Christian Schoenebeck | 30e702a | 2021-10-01 16:26:17 +0200 | [diff] [blame] | 1 | /* |
| 2 | * P9Array - deep auto free C-array |
| 3 | * |
| 4 | * Copyright (c) 2021 Crudebyte |
| 5 | * |
| 6 | * Authors: |
| 7 | * Christian Schoenebeck <qemu_oss@crudebyte.com> |
| 8 | * |
| 9 | * Permission is hereby granted, free of charge, to any person obtaining a copy |
| 10 | * of this software and associated documentation files (the "Software"), to deal |
| 11 | * in the Software without restriction, including without limitation the rights |
| 12 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| 13 | * copies 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 included in |
| 17 | * all copies or substantial portions of the Software. |
| 18 | * |
| 19 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| 20 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| 21 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
| 22 | * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| 23 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| 24 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| 25 | * THE SOFTWARE. |
| 26 | */ |
| 27 | #ifndef QEMU_P9ARRAY_H |
| 28 | #define QEMU_P9ARRAY_H |
| 29 | |
| 30 | /** |
| 31 | * P9Array provides a mechanism to access arrays in common C-style (e.g. by |
| 32 | * square bracket [] operator) in conjunction with reference variables that |
| 33 | * perform deep auto free of the array when leaving the scope of the auto |
| 34 | * reference variable. That means not only is the array itself automatically |
| 35 | * freed, but also memory dynamically allocated by the individual array |
| 36 | * elements. |
| 37 | * |
| 38 | * Example: |
| 39 | * |
| 40 | * Consider the following user struct @c Foo which shall be used as scalar |
| 41 | * (element) type of an array: |
| 42 | * @code |
| 43 | * typedef struct Foo { |
| 44 | * int i; |
| 45 | * char *s; |
| 46 | * } Foo; |
| 47 | * @endcode |
| 48 | * and assume it has the following function to free memory allocated by @c Foo |
| 49 | * instances: |
| 50 | * @code |
| 51 | * void free_foo(Foo *foo) { |
| 52 | * free(foo->s); |
| 53 | * } |
| 54 | * @endcode |
| 55 | * Add the following to a shared header file: |
| 56 | * @code |
| 57 | * P9ARRAY_DECLARE_TYPE(Foo); |
| 58 | * @endcode |
| 59 | * and the following to a C unit file: |
| 60 | * @code |
| 61 | * P9ARRAY_DEFINE_TYPE(Foo, free_foo); |
| 62 | * @endcode |
| 63 | * Finally the array may then be used like this: |
| 64 | * @code |
| 65 | * void doSomething(size_t n) { |
| 66 | * P9ARRAY_REF(Foo) foos = NULL; |
| 67 | * P9ARRAY_NEW(Foo, foos, n); |
| 68 | * for (size_t i = 0; i < n; ++i) { |
| 69 | * foos[i].i = i; |
| 70 | * foos[i].s = calloc(4096, 1); |
| 71 | * snprintf(foos[i].s, 4096, "foo %d", i); |
| 72 | * if (...) { |
| 73 | * return; // array auto freed here |
| 74 | * } |
| 75 | * } |
| 76 | * // array auto freed here |
| 77 | * } |
| 78 | * @endcode |
| 79 | */ |
| 80 | |
| 81 | /** |
Christian Schoenebeck | 35b6466 | 2022-03-03 14:37:29 +0100 | [diff] [blame] | 82 | * P9ARRAY_DECLARE_TYPE() - Declares an array type for the passed @scalar_type. |
| 83 | * |
| 84 | * @scalar_type: type of the individual array elements |
Christian Schoenebeck | 30e702a | 2021-10-01 16:26:17 +0200 | [diff] [blame] | 85 | * |
| 86 | * This is typically used from a shared header file. |
Christian Schoenebeck | 30e702a | 2021-10-01 16:26:17 +0200 | [diff] [blame] | 87 | */ |
| 88 | #define P9ARRAY_DECLARE_TYPE(scalar_type) \ |
| 89 | typedef struct P9Array##scalar_type { \ |
| 90 | size_t len; \ |
| 91 | scalar_type first[]; \ |
| 92 | } P9Array##scalar_type; \ |
| 93 | \ |
| 94 | void p9array_new_##scalar_type(scalar_type **auto_var, size_t len); \ |
