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109 lines
3.4 KiB
C
109 lines
3.4 KiB
C
/* See the end of this file for copyright and license terms. */
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#pragma once
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#include "neo/_types.h"
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void _neo_nref_init(struct _neo_nref *ref, void (*destroy)(void *ptr), usize offset);
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int _neo_nget(struct _neo_nref *ref);
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int _neo_nput(struct _neo_nref *ref);
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/**
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* @defgroup nref Reference Counting
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*
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* @{
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*/
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/**
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* @brief Initialize the reference counter in a structure.
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*
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* The count is initialized to 1 and can be incremented and decremented using
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* `nget()` and `nput()` respectively. If the count reaches 0, the `destroy`
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* callback is invoked where the structure and all resources tied to it must
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* be released. The reference counter must be embedded in the struct using
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* the `NREF_FIELD` macro.
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*
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* @param ptr The `struct *` containing the `NREF_FIELD`
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* @param destroy A callback accepting a pointer to the original struct as its
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* only parameter and return type `void`, which will deallocate the struct
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*/
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#define nref_init(ptr, destroy) ({ \
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void (*__destroy_typechecked)(typeof(ptr)) = (destroy); \
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_neo_nref_init(&(ptr)->__neo_nref, \
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(void (*)(void *))__destroy_typechecked, \
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offsetof(typeof(*(ptr)), __neo_nref)); \
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})
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/**
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* @brief Increment the reference counter of a structure embedding `NREF_FIELD`.
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*
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* @param ptr The `struct *` to increment the reference counter of
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*/
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#define nget(ptr) ((void)_neo_nget( &(ptr)->__neo_nref ))
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/**
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* @brief Decrement the reference counter of a structure embedding `NREF_FIELD`.
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*
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* If the counter reaches zero, the destroy callback passed to `nref_init`
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* is invoked and the pointer is set to `nil` to prevent any further usage.
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*
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* @param ptr The `struct *` to decrement the reference counter of
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*/
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#define nput(ptr) ({ \
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if (_neo_nput(&(ptr)->__neo_nref) == 0) \
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ptr = nil; \
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})
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/**
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* @brief Borrow a refcounted structure.
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*
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* Increment the refcounter of a structure embedding `NREF_FIELD` and return
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* a pointer to its `nref_t` field so that it can be stored in your own struct
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* that depends on its existence.
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*
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* The borrowed structure is guaranteed to not be destroyed before you call
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* `unborrow()` (unless you make the error of calling `nput()` )
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*
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* @param ptr Pointer to the refcounted entity to borrow
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* @returns An `nref_t *` that must be passed to `unborrow()` when the borrow
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* is no longer used
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*/
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#define borrow(ptr) ({ \
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nref_t *__nref = &(ptr)->__neo_nref; \
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_neo_nget(__nref); \
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__nref; \
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})
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/**
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* @brief Decrement the reference counter of a borrowed structure after usage.
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* Call this in the borrowing structure's teardown routine.
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*
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* @param nref The `nref_t *` returned by `borrow()`
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*/
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#define unborrow(nref) ((void)_neo_nput(nref))
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/**
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* @brief Return the current reference count of a structure embedding `NREF_FIELD`.
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* You usually shouldn't need this though.
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*
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* @param ptr The `struct *` embedding `NREF_FIELD`
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* @returns The structure's current refcount value as a `const int`
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*/
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#define nref_count(ptr) ((const int)(ptr)->__neo_nref._count)
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/** @} */
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/*
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* This file is part of libneo.
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* Copyright (c) 2021 Fefie <owo@fef.moe>.
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*
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* libneo is non-violent software: you may only use, redistribute,
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* and/or modify it under the terms of the CNPLv6+ as found in
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* the LICENSE file in the source code root directory or at
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* <https://git.pixie.town/thufie/CNPL>.
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*
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* libneo comes with ABSOLUTELY NO WARRANTY, to the extent
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* permitted by applicable law. See the CNPLv6+ for details.
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*/
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