LXR uboot/lib/div64.c

   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 <div64.h>
  20#include <linux/types.h>
  21#include <linux/compiler.h>
  22
  23uint32_t notrace __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}
  55