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Diffstat (limited to 'fsdev/p9array.h')
| -rw-r--r-- | fsdev/p9array.h | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/fsdev/p9array.h b/fsdev/p9array.h new file mode 100644 index 0000000000..fff946a3d7 --- /dev/null +++ b/fsdev/p9array.h @@ -0,0 +1,154 @@ +/* + * P9Array - deep auto free C-array + * + * Copyright (c) 2021 Crudebyte + * + * Authors: + * Christian Schoenebeck <qemu_oss@crudebyte.com> + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ +#ifndef QEMU_P9ARRAY_H +#define QEMU_P9ARRAY_H + +/** + * P9Array provides a mechanism to access arrays in common C-style (e.g. by + * square bracket [] operator) in conjunction with reference variables that + * perform deep auto free of the array when leaving the scope of the auto + * reference variable. That means not only is the array itself automatically + * freed, but also memory dynamically allocated by the individual array + * elements. + * + * Example: + * + * Consider the following user struct @c Foo which shall be used as scalar + * (element) type of an array: + * @code + * typedef struct Foo { + * int i; + * char *s; + * } Foo; + * @endcode + * and assume it has the following function to free memory allocated by @c Foo + * instances: + * @code + * void free_foo(Foo *foo) { + * free(foo->s); + * } + * @endcode + * Add the following to a shared header file: + * @code + * P9ARRAY_DECLARE_TYPE(Foo); + * @endcode + * and the following to a C unit file: + * @code + * P9ARRAY_DEFINE_TYPE(Foo, free_foo); + * @endcode + * Finally the array may then be used like this: + * @code + * void doSomething(size_t n) { + * P9ARRAY_REF(Foo) foos = NULL; + * P9ARRAY_NEW(Foo, foos, n); + * for (size_t i = 0; i < n; ++i) { + * foos[i].i = i; + * foos[i].s = calloc(4096, 1); + * snprintf(foos[i].s, 4096, "foo %d", i); + * if (...) { + * return; // array auto freed here + * } + * } + * // array auto freed here + * } + * @endcode + */ + +/** + * Declares an array type for the passed @a scalar_type. + * + * This is typically used from a shared header file. + * + * @param scalar_type - type of the individual array elements + */ +#define P9ARRAY_DECLARE_TYPE(scalar_type) \ + typedef struct P9Array##scalar_type { \ + size_t len; \ + scalar_type first[]; \ + } P9Array##scalar_type; \ + \ + void p9array_new_##scalar_type(scalar_type **auto_var, size_t len); \ + void p9array_auto_free_##scalar_type(scalar_type **auto_var); \ + +/** + * Defines an array type for the passed @a scalar_type and appropriate + * @a scalar_cleanup_func. + * + * This is typically used from a C unit file. + * + * @param scalar_type - type of the individual array elements + * @param scalar_cleanup_func - appropriate function to free memory dynamically + * allocated by individual array elements before + */ +#define P9ARRAY_DEFINE_TYPE(scalar_type, scalar_cleanup_func) \ + void p9array_new_##scalar_type(scalar_type **auto_var, size_t len) \ + { \ + p9array_auto_free_##scalar_type(auto_var); \ + P9Array##scalar_type *arr = g_malloc0(sizeof(P9Array##scalar_type) + \ + len * sizeof(scalar_type)); \ + arr->len = len; \ + *auto_var = &arr->first[0]; \ + } \ + \ + void p9array_auto_free_##scalar_type(scalar_type **auto_var) \ + { \ + scalar_type *first = (*auto_var); \ + if (!first) { \ + return; \ + } \ + P9Array##scalar_type *arr = (P9Array##scalar_type *) ( \ + ((char *)first) - offsetof(P9Array##scalar_type, first) \ + ); \ + for (size_t i = 0; i < arr->len; ++i) { \ + scalar_cleanup_func(&arr->first[i]); \ + } \ + g_free(arr); \ + } \ + +/** + * Used to declare a reference variable (unique pointer) for an array. After + * leaving the scope of the reference variable, the associated array is + * automatically freed. + * + * @param scalar_type - type of the individual array elements + */ +#define P9ARRAY_REF(scalar_type) \ + __attribute((__cleanup__(p9array_auto_free_##scalar_type))) scalar_type* + +/** + * Allocates a new array of passed @a scalar_type with @a len number of array + * elements and assigns the created array to the reference variable + * @a auto_var. + * + * @param scalar_type - type of the individual array elements + * @param auto_var - destination reference variable + * @param len - amount of array elements to be allocated immediately + */ +#define P9ARRAY_NEW(scalar_type, auto_var, len) \ + p9array_new_##scalar_type((&auto_var), len) + +#endif /* QEMU_P9ARRAY_H */ |