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