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2758
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1 /* @(#)s_floor.c 5.1 93/09/24 */
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2 /*
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3 * ====================================================
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4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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5 *
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6 * Developed at SunPro, a Sun Microsystems, Inc. business.
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7 * Permission to use, copy, modify, and distribute this
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8 * software is freely granted, provided that this notice
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9 * is preserved.
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10 * ====================================================
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11 */
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12
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13 #if defined(LIBM_SCCS) && !defined(lint)
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14 static char rcsid[] =
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15 "$NetBSD: s_floor.c,v 1.8 1995/05/10 20:47:20 jtc Exp $";
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16 #endif
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17
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18 /*
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19 * floor(x)
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20 * Return x rounded toward -inf to integral value
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21 * Method:
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22 * Bit twiddling.
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23 * Exception:
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24 * Inexact flag raised if x not equal to floor(x).
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25 */
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26
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27 #include "math.h"
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28 #include "math_private.h"
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29
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30 #ifdef __STDC__
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31 static const double huge = 1.0e300;
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32 #else
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33 static double huge = 1.0e300;
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34 #endif
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35
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36 libm_hidden_proto(floor)
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37 #ifdef __STDC__
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38 double floor(double x)
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39 #else
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40 double floor(x)
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41 double x;
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42 #endif
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43 {
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44 int32_t i0, i1, j0;
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45 u_int32_t i, j;
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46 EXTRACT_WORDS(i0, i1, x);
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47 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
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48 if (j0 < 20) {
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49 if (j0 < 0) { /* raise inexact if x != 0 */
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50 if (huge + x > 0.0) { /* return 0*sign(x) if |x|<1 */
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51 if (i0 >= 0) {
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52 i0 = i1 = 0;
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53 } else if (((i0 & 0x7fffffff) | i1) != 0) {
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54 i0 = 0xbff00000;
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55 i1 = 0;
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56 }
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57 }
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58 } else {
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59 i = (0x000fffff) >> j0;
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60 if (((i0 & i) | i1) == 0)
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61 return x; /* x is integral */
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62 if (huge + x > 0.0) { /* raise inexact flag */
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63 if (i0 < 0)
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64 i0 += (0x00100000) >> j0;
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65 i0 &= (~i);
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66 i1 = 0;
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67 }
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68 }
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69 } else if (j0 > 51) {
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70 if (j0 == 0x400)
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71 return x + x; /* inf or NaN */
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72 else
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73 return x; /* x is integral */
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74 } else {
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75 i = ((u_int32_t) (0xffffffff)) >> (j0 - 20);
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76 if ((i1 & i) == 0)
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77 return x; /* x is integral */
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78 if (huge + x > 0.0) { /* raise inexact flag */
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79 if (i0 < 0) {
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80 if (j0 == 20)
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81 i0 += 1;
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82 else {
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83 j = i1 + (1 << (52 - j0));
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84 if (j < i1)
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85 i0 += 1; /* got a carry */
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86 i1 = j;
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87 }
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88 }
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89 i1 &= (~i);
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90 }
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91 }
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92 INSERT_WORDS(x, i0, i1);
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93 return x;
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94 }
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95
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96 libm_hidden_def(floor)
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