erand48_r.c 1.8 KB

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  1. /* Copyright (C) 1995, 1997, 2001 Free Software Foundation, Inc.
  2. This file is part of the GNU C Library.
  3. Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu <mailto:drepper@gnu.ai.mit.edu>>, August 1995.
  4. The GNU C Library is free software; you can redistribute it and/or
  5. modify it under the terms of the GNU Lesser General Public
  6. License as published by the Free Software Foundation; either
  7. version 2.1 of the License, or (at your option) any later version.
  8. The GNU C Library is distributed in the hope that it will be useful,
  9. but WITHOUT ANY WARRANTY; without even the implied warranty of
  10. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  11. Lesser General Public License for more details.
  12. You should have received a copy of the GNU Lesser General Public
  13. License along with the GNU C Library; if not, write to the Free
  14. Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  15. 02111-1307 USA. */
  16. #include <ieee754.h>
  17. #include <stdlib.h>
  18. #include <limits.h>
  19. extern int __drand48_iterate(unsigned short xsubi[3],
  20. struct drand48_data *buffer) attribute_hidden;
  21. libc_hidden_proto(erand48_r)
  22. int erand48_r (unsigned short int xsubi[3], struct drand48_data *buffer, double *result)
  23. {
  24. union ieee754_double temp;
  25. /* Compute next state. */
  26. if (__drand48_iterate (xsubi, buffer) < 0)
  27. return -1;
  28. /* Construct a positive double with the 48 random bits distributed over
  29. its fractional part so the resulting FP number is [0.0,1.0). */
  30. temp.ieee.negative = 0;
  31. temp.ieee.exponent = IEEE754_DOUBLE_BIAS;
  32. temp.ieee.mantissa0 = (xsubi[2] << 4) | (xsubi[1] >> 12);
  33. temp.ieee.mantissa1 = ((xsubi[1] & 0xfff) << 20) | (xsubi[0] << 4);
  34. /* Please note the lower 4 bits of mantissa1 are always 0. */
  35. *result = temp.d - 1.0;
  36. return 0;
  37. }
  38. libc_hidden_def(erand48_r)