linux/include/asm-generic/div64.h
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   1#ifndef _ASM_GENERIC_DIV64_H
   2#define _ASM_GENERIC_DIV64_H
   3/*
   4 * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
   5 * Based on former asm-ppc/div64.h and asm-m68knommu/div64.h
   6 *
   7 * The semantics of do_div() are:
   8 *
   9 * uint32_t do_div(uint64_t *n, uint32_t base)
  10 * {
  11 *      uint32_t remainder = *n % base;
  12 *      *n = *n / base;
  13 *      return remainder;
  14 * }
  15 *
  16 * NOTE: macro parameter n is evaluated multiple times,
  17 *       beware of side effects!
  18 */
  19
  20#include <linux/types.h>
  21#include <linux/compiler.h>
  22
  23#if BITS_PER_LONG == 64
  24
  25# define do_div(n,base) ({                                      \
  26        uint32_t __base = (base);                               \
  27        uint32_t __rem;                                         \
  28        __rem = ((uint64_t)(n)) % __base;                       \
  29        (n) = ((uint64_t)(n)) / __base;                         \
  30        __rem;                                                  \
  31 })
  32
  33#elif BITS_PER_LONG == 32
  34
  35extern uint32_t __div64_32(uint64_t *dividend, uint32_t divisor);
  36
  37/* The unnecessary pointer compare is there
  38 * to check for type safety (n must be 64bit)
  39 */
  40# define do_div(n,base) ({                              \
  41        uint32_t __base = (base);                       \
  42        uint32_t __rem;                                 \
  43        (void)(((typeof((n)) *)0) == ((uint64_t *)0));  \
  44        if (likely(((n) >> 32) == 0)) {                 \
  45                __rem = (uint32_t)(n) % __base;         \
  46                (n) = (uint32_t)(n) / __base;           \
  47        } else                                          \
  48                __rem = __div64_32(&(n), __base);       \
  49        __rem;                                          \
  50 })
  51
  52#else /* BITS_PER_LONG == ?? */
  53
  54# error do_div() does not yet support the C64
  55
  56#endif /* BITS_PER_LONG */
  57
  58#endif /* _ASM_GENERIC_DIV64_H */
  59
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