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https://git.code.sf.net/p/quake/quakeforge
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74 lines
2.1 KiB
C
74 lines
2.1 KiB
C
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/*
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bitop.h
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bit-op functions
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Copyright (C) 2022 Bill Currie <bill@taniwha.org>
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Author: Bill Currie <bill@taniwha.org>
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Date: 2022/1/23
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program 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.
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See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to:
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Free Software Foundation, Inc.
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59 Temple Place - Suite 330
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Boston, MA 02111-1307, USA
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*/
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#ifndef __QF_math_bitop_h
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#define __QF_math_bitop_h
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/** \defgroup mathlib_bitop Bit-op functions
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\ingroup utils
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*/
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///@{
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#include "QF/qtypes.h"
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#define BITOP_RUP1__(x) ( (x) | ( (x) >> 1))
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#define BITOP_RUP2__(x) (BITOP_RUP1__(x) | (BITOP_RUP1__(x) >> 2))
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#define BITOP_RUP4__(x) (BITOP_RUP2__(x) | (BITOP_RUP2__(x) >> 4))
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#define BITOP_RUP8__(x) (BITOP_RUP4__(x) | (BITOP_RUP4__(x) >> 8))
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#define BITOP_RUP16__(x) (BITOP_RUP8__(x) | (BITOP_RUP8__(x) >> 16))
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/** Round x up to the next power of two.
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Rounds x up to the next power of two leaving exact powers of two
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untouched.
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\param x The value to round
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\return The next higher power of two or x if it already is a power
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of two.
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*/
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#define BITOP_RUP(x) (BITOP_RUP16__((uint32_t)(x) - 1) + 1)
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#define BITOP_LOG2__(x) (((((x) & 0xffff0000) != 0) << 4) \
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|((((x) & 0xff00ff00) != 0) << 3) \
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|((((x) & 0xf0f0f0f0) != 0) << 2) \
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|((((x) & 0xcccccccc) != 0) << 1) \
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|((((x) & 0xaaaaaaaa) != 0) << 0))
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/** Log base 2 rounded up.
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Finds the base 2 logarithm of x rounded up (ceil(log2(x))).
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\param x The value for which to find the base 2 logarithm.
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\return Log base 2 of x, rounded up (2 -> 1, 3 -> 2, 4 -> 2)
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*/
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#define BITOP_LOG2(x) BITOP_LOG2__(BITOP_RUP(x))
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///@}
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#endif // __QF_math_bitop_h
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