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annotate libs/assimp/qnan.h @ 1:e7ca128b8713

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looks nice :)
author John Tsiombikas <nuclear@member.fsf.org>
date Sun, 02 Feb 2014 00:35:22 +0200
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nuclear@0 1 /*
nuclear@0 2 ---------------------------------------------------------------------------
nuclear@0 3 Open Asset Import Library (assimp)
nuclear@0 4 ---------------------------------------------------------------------------
nuclear@0 5
nuclear@0 6 Copyright (c) 2006-2012, assimp team
nuclear@0 7
nuclear@0 8 All rights reserved.
nuclear@0 9
nuclear@0 10 Redistribution and use of this software in source and binary forms,
nuclear@0 11 with or without modification, are permitted provided that the following
nuclear@0 12 conditions are met:
nuclear@0 13
nuclear@0 14 * Redistributions of source code must retain the above
nuclear@0 15 copyright notice, this list of conditions and the
nuclear@0 16 following disclaimer.
nuclear@0 17
nuclear@0 18 * Redistributions in binary form must reproduce the above
nuclear@0 19 copyright notice, this list of conditions and the
nuclear@0 20 following disclaimer in the documentation and/or other
nuclear@0 21 materials provided with the distribution.
nuclear@0 22
nuclear@0 23 * Neither the name of the assimp team, nor the names of its
nuclear@0 24 contributors may be used to endorse or promote products
nuclear@0 25 derived from this software without specific prior
nuclear@0 26 written permission of the assimp team.
nuclear@0 27
nuclear@0 28 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
nuclear@0 29 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
nuclear@0 30 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
nuclear@0 31 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
nuclear@0 32 OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
nuclear@0 33 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
nuclear@0 34 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
nuclear@0 35 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
nuclear@0 36 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
nuclear@0 37 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
nuclear@0 38 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
nuclear@0 39 ---------------------------------------------------------------------------
nuclear@0 40 */
nuclear@0 41
nuclear@0 42 /** @file qnan.h
nuclear@0 43 * @brief Some utilities for our dealings with qnans.
nuclear@0 44 *
nuclear@0 45 * @note Some loaders use qnans to mark invalid values tempoarily, also
nuclear@0 46 * Assimp explicitly enforces undefined normals to be set to qnan.
nuclear@0 47 * qnan utilities are available in standard libraries (C99 for example)
nuclear@0 48 * but last time I checked compiler coverage was so bad that I decided
nuclear@0 49 * to reinvent the wheel.
nuclear@0 50 */
nuclear@0 51
nuclear@0 52 #ifndef AI_QNAN_H_INCLUDED
nuclear@0 53 #define AI_QNAN_H_INCLUDED
nuclear@0 54
nuclear@0 55 // ---------------------------------------------------------------------------
nuclear@0 56 /** Data structure to represent the bit pattern of a 32 Bit
nuclear@0 57 * IEEE 754 floating-point number. */
nuclear@0 58 union _IEEESingle
nuclear@0 59 {
nuclear@0 60 float Float;
nuclear@0 61 struct
nuclear@0 62 {
nuclear@0 63 uint32_t Frac : 23;
nuclear@0 64 uint32_t Exp : 8;
nuclear@0 65 uint32_t Sign : 1;
nuclear@0 66 } IEEE;
nuclear@0 67 } ;
nuclear@0 68
nuclear@0 69 // ---------------------------------------------------------------------------
nuclear@0 70 /** Check whether a given float is qNaN.
nuclear@0 71 * @param in Input value */
nuclear@0 72 AI_FORCE_INLINE bool is_qnan(float in)
nuclear@0 73 {
nuclear@0 74 // the straightforward solution does not work:
nuclear@0 75 // return (in != in);
nuclear@0 76 // compiler generates code like this
nuclear@0 77 // load <in> to <register-with-different-width>
nuclear@0 78 // compare <register-with-different-width> against <in>
nuclear@0 79
nuclear@0 80 // FIXME: Use <float> stuff instead? I think fpclassify needs C99
nuclear@0 81 return (reinterpret_cast<_IEEESingle*>(&in)->IEEE.Exp == (1u << 8)-1 &&
nuclear@0 82 reinterpret_cast<_IEEESingle*>(&in)->IEEE.Frac);
nuclear@0 83 }
nuclear@0 84
nuclear@0 85 // ---------------------------------------------------------------------------
nuclear@0 86 /** Check whether a float is NOT qNaN.
nuclear@0 87 * @param in Input value */
nuclear@0 88 AI_FORCE_INLINE bool is_not_qnan(float in)
nuclear@0 89 {
nuclear@0 90 return !is_qnan(in);
nuclear@0 91 }
nuclear@0 92
nuclear@0 93 // ---------------------------------------------------------------------------
nuclear@0 94 /** @brief check whether a float is either NaN or (+/-) INF.
nuclear@0 95 *
nuclear@0 96 * Denorms return false, they're treated like normal values.
nuclear@0 97 * @param in Input value */
nuclear@0 98 AI_FORCE_INLINE bool is_special_float(float in)
nuclear@0 99 {
nuclear@0 100 return (reinterpret_cast<_IEEESingle*>(&in)->IEEE.Exp == (1u << 8)-1);
nuclear@0 101 }
nuclear@0 102
nuclear@0 103 // ---------------------------------------------------------------------------
nuclear@0 104 /** @brief Get a fresh qnan. */
nuclear@0 105 AI_FORCE_INLINE float get_qnan()
nuclear@0 106 {
nuclear@0 107 return std::numeric_limits<float>::quiet_NaN();
nuclear@0 108 }
nuclear@0 109
nuclear@0 110 #endif // !! AI_QNAN_H_INCLUDED