| 95 | void p9array_auto_free_##scalar_type(scalar_type **auto_var); \ |
| 96 | |
| 97 | /** |
Christian Schoenebeck | 35b6466 | 2022-03-03 14:37:29 +0100 | [diff] [blame] | 98 | * P9ARRAY_DEFINE_TYPE() - Defines an array type for the passed @scalar_type |
| 99 | * and appropriate @scalar_cleanup_func. |
| 100 | * |
| 101 | * @scalar_type: type of the individual array elements |
| 102 | * @scalar_cleanup_func: appropriate function to free memory dynamically |
| 103 | * allocated by individual array elements before |
Christian Schoenebeck | 30e702a | 2021-10-01 16:26:17 +0200 | [diff] [blame] | 104 | * |
| 105 | * This is typically used from a C unit file. |
Christian Schoenebeck | 30e702a | 2021-10-01 16:26:17 +0200 | [diff] [blame] | 106 | */ |
| 107 | #define P9ARRAY_DEFINE_TYPE(scalar_type, scalar_cleanup_func) \ |
| 108 | void p9array_new_##scalar_type(scalar_type **auto_var, size_t len) \ |
| 109 | { \ |
| 110 | p9array_auto_free_##scalar_type(auto_var); \ |
| 111 | P9Array##scalar_type *arr = g_malloc0(sizeof(P9Array##scalar_type) + \ |
| 112 | len * sizeof(scalar_type)); \ |
| 113 | arr->len = len; \ |
| 114 | *auto_var = &arr->first[0]; \ |
| 115 | } \ |
| 116 | \ |
| 117 | void p9array_auto_free_##scalar_type(scalar_type **auto_var) \ |
| 118 | { \ |
| 119 | scalar_type *first = (*auto_var); \ |
| 120 | if (!first) { \ |
| 121 | return; \ |
| 122 | } \ |
| 123 | P9Array##scalar_type *arr = (P9Array##scalar_type *) ( \ |
| 124 | ((char *)first) - offsetof(P9Array##scalar_type, first) \ |
| 125 | ); \ |
| 126 | for (size_t i = 0; i < arr->len; ++i) { \ |
| 127 | scalar_cleanup_func(&arr->first[i]); \ |
| 128 | } \ |
| 129 | g_free(arr); \ |
| 130 | } \ |
| 131 | |
| 132 | /** |
Christian Schoenebeck | 35b6466 | 2022-03-03 14:37:29 +0100 | [diff] [blame] | 133 | * P9ARRAY_REF() - Declare a reference variable for an array. |
| 134 | * |
| 135 | * @scalar_type: type of the individual array elements |
| 136 | * |
Christian Schoenebeck | 30e702a | 2021-10-01 16:26:17 +0200 | [diff] [blame] | 137 | * Used to declare a reference variable (unique pointer) for an array. After |
| 138 | * leaving the scope of the reference variable, the associated array is |
| 139 | * automatically freed. |
Christian Schoenebeck | 30e702a | 2021-10-01 16:26:17 +0200 | [diff] [blame] | 140 | */ |
| 141 | #define P9ARRAY_REF(scalar_type) \ |
| 142 | __attribute((__cleanup__(p9array_auto_free_##scalar_type))) scalar_type* |
| 143 | |
| 144 | /** |
Christian Schoenebeck | 35b6466 | 2022-03-03 14:37:29 +0100 | [diff] [blame] | 145 | * P9ARRAY_NEW() - Allocate a new array. |
Christian Schoenebeck | 30e702a | 2021-10-01 16:26:17 +0200 | [diff] [blame] | 146 | * |
Christian Schoenebeck | 35b6466 | 2022-03-03 14:37:29 +0100 | [diff] [blame] | 147 | * @scalar_type: type of the individual array elements |
| 148 | * @auto_var: destination reference variable |
| 149 | * @len: amount of array elements to be allocated immediately |
| 150 | * |
| 151 | * Allocates a new array of passed @scalar_type with @len number of array |
| 152 | * elements and assigns the created array to the reference variable |
| 153 | * @auto_var. |
Christian Schoenebeck | 30e702a | 2021-10-01 16:26:17 +0200 | [diff] [blame] | 154 | */ |
| 155 | #define P9ARRAY_NEW(scalar_type, auto_var, len) \ |
Christian Schoenebeck | c0451f0 | 2021-10-01 16:27:13 +0200 | [diff] [blame] | 156 | QEMU_BUILD_BUG_MSG( \ |
| 157 | !__builtin_types_compatible_p(scalar_type, typeof(*auto_var)), \ |
| 158 | "P9Array scalar type mismatch" \ |
| 159 | ); \ |
Christian Schoenebeck | 30e702a | 2021-10-01 16:26:17 +0200 | [diff] [blame] | 160 | p9array_new_##scalar_type((&auto_var), len) |
| 161 | |
| 162 | #endif /* QEMU_P9ARRAY_H */ |