src/ucx/mempool.h

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2016 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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 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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 */

/**
 * @file mempool.h
 * 
 * Memory pool implementation.
 * 
 * @author Mike Becker
 * @author Olaf Wintermann
 */

#ifndef UCX_MEMPOOL_H
#define	UCX_MEMPOOL_H

#include "ucx.h"
#include <stddef.h>
#include "allocator.h"

#ifdef	__cplusplus
extern "C" {
#endif

/**
 * UCX mempool structure.
 */
typedef struct {
    /** UcxAllocator based on this pool */
    UcxAllocator *allocator;
    
    /** List of pointers to pooled memory. */
    void         **data;
    
    /** Count of pooled memory items. */
    size_t       ndata;
    
    /** Memory pool size. */
    size_t       size;
} UcxMempool;

/** Shorthand for a new default memory pool with a capacity of 16 elements. */
#define ucx_mempool_new_default() ucx_mempool_new(16)


/**
 * Creates a memory pool with the specified initial size.
 * 
 * As the created memory pool automatically grows in size by 16 elements, when
 * trying to allocate memory on a full pool, it is recommended that you use
 * a multiple of 16 for the initial size.
 * 
 * @param n initial pool size (should be a multiple of 16)
 * @return a pointer to the new memory pool
 */
UcxMempool *ucx_mempool_new(size_t n);

/**
 * Resizes a memory pool.
 * 
 * @param pool the pool to resize
 * @param newcap the new capacity
 * @return <code>EXIT_SUCCESS</code> on success or
 * <code>EXIT_FAILURE</code> on failure
 */
int ucx_mempool_chcap(UcxMempool *pool, size_t newcap);

/**
 * Changes the pool size to the next smallest multiple of 16.
 * 
 * You may use this macro, to reduce the pool size after freeing
 * many pooled memory items.
 * 
 * @param pool the pool to clamp
 * @return <code>EXIT_SUCCESS</code> on success or
 * <code>EXIT_FAILURE</code> on failure
 */
#define ucx_mempool_clamp(pool) ucx_mempool_chcap(pool, \
        (pool->ndata & ~0xF)+0x10)

/**
 * Allocates pooled memory.
 * 
 * @param pool the memory pool
 * @param n amount of memory to allocate
 * @return a pointer to the allocated memory
 * @see ucx_allocator_malloc()
 */
void *ucx_mempool_malloc(UcxMempool *pool, size_t n);
/**
 * Allocates a pooled memory array.
 * 
 * The content of the allocated memory is set to zero.
 * 
 * @param pool the memory pool
 * @param nelem amount of elements to allocate
 * @param elsize amount of memory per element
 * @return a pointer to the allocated memory
 * @see ucx_allocator_calloc()
 */
void *ucx_mempool_calloc(UcxMempool *pool, size_t nelem, size_t elsize);

/**
 * Reallocates pooled memory.
 * 
 * If the memory to be reallocated is not contained by the specified pool, the
 * behavior is undefined.
 * 
 * @param pool the memory pool
 * @param ptr a pointer to the memory that shall be reallocated
 * @param n the new size of the memory
 * @return a pointer to the new location of the memory
 * @see ucx_allocator_realloc()
 */
void *ucx_mempool_realloc(UcxMempool *pool, void *ptr, size_t n);

/**
 * Frees pooled memory.
 * 
 * Before freeing the memory, the specified destructor function (if any)
 * is called.
 * 
 * If you specify memory, that is not pooled by the specified memory pool, the
 * behavior is undefined.
 * 
 * @param pool the memory pool
 * @param ptr a pointer to the memory that shall be freed
 * @see ucx_mempool_set_destr()
 */
void ucx_mempool_free(UcxMempool *pool, void *ptr);

/**
 * Destroys a memory pool.
 * 
 * For each element the destructor function (if any) is called and the element
 * is freed.
 * 
 * Each of the registered destructor function that has no corresponding element
 * within the pool (namely those registered by ucx_mempool_reg_destr) is
 * called interleaving with the element destruction, but with guarantee to the
 * order in which they were registered (FIFO order).
 * 
 * 
 * @param pool the mempool to destroy
 */
void ucx_mempool_destroy(UcxMempool *pool);

/**
 * Sets a destructor function for the specified memory.
 * 
 * The destructor is automatically called when the memory is freed or the
 * pool is destroyed.
 * 
 * The only requirement for the specified memory is, that it <b>MUST</b> be
 * pooled memory by a UcxMempool or an element-compatible mempool. The pointer
 * to the destructor function is saved in a reserved area before the actual
 * memory.
 * 
 * @param ptr pooled memory
 * @param func a pointer to the destructor function
 * @see ucx_mempool_free()
 * @see ucx_mempool_destroy()
 */
void ucx_mempool_set_destr(void *ptr, ucx_destructor func);

/**
 * Registers a destructor function for the specified (non-pooled) memory.
 * 
 * This is useful, if you have memory that has not been allocated by a mempool,
 * but shall be managed by a mempool.
 * 
 * This function creates an entry in the specified mempool and the memory will
 * therefore (logically) convert to pooled memory.
 * 
 * @param pool the memory pool
 * @param ptr data the destructor is registered for
 * @param destr a pointer to the destructor function
 */
void ucx_mempool_reg_destr(UcxMempool *pool, void *ptr, ucx_destructor destr);

#ifdef	__cplusplus
}
#endif

#endif	/* UCX_MEMPOOL_H */