Wolfgang Denk | 83c1585 | 2006-10-24 14:21:16 +0200 | [diff] [blame] | 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/types.h> |
| 20 | |
| 21 | #include <asm/div64.h> |
| 22 | |
| 23 | uint32_t __div64_32(uint64_t *n, uint32_t base) |
| 24 | { |
| 25 | uint64_t rem = *n; |
| 26 | uint64_t b = base; |
| 27 | uint64_t res, d = 1; |
| 28 | uint32_t high = rem >> 32; |
| 29 | |
| 30 | /* Reduce the thing a bit first */ |
| 31 | res = 0; |
| 32 | if (high >= base) { |
| 33 | high /= base; |
| 34 | res = (uint64_t) high << 32; |
| 35 | rem -= (uint64_t) (high*base) << 32; |
| 36 | } |
| 37 | |
| 38 | while ((int64_t)b > 0 && b < rem) { |
| 39 | b = b+b; |
| 40 | d = d+d; |
| 41 | } |
| 42 | |
| 43 | do { |
| 44 | if (rem >= b) { |
| 45 | rem -= b; |
| 46 | res += d; |
| 47 | } |
| 48 | b >>= 1; |
| 49 | d >>= 1; |
| 50 | } while (d); |
| 51 | |
| 52 | *n = res; |
| 53 | return rem; |
| 54 | } |