s_lrint.c 2.3 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, see
  16. <http://www.gnu.org/licenses/>. */
  17. #include <features.h>
  18. /* Prevent math.h from defining a colliding inline */
  19. #undef __USE_EXTERN_INLINES
  20. #include <math.h>
  21. #include "math_private.h"
  22. static const double two52[2] =
  23. {
  24. 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
  25. -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
  26. };
  27. long int
  28. lrint (double x)
  29. {
  30. int32_t _j0;
  31. u_int32_t i0,i1;
  32. volatile double w;
  33. double t;
  34. long int result;
  35. int sx;
  36. EXTRACT_WORDS (i0, i1, x);
  37. _j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  38. sx = i0 >> 31;
  39. i0 &= 0xfffff;
  40. i0 |= 0x100000;
  41. if (_j0 < 20)
  42. {
  43. if (_j0 < -1)
  44. return 0;
  45. else
  46. {
  47. w = two52[sx] + x;
  48. t = w - two52[sx];
  49. EXTRACT_WORDS (i0, i1, t);
  50. _j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  51. i0 &= 0xfffff;
  52. i0 |= 0x100000;
  53. result = i0 >> (20 - _j0);
  54. }
  55. }
  56. else if (_j0 < (int32_t) (8 * sizeof (long int)) - 1)
  57. {
  58. if (_j0 >= 52)
  59. result = ((long int) i0 << (_j0 - 20)) | (i1 << (_j0 - 52));
  60. else
  61. {
  62. w = two52[sx] + x;
  63. t = w - two52[sx];
  64. EXTRACT_WORDS (i0, i1, t);
  65. _j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  66. i0 &= 0xfffff;
  67. i0 |= 0x100000;
  68. if (_j0 == 20)
  69. result = (long int) i0;
  70. else
  71. result = ((long int) i0 << (_j0 - 20)) | (i1 >> (52 - _j0));
  72. }
  73. }
  74. else
  75. {
  76. /* The number is too large. It is left implementation defined
  77. what happens. */
  78. return (long int) x;
  79. }
  80. return sx ? -result : result;
  81. }
  82. libm_hidden_def(lrint)