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1da177e4
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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
8bc3bcc9
PG
19#include <linux/export.h>
20#include <linux/kernel.h>
2418f4f2 21#include <linux/math64.h>
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22
23/* Not needed on 64bit architectures */
24#if BITS_PER_LONG == 32
25
cb8c181f 26uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
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LT
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
59EXPORT_SYMBOL(__div64_32);
60
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61#ifndef div_s64_rem
62s64 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}
78EXPORT_SYMBOL(div_s64_rem);
79#endif
80
658716d1 81/**
f7926850 82 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and 64bit remainder
658716d1
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83 * @dividend: 64bit dividend
84 * @divisor: 64bit divisor
f7926850 85 * @remainder: 64bit remainder
658716d1
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86 *
87 * This implementation is a modified version of the algorithm proposed
88 * by the book 'Hacker's Delight'. The original source and full proof
89 * can be found here and is available for use without restriction.
90 *
422aa274 91 * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c.txt'
658716d1 92 */
f7926850
FW
93#ifndef div64_u64_rem
94u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
3927f2e8 95{
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96 u32 high = divisor >> 32;
97 u64 quot;
3927f2e8 98
658716d1 99 if (high == 0) {
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100 u32 rem32;
101 quot = div_u64_rem(dividend, divisor, &rem32);
102 *remainder = rem32;
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103 } else {
104 int n = 1 + fls(high);
105 quot = div_u64(dividend >> n, divisor >> n);
3927f2e8 106
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107 if (quot != 0)
108 quot--;
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109
110 *remainder = dividend - quot * divisor;
111 if (*remainder >= divisor) {
658716d1 112 quot++;
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113 *remainder -= divisor;
114 }
658716d1 115 }
3927f2e8 116
658716d1 117 return quot;
3927f2e8 118}
f7926850 119EXPORT_SYMBOL(div64_u64_rem);
6f6d6a1a 120#endif
3927f2e8 121
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122/**
123 * div64_s64 - signed 64bit divide with 64bit divisor
124 * @dividend: 64bit dividend
125 * @divisor: 64bit divisor
126 */
127#ifndef div64_s64
128s64 div64_s64(s64 dividend, s64 divisor)
129{
130 s64 quot, t;
131
132 quot = div64_u64(abs64(dividend), abs64(divisor));
133 t = (dividend ^ divisor) >> 63;
134
135 return (quot ^ t) - t;
136}
137EXPORT_SYMBOL(div64_s64);
138#endif
139
1da177e4 140#endif /* BITS_PER_LONG == 32 */
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141
142/*
143 * Iterative div/mod for use when dividend is not expected to be much
144 * bigger than divisor.
145 */
146u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
147{
d5e181f7 148 return __iter_div_u64_rem(dividend, divisor, remainder);
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149}
150EXPORT_SYMBOL(iter_div_u64_rem);