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 * or by defining a preprocessor macro in arch/include/asm/div64.h.
18 */
19
20 #include <linux/compat.h>
21 #include <linux/kernel.h>
22 #include <linux/math64.h>
23
24 /* Not needed on 64bit architectures */
25 #if BITS_PER_LONG == 32
26
27 #ifndef __div64_32
__div64_32(uint64_t * n,uint32_t base)28 uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
29 {
30 uint64_t rem = *n;
31 uint64_t b = base;
32 uint64_t res, d = 1;
33 uint32_t high = rem >> 32;
34
35 /* Reduce the thing a bit first */
36 res = 0;
37 if (high >= base) {
38 high /= base;
39 res = (uint64_t) high << 32;
40 rem -= (uint64_t) (high*base) << 32;
41 }
42
43 while ((int64_t)b > 0 && b < rem) {
44 b = b+b;
45 d = d+d;
46 }
47
48 do {
49 if (rem >= b) {
50 rem -= b;
51 res += d;
52 }
53 b >>= 1;
54 d >>= 1;
55 } while (d);
56
57 *n = res;
58 return rem;
59 }
60 EXPORT_SYMBOL(__div64_32);
61 #endif
62
63 #ifndef div_s64_rem
div_s64_rem(s64 dividend,s32 divisor,s32 * remainder)64 s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
65 {
66 u64 quotient;
67
68 if (dividend < 0) {
69 quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
70 *remainder = -*remainder;
71 if (divisor > 0)
72 quotient = -quotient;
73 } else {
74 quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
75 if (divisor < 0)
76 quotient = -quotient;
77 }
78 return quotient;
79 }
80 EXPORT_SYMBOL(div_s64_rem);
81 #endif
82
83 /**
84 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
85 * @dividend: 64bit dividend
86 * @divisor: 64bit divisor
87 * @remainder: 64bit remainder
88 *
89 * This implementation is a comparable to algorithm used by div64_u64.
90 * But this operation, which includes math for calculating the remainder,
91 * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
92 * systems.
93 */
94 #ifndef div64_u64_rem
div64_u64_rem(u64 dividend,u64 divisor,u64 * remainder)95 u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
96 {
97 u32 high = divisor >> 32;
98 u64 quot;
99
100 if (high == 0) {
101 u32 rem32;
102 quot = div_u64_rem(dividend, divisor, &rem32);
103 *remainder = rem32;
104 } else {
105 int n = 1 + fls(high);
106 quot = div_u64(dividend >> n, divisor >> n);
107
108 if (quot != 0)
109 quot--;
110
111 *remainder = dividend - quot * divisor;
112 if (*remainder >= divisor) {
113 quot++;
114 *remainder -= divisor;
115 }
116 }
117
118 return quot;
119 }
120 EXPORT_SYMBOL(div64_u64_rem);
121 #endif
122
123 /**
124 * div64_u64 - unsigned 64bit divide with 64bit divisor
125 * @dividend: 64bit dividend
126 * @divisor: 64bit divisor
127 *
128 * This implementation is a modified version of the algorithm proposed
129 * by the book 'Hacker's Delight'. The original source and full proof
130 * can be found here and is available for use without restriction.
131 *
132 * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
133 */
134 #ifndef div64_u64
div64_u64(u64 dividend,u64 divisor)135 u64 div64_u64(u64 dividend, u64 divisor)
136 {
137 u32 high = divisor >> 32;
138 u64 quot;
139
140 if (high == 0) {
141 quot = div_u64(dividend, divisor);
142 } else {
143 int n = 1 + fls(high);
144 quot = div_u64(dividend >> n, divisor >> n);
145
146 if (quot != 0)
147 quot--;
148 if ((dividend - quot * divisor) >= divisor)
149 quot++;
150 }
151
152 return quot;
153 }
154 EXPORT_SYMBOL(div64_u64);
155 #endif
156
157 /**
158 * div64_s64 - signed 64bit divide with 64bit divisor
159 * @dividend: 64bit dividend
160 * @divisor: 64bit divisor
161 */
162 #ifndef div64_s64
div64_s64(s64 dividend,s64 divisor)163 s64 div64_s64(s64 dividend, s64 divisor)
164 {
165 s64 quot, t;
166
167 quot = div64_u64(abs(dividend), abs(divisor));
168 t = (dividend ^ divisor) >> 63;
169
170 return (quot ^ t) - t;
171 }
172 EXPORT_SYMBOL(div64_s64);
173 #endif
174
175 #endif /* BITS_PER_LONG == 32 */
176
177 /*
178 * Iterative div/mod for use when dividend is not expected to be much
179 * bigger than divisor.
180 */
iter_div_u64_rem(u64 dividend,u32 divisor,u64 * remainder)181 u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
182 {
183 return __iter_div_u64_rem(dividend, divisor, remainder);
184 }
185 EXPORT_SYMBOL(iter_div_u64_rem);
186