYMBOL(div_s64_rem);
79 : #endif
80 :
81 : /**
82 : * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
83 : * @dividend: 64bit dividend
84 : * @divisor: 64bit divisor
85 : * @remainder: 64bit remainder
86 : *
87 : * This implementation is a comparable to algorithm used by div64_u64.
88 : * But this operation, which includes math for calculating the remainder,
89 : * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
90 : * systems.
91 : */
92 : #ifndef div64_u64_rem
93 0 : u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
94 : {
95 0 : u32 high = divisor >> 32;
96 : u64 quot;
97 :
98 0 : if (high == 0) {
99 : u32 rem32;
100 0 : quot = div_u64_rem(dividend, divisor, &rem32);
101 0 : *remainder = rem32;
102 : } else {
103 0 : int n = 1 + fls(high);
104 0 : quot = div_u64(dividend >> n, divisor >> n);
105 :
106 0 : if (quot != 0)
107 0 : quot--;
108 :
109 0 : *remainder = dividend - quot * divisor;
110 0 : if (*remainder >= divisor) {
111 0 : quot++;
112 0 : *remainder -= divisor;
113 : }
114 : }
115 :
116 0 : return quot;
117 : }
118 : EXPORT_SYMBOL(div64_u64_rem);
119 : #endif
120 :
121 : /**
122 : * div64_u64 - unsigned 64bit divide with 64bit divisor
123 : * @dividend: 64bit dividend
124 : * @divisor: 64bit divisor
125 : *
126 : * This implementation is a modified version of the algorithm proposed
127 : * by the book 'Hacker's Delight'. The original source and full proof
128 : * can be found here and is available for use without restriction.
129 : *
130 : * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c.txt'
131 : */
132 : #ifndef div64_u64
133 2 : u64 div64_u64(u64 dividend, u64 divisor)
134 : {
135 2 : u32 high = divisor >> 32;
136 : u64 quot;
137 :
138 2 : if (high == 0) {
139 2 : quot = div_u64(dividend, divisor);
140 : } else {
141 0 : int n = 1 + fls(high);
142 0 : quot = div_u64(dividend >> n, divisor >> n);
143 :
144 0 : if (quot != 0)
145 0 : quot--;
146 0 : if ((dividend - quot * divisor) >= divisor)
147 0 : quot++;
148 : }
149 :
150 2 : return quot;
151 : }
152 : EXPORT_SYMBOL(div64_u64);
153 : #endif
154 :
155 : /**
156 : * div64_s64 - signed 64bit divide with 64bit divisor
157 : * @dividend: 64bit dividend
158 : * @divisor: 64bit divisor
159 : */
160 : #ifndef div64_s64
161 0 : s64 div64_s64(s64 dividend, s64 divisor)
162 : {
163 : s64 quot, t;
164 :
165 0 : quot = div64_u64(abs64(dividend), abs64(divisor));
166 0 : t = (dividend ^ divisor) >> 63;
167 :
168 0 : return (quot ^ t) - t;
169 : }
170 : EXPORT_SYMBOL(div64_s64);
171 : #endif
172 :
173 : #endif /* BITS_PER_LONG == 32 */
174 :
175 : /*
176 : * Iterative div/mod for use when dividend is not expected to be much
177 : * bigger than divisor.
178 : */
179 0 : u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
180 : {
181 0 : return __iter_div_u64_rem(dividend, divisor, remainder);
182 : }
183 : EXPORT_SYMBOL(iter_div_u64_rem);
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