85 lines
3.1 KiB
C++
85 lines
3.1 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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* $LicenseInfo:firstyear=2009&license=viewergpl$
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*
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* Copyright (c) 2009, Linden Research, Inc.
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*
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* Second Life Viewer Source Code
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* The source code in this file ("Source Code") is provided by Linden Lab
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* to you under the terms of the GNU General Public License, version 2.0
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* ("GPL"), unless you have obtained a separate licensing agreement
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* ("Other License"), formally executed by you and Linden Lab. Terms of
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* the GPL can be found in doc/GPL-license.txt in this distribution, or
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* online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
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*
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* There are special exceptions to the terms and conditions of the GPL as
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* it is applied to this Source Code. View the full text of the exception
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* in the file doc/FLOSS-exception.txt in this software distribution, or
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* online at
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* http://secondlifegrid.net/programs/open_source/licensing/flossexception
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*
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* By copying, modifying or distributing this software, you acknowledge
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* that you have read and understood your obligations described above,
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* and agree to abide by those obligations.
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*
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* ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
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* WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
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* COMPLETENESS OR PERFORMANCE.
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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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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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return false;
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}
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return true;
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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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