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
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 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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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"

/** A memory block in a simple memory pool. */
struct cx_mempool_memory_s {
    /** The destructor. */
    cx_destructor_func destructor;
    /** The actual memory. */
    char c[];
};

/** A memory block in an advanced memory pool. */
struct cx_mempool_memory2_s {
    /** The destructor. */
    cx_destructor_func2 destructor;
    /** Data for the destructor. */
    void *data;
    /** The actual memory. */
    char c[];
};

/** Represents memory that is not allocated by, but registered with a pool. */
struct cx_mempool_foreign_memory_s {
    /** The foreign memory. */
    void* mem;
    union {
        /** Simple destructor. */
        cx_destructor_func destr;
        /** Advanced destructor. */
        cx_destructor_func2 destr2;
    };
    /** Data for the advanced destructor. */
    void *destr2_data;
};

/** Specifies how individual blocks are allocated. */
enum cx_mempool_type {
    /**
     * Allows registration of cx_destructor_func for each memory block.
     */
    CX_MEMPOOL_TYPE_SIMPLE,
    /**
     * Allows registration of cx_destructor_func2 for each memory block.
     */
    CX_MEMPOOL_TYPE_ADVANCED,
    /**
     * No individual destructor registration allowed.
     *
     * In this mode, no additional memory per block is allocated.
     */
    CX_MEMPOOL_TYPE_PURE,
};

/**
 * The basic structure of a memory pool.
 * Should be the first member of an actual memory pool implementation.
 */
struct cx_mempool_s {
    /** The used allocator, initialized with the cxDefaultAllocator. */
    const CxAllocator * const base_allocator;

    /** The provided allocator. */
    const CxAllocator *allocator;

    /** Array of pooled memory. */
    void **data;

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

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

    /** Array of registered memory. */
    struct cx_mempool_foreign_memory_s *registered;

    /** Number of registered memory items. */
    size_t registered_size;

    /** Capacity for registered memory. */
    size_t registered_capacity;

    /**
     * A destructor that shall be called before deallocating a memory block.
     * This destructor MUST NOT free the memory itself.
     *
     * It is guaranteed that this destructor is called after the individual
     * destructor of the memory block and before @c destr2.
     */
    cx_destructor_func destr;

    /**
     * A destructor that shall be called before deallocating a memory block.
     * This destructor MUST NOT free the memory itself.
     *
    * It is guaranteed that this destructor is called after the individual
     * destructor of the memory block and @c destr.
     */
    cx_destructor_func2 destr2;

    /**
     * Additional data for the @c destr2.
     */
    void *destr2_data;
};

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

/**
 * Deallocates a memory pool and frees the managed memory.
 *
 * @param pool the memory pool to free
 */
CX_EXTERN
void cxMempoolFree(CxMempool *pool);

/**
 * Creates an array-based memory pool.
 *
 * The type determines how much additional memory is allocated per block
 * to register a destructor function.
 *
 * @param capacity the initial capacity of the pool (an implementation default if zero)
 * @param type the type of memory pool
 * @return the created memory pool or @c NULL if allocation failed
 */
CX_EXTERN CX_NODISCARD CX_MALLOC CX_DEALLOC(cxMempoolFree, 1)
CxMempool *cxMempoolCreate(size_t capacity, enum cx_mempool_type type);

/**
 * Creates a basic array-based memory pool.
 *
 * Convenience macro to create a memory pool of type #CX_MEMPOOL_TYPE_SIMPLE.
 *
 * @param capacity (@c size_t) the initial capacity of the pool
 * @return (@c CxMempool*) the created memory pool or @c NULL if allocation failed
 */
#define cxMempoolCreateSimple(capacity) cxMempoolCreate(capacity, CX_MEMPOOL_TYPE_SIMPLE)

/**
 * Creates a basic array-based memory pool.
 *
 * Convenience macro to create a memory pool of type #CX_MEMPOOL_TYPE_ADVANCED.
 *
 * @param capacity (@c size_t) the initial capacity of the pool
 * @return (@c CxMempool*) the created memory pool or @c NULL if allocation failed
 */
#define cxMempoolCreateAdvanced(capacity) cxMempoolCreate(capacity, CX_MEMPOOL_TYPE_ADVANCED)

/**
 * Creates a basic array-based memory pool.
 *
 * Convenience macro to create a memory pool of type #CX_MEMPOOL_TYPE_PURE.
 *
 * @param capacity (@c size_t) the initial capacity of the pool
 * @return (@c CxMempool*) the created memory pool or @c NULL if allocation failed
 */
#define cxMempoolCreatePure(capacity) cxMempoolCreate(capacity, CX_MEMPOOL_TYPE_PURE)

/**
 * Sets the global destructor for all memory blocks within the specified pool.
 *
 * @param pool the memory pool
 * @param fnc the destructor that shall be applied to all memory blocks
 */
CX_EXTERN CX_NONNULL_ARG(1)
void cxMempoolGlobalDestructor(CxMempool *pool, cx_destructor_func fnc);

