69 lines
2.2 KiB
C
69 lines
2.2 KiB
C
/* Round to nearest integer value, rounding halfway cases to even.
|
|
flt-32 version.
|
|
Copyright (C) 2016-2017 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library; if not, see
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
#include <math.h>
|
|
#include <math_private.h>
|
|
#include <stdint.h>
|
|
|
|
#define BIAS 0x7f
|
|
#define MANT_DIG 24
|
|
#define MAX_EXP (2 * BIAS + 1)
|
|
|
|
float
|
|
roundevenf (float x)
|
|
{
|
|
uint32_t ix, ux;
|
|
GET_FLOAT_WORD (ix, x);
|
|
ux = ix & 0x7fffffff;
|
|
int exponent = ux >> (MANT_DIG - 1);
|
|
if (exponent >= BIAS + MANT_DIG - 1)
|
|
{
|
|
/* Integer, infinity or NaN. */
|
|
if (exponent == MAX_EXP)
|
|
/* Infinity or NaN; quiet signaling NaNs. */
|
|
return x + x;
|
|
else
|
|
return x;
|
|
}
|
|
else if (exponent >= BIAS)
|
|
{
|
|
/* At least 1; not necessarily an integer. Locate the bits with
|
|
exponents 0 and -1 (when the unbiased exponent is 0, the bit
|
|
with exponent 0 is implicit, but as the bias is odd it is OK
|
|
to take it from the low bit of the exponent). */
|
|
int int_pos = (BIAS + MANT_DIG - 1) - exponent;
|
|
int half_pos = int_pos - 1;
|
|
uint32_t half_bit = 1U << half_pos;
|
|
uint32_t int_bit = 1U << int_pos;
|
|
if ((ix & (int_bit | (half_bit - 1))) != 0)
|
|
/* Carry into the exponent works correctly. No need to test
|
|
whether HALF_BIT is set. */
|
|
ix += half_bit;
|
|
ix &= ~(int_bit - 1);
|
|
}
|
|
else if (exponent == BIAS - 1 && ux > 0x3f000000)
|
|
/* Interval (0.5, 1). */
|
|
ix = (ix & 0x80000000) | 0x3f800000;
|
|
else
|
|
/* Rounds to 0. */
|
|
ix &= 0x80000000;
|
|
SET_FLOAT_WORD (x, ix);
|
|
return x;
|
|
}
|