root/lib/div64.c

DEFINITIONS

1. __div64_32
2. div_s64_rem
3. div64_u64
4. iter_div_u64_rem

/*
 * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
 *
 * Based on former do_div() implementation from asm-parisc/div64.h:
 *      Copyright (C) 1999 Hewlett-Packard Co
 *      Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
 *
 *
 * Generic C version of 64bit/32bit division and modulo, with
 * 64bit result and 32bit remainder.
 *
 * The fast case for (n>>32 == 0) is handled inline by do_div(). 
 *
 * Code generated for this function might be very inefficient
 * for some CPUs. __div64_32() can be overridden by linking arch-specific
 * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S.
 */

#include <linux/module.h>
#include <linux/math64.h>

/* Not needed on 64bit architectures */
#if BITS_PER_LONG == 32

uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
{
        uint64_t rem = *n;
        uint64_t b = base;
        uint64_t res, d = 1;
        uint32_t high = rem >> 32;

        /* Reduce the thing a bit first */
        res = 0;
        if (high >= base) {
                high /= base;
                res = (uint64_t) high << 32;
                rem -= (uint64_t) (high*base) << 32;
        }

        while ((int64_t)b > 0 && b < rem) {
                b = b+b;
                d = d+d;
        }

        do {
                if (rem >= b) {
                        rem -= b;
                        res += d;
                }
                b >>= 1;
                d >>= 1;
        } while (d);

        *n = res;
        return rem;
}

EXPORT_SYMBOL(__div64_32);

#ifndef div_s64_rem
s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
{
        u64 quotient;

        if (dividend < 0) {
                quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
                *remainder = -*remainder;
                if (divisor > 0)
                        quotient = -quotient;
        } else {
                quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
                if (divisor < 0)
                        quotient = -quotient;
        }
        return quotient;
}
EXPORT_SYMBOL(div_s64_rem);
#endif

/* 64bit divisor, dividend and result. dynamic precision */
#ifndef div64_u64
u64 div64_u64(u64 dividend, u64 divisor)
{
        u32 high, d;

        high = divisor >> 32;
        if (high) {
                unsigned int shift = fls(high);

                d = divisor >> shift;
                dividend >>= shift;
        } else
                d = divisor;

        return div_u64(dividend, d);
}
EXPORT_SYMBOL(div64_u64);
#endif

#endif /* BITS_PER_LONG == 32 */

/*
 * Iterative div/mod for use when dividend is not expected to be much
 * bigger than divisor.
 */
u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
{
        return __iter_div_u64_rem(dividend, divisor, remainder);
}
EXPORT_SYMBOL(iter_div_u64_rem);