s_lrint.c 2.4 KB

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  1. /* Round argument to nearest integral value according to current rounding
  2. direction.
  3. Copyright (C) 1997, 2004 Free Software Foundation, Inc.
  4. This file is part of the GNU C Library.
  5. Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
  6. The GNU C Library is free software; you can redistribute it and/or
  7. modify it under the terms of the GNU Lesser General Public
  8. License as published by the Free Software Foundation; either
  9. version 2.1 of the License, or (at your option) any later version.
  10. The GNU C Library is distributed in the hope that it will be useful,
  11. but WITHOUT ANY WARRANTY; without even the implied warranty of
  12. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  13. Lesser General Public License for more details.
  14. You should have received a copy of the GNU Lesser General Public
  15. License along with the GNU C Library; if not, write to the Free
  16. Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17. 02111-1307 USA. */
  18. #include <features.h>
  19. /* Prevent math.h from defining a colliding inline */
  20. #undef __USE_EXTERN_INLINES
  21. #include <math.h>
  22. #include "math_private.h"
  23. static const double two52[2] =
  24. {
  25. 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
  26. -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
  27. };
  28. long int
  29. lrint (double x)
  30. {
  31. int32_t j0;
  32. u_int32_t i0,i1;
  33. volatile double w;
  34. double t;
  35. long int result;
  36. int sx;
  37. EXTRACT_WORDS (i0, i1, x);
  38. j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  39. sx = i0 >> 31;
  40. i0 &= 0xfffff;
  41. i0 |= 0x100000;
  42. if (j0 < 20)
  43. {
  44. if (j0 < -1)
  45. return 0;
  46. else
  47. {
  48. w = two52[sx] + x;
  49. t = w - two52[sx];
  50. EXTRACT_WORDS (i0, i1, t);
  51. j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  52. i0 &= 0xfffff;
  53. i0 |= 0x100000;
  54. result = i0 >> (20 - j0);
  55. }
  56. }
  57. else if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
  58. {
  59. if (j0 >= 52)
  60. result = ((long int) i0 << (j0 - 20)) | (i1 << (j0 - 52));
  61. else
  62. {
  63. w = two52[sx] + x;
  64. t = w - two52[sx];
  65. EXTRACT_WORDS (i0, i1, t);
  66. j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  67. i0 &= 0xfffff;
  68. i0 |= 0x100000;
  69. if (j0 == 20)
  70. result = (long int) i0;
  71. else
  72. result = ((long int) i0 << (j0 - 20)) | (i1 >> (52 - j0));
  73. }
  74. }
  75. else
  76. {
  77. /* The number is too large. It is left implementation defined
  78. what happens. */
  79. return (long int) x;
  80. }
  81. return sx ? -result : result;
  82. }
  83. libm_hidden_def(lrint)