src/common/make-unique-wrapper.hpp

   1 /*
   2  * Copyright (C) 2022 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7
   8 #ifndef LTTNG_MAKE_UNIQUE_WRAPPER_H
   9 #define LTTNG_MAKE_UNIQUE_WRAPPER_H
  10
  11 #include <common/macros.hpp>
  12 #include <common/meta-helpers.hpp>
  13
  14 #include <memory>
  15
  16 namespace lttng {
  17
  18 /*
  19  * make_unique_wrapper is intended to facilitate the use of std::unique_ptr
  20  * to wrap C-style APIs that don't provide RAII resource management facilities.
  21  *
  22  * Usage example:
  23  *
  24  *    // API
  25  *    struct my_c_struct {
  26  *            // ...
  27  *    };
  28  *
  29  *    struct my_c_struct *create_my_c_struct(void);
  30  *    void destroy_my_c_struct(struct my_c_struct *value);
  31  *
  32  *    // Creating a unique_ptr to my_c_struct.
  33  *    auto safe_c_struct =
  34  *            lttng::make_unique_wrapper<my_c_struct, destroy_my_c_struct>(
  35  *                    create_my_c_struct());
  36  *
  37  * Note that this facility is intended for use in the scope of a function.
  38  * If you need to return this unique_ptr instance, you should consider writing
  39  * a proper, idiomatic, wrapper.
  40  */
  41
  42 namespace memory {
  43 /*
  44  * 'free' is a utility function for use with make_unique_wrapper. It makes it easier to
  45  * wrap raw pointers that have to be deleted with `free`. Using libc's 'free' as
  46  * a make_unique_wrapper template argument will result in an error as 'WrappedType *' will
  47  * not match free's 'void *' argument.
  48  */
  49 template <class Type>
  50 void free(Type *ptr)
  51 {
  52         std::free(ptr);
  53 }
  54 } /* namespace memory */
  55
  56 template <typename WrappedType, void (*DeleterFunc)(WrappedType *)>
  57 std::unique_ptr<WrappedType,
  58                 typename memory::create_deleter_class<WrappedType, DeleterFunc>::deleter>
  59 make_unique_wrapper(WrappedType *instance = nullptr)
  60 {
  61         const memory::create_deleter_class<WrappedType, DeleterFunc> unique_deleter;
  62
  63         return unique_deleter(instance);
  64 }
  65
  66 } /* namespace lttng */
  67
  68 #endif /* LTTNG_MAKE_UNIQUE_WRAPPER_H */