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
__div64_32(uint64_t * n,uint32_t base)26 uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
27 {
28 uint64_t rem = *n;
29 uint64_t b = base;
30 uint64_t res, d = 1;
31 uint32_t high = rem >> 32;
32
33 /* Reduce the thing a bit first */
34 res = 0;
35 if (high >= base) {
36 high /= base;
37 res = (uint64_t) high << 32;
38 rem -= (uint64_t) (high*base) << 32;
39 }
40
41 while ((int64_t)b > 0 && b < rem) {
42 b = b+b;
43 d = d+d;
44 }
45
46 do {
47 if (rem >= b) {
48 rem -= b;
49 res += d;
50 }
51 b >>= 1;
52 d >>= 1;
53 } while (d);
54
55 *n = res;
56 return rem;
57 }
58
59 EXPORT_SYMBOL(__div64_32);
60
61 #ifndef div_s64_rem
div_s64_rem(s64 dividend,s32 divisor,s32 * remainder)62 s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
63 {
64 u64 quotient;
65
66 if (dividend < 0) {
67 quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
68 *remainder = -*remainder;
69 if (divisor > 0)
70 quotient = -quotient;
71 } else {
72 quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
73 if (divisor < 0)
74 quotient = -quotient;
75 }
76 return quotient;
77 }
78 EXPORT_SYMBOL(div_s64_rem);
79 #endif
80
81 /**
82 * div64_u64 - unsigned 64bit divide with 64bit divisor
83 * @dividend: 64bit dividend
84 * @divisor: 64bit divisor
85 *
86 * This implementation is a modified version of the algorithm proposed
87 * by the book 'Hacker's Delight'. The original source and full proof
88 * can be found here and is available for use without restriction.
89 *
90 * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c'
91 */
92 #ifndef div64_u64
div64_u64(u64 dividend,u64 divisor)93 u64 div64_u64(u64 dividend, u64 divisor)
94 {
95 u32 high = divisor >> 32;
96 u64 quot;
97
98 if (high == 0) {
99 quot = div_u64(dividend, divisor);
100 } else {
101 int n = 1 + fls(high);
102 quot = div_u64(dividend >> n, divisor >> n);
103
104 if (quot != 0)
105 quot--;
106 if ((dividend - quot * divisor) >= divisor)
107 quot++;
108 }
109
110 return quot;
111 }
112 EXPORT_SYMBOL(div64_u64);
113 #endif
114
115 /**
116 * div64_s64 - signed 64bit divide with 64bit divisor
117 * @dividend: 64bit dividend
118 * @divisor: 64bit divisor
119 */
120 #ifndef div64_s64
div64_s64(s64 dividend,s64 divisor)121 s64 div64_s64(s64 dividend, s64 divisor)
122 {
123 s64 quot, t;
124
125 quot = div64_u64(abs64(dividend), abs64(divisor));
126 t = (dividend ^ divisor) >> 63;
127
128 return (quot ^ t) - t;
129 }
130 EXPORT_SYMBOL(div64_s64);
131 #endif
132
133 #endif /* BITS_PER_LONG == 32 */
134
135 /*
136 * Iterative div/mod for use when dividend is not expected to be much
137 * bigger than divisor.
138 */
iter_div_u64_rem(u64 dividend,u32 divisor,u64 * remainder)139 u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
140 {
141 return __iter_div_u64_rem(dividend, divisor, remainder);
142 }
143 EXPORT_SYMBOL(iter_div_u64_rem);
144