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c3489a0a22
This function could be used in many places in Cogl so it makes sense to share it in cogl-util.h as _cogl_util_is_pot().
72 lines
2.3 KiB
C
72 lines
2.3 KiB
C
/*
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* Cogl
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*
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* An object oriented GL/GLES Abstraction/Utility Layer
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*
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* Copyright (C) 2007,2008,2009,2010 Intel Corporation.
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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; either
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* version 2 of the License, or (at your option) any later version.
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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, see <http://www.gnu.org/licenses/>.
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*
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*
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*/
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#ifndef __COGL_UTIL_H
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#define __COGL_UTIL_H
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#include <glib.h>
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#include <math.h>
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int
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cogl_util_next_p2 (int a);
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/* The signbit macro is defined by ISO C99 so it should be available,
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however if it's not we can fallback to an evil hack */
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#ifdef signbit
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#define cogl_util_float_signbit(x) signbit(x)
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#else
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/* This trick was stolen from here:
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http://lists.boost.org/Archives/boost/2006/08/108731.php
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It xors the integer reinterpretations of -1.0f and 1.0f. In theory
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they should only differ by the signbit so that gives a mask for the
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sign which we can just test against the value */
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static inline gboolean
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cogl_util_float_signbit (float x)
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{
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static const union { float f; guint32 i; } negative_one = { -1.0f };
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static const union { float f; guint32 i; } positive_one = { +1.0f };
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union { float f; guint32 i; } value = { x };
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return !!((negative_one.i ^ positive_one.i) & value.i);
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}
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#endif
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/* This is a replacement for the nearbyint function which always
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rounds to the nearest integer. nearbyint is apparently a C99
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function so it might not always be available but also it seems in
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glibc it is defined as a function call so this macro could end up
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faster anyway. We can't just add 0.5f because it will break for
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negative numbers. */
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#define COGL_UTIL_NEARBYINT(x) ((int) ((x) < 0.0f ? (x) - 0.5f : (x) + 0.5f))
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/* Returns whether the given integer is a power of two */
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static inline gboolean
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_cogl_util_is_pot (unsigned int num)
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{
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/* Make sure there is only one bit set */
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return (num & (num - 1)) == 0;
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}
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#endif /* __COGL_UTIL_H */
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