| 1 | /* |
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| 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 | <<lround>>, <<lroundf>>, <<llround>>, <<llroundf>>---round to integer, to nearest |
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| 14 | INDEX |
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| 15 | lround |
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| 16 | INDEX |
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| 17 | lroundf |
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| 18 | INDEX |
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| 19 | llround |
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| 20 | INDEX |
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| 21 | llroundf |
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| 22 | |
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| 23 | SYNOPSIS |
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| 24 | #include <math.h> |
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| 25 | long int lround(double <[x]>); |
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| 26 | long int lroundf(float <[x]>); |
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| 27 | long long int llround(double <[x]>); |
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| 28 | long long int llroundf(float <[x]>); |
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| 29 | |
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| 30 | DESCRIPTION |
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| 31 | The <<lround>> and <<llround>> functions round their argument to the |
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| 32 | nearest integer value, rounding halfway cases away from zero, regardless |
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| 33 | of the current rounding direction. If the rounded value is outside the |
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| 34 | range of the return type, the numeric result is unspecified (depending |
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| 35 | upon the floating-point implementation, not the library). A range |
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| 36 | error may occur if the magnitude of x is too large. |
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| 37 | |
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| 38 | RETURNS |
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| 39 | <[x]> rounded to an integral value as an integer. |
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| 40 | |
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| 41 | SEEALSO |
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| 42 | See the <<round>> functions for the return being the same floating-point type |
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| 43 | as the argument. <<lrint>>, <<llrint>>. |
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| 44 | |
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| 45 | PORTABILITY |
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| 46 | ANSI C, POSIX |
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| 47 | |
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| 48 | */ |
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| 49 | |
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| 50 | #include "fdlibm.h" |
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| 51 | |
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| 52 | #ifndef _DOUBLE_IS_32BITS |
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| 53 | |
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| 54 | #ifdef __STDC__ |
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| 55 | long int lround(double x) |
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| 56 | #else |
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| 57 | long int lround(x) |
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| 58 | double x; |
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| 59 | #endif |
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| 60 | { |
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| 61 | __int32_t sign, exponent_less_1023; |
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| 62 | /* Most significant word, least significant word. */ |
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| 63 | __uint32_t msw, lsw; |
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| 64 | long int result; |
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| 65 | |
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| 66 | EXTRACT_WORDS(msw, lsw, x); |
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| 67 | |
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| 68 | /* Extract sign. */ |
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| 69 | sign = ((msw & 0x80000000) ? -1 : 1); |
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| 70 | /* Extract exponent field. */ |
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| 71 | exponent_less_1023 = ((msw & 0x7ff00000) >> 20) - 1023; |
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| 72 | msw &= 0x000fffff; |
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| 73 | msw |= 0x00100000; |
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| 74 | /* exponent_less_1023 in [-1023,1024] */ |
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| 75 | if (exponent_less_1023 < 20) |
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| 76 | { |
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| 77 | /* exponent_less_1023 in [-1023,19] */ |
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| 78 | if (exponent_less_1023 < 0) |
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| 79 | { |
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| 80 | if (exponent_less_1023 < -1) |
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| 81 | return 0; |
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| 82 | else |
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| 83 | return sign; |
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| 84 | } |
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| 85 | else |
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| 86 | { |
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| 87 | /* exponent_less_1023 in [0,19] */ |
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| 88 | /* shift amt in [0,19] */ |
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| 89 | msw += 0x80000 >> exponent_less_1023; |
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| 90 | /* shift amt in [20,1] */ |
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| 91 | result = msw >> (20 - exponent_less_1023); |
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| 92 | } |
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| 93 | } |
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| 94 | else if (exponent_less_1023 < (8 * sizeof (long int)) - 1) |
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| 95 | { |
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| 96 | /* 32bit long: exponent_less_1023 in [20,30] */ |
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| 97 | /* 64bit long: exponent_less_1023 in [20,62] */ |
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| 98 | if (exponent_less_1023 >= 52) |
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| 99 | /* 64bit long: exponent_less_1023 in [52,62] */ |
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| 100 | /* 64bit long: shift amt in [32,42] */ |
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| 101 | result = ((long int) msw << (exponent_less_1023 - 20)) |
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| 102 | /* 64bit long: shift amt in [0,10] */ |
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| 103 | | (lsw << (exponent_less_1023 - 52)); |
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| 104 | else |
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| 105 | { |
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| 106 | /* 32bit long: exponent_less_1023 in [20,30] */ |
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| 107 | /* 64bit long: exponent_less_1023 in [20,51] */ |
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| 108 | unsigned int tmp = lsw |
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| 109 | /* 32bit long: shift amt in [0,10] */ |
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| 110 | /* 64bit long: shift amt in [0,31] */ |
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| 111 | + (0x80000000 >> (exponent_less_1023 - 20)); |
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| 112 | if (tmp < lsw) |
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| 113 | ++msw; |
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| 114 | /* 32bit long: shift amt in [0,10] */ |
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| 115 | /* 64bit long: shift amt in [0,31] */ |
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| 116 | result = ((long int) msw << (exponent_less_1023 - 20)) |
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| 117 | /* ***32bit long: shift amt in [32,22] */ |
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| 118 | /* ***64bit long: shift amt in [32,1] */ |
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| 119 | | SAFE_RIGHT_SHIFT (tmp, (52 - exponent_less_1023)); |
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| 120 | } |
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| 121 | } |
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| 122 | else |
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| 123 | /* Result is too large to be represented by a long int. */ |
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| 124 | return (long int)x; |
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| 125 | |
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| 126 | return sign * result; |
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| 127 | } |
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| 128 | |
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| 129 | #endif /* _DOUBLE_IS_32BITS */ |
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