s_floor.c 1.9 KB

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  1. #if !defined(__ppc__)
  2. /* @(#)s_floor.c 5.1 93/09/24 */
  3. /*
  4. * ====================================================
  5. * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
  6. *
  7. * Developed at SunPro, a Sun Microsystems, Inc. business.
  8. * Permission to use, copy, modify, and distribute this
  9. * software is freely granted, provided that this notice
  10. * is preserved.
  11. * ====================================================
  12. */
  13. #if defined(LIBM_SCCS) && !defined(lint)
  14. static char rcsid[] = "$NetBSD: s_floor.c,v 1.8 1995/05/10 20:47:20 jtc Exp $";
  15. #endif
  16. /*
  17. * floor(x)
  18. * Return x rounded toward -inf to integral value
  19. * Method:
  20. * Bit twiddling.
  21. * Exception:
  22. * Inexact flag raised if x not equal to floor(x).
  23. */
  24. #include "math.h"
  25. #include "math_private.h"
  26. #ifdef __STDC__
  27. static const double huge = 1.0e300;
  28. #else
  29. static double huge = 1.0e300;
  30. #endif
  31. #ifdef __STDC__
  32. double floor(double x)
  33. #else
  34. double floor(x)
  35. double x;
  36. #endif
  37. {
  38. int32_t i0,i1,j0;
  39. u_int32_t i,j;
  40. EXTRACT_WORDS(i0,i1,x);
  41. j0 = ((i0>>20)&0x7ff)-0x3ff;
  42. if(j0<20) {
  43. if(j0<0) { /* raise inexact if x != 0 */
  44. if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
  45. if(i0>=0) {i0=i1=0;}
  46. else if(((i0&0x7fffffff)|i1)!=0)
  47. { i0=0xbff00000;i1=0;}
  48. }
  49. } else {
  50. i = (0x000fffff)>>j0;
  51. if(((i0&i)|i1)==0) return x; /* x is integral */
  52. if(huge+x>0.0) { /* raise inexact flag */
  53. if(i0<0) i0 += (0x00100000)>>j0;
  54. i0 &= (~i); i1=0;
  55. }
  56. }
  57. } else if (j0>51) {
  58. if(j0==0x400) return x+x; /* inf or NaN */
  59. else return x; /* x is integral */
  60. } else {
  61. i = ((u_int32_t)(0xffffffff))>>(j0-20);
  62. if((i1&i)==0) return x; /* x is integral */
  63. if(huge+x>0.0) { /* raise inexact flag */
  64. if(i0<0) {
  65. if(j0==20) i0+=1;
  66. else {
  67. j = i1+(1<<(52-j0));
  68. if(j<i1) i0 +=1 ; /* got a carry */
  69. i1=j;
  70. }
  71. }
  72. i1 &= (~i);
  73. }
  74. }
  75. INSERT_WORDS(x,i0,i1);
  76. return x;
  77. }
  78. #endif /* !__ppc__ */