/src/FreeImage/Source/OpenEXR/IlmImf/ImfRational.cpp

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  2//
  3// Copyright (c) 2006, Industrial Light & Magic, a division of Lucas
  4// Digital Ltd. LLC
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 33///////////////////////////////////////////////////////////////////////////
 34
 35//-----------------------------------------------------------------------------
 36//
 37//	Rational numbers
 38//
 39//	The double-to-Rational conversion code below
 40//	was contributed to OpenEXR by Greg Ward.
 41//
 42//-----------------------------------------------------------------------------
 43
 44#include <ImfRational.h>
 45#include <cmath>
 46
 47using namespace std;
 48
 49namespace Imf {
 50namespace {
 51
 52double
 53frac (double x, double e)
 54{
 55    return x - floor (x + e);
 56}
 57
 58
 59double
 60square (double x)
 61{
 62    return x * x;
 63}
 64
 65
 66double
 67denom (double x, double e)
 68{
 69    if (e > frac (x, e))
 70    {
 71        return 1;
 72    }
 73    else
 74    {
 75	double r = frac (1 / x, e);
 76	
 77        if (e > r)
 78        {
 79            return floor (1 / x + e);
 80        }
 81        else
 82        {
 83            return denom (frac (1 / r, e), e / square (x * r)) +
 84                   floor (1 / x + e) * denom (frac (1 / x, e), e / square (x));
 85        }
 86    }
 87}
 88
 89} // namespace
 90
 91
 92Rational::Rational (double x)
 93{
 94    int sign;
 95
 96    if (x >= 0)
 97    {
 98	sign = 1;	// positive
 99    }
100    else if (x < 0)
101    {
102	sign = -1;	// negative
103	x = -x;
104    }
105    else
106    {
107	n = 0;		// NaN
108	d = 0;
109	return;
110    }
111
112    if (x >= (1U << 31) - 0.5)
113    {
114	n = sign;	// infinity
115	d = 0;
116	return;
117    }
118
119    double e = (x < 1? 1: x) / (1U << 30);
120    d = (unsigned int) denom (x, e);
121    n = sign * (int) floor (x * d + 0.5);
122}
123
124
125} // namespace Imf