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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 | ||
c0451f0b CS |
30 | #include "qemu/compiler.h" |
31 | ||
30e702ab CS |
32 | /** |
33 | * P9Array provides a mechanism to access arrays in common C-style (e.g. by | |
34 | * square bracket [] operator) in conjunction with reference variables that | |
35 | * perform deep auto free of the array when leaving the scope of the auto | |
36 | * reference variable. That means not only is the array itself automatically | |
37 | * freed, but also memory dynamically allocated by the individual array | |
38 | * elements. | |
39 | * | |
40 | * Example: | |
41 | * | |
42 | * Consider the following user struct @c Foo which shall be used as scalar | |
43 | * (element) type of an array: | |
44 | * @code | |
45 | * typedef struct Foo { | |
46 | * int i; | |
47 | * char *s; | |
48 | * } Foo; | |
49 | * @endcode | |
50 | * and assume it has the following function to free memory allocated by @c Foo | |
51 | * instances: | |
52 | * @code | |
53 | * void free_foo(Foo *foo) { | |
54 | * free(foo->s); | |
55 | * } | |
56 | * @endcode | |
57 | * Add the following to a shared header file: | |
58 | * @code | |
59 | * P9ARRAY_DECLARE_TYPE(Foo); | |
60 | * @endcode | |
61 | * and the following to a C unit file: | |
62 | * @code | |
63 | * P9ARRAY_DEFINE_TYPE(Foo, free_foo); | |
64 | * @endcode | |
65 | * Finally the array may then be used like this: | |
66 | * @code | |
67 | * void doSomething(size_t n) { | |
68 | * P9ARRAY_REF(Foo) foos = NULL; | |
69 | * P9ARRAY_NEW(Foo, foos, n); | |
70 | * for (size_t i = 0; i < n; ++i) { | |
71 | * foos[i].i = i; | |
72 | * foos[i].s = calloc(4096, 1); | |
73 | * snprintf(foos[i].s, 4096, "foo %d", i); | |
74 | * if (...) { | |
75 | * return; // array auto freed here | |
76 | * } | |
77 | * } | |
78 | * // array auto freed here | |
79 | * } | |
80 | * @endcode | |
81 | */ | |
82 | ||
83 | /** | |
84 | * Declares an array type for the passed @a scalar_type. | |
85 | * | |
86 | * This is typically used from a shared header file. | |
87 | * | |
88 | * @param scalar_type - type of the individual array elements | |
89 | */ | |
90 | #define P9ARRAY_DECLARE_TYPE(scalar_type) \ | |
91 | typedef struct P9Array##scalar_type { \ | |
92 | size_t len; \ | |
93 | scalar_type first[]; \ | |
94 | } P9Array##scalar_type; \ | |
95 | \ | |
96 | void p9array_new_##scalar_type(scalar_type **auto_var, size_t len); \ | |
97 | void p9array_auto_free_##scalar_type(scalar_type **auto_var); \ | |
98 | ||
99 | /** | |
100 | * Defines an array type for the passed @a scalar_type and appropriate | |
101 | * @a scalar_cleanup_func. | |
102 | * | |
103 | * This is typically used from a C unit file. | |
104 | * | |
105 | * @param scalar_type - type of the individual array elements | |
106 | * @param scalar_cleanup_func - appropriate function to free memory dynamically | |
107 | * allocated by individual array elements before | |
108 | */ | |
109 | #define P9ARRAY_DEFINE_TYPE(scalar_type, scalar_cleanup_func) \ | |
110 | void p9array_new_##scalar_type(scalar_type **auto_var, size_t len) \ | |
111 | { \ | |
112 | p9array_auto_free_##scalar_type(auto_var); \ | |
113 | P9Array##scalar_type *arr = g_malloc0(sizeof(P9Array##scalar_type) + \ | |
114 | len * sizeof(scalar_type)); \ | |
115 | arr->len = len; \ | |
116 | *auto_var = &arr->first[0]; \ | |
117 | } \ | |
118 | \ | |
119 | void p9array_auto_free_##scalar_type(scalar_type **auto_var) \ | |
120 | { \ | |
121 | scalar_type *first = (*auto_var); \ | |
122 | if (!first) { \ | |
123 | return; \ | |
124 | } \ | |
125 | P9Array##scalar_type *arr = (P9Array##scalar_type *) ( \ | |
126 | ((char *)first) - offsetof(P9Array##scalar_type, first) \ | |
127 | ); \ | |
128 | for (size_t i = 0; i < arr->len; ++i) { \ | |
129 | scalar_cleanup_func(&arr->first[i]); \ | |
130 | } \ | |
131 | g_free(arr); \ | |
132 | } \ | |
133 | ||
134 | /** | |
135 | * Used to declare a reference variable (unique pointer) for an array. After | |
136 | * leaving the scope of the reference variable, the associated array is | |
137 | * automatically freed. | |
138 | * | |
139 | * @param scalar_type - type of the individual array elements | |
140 | */ | |
141 | #define P9ARRAY_REF(scalar_type) \ | |
142 | __attribute((__cleanup__(p9array_auto_free_##scalar_type))) scalar_type* | |
143 | ||
144 | /** | |
145 | * Allocates a new array of passed @a scalar_type with @a len number of array | |
146 | * elements and assigns the created array to the reference variable | |
147 | * @a auto_var. | |
148 | * | |
149 | * @param scalar_type - type of the individual array elements | |
150 | * @param auto_var - destination reference variable | |
151 | * @param len - amount of array elements to be allocated immediately | |
152 | */ | |
153 | #define P9ARRAY_NEW(scalar_type, auto_var, len) \ | |
c0451f0b CS |
154 | QEMU_BUILD_BUG_MSG( \ |
155 | !__builtin_types_compatible_p(scalar_type, typeof(*auto_var)), \ | |
156 | "P9Array scalar type mismatch" \ | |
157 | ); \ | |
30e702ab CS |
158 | p9array_new_##scalar_type((&auto_var), len) |
159 | ||
160 | #endif /* QEMU_P9ARRAY_H */ |