/**
 * Sets the global destructor for all memory blocks within the specified pool.
 *
 * @param pool the memory pool
 * @param fnc the destructor that shall be applied to all memory blocks
 * @param data additional data for the destructor function
 */
CX_EXTERN CX_NONNULL_ARG(1)
void cxMempoolGlobalDestructor2(CxMempool *pool, cx_destructor_func2 fnc, void *data);

/**
 * Sets the destructor function for a specific allocated memory object.
 *
 * If the type of memory pool is not #CX_MEMPOOL_TYPE_SIMPLE, the behavior is undefined.
 * 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
 */
CX_EXTERN CX_NONNULL
void cxMempoolSetDestructor(void *memory, cx_destructor_func fnc);

/**
 * Sets the destructor function for a specific allocated memory object.
 *
 * If the type of memory pool is not #CX_MEMPOOL_TYPE_ADVANCED, the behavior is undefined.
 * 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
 * @param data additional data for the destructor function
 */
CX_EXTERN CX_NONNULL
void cxMempoolSetDestructor2(void *memory, cx_destructor_func2 fnc, void *data);

/**
 * Removes the destructor function for a specific allocated memory object.
 *
 * If the type of memory pool is not #CX_MEMPOOL_TYPE_SIMPLE, the behavior is undefined.
 * If the memory is not managed by a UCX memory pool, the behavior is undefined.
 *
 * @param memory the object allocated in the pool
 */
CX_EXTERN CX_NONNULL
void cxMempoolRemoveDestructor(void *memory);

/**
 * Removes the destructor function for a specific allocated memory object.
 *
 * If the type of memory pool is not #CX_MEMPOOL_TYPE_ADVANCED, the behavior is undefined.
 * If the memory is not managed by a UCX memory pool, the behavior is undefined.
 *
 * @param memory the object allocated in the pool
 */
CX_EXTERN CX_NONNULL
void cxMempoolRemoveDestructor2(void *memory);

/**
 * Registers foreign memory with this pool.
 *
 * The destructor, in contrast to memory allocated by the pool, MUST free the memory.
 * This function can be used with any pool of any type, since destructors for registered memory
 * are entirely independent of the pool's memory management.
 *
 * The destructor for the registered memory will be called after all pooled items have been freed.
 *
 * @param pool the pool
 * @param memory the object to register (MUST NOT be already allocated in the pool)
 * @param destr the destructor function
 * @retval zero success
 * @retval non-zero failure
 */
CX_EXTERN CX_NONNULL
int cxMempoolRegister(CxMempool *pool, void *memory, cx_destructor_func destr);

/**
 * Registers foreign memory with this pool.
 *
 * The destructor, in contrast to memory allocated by the pool, MUST free the memory.
 * This function can be used with any pool of any type, since destructors for registered memory
 * are entirely independent of the pool's memory management.
 *
 * The destructor for the registered memory will be called after all pooled items have been freed.
 *
 * @attention The data pointer MUST NOT be @c NULL.
 * If you wish to register a destructor without additional data, use cxMempoolRegister().
 *
 * @param pool the pool
 * @param memory the object to register (MUST NOT be already allocated in the pool)
 * @param destr the destructor function
 * @param data additional data for the destructor function
 * @retval zero success
 * @retval non-zero failure
 */
CX_EXTERN CX_NONNULL
int cxMempoolRegister2(CxMempool *pool, void *memory, cx_destructor_func2 destr, void *data);

/**
 * Transfers all the memory managed by one pool to another.
 *
 * The allocator of the source pool will also be transferred and registered with the destination pool
 * and stays valid, as long as the destination pool is not destroyed.
 *
 * The source pool will get a completely new allocator and can be reused or destroyed afterward.
 *
 * This function fails when the destination pool has a different type than the source pool.
 *
 * @param source the pool to move the memory from
 * @param dest the pool where to transfer the memory to
 * @retval zero success
 * @retval non-zero allocation failure or incompatible pools
 */
CX_EXTERN CX_NONNULL
int cxMempoolTransfer(CxMempool *source, CxMempool *dest);

/**
 * Transfers an object from one pool to another.
 *
 * This function fails when the destination pool has a different type than the source pool.
 *
 * @attention If the object maintains a reference to the pool's allocator,
 * you must make sure to update that reference to the allocator of the destination pool.
 *
 * @param source the pool to move the memory from
 * @param dest the pool where to transfer the memory to
 * @param obj pointer to the object that shall be transferred
 * @retval zero success
 * @retval non-zero failure, or the object was not found in the source pool, or the pools are incompatible
 */
CX_EXTERN CX_NONNULL
int cxMempoolTransferObject(CxMempool *source, CxMempool *dest, const void *obj);

#endif // UCX_MEMPOOL_H