floating.h

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/*
 * Copyright (C) 2012-2015 Paul Davis <paul@linuxaudiosystems.com>
 * Copyright (C) 2013 John Emmas <john@creativepost.co.uk>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
/* Taken from
 * http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm
 *
 * Code assumed to be in the public domain.
 */
 
#ifndef __libpbd__floating_h__
#define __libpbd__floating_h__
 
#include <stdint.h>
 
#include <cstdlib> // abs(int)
#include <cmath>
 
#include "pbd/libpbd_visibility.h"
 
namespace PBD {
 
union /*LIBPBD_API*/ Float_t
{
    Float_t (float num = 0.0f) : f(num) {}
 
    // Portable extraction of components.
    bool    negative() const { return (i >> 31) != 0; }
    int32_t raw_mantissa() const { return i & ((1 << 23) - 1); }
    int32_t raw_exponent() const { return (i >> 23) & 0xFF; }
 
    int32_t i;
    float f;
};
 
/* Note: ULPS = Units in the Last Place */
 
static inline bool floateq (float a, float b, int max_ulps_diff)
{
    Float_t ua (a);
    Float_t ub (b);
 
    if (a == b) {
            return true;
    }
 
    // Different signs means they do not match.
    if (ua.negative() != ub.negative()) {
            return false;
    }
 
    // Find the difference in ULPs.
    int ulps_diff = abs (ua.i - ub.i);
 
    if (ulps_diff <= max_ulps_diff) {
        return true;
    }
 
    return false;
}
 
} /* namespace */
 
#endif /* __libpbd__floating_h__ */