Root/lib/div64.c

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/module.h>
20#include <linux/math64.h>
21
22/* Not needed on 64bit architectures */
23#if BITS_PER_LONG == 32
24
25uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
26{
27    uint64_t rem = *n;
28    uint64_t b = base;
29    uint64_t res, d = 1;
30    uint32_t high = rem >> 32;
31
32    /* Reduce the thing a bit first */
33    res = 0;
34    if (high >= base) {
35        high /= base;
36        res = (uint64_t) high << 32;
37        rem -= (uint64_t) (high*base) << 32;
38    }
39
40    while ((int64_t)b > 0 && b < rem) {
41        b = b+b;
42        d = d+d;
43    }
44
45    do {
46        if (rem >= b) {
47            rem -= b;
48            res += d;
49        }
50        b >>= 1;
51        d >>= 1;
52    } while (d);
53
54    *n = res;
55    return rem;
56}
57
58EXPORT_SYMBOL(__div64_32);
59
60#ifndef div_s64_rem
61s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
62{
63    u64 quotient;
64
65    if (dividend < 0) {
66        quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
67        *remainder = -*remainder;
68        if (divisor > 0)
69            quotient = -quotient;
70    } else {
71        quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
72        if (divisor < 0)
73            quotient = -quotient;
74    }
75    return quotient;
76}
77EXPORT_SYMBOL(div_s64_rem);
78#endif
79
80/* 64bit divisor, dividend and result. dynamic precision */
81#ifndef div64_u64
82u64 div64_u64(u64 dividend, u64 divisor)
83{
84    u32 high, d;
85
86    high = divisor >> 32;
87    if (high) {
88        unsigned int shift = fls(high);
89
90        d = divisor >> shift;
91        dividend >>= shift;
92    } else
93        d = divisor;
94
95    return div_u64(dividend, d);
96}
97EXPORT_SYMBOL(div64_u64);
98#endif
99
100#endif /* BITS_PER_LONG == 32 */
101
102/*
103 * Iterative div/mod for use when dividend is not expected to be much
104 * bigger than divisor.
105 */
106u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
107{
108    return __iter_div_u64_rem(dividend, divisor, remainder);
109}
110EXPORT_SYMBOL(iter_div_u64_rem);
111

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