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/powerpc/lib/div64.S and arch/sh/lib/div64.S. 17 */ 18 19 #include <linux/types.h> 20 21 uint32_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 } 53