blob: 19ea7ed4b948297ae8f03367d3484840ec4456f6 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
Paul Gortmaker8bc3bcc2011-11-16 21:29:17 -050019#include <linux/export.h>
20#include <linux/kernel.h>
Roman Zippel2418f4f2008-05-01 04:34:25 -070021#include <linux/math64.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070022
23/* Not needed on 64bit architectures */
24#if BITS_PER_LONG == 32
25
David S. Millercb8c1812007-04-10 22:10:39 -070026uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
Linus Torvalds1da177e2005-04-16 15:20:36 -070027{
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
Roman Zippel2418f4f2008-05-01 04:34:25 -070061#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
Brian Behlendorf658716d2010-10-26 14:23:10 -070081/**
Mike Snitzereb18cba2013-08-20 15:05:17 -040082 * 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
93u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
94{
95 u32 high = divisor >> 32;
96 u64 quot;
97
98 if (high == 0) {
99 u32 rem32;
100 quot = div_u64_rem(dividend, divisor, &rem32);
101 *remainder = rem32;
102 } else {
103 int n = 1 + fls(high);
104 quot = div_u64(dividend >> n, divisor >> n);
105
106 if (quot != 0)
107 quot--;
108
109 *remainder = dividend - quot * divisor;
110 if (*remainder >= divisor) {
111 quot++;
112 *remainder -= divisor;
113 }
114 }
115
116 return quot;
117}
118EXPORT_SYMBOL(div64_u64_rem);
119#endif
120
121/**
Stanislaw Gruszkaf3002132013-04-30 11:35:07 +0200122 * div64_u64 - unsigned 64bit divide with 64bit divisor
Brian Behlendorf658716d2010-10-26 14:23:10 -0700123 * @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 *
Heinrich Schuchardt28ca84e2015-02-26 20:19:03 +0100130 * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
Brian Behlendorf658716d2010-10-26 14:23:10 -0700131 */
Stanislaw Gruszkaf3002132013-04-30 11:35:07 +0200132#ifndef div64_u64
133u64 div64_u64(u64 dividend, u64 divisor)
Stephen Hemminger3927f2e2007-03-25 19:54:23 -0700134{
Brian Behlendorf658716d2010-10-26 14:23:10 -0700135 u32 high = divisor >> 32;
136 u64 quot;
Stephen Hemminger3927f2e2007-03-25 19:54:23 -0700137
Brian Behlendorf658716d2010-10-26 14:23:10 -0700138 if (high == 0) {
Stanislaw Gruszkaf3002132013-04-30 11:35:07 +0200139 quot = div_u64(dividend, divisor);
Brian Behlendorf658716d2010-10-26 14:23:10 -0700140 } else {
141 int n = 1 + fls(high);
142 quot = div_u64(dividend >> n, divisor >> n);
Stephen Hemminger3927f2e2007-03-25 19:54:23 -0700143
Brian Behlendorf658716d2010-10-26 14:23:10 -0700144 if (quot != 0)
145 quot--;
Stanislaw Gruszkaf3002132013-04-30 11:35:07 +0200146 if ((dividend - quot * divisor) >= divisor)
Brian Behlendorf658716d2010-10-26 14:23:10 -0700147 quot++;
148 }
Stephen Hemminger3927f2e2007-03-25 19:54:23 -0700149
Brian Behlendorf658716d2010-10-26 14:23:10 -0700150 return quot;
Stephen Hemminger3927f2e2007-03-25 19:54:23 -0700151}
Stanislaw Gruszkaf3002132013-04-30 11:35:07 +0200152EXPORT_SYMBOL(div64_u64);
Roman Zippel6f6d6a12008-05-01 04:34:28 -0700153#endif
Stephen Hemminger3927f2e2007-03-25 19:54:23 -0700154
Brian Behlendorf658716d2010-10-26 14:23:10 -0700155/**
156 * div64_s64 - signed 64bit divide with 64bit divisor
157 * @dividend: 64bit dividend
158 * @divisor: 64bit divisor
159 */
160#ifndef div64_s64
161s64 div64_s64(s64 dividend, s64 divisor)
162{
163 s64 quot, t;
164
165 quot = div64_u64(abs64(dividend), abs64(divisor));
166 t = (dividend ^ divisor) >> 63;
167
168 return (quot ^ t) - t;
169}
170EXPORT_SYMBOL(div64_s64);
171#endif
172
Linus Torvalds1da177e2005-04-16 15:20:36 -0700173#endif /* BITS_PER_LONG == 32 */
Jeremy Fitzhardingef595ec92008-06-12 10:47:56 +0200174
175/*
176 * Iterative div/mod for use when dividend is not expected to be much
177 * bigger than divisor.
178 */
179u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
180{
Jeremy Fitzhardinged5e181f2008-06-12 10:47:58 +0200181 return __iter_div_u64_rem(dividend, divisor, remainder);
Jeremy Fitzhardingef595ec92008-06-12 10:47:56 +0200182}
183EXPORT_SYMBOL(iter_div_u64_rem);