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102 lines
2.2 KiB
C
102 lines
2.2 KiB
C
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/* @(#)sf_lrint.c 5.1 93/09/24 */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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/*
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* lrintf(x)
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* Return x rounded to integral value according to the prevailing
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* rounding mode.
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* Method:
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* Using floating addition.
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* Exception:
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* Inexact flag raised if x not equal to lrintf(x).
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*/
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#include "fdlibm.h"
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#ifdef __STDC__
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static const float
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#else
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static float
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#endif
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/* Adding a float, x, to 2^23 will cause the result to be rounded based on
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the fractional part of x, according to the implementation's current rounding
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mode. 2^23 is the smallest float that can be represented using all 23 significant
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digits. */
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TWO23[2]={
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8.3886080000e+06, /* 0x4b000000 */
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-8.3886080000e+06, /* 0xcb000000 */
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};
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#ifdef __STDC__
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long int lrintf(float x)
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#else
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long int lrintf(x)
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float x;
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#endif
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{
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__int32_t j0,sx;
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__uint32_t i0;
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float t;
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volatile float w;
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long int result;
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GET_FLOAT_WORD(i0,x);
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/* Extract sign bit. */
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sx = (i0 >> 31);
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/* Extract exponent field. */
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j0 = ((i0 & 0x7f800000) >> 23) - 127;
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if (j0 < (int)(sizeof (long int) * 8) - 1)
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{
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if (j0 < -1)
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return 0;
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else if (j0 >= 23)
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result = (long int) ((i0 & 0x7fffff) | 0x800000) << (j0 - 23);
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else
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{
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w = TWO23[sx] + x;
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t = w - TWO23[sx];
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GET_FLOAT_WORD (i0, t);
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/* Detect the all-zeros representation of plus and
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minus zero, which fails the calculation below. */
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if ((i0 & ~(1L << 31)) == 0)
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return 0;
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j0 = ((i0 >> 23) & 0xff) - 0x7f;
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i0 &= 0x7fffff;
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i0 |= 0x800000;
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result = i0 >> (23 - j0);
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}
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}
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else
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{
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return (long int) x;
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}
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return sx ? -result : result;
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}
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#ifdef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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long int lrint(double x)
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#else
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long int lrint(x)
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double x;
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#endif
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{
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return lrintf((float) x);
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */
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