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