Version:  2.6.24 2.6.25 2.6.26 2.6.27 2.6.28

Architecture:  x86 m68k m68knommu mips powerpc sh blackfin

Linux/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/ppc/lib/div64.S and arch/sh/lib/div64.S.
 17  */
 18 
 19 #include <linux/module.h>
 20 #include <linux/math64.h>
 21 
 22 /* Not needed on 64bit architectures */
 23 #if BITS_PER_LONG == 32
 24 
 25 uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
 26 {
 27         uint64_t rem = *n;
 28         uint64_t b = base;
 29         uint64_t res, d = 1;
 30         uint32_t high = rem >> 32;
 31 
 32         /* Reduce the thing a bit first */
 33         res = 0;
 34         if (high >= base) {
 35                 high /= base;
 36                 res = (uint64_t) high << 32;
 37                 rem -= (uint64_t) (high*base) << 32;
 38         }
 39 
 40         while ((int64_t)b > 0 && b < rem) {
 41                 b = b+b;
 42                 d = d+d;
 43         }
 44 
 45         do {
 46                 if (rem >= b) {
 47                         rem -= b;
 48                         res += d;
 49                 }
 50                 b >>= 1;
 51                 d >>= 1;
 52         } while (d);
 53 
 54         *n = res;
 55         return rem;
 56 }
 57 
 58 EXPORT_SYMBOL(__div64_32);
 59 
 60 #ifndef div_s64_rem
 61 s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
 62 {
 63         u64 quotient;
 64 
 65         if (dividend < 0) {
 66                 quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
 67                 *remainder = -*remainder;
 68                 if (divisor > 0)
 69                         quotient = -quotient;
 70         } else {
 71                 quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
 72                 if (divisor < 0)
 73                         quotient = -quotient;
 74         }
 75         return quotient;
 76 }
 77 EXPORT_SYMBOL(div_s64_rem);
 78 #endif
 79 
 80 /* 64bit divisor, dividend and result. dynamic precision */
 81 #ifndef div64_u64
 82 u64 div64_u64(u64 dividend, u64 divisor)
 83 {
 84         u32 high, d;
 85 
 86         high = divisor >> 32;
 87         if (high) {
 88                 unsigned int shift = fls(high);
 89 
 90                 d = divisor >> shift;
 91                 dividend >>= shift;
 92         } else
 93                 d = divisor;
 94 
 95         return div_u64(dividend, d);
 96 }
 97 EXPORT_SYMBOL(div64_u64);
 98 #endif
 99 
100 #endif /* BITS_PER_LONG == 32 */
101 
102 /*
103  * Iterative div/mod for use when dividend is not expected to be much
104  * bigger than divisor.
105  */
106 u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
107 {
108         return __iter_div_u64_rem(dividend, divisor, remainder);
109 }
110 EXPORT_SYMBOL(iter_div_u64_rem);
111

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