1 /* 2 * Copyright © 2015 Samsung Electronics Co., Ltd 3 * 4 * Permission is hereby granted, free of charge, to any person obtaining 5 * a copy of this software and associated documentation files (the 6 * "Software"), to deal in the Software without restriction, including 7 * without limitation the rights to use, copy, modify, merge, publish, 8 * distribute, sublicense, and/or sell copies of the Software, and to 9 * permit persons to whom the Software is furnished to do so, subject to 10 * the following conditions: 11 * 12 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 13 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 14 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 15 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 16 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 17 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 18 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 19 * SOFTWARE. 20 */ 21 22 #ifndef WESTON_HELPERS_H 23 #define WESTON_HELPERS_H 24 25 #ifdef __cplusplus 26 extern "C" { 27 #endif 28 29 /** 30 * @file 31 * Simple misc helper macros. 32 */ 33 34 /** 35 * Compile-time computation of number of items in a hardcoded array. 36 * 37 * @param a the array being measured. 38 * @return the number of items hardcoded into the array. 39 */ 40 #ifndef ARRAY_LENGTH 41 #define ARRAY_LENGTH(a) (sizeof (a) / sizeof (a)[0]) 42 #endif 43 44 /** 45 * Returns the smaller of two values. 46 * 47 * @param x the first item to compare. 48 * @param y the second item to compare. 49 * @return the value that evaluates to lesser than the other. 50 */ 51 #ifndef MIN 52 #define MIN(x,y) (((x) < (y)) ? (x) : (y)) 53 #endif 54 55 /** 56 * Returns the bigger of two values. 57 * 58 * @param x the first item to compare. 59 * @param y the second item to compare. 60 * @return the value that evaluates to more than the other. 61 */ 62 #ifndef MAX 63 #define MAX(x,y) (((x) > (y)) ? (x) : (y)) 64 #endif 65 66 /** 67 * Returns a pointer to the containing struct of a given member item. 68 * 69 * To demonstrate, the following example retrieves a pointer to 70 * `example_container` given only its `destroy_listener` member: 71 * 72 * @code 73 * struct example_container { 74 * struct wl_listener destroy_listener; 75 * // other members... 76 * }; 77 * 78 * void example_container_destroy(struct wl_listener *listener, void *data) 79 * { 80 * struct example_container *ctr; 81 * 82 * ctr = wl_container_of(listener, ctr, destroy_listener); 83 * // destroy ctr... 84 * } 85 * @endcode 86 * 87 * @param ptr A valid pointer to the contained item. 88 * 89 * @param type A pointer to the type of content that the list item 90 * stores. Type does not need be a valid pointer; a null or 91 * an uninitialised pointer will suffice. 92 * 93 * @param member The named location of ptr within the sample type. 94 * 95 * @return The container for the specified pointer. 96 */ 97 #ifndef container_of 98 #define container_of(ptr, type, member) ({ \ 99 const __typeof__( ((type *)0)->member ) *__mptr = (ptr); \ 100 (type *)( (char *)__mptr - offsetof(type,member) );}) 101 #endif 102 103 /** 104 * Build-time static assertion support 105 * 106 * A build-time equivalent to assert(), will generate a compilation error 107 * if the supplied condition does not evaluate true. 108 * 109 * The following example demonstrates use of static_assert to ensure that 110 * arrays which are supposed to mirror each other have a consistent 111 * size. 112 * 113 * This is only a fallback definition; support must be provided by the 114 * compiler itself. 115 * 116 * @code 117 * int small[4]; 118 * long expanded[4]; 119 * 120 * static_assert(ARRAY_LENGTH(small) == ARRAY_LENGTH(expanded), 121 * "size mismatch between small and expanded arrays"); 122 * for (i = 0; i < ARRAY_LENGTH(small); i++) 123 * expanded[i] = small[4]; 124 * @endcode 125 * 126 * @param cond Expression to check for truth 127 * @param msg Message to print on failure 128 */ 129 #ifndef static_assert 130 # ifdef _Static_assert 131 # define static_assert(cond, msg) _Static_assert(cond, msg) 132 # else 133 # define static_assert(cond, msg) 134 # endif 135 #endif 136 137 #ifdef __cplusplus 138 } 139 #endif 140 141 #endif /* WESTON_HELPERS_H */ 142