/* * Copyright (c) 2015 Jiri Svoboda * Copyright (c) 2014 Martin Decky * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * - The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /** @addtogroup libmath * @{ */ /** @file */ #include <math.h> #include <float.h> #include <stdint.h> /** Truncate fractional part (round towards zero) * * Truncate the fractional part of IEEE 754 single * precision floating point number by zeroing fraction * bits, effectively rounding the number towards zero * to the nearest whole number. * * If the argument is infinity or NaN, an exception * should be indicated. This is not implemented yet. * * @param val Floating point number. * * @return Number rounded towards zero. * */ float truncf(float val) { const int exp_bias = FLT_MAX_EXP - 1; const int mant_bits = FLT_MANT_DIG - 1; const uint32_t mant_mask = (UINT32_C(1) << mant_bits) - 1; union { float f; uint32_t i; } u = { .f = fabsf(val) }; int exp = (u.i >> mant_bits) - exp_bias; /* If value is less than one, return zero with appropriate sign. */ if (exp < 0) return copysignf(0.0f, val); if (exp >= mant_bits) return val; /* Truncate irrelevant fraction bits */ u.i &= ~(mant_mask >> exp); return copysignf(u.f, val); } /** Truncate fractional part (round towards zero) * * Truncate the fractional part of IEEE 754 double * precision floating point number by zeroing fraction * bits, effectively rounding the number towards zero * to the nearest whole number. * * If the argument is infinity or NaN, an exception * should be indicated. This is not implemented yet. * * @param val Floating point number. * * @return Number rounded towards zero. * */ double trunc(double val) { const int exp_bias = DBL_MAX_EXP - 1; const int mant_bits = DBL_MANT_DIG - 1; const uint64_t mant_mask = (UINT64_C(1) << mant_bits) - 1; union { double f; uint64_t i; } u = { .f = fabs(val) }; int exp = ((int)(u.i >> mant_bits)) - exp_bias; /* If value is less than one, return zero with appropriate sign. */ if (exp < 0) return copysign(0.0, val); if (exp >= mant_bits) return val; /* Truncate irrelevant fraction bits */ u.i &= ~(mant_mask >> exp); return copysign(u.f, val); } /** @} */