[444] | 1 | |
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| 2 | /* @(#)s_floor.c 5.1 93/09/24 */ |
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| 3 | /* |
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| 4 | * ==================================================== |
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| 5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 6 | * |
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| 7 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 8 | * Permission to use, copy, modify, and distribute this |
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| 9 | * software is freely granted, provided that this notice |
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| 10 | * is preserved. |
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| 11 | * ==================================================== |
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| 12 | */ |
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| 13 | |
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| 14 | /* |
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| 15 | FUNCTION |
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| 16 | <<floor>>, <<floorf>>, <<ceil>>, <<ceilf>>---floor and ceiling |
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| 17 | INDEX |
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| 18 | floor |
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| 19 | INDEX |
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| 20 | floorf |
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| 21 | INDEX |
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| 22 | ceil |
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| 23 | INDEX |
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| 24 | ceilf |
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| 25 | |
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| 26 | SYNOPSIS |
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| 27 | #include <math.h> |
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| 28 | double floor(double <[x]>); |
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| 29 | float floorf(float <[x]>); |
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| 30 | double ceil(double <[x]>); |
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| 31 | float ceilf(float <[x]>); |
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| 32 | |
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| 33 | DESCRIPTION |
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| 34 | <<floor>> and <<floorf>> find |
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| 35 | @tex |
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| 36 | $\lfloor x \rfloor$, |
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| 37 | @end tex |
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| 38 | the nearest integer less than or equal to <[x]>. |
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| 39 | <<ceil>> and <<ceilf>> find |
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| 40 | @tex |
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| 41 | $\lceil x\rceil$, |
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| 42 | @end tex |
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| 43 | the nearest integer greater than or equal to <[x]>. |
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| 44 | |
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| 45 | RETURNS |
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| 46 | <<floor>> and <<ceil>> return the integer result as a double. |
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| 47 | <<floorf>> and <<ceilf>> return the integer result as a float. |
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| 48 | |
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| 49 | PORTABILITY |
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| 50 | <<floor>> and <<ceil>> are ANSI. |
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| 51 | <<floorf>> and <<ceilf>> are extensions. |
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| 52 | |
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| 53 | |
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| 54 | */ |
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| 55 | |
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| 56 | /* |
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| 57 | * floor(x) |
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| 58 | * Return x rounded toward -inf to integral value |
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| 59 | * Method: |
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| 60 | * Bit twiddling. |
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| 61 | * Exception: |
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| 62 | * Inexact flag raised if x not equal to floor(x). |
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| 63 | */ |
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| 64 | |
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| 65 | #include "fdlibm.h" |
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| 66 | |
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| 67 | #ifndef _DOUBLE_IS_32BITS |
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| 68 | |
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| 69 | #ifdef __STDC__ |
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| 70 | static const double huge = 1.0e300; |
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| 71 | #else |
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| 72 | static double huge = 1.0e300; |
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| 73 | #endif |
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| 74 | |
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| 75 | #ifdef __STDC__ |
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| 76 | double floor(double x) |
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| 77 | #else |
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| 78 | double floor(x) |
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| 79 | double x; |
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| 80 | #endif |
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| 81 | { |
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| 82 | __int32_t i0,i1,j0; |
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| 83 | __uint32_t i,j; |
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| 84 | EXTRACT_WORDS(i0,i1,x); |
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| 85 | j0 = ((i0>>20)&0x7ff)-0x3ff; |
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| 86 | if(j0<20) { |
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| 87 | if(j0<0) { /* raise inexact if x != 0 */ |
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| 88 | if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */ |
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| 89 | if(i0>=0) {i0=i1=0;} |
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| 90 | else if(((i0&0x7fffffff)|i1)!=0) |
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| 91 | { i0=0xbff00000;i1=0;} |
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| 92 | } |
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| 93 | } else { |
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| 94 | i = (0x000fffff)>>j0; |
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| 95 | if(((i0&i)|i1)==0) return x; /* x is integral */ |
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| 96 | if(huge+x>0.0) { /* raise inexact flag */ |
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| 97 | if(i0<0) i0 += (0x00100000)>>j0; |
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| 98 | i0 &= (~i); i1=0; |
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| 99 | } |
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| 100 | } |
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| 101 | } else if (j0>51) { |
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| 102 | if(j0==0x400) return x+x; /* inf or NaN */ |
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| 103 | else return x; /* x is integral */ |
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| 104 | } else { |
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| 105 | i = ((__uint32_t)(0xffffffff))>>(j0-20); |
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| 106 | if((i1&i)==0) return x; /* x is integral */ |
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| 107 | if(huge+x>0.0) { /* raise inexact flag */ |
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| 108 | if(i0<0) { |
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| 109 | if(j0==20) i0+=1; |
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| 110 | else { |
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| 111 | j = i1+(1<<(52-j0)); |
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| 112 | if(j<i1) i0 +=1 ; /* got a carry */ |
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| 113 | i1=j; |
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| 114 | } |
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| 115 | } |
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| 116 | i1 &= (~i); |
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| 117 | } |
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| 118 | } |
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| 119 | INSERT_WORDS(x,i0,i1); |
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| 120 | return x; |
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| 121 | } |
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| 122 | |
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| 123 | #endif /* _DOUBLE_IS_32BITS */ |
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