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/**
* @file is_approx_equal_fraction.h
* @author Nat Goodspeed
* @date 2009-01-28
* @brief lltut.h uses is_approx_equal_fraction(). Moved to this header
* file in llcommon so we can use lltut.h for llcommon tests without
* making llcommon depend on llmath.
*
* $LicenseInfo:firstyear=2009&license=viewerlgpl$
* Second Life Viewer Source Code
* Copyright (C) 2010, Linden Research, Inc.
*
* This 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;
* version 2.1 of the License only.
*
* This 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 this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
* $/LicenseInfo$
*/
#if ! defined(LL_IS_APPROX_EQUAL_FRACTION_H)
#define LL_IS_APPROX_EQUAL_FRACTION_H
#include "lldefs.h"
#include <cmath>
/**
* Originally llmath.h contained two complete implementations of
* is_approx_equal_fraction(), with signatures as below, bodies identical save
* where they specifically mentioned F32/F64. Unifying these into a template
* makes sense -- but to preserve the compiler's overload-selection behavior,
* we still wrap the template implementation with the specific overloaded
* signatures.
*/
template <typename FTYPE>
inline bool is_approx_equal_fraction_impl(FTYPE x, FTYPE y, U32 frac_bits)
{
bool ret = true;
FTYPE diff = (FTYPE) fabs(x - y);
S32 diffInt = (S32) diff;
S32 diffFracTolerance = (S32) ((diff - (FTYPE) diffInt) * (1 << frac_bits));
// if integer portion is not equal, not enough bits were used for packing
// so error out since either the use case is not correct OR there is
// an issue with pack/unpack. should fail in either case.
// for decimal portion, make sure that the delta is no more than 1
// based on the number of bits used for packing decimal portion.
if (diffInt != 0 || diffFracTolerance > 1)
{
ret = false;
}
return ret;
}
/// F32 flavor
inline bool is_approx_equal_fraction(F32 x, F32 y, U32 frac_bits)
{
return is_approx_equal_fraction_impl<F32>(x, y, frac_bits);
}
/// F64 flavor
inline bool is_approx_equal_fraction(F64 x, F64 y, U32 frac_bits)
{
return is_approx_equal_fraction_impl<F64>(x, y, frac_bits);
}
#endif /* ! defined(LL_IS_APPROX_EQUAL_FRACTION_H) */
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