s_ceil.c 1.9 KB

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  1. /* @(#)s_ceil.c 5.1 93/09/24 */
  2. /*
  3. * ====================================================
  4. * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
  5. *
  6. * Developed at SunPro, a Sun Microsystems, Inc. business.
  7. * Permission to use, copy, modify, and distribute this
  8. * software is freely granted, provided that this notice
  9. * is preserved.
  10. * ====================================================
  11. */
  12. #if defined(LIBM_SCCS) && !defined(lint)
  13. static char rcsid[] = "$NetBSD: s_ceil.c,v 1.8 1995/05/10 20:46:53 jtc Exp $";
  14. #endif
  15. /*
  16. * ceil(x)
  17. * Return x rounded toward -inf to integral value
  18. * Method:
  19. * Bit twiddling.
  20. * Exception:
  21. * Inexact flag raised if x not equal to ceil(x).
  22. */
  23. #include "math.h"
  24. #include "math_private.h"
  25. #ifdef __STDC__
  26. static const double huge = 1.0e300;
  27. #else
  28. static double huge = 1.0e300;
  29. #endif
  30. #ifdef __STDC__
  31. double ceil(double x)
  32. #else
  33. double ceil(x)
  34. double x;
  35. #endif
  36. {
  37. int32_t i0,i1,j0;
  38. u_int32_t i,j;
  39. EXTRACT_WORDS(i0,i1,x);
  40. j0 = ((i0>>20)&0x7ff)-0x3ff;
  41. if(j0<20) {
  42. if(j0<0) { /* raise inexact if x != 0 */
  43. if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
  44. if(i0<0) {i0=0x80000000;i1=0;}
  45. else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;}
  46. }
  47. } else {
  48. i = (0x000fffff)>>j0;
  49. if(((i0&i)|i1)==0) return x; /* x is integral */
  50. if(huge+x>0.0) { /* raise inexact flag */
  51. if(i0>0) i0 += (0x00100000)>>j0;
  52. i0 &= (~i); i1=0;
  53. }
  54. }
  55. } else if (j0>51) {
  56. if(j0==0x400) return x+x; /* inf or NaN */
  57. else return x; /* x is integral */
  58. } else {
  59. i = ((u_int32_t)(0xffffffff))>>(j0-20);
  60. if((i1&i)==0) return x; /* x is integral */
  61. if(huge+x>0.0) { /* raise inexact flag */
  62. if(i0>0) {
  63. if(j0==20) i0+=1;
  64. else {
  65. j = i1 + (1<<(52-j0));
  66. if(j<i1) i0+=1; /* got a carry */
  67. i1 = j;
  68. }
  69. }
  70. i1 &= (~i);
  71. }
  72. }
  73. INSERT_WORDS(x,i0,i1);
  74. return x;
  75. }
  76. libm_hidden_def(ceil)