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_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
div64_u64_rem(u64 dividend,u64 divisor,u64 * remainder)93 u64 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 = 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 }
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/hdcodetxt/divDouble.c.txt'
131 */
132 #ifndef div64_u64
div64_u64(u64 dividend,u64 divisor)133 u64 div64_u64(u64 dividend, u64 divisor)
134 {
135 u32 high = divisor >> 32;
136 u64 quot;
137
138 if (high == 0) {
139 quot = div_u64(dividend, divisor);
140 } else {
141 int n = fls(high);
142 quot = div_u64(dividend >> n, divisor >> n);
143
144 if (quot != 0)
145 quot--;
146 if ((dividend - quot * divisor) >= divisor)
147 quot++;
148 }
149
150 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
div64_s64(s64 dividend,s64 divisor)161 s64 div64_s64(s64 dividend, s64 divisor)
162 {
163 s64 quot, t;
164
165 quot = div64_u64(abs(dividend), abs(divisor));
166 t = (dividend ^ divisor) >> 63;
167
168 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 */
iter_div_u64_rem(u64 dividend,u32 divisor,u64 * remainder)179 u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
180 {
181 return __iter_div_u64_rem(dividend, divisor, remainder);
182 }
183 EXPORT_SYMBOL(iter_div_u64_rem);
184