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4349 | Serge | 1 | /* |
2 | * ==================================================== |
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3 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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4 | * |
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5 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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6 | * Permission to use, copy, modify, and distribute this |
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7 | * software is freely granted, provided that this notice |
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8 | * is preserved. |
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9 | * ==================================================== |
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10 | */ |
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11 | /* |
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12 | FUNCTION |
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13 | < |
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14 | INDEX |
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15 | round |
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16 | INDEX |
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17 | roundf |
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18 | |||
19 | ANSI_SYNOPSIS |
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20 | #include |
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21 | double round(double <[x]>); |
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22 | float roundf(float <[x]>); |
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23 | |||
24 | DESCRIPTION |
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25 | The < |
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26 | value in floating-point format, rounding halfway cases away from zero, |
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27 | regardless of the current rounding direction. (While the "inexact" |
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28 | floating-point exception behavior is unspecified by the C standard, the |
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29 | < |
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30 | result does not equal the argument, which behavior is as recommended by |
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31 | IEEE 754 for its related functions.) |
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32 | |||
33 | RETURNS |
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34 | <[x]> rounded to an integral value. |
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35 | |||
36 | PORTABILITY |
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37 | ANSI C, POSIX |
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38 | |||
39 | SEEALSO |
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40 | < |
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41 | |||
42 | */ |
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43 | |||
44 | #include "fdlibm.h" |
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45 | |||
46 | #ifndef _DOUBLE_IS_32BITS |
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47 | |||
48 | #ifdef __STDC__ |
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49 | double round(double x) |
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50 | #else |
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51 | double round(x) |
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52 | double x; |
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53 | #endif |
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54 | { |
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55 | /* Most significant word, least significant word. */ |
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56 | __int32_t msw, exponent_less_1023; |
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57 | __uint32_t lsw; |
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58 | |||
59 | EXTRACT_WORDS(msw, lsw, x); |
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60 | |||
61 | /* Extract exponent field. */ |
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62 | exponent_less_1023 = ((msw & 0x7ff00000) >> 20) - 1023; |
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63 | |||
64 | if (exponent_less_1023 < 20) |
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65 | { |
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66 | if (exponent_less_1023 < 0) |
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67 | { |
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68 | msw &= 0x80000000; |
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69 | if (exponent_less_1023 == -1) |
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70 | /* Result is +1.0 or -1.0. */ |
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71 | msw |= (1023 << 20); |
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72 | lsw = 0; |
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73 | } |
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74 | else |
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75 | { |
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76 | __uint32_t exponent_mask = 0x000fffff >> exponent_less_1023; |
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77 | if ((msw & exponent_mask) == 0 && lsw == 0) |
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78 | /* x in an integral value. */ |
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79 | return x; |
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80 | |||
81 | msw += 0x00080000 >> exponent_less_1023; |
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82 | msw &= ~exponent_mask; |
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83 | lsw = 0; |
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84 | } |
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85 | } |
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86 | else if (exponent_less_1023 > 51) |
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87 | { |
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88 | if (exponent_less_1023 == 1024) |
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89 | /* x is NaN or infinite. */ |
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90 | return x + x; |
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91 | else |
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92 | return x; |
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93 | } |
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94 | else |
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95 | { |
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96 | __uint32_t exponent_mask = 0xffffffff >> (exponent_less_1023 - 20); |
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97 | __uint32_t tmp; |
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98 | |||
99 | if ((lsw & exponent_mask) == 0) |
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100 | /* x is an integral value. */ |
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101 | return x; |
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102 | |||
103 | tmp = lsw + (1 << (51 - exponent_less_1023)); |
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104 | if (tmp < lsw) |
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105 | msw += 1; |
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106 | lsw = tmp; |
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107 | |||
108 | lsw &= ~exponent_mask; |
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109 | } |
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110 | INSERT_WORDS(x, msw, lsw); |
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111 | |||
112 | return x; |
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113 | } |
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114 | |||
115 | #endif /* _DOUBLE_IS_32BITS */>><>><>>> |