div64.c 1.7 KB

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  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. #include <linux/types.h>
  19. #include <linux/module.h>
  20. #include <asm/div64.h>
  21. /* Not needed on 64bit architectures */
  22. #if BITS_PER_LONG == 32
  23. uint32_t __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. /* Reduce the thing a bit first */
  30. res = 0;
  31. if (high >= base) {
  32. high /= base;
  33. res = (uint64_t) high << 32;
  34. rem -= (uint64_t) (high*base) << 32;
  35. }
  36. while ((int64_t)b > 0 && b < rem) {
  37. b = b+b;
  38. d = d+d;
  39. }
  40. do {
  41. if (rem >= b) {
  42. rem -= b;
  43. res += d;
  44. }
  45. b >>= 1;
  46. d >>= 1;
  47. } while (d);
  48. *n = res;
  49. return rem;
  50. }
  51. EXPORT_SYMBOL(__div64_32);
  52. /* 64bit divisor, dividend and result. dynamic precision */
  53. uint64_t div64_64(uint64_t dividend, uint64_t divisor)
  54. {
  55. uint32_t d = divisor;
  56. if (divisor > 0xffffffffULL) {
  57. unsigned int shift = fls(divisor >> 32);
  58. d = divisor >> shift;
  59. dividend >>= shift;
  60. }
  61. /* avoid 64 bit division if possible */
  62. if (dividend >> 32)
  63. do_div(dividend, d);
  64. else
  65. dividend = (uint32_t) dividend / d;
  66. return dividend;
  67. }
  68. EXPORT_SYMBOL(div64_64);
  69. #endif /* BITS_PER_LONG == 32 */