2 * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
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>
9 * Generic C version of 64bit/32bit division and modulo, with
10 * 64bit result and 32bit remainder.
12 * The fast case for (n>>32 == 0) is handled inline by do_div().
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.
20 #include <linux/compat.h>
21 #include <linux/kernel.h>
22 #include <linux/math64.h>
24 /* Not needed on 64bit architectures */
25 #if BITS_PER_LONG == 32
28 uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
33 uint32_t high = rem >> 32;
35 /* Reduce the thing a bit first */
39 res = (uint64_t) high << 32;
40 rem -= (uint64_t) (high*base) << 32;
43 while ((int64_t)b > 0 && b < rem) {
60 EXPORT_SYMBOL(__div64_32);
64 s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
69 quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
70 *remainder = -*remainder;
74 quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
80 EXPORT_SYMBOL(div_s64_rem);
84 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
85 * @dividend: 64bit dividend
86 * @divisor: 64bit divisor
87 * @remainder: 64bit remainder
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
95 u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
97 u32 high = divisor >> 32;
102 quot = div_u64_rem(dividend, divisor, &rem32);
105 int n = 1 + fls(high);
106 quot = div_u64(dividend >> n, divisor >> n);
111 *remainder = dividend - quot * divisor;
112 if (*remainder >= divisor) {
114 *remainder -= divisor;
120 EXPORT_SYMBOL(div64_u64_rem);
124 * div64_u64 - unsigned 64bit divide with 64bit divisor
125 * @dividend: 64bit dividend
126 * @divisor: 64bit divisor
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.
132 * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
135 u64 div64_u64(u64 dividend, u64 divisor)
137 u32 high = divisor >> 32;
141 quot = div_u64(dividend, divisor);
143 int n = 1 + fls(high);
144 quot = div_u64(dividend >> n, divisor >> n);
148 if ((dividend - quot * divisor) >= divisor)
154 EXPORT_SYMBOL(div64_u64);
158 * div64_s64 - signed 64bit divide with 64bit divisor
159 * @dividend: 64bit dividend
160 * @divisor: 64bit divisor
163 s64 div64_s64(s64 dividend, s64 divisor)
167 quot = div64_u64(abs(dividend), abs(divisor));
168 t = (dividend ^ divisor) >> 63;
170 return (quot ^ t) - t;
172 EXPORT_SYMBOL(div64_s64);
175 #endif /* BITS_PER_LONG == 32 */
178 * Iterative div/mod for use when dividend is not expected to be much
179 * bigger than divisor.
181 u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
183 return __iter_div_u64_rem(dividend, divisor, remainder);
185 EXPORT_SYMBOL(iter_div_u64_rem);