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[/] [openrisc/] [trunk/] [gnu-stable/] [newlib-1.18.0/] [newlib/] [libm/] [common/] [s_round.c] - Rev 859
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/* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunPro, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== */ /* FUNCTION <<round>>, <<roundf>>--round to integer, to nearest INDEX round INDEX roundf ANSI_SYNOPSIS #include <math.h> double round(double <[x]>); float roundf(float <[x]>); DESCRIPTION The <<round>> functions round their argument to the nearest integer value in floating-point format, rounding halfway cases away from zero, regardless of the current rounding direction. (While the "inexact" floating-point exception behavior is unspecified by the C standard, the <<round>> functions are written so that "inexact" is not raised if the result does not equal the argument, which behavior is as recommended by IEEE 754 for its related functions.) RETURNS <[x]> rounded to an integral value. PORTABILITY ANSI C, POSIX SEEALSO <<nearbyint>>, <<rint>> */ #include "fdlibm.h" #ifndef _DOUBLE_IS_32BITS #ifdef __STDC__ double round(double x) #else double round(x) double x; #endif { /* Most significant word, least significant word. */ __int32_t msw, exponent_less_1023; __uint32_t lsw; EXTRACT_WORDS(msw, lsw, x); /* Extract exponent field. */ exponent_less_1023 = ((msw & 0x7ff00000) >> 20) - 1023; if (exponent_less_1023 < 20) { if (exponent_less_1023 < 0) { msw &= 0x80000000; if (exponent_less_1023 == -1) /* Result is +1.0 or -1.0. */ msw |= (1023 << 20); lsw = 0; } else { __uint32_t exponent_mask = 0x000fffff >> exponent_less_1023; if ((msw & exponent_mask) == 0 && lsw == 0) /* x in an integral value. */ return x; msw += 0x00080000 >> exponent_less_1023; msw &= ~exponent_mask; lsw = 0; } } else if (exponent_less_1023 > 51) { if (exponent_less_1023 == 1024) /* x is NaN or infinite. */ return x + x; else return x; } else { __uint32_t exponent_mask = 0xffffffff >> (exponent_less_1023 - 20); __uint32_t tmp; if ((lsw & exponent_mask) == 0) /* x is an integral value. */ return x; tmp = lsw + (1 << (51 - exponent_less_1023)); if (tmp < lsw) msw += 1; lsw = tmp; lsw &= ~exponent_mask; } INSERT_WORDS(x, msw, lsw); return x; } #endif /* _DOUBLE_IS_32BITS */
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