div64.c 3.98 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
/*
 * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
 *
 * Based on former do_div() implementation from asm-parisc/div64.h:
 *	Copyright (C) 1999 Hewlett-Packard Co
 *	Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
 *
 *
 * Generic C version of 64bit/32bit division and modulo, with
 * 64bit result and 32bit remainder.
 *
 * The fast case for (n>>32 == 0) is handled inline by do_div(). 
 *
 * Code generated for this function might be very inefficient
 * for some CPUs. __div64_32() can be overridden by linking arch-specific
 * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S.
 */

19 20
#include <linux/export.h>
#include <linux/kernel.h>
21
#include <linux/math64.h>
Linus Torvalds's avatar
Linus Torvalds committed
22 23 24 25

/* Not needed on 64bit architectures */
#if BITS_PER_LONG == 32

26
uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
Linus Torvalds's avatar
Linus Torvalds committed
27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
{
	uint64_t rem = *n;
	uint64_t b = base;
	uint64_t res, d = 1;
	uint32_t high = rem >> 32;

	/* Reduce the thing a bit first */
	res = 0;
	if (high >= base) {
		high /= base;
		res = (uint64_t) high << 32;
		rem -= (uint64_t) (high*base) << 32;
	}

	while ((int64_t)b > 0 && b < rem) {
		b = b+b;
		d = d+d;
	}

	do {
		if (rem >= b) {
			rem -= b;
			res += d;
		}
		b >>= 1;
		d >>= 1;
	} while (d);

	*n = res;
	return rem;
}

EXPORT_SYMBOL(__div64_32);

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
#ifndef div_s64_rem
s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
{
	u64 quotient;

	if (dividend < 0) {
		quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
		*remainder = -*remainder;
		if (divisor > 0)
			quotient = -quotient;
	} else {
		quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
		if (divisor < 0)
			quotient = -quotient;
	}
	return quotient;
}
EXPORT_SYMBOL(div_s64_rem);
#endif

81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120
/**
 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
 * @dividend:	64bit dividend
 * @divisor:	64bit divisor
 * @remainder:  64bit remainder
 *
 * This implementation is a comparable to algorithm used by div64_u64.
 * But this operation, which includes math for calculating the remainder,
 * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
 * systems.
 */
#ifndef div64_u64_rem
u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
{
	u32 high = divisor >> 32;
	u64 quot;

	if (high == 0) {
		u32 rem32;
		quot = div_u64_rem(dividend, divisor, &rem32);
		*remainder = rem32;
	} else {
		int n = 1 + fls(high);
		quot = div_u64(dividend >> n, divisor >> n);

		if (quot != 0)
			quot--;

		*remainder = dividend - quot * divisor;
		if (*remainder >= divisor) {
			quot++;
			*remainder -= divisor;
		}
	}

	return quot;
}
EXPORT_SYMBOL(div64_u64_rem);
#endif

121
/**
122
 * div64_u64 - unsigned 64bit divide with 64bit divisor
123 124 125 126 127 128 129
 * @dividend:	64bit dividend
 * @divisor:	64bit divisor
 *
 * This implementation is a modified version of the algorithm proposed
 * by the book 'Hacker's Delight'.  The original source and full proof
 * can be found here and is available for use without restriction.
 *
130
 * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c.txt'
131
 */
132 133
#ifndef div64_u64
u64 div64_u64(u64 dividend, u64 divisor)
134
{
135 136
	u32 high = divisor >> 32;
	u64 quot;
137

138
	if (high == 0) {
139
		quot = div_u64(dividend, divisor);
140 141 142
	} else {
		int n = 1 + fls(high);
		quot = div_u64(dividend >> n, divisor >> n);
143

144 145
		if (quot != 0)
			quot--;
146
		if ((dividend - quot * divisor) >= divisor)
147 148
			quot++;
	}
149

150
	return quot;
151
}
152
EXPORT_SYMBOL(div64_u64);
Roman Zippel's avatar
Roman Zippel committed
153
#endif
154

155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172
/**
 * div64_s64 - signed 64bit divide with 64bit divisor
 * @dividend:	64bit dividend
 * @divisor:	64bit divisor
 */
#ifndef div64_s64
s64 div64_s64(s64 dividend, s64 divisor)
{
	s64 quot, t;

	quot = div64_u64(abs64(dividend), abs64(divisor));
	t = (dividend ^ divisor) >> 63;

	return (quot ^ t) - t;
}
EXPORT_SYMBOL(div64_s64);
#endif

Linus Torvalds's avatar
Linus Torvalds committed
173
#endif /* BITS_PER_LONG == 32 */
174 175 176 177 178 179 180

/*
 * Iterative div/mod for use when dividend is not expected to be much
 * bigger than divisor.
 */
u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
{
181
	return __iter_div_u64_rem(dividend, divisor, remainder);
182 183
}
EXPORT_SYMBOL(iter_div_u64_rem);