| 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 | * floor(x) |
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| 16 | * Return x rounded toward -inf to integral value |
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| 17 | * Method: |
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| 18 | * Bit twiddling. |
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| 19 | * Exception: |
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| 20 | * Inexact flag raised if x not equal to floor(x). |
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| 21 | */ |
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| 22 | |
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| 23 | #include <libm/fdlibm.h> |
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| 24 | |
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| 25 | #ifdef __STDC__ |
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| 26 | static const double one = 1.0,huge = 1.0e300; |
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| 27 | #else |
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| 28 | static double one = 1.0,huge = 1.0e300; |
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| 29 | #endif |
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| 30 | |
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| 31 | #ifdef __STDC__ |
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| 32 | double floor(double x) |
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| 33 | #else |
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| 34 | double floor(x) |
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| 35 | double x; |
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| 36 | #endif |
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| 37 | { |
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| 38 | int i0,i1,n0,j0; |
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| 39 | unsigned i,j; |
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| 40 | n0 = (*((int *)&one)>>29)^1; |
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| 41 | i0 = *(n0+(int*)&x); |
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| 42 | i1 = *(1-n0+(int*)&x); |
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| 43 | j0 = ((i0>>20)&0x7ff)-0x3ff; |
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| 44 | if(j0<20) { |
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| 45 | if(j0<0) { /* raise inexact if x != 0 */ |
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| 46 | if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */ |
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| 47 | if(i0>=0) {i0=i1=0;} |
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| 48 | else if(((i0&0x7fffffff)|i1)!=0) |
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| 49 | { i0=0xbff00000;i1=0;} |
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| 50 | } |
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| 51 | } else { |
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| 52 | i = (0x000fffff)>>j0; |
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| 53 | if(((i0&i)|i1)==0) return x; /* x is integral */ |
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| 54 | if(huge+x>0.0) { /* raise inexact flag */ |
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| 55 | if(i0<0) i0 += (0x00100000)>>j0; |
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| 56 | i0 &= (~i); i1=0; |
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| 57 | } |
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| 58 | } |
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| 59 | } else if (j0>51) { |
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| 60 | if(j0==0x400) return x+x; /* inf or NaN */ |
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| 61 | else return x; /* x is integral */ |
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| 62 | } else { |
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| 63 | i = ((unsigned)(0xffffffff))>>(j0-20); |
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| 64 | if((i1&i)==0) return x; /* x is integral */ |
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| 65 | if(huge+x>0.0) { /* raise inexact flag */ |
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| 66 | if(i0<0) { |
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| 67 | if(j0==20) i0+=1; |
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| 68 | else { |
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| 69 | j = i1+(1<<(52-j0)); |
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| 70 | if(j<(unsigned)i1) i0 +=1 ; /* got a carry */ |
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| 71 | i1=j; |
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| 72 | } |
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| 73 | } |
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| 74 | i1 &= (~i); |
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| 75 | } |
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| 76 | } |
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| 77 | *(n0+(int*)&x) = i0; |
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| 78 | *(1-n0+(int*)&x) = i1; |
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| 79 | return x; |
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| 80 | } |
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