src/cx/mempool.h

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 */
/**
 * \file mempool.h
 * \brief Interface for memory pool implementations.
 * \author Mike Becker
 * \author Olaf Wintermann
 * \copyright 2-Clause BSD License
 */

#ifndef UCX_MEMPOOL_H
#define UCX_MEMPOOL_H

#include "common.h"
#include "allocator.h"

#ifdef __cplusplus
extern "C" {
#endif

/** Internal structure for pooled memory. */
struct cx_mempool_memory_s;

/**
 * The basic structure of a memory pool.
 * Should be the first member of an actual memory pool implementation.
 */
struct cx_mempool_s {
    /** The provided allocator. */
    CxAllocator const *allocator;

    /**
     * A destructor that shall be automatically registered for newly allocated memory.
     * This destructor MUST NOT free the memory.
     */
    cx_destructor_func auto_destr;

    /** Array of pooled memory. */
    struct cx_mempool_memory_s **data;

    /** Number of pooled memory items. */
    size_t size;

    /** Memory pool capacity. */
    size_t capacity;
};

/**
 * Common type for all memory pool implementations.
 */
typedef struct cx_mempool_s CxMempool;

/**
 * Creates an array-based memory pool with a shared destructor function.
 *
 * This destructor MUST NOT free the memory.
 *
 * @param capacity the initial capacity of the pool
 * @param destr the destructor function to use for allocated memory
 * @return the created memory pool or \c NULL if allocation failed
 */
__attribute__((__warn_unused_result__))
CxMempool *cxMempoolCreate(size_t capacity, cx_destructor_func destr);

/**
 * Creates a basic array-based memory pool.
 *
 * @param capacity the initial capacity of the pool
 * @return the created memory pool or \c NULL if allocation failed
 */
__attribute__((__warn_unused_result__))
static inline CxMempool *cxBasicMempoolCreate(size_t capacity) {
    return cxMempoolCreate(capacity, NULL);
}

/**
 * Destroys a memory pool and frees the managed memory.
 *
 * @param pool the memory pool to destroy
 */
__attribute__((__nonnull__))
void cxMempoolDestroy(CxMempool *pool);

/**
 * Sets the destructor function for a specific allocated memory object.
 *
 * If the memory is not managed by a UCX memory pool, the behavior is undefined.
 * The destructor MUST NOT free the memory.
 *
 * @param memory the object allocated in the pool
 * @param fnc the destructor function
 */
__attribute__((__nonnull__))
void cxMempoolSetDestructor(
        void *memory,
        cx_destructor_func fnc
);

/**
 * Registers foreign memory with this pool.
 *
 * The destructor, in contrast to memory allocated by the pool, MUST free the memory.
 *
 * A small portion of memory will be allocated to register the information in the pool.
 * If that allocation fails, this function will return non-zero.
 *
 * @param pool the pool
 * @param memory the object allocated in the pool
 * @param destr the destructor function
 * @return zero on success, non-zero on failure
 */
__attribute__((__nonnull__))
int cxMempoolRegister(
        CxMempool *pool,
        void *memory,
        cx_destructor_func destr
);

#ifdef __cplusplus
} // extern "C"
#endif

#endif // UCX_MEMPOOL_H