div64.c 1.1 KB

12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152
  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. uint32_t __div64_32(uint64_t *n, uint32_t base)
  20. {
  21. uint64_t rem = *n;
  22. uint64_t b = base;
  23. uint64_t res, d = 1;
  24. uint32_t high = rem >> 32;
  25. /* Reduce the thing a bit first */
  26. res = 0;
  27. if (high >= base) {
  28. high /= base;
  29. res = (uint64_t) high << 32;
  30. rem -= (uint64_t) (high*base) << 32;
  31. }
  32. while ((int64_t)b > 0 && b < rem) {
  33. b = b+b;
  34. d = d+d;
  35. }
  36. do {
  37. if (rem >= b) {
  38. rem -= b;
  39. res += d;
  40. }
  41. b >>= 1;
  42. d >>= 1;
  43. } while (d);
  44. *n = res;
  45. return rem;
  46. }