90 lines
3.2 KiB
C
90 lines
3.2 KiB
C
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/*
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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) 2011 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, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*
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* Authors:
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* Neil Roberts <neil@linux.intel.com>
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*/
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#ifndef __COGL_FLAGS_H
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#define __COGL_FLAGS_H
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#include <glib.h>
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G_BEGIN_DECLS
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/* These are macros used to implement a fixed-size array of bits. This
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should be used instead of CoglBitmask when the maximum bit number
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that will be set is known at compile time, for example when setting
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for recording a set of known available features */
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/* The bits are stored in an array of unsigned ints. It would probably
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make sense to use unsigned long instead because then on 64-bit
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systems where it can handle 64-bits just as easily and it can test
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more bits. However GDebugKey uses a guint for the mask and we need
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to fit the masks into this */
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/* To use these macros, you would typically have an enum defining the
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available bits with an extra last enum to define the maximum
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value. Then to store the flags you would declare an array of
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unsigned ints sized using COGL_FLAGS_N_INTS_FOR_SIZE, eg:
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typedef enum { FEATURE_A, FEATURE_B, FEATURE_C, N_FEATURES } Features;
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unsigned int feature_flags[COGL_FLAGS_N_INTS_FOR_SIZE (N_FEATURES)];
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*/
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#define COGL_FLAGS_N_INTS_FOR_SIZE(size) \
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(((size) + \
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(sizeof (unsigned int) * 8 - 1)) \
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/ (sizeof (unsigned int) * 8))
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/* @flag is expected to be constant so these should result in a
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constant expression. This means that setting a flag is equivalent
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to just setting in a bit in a global variable at a known
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location */
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#define COGL_FLAGS_GET_INDEX(flag) \
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((flag) / (sizeof (unsigned int) * 8))
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#define COGL_FLAGS_GET_MASK(flag) \
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(1U << ((unsigned int) (flag) & \
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(sizeof (unsigned int) * 8 - 1)))
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#define COGL_FLAGS_GET(array, flag) \
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(!!((array)[COGL_FLAGS_GET_INDEX (flag)] & \
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COGL_FLAGS_GET_MASK (flag)))
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/* The expectation here is that @value will be constant so the if
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statement will be optimised out */
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#define COGL_FLAGS_SET(array, flag, value) \
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G_STMT_START { \
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if (value) \
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((array)[COGL_FLAGS_GET_INDEX (flag)] |= \
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COGL_FLAGS_GET_MASK (flag)); \
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else \
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((array)[COGL_FLAGS_GET_INDEX (flag)] &= \
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~COGL_FLAGS_GET_MASK (flag)); \
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} G_STMT_END
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G_END_DECLS
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#endif /* __COGL_FLAGS_H */
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