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Wolfgang Denk7b64fef2006-10-24 14:21:16 +02001/*
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
Stefan Roesea47a12b2010-04-15 16:07:28 +020016 * assembly versions such as arch/powerpc/lib/div64.S and arch/sh/lib/div64.S.
Wolfgang Denk7b64fef2006-10-24 14:21:16 +020017 */
18
19#include <linux/types.h>
20
Wolfgang Denk7b64fef2006-10-24 14:21:16 +020021uint32_t __div64_32(uint64_t *n, uint32_t base)
22{
23 uint64_t rem = *n;
24 uint64_t b = base;
25 uint64_t res, d = 1;
26 uint32_t high = rem >> 32;
27
28 /* Reduce the thing a bit first */
29 res = 0;
30 if (high >= base) {
31 high /= base;
32 res = (uint64_t) high << 32;
33 rem -= (uint64_t) (high*base) << 32;
34 }
35
36 while ((int64_t)b > 0 && b < rem) {
37 b = b+b;
38 d = d+d;
39 }
40
41 do {
42 if (rem >= b) {
43 rem -= b;
44 res += d;
45 }
46 b >>= 1;
47 d >>= 1;
48 } while (d);
49
50 *n = res;
51 return rem;
52}