1 /* 2 * Cogl 3 * 4 * A Low Level GPU Graphics and Utilities API 5 * 6 * Copyright (C) 2011 Intel Corporation. 7 * 8 * Permission is hereby granted, free of charge, to any person 9 * obtaining a copy of this software and associated documentation 10 * files (the "Software"), to deal in the Software without 11 * restriction, including without limitation the rights to use, copy, 12 * modify, merge, publish, distribute, sublicense, and/or sell copies 13 * of the Software, and to permit persons to whom the Software is 14 * furnished to do so, subject to the following conditions: 15 * 16 * The above copyright notice and this permission notice shall be 17 * included in all copies or substantial portions of the Software. 18 * 19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 20 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 21 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 22 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 23 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 24 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 25 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 26 * SOFTWARE. 27 * 28 * Authors: 29 * Neil Roberts <neil@linux.intel.com> 30 */ 31 32 #ifndef __COGL_FLAGS_H 33 #define __COGL_FLAGS_H 34 35 #include <glib.h> 36 37 #include "cogl-util.h" 38 39 G_BEGIN_DECLS 40 41 /* These are macros used to implement a fixed-size array of bits. This 42 should be used instead of CoglBitmask when the maximum bit number 43 that will be set is known at compile time, for example when setting 44 for recording a set of known available features */ 45 46 /* The bits are stored in an array of unsigned longs. To use these 47 macros, you would typically have an enum defining the available 48 bits with an extra last enum to define the maximum value. Then to 49 store the flags you would declare an array of unsigned longs sized 50 using COGL_FLAGS_N_LONGS_FOR_SIZE, eg: 51 52 typedef enum { FEATURE_A, FEATURE_B, FEATURE_C, N_FEATURES } Features; 53 54 unsigned long feature_flags[COGL_FLAGS_N_LONGS_FOR_SIZE (N_FEATURES)]; 55 */ 56 57 #define COGL_FLAGS_N_LONGS_FOR_SIZE(size) \ 58 (((size) + \ 59 (sizeof (unsigned long) * 8 - 1)) \ 60 / (sizeof (unsigned long) * 8)) 61 62 /* @flag is expected to be constant so these should result in a 63 constant expression. This means that setting a flag is equivalent 64 to just setting in a bit in a global variable at a known 65 location */ 66 #define COGL_FLAGS_GET_INDEX(flag) \ 67 ((flag) / (sizeof (unsigned long) * 8)) 68 #define COGL_FLAGS_GET_MASK(flag) \ 69 (1UL << ((unsigned long) (flag) & \ 70 (sizeof (unsigned long) * 8 - 1))) 71 72 #define COGL_FLAGS_GET(array, flag) \ 73 (!!((array)[COGL_FLAGS_GET_INDEX (flag)] & \ 74 COGL_FLAGS_GET_MASK (flag))) 75 76 /* The expectation here is that @value will be constant so the if 77 statement will be optimised out */ 78 #define COGL_FLAGS_SET(array, flag, value) \ 79 G_STMT_START { \ 80 if (value) \ 81 ((array)[COGL_FLAGS_GET_INDEX (flag)] |= \ 82 COGL_FLAGS_GET_MASK (flag)); \ 83 else \ 84 ((array)[COGL_FLAGS_GET_INDEX (flag)] &= \ 85 ~COGL_FLAGS_GET_MASK (flag)); \ 86 } G_STMT_END 87 88 /* Macros to help iterate an array of flags. It should be used like 89 * this: 90 * 91 * int n_longs = COGL_FLAGS_N_LONGS_FOR_SIZE (...); 92 * unsigned long flags[n_longs]; 93 * int bit_num; 94 * 95 * COGL_FLAGS_FOREACH_START (flags, n_longs, bit_num) 96 * { 97 * do_something_with_the_bit (bit_num); 98 * } 99 * COGL_FLAGS_FOREACH_END; 100 */ 101 #define COGL_FLAGS_FOREACH_START(array, n_longs, bit) \ 102 G_STMT_START { \ 103 const unsigned long *_p = (array); \ 104 int _n_longs = (n_longs); \ 105 int _i; \ 106 \ 107 for (_i = 0; _i < _n_longs; _i++) \ 108 { \ 109 unsigned long _mask = *(_p++); \ 110 \ 111 (bit) = _i * sizeof (unsigned long) * 8 - 1; \ 112 \ 113 while (_mask) \ 114 { \ 115 int _next_bit = _cogl_util_ffsl (_mask); \ 116 (bit) += _next_bit; \ 117 /* This odd two-part shift is to avoid */ \ 118 /* shifting by sizeof (long)*8 which has */ \ 119 /* undefined results according to the */ \ 120 /* C spec (and seems to be a no-op in */ \ 121 /* practice) */ \ 122 _mask = (_mask >> (_next_bit - 1)) >> 1; \ 123 124 #define COGL_FLAGS_FOREACH_END \ 125 } } } G_STMT_END 126 127 G_END_DECLS 128 129 #endif /* __COGL_FLAGS_H */ 130 131