src/cx/allocator.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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 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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/**
 * \file allocator.h
 * Interface for custom allocators.
 */

#ifndef UCX_ALLOCATOR_H
#define UCX_ALLOCATOR_H

#include <stdlib.h>

#ifdef __cplusplus
extern "C" {
#endif

/**
 * The class definition for an allocator.
 */
typedef struct {
    /**
     * Allocate \p n bytes of memory.
     *
     * @param data the allocator's data
     * @param n the number of bytes
     * @return a pointer to the allocated memory
     */
    void *(*malloc)(void *data, size_t n);

    /**
     * Re-allocate the previously allocated block in \p mem, making the new block \p n bytes long.
     * This function may return the same pointer that was passed to it, if moving the memory
     * was not necessary.
     *
     * \note Re-allocating a block allocated by a different allocator is undefined.
     *
     * @param data the allocator's data
     * @param mem pointer to the previously allocated block
     * @param n the new size in bytes
     * @return a pointer to the re-allocated memory
     */
    void *(*realloc)(void *data, void *mem, size_t n);

    /**
     * Allocate \p nelem elements of \p n bytes each, all initialized to zero.
     *
     * @param data the allocator's data
     * @param nelem the number of elements
     * @param n the size of each element in bytes
     * @return a pointer to the allocated memory
     */
    void *(*calloc)(void *data, size_t nelem, size_t n);

    /**
     * Free a block allocated by this allocator.
     *
     * \note Freeing a block of a different allocator is undefined.
     *
     * @param data the allocator's data
     * @param mem a pointer to the block to free
     */
    void (*free)(void *data, void *mem);
} cx_allocator_class;

/**
 * Structure holding the data for an allocator.
 */
struct cx_allocator_s {
    /**
     * A pointer to the instance of the allocator class.
     */
    cx_allocator_class *cl;
    /**
     * A pointer to the data this allocator uses.
     */
    void *data;
};

/**
 * High-Level type alias for the allocator type.
 */
typedef struct cx_allocator_s *CxAllocator;

/**
 * A default allocator using standard library malloc() etc.
 */
extern CxAllocator cxDefaultAllocator;

/**
 * Allocate \p n bytes of memory.
 *
 * @param allocator the allocator
 * @param n the number of bytes
 * @return a pointer to the allocated memory
 */
__attribute__ ((malloc))
void *cxMalloc(CxAllocator allocator, size_t n);

/**
 * Re-allocate the previously allocated block in \p mem, making the new block \p n bytes long.
 * This function may return the same pointer that was passed to it, if moving the memory
 * was not necessary.
 *
 * \note Re-allocating a block allocated by a different allocator is undefined.
 *
 * @param allocator the allocator
 * @param mem pointer to the previously allocated block
 * @param n the new size in bytes
 * @return a pointer to the re-allocated memory
 */
void *cxRealloc(CxAllocator allocator, void *mem, size_t n);

/**
 * Re-allocate a previously allocated block and changes the pointer in-place, if necessary.
 * This function acts like cxRealloc() using the pointer pointed to by \p mem.
 * On success, the pointer is changed to the new location (in case the
 *
 * \note Re-allocating a block allocated by a different allocator is undefined.
 *
 * \par Error handling
 * \c errno will be set, if the underlying realloc function does so.
 *
 * @param allocator the allocator
 * @param mem pointer to the pointer to allocated block
 * @param n the new size in bytes
 * @return zero on success, non-zero on failure
 */
__attribute__ ((nonnull))
int cxReallocate(CxAllocator allocator, void **mem, size_t n);

/**
 * Allocate \p nelem elements of \p n bytes each, all initialized to zero.
 *
 * @param allocator the allocator
 * @param nelem the number of elements
 * @param n the size of each element in bytes
 * @return a pointer to the allocated memory
 */
__attribute__ ((malloc))
void *cxCalloc(CxAllocator allocator, size_t nelem, size_t n);

/**
 * Free a block allocated by this allocator.
 *
 * \note Freeing a block of a different allocator is undefined.
 *
 * @param allocator the allocator
 * @param mem a pointer to the block to free
 */
__attribute__((nonnull))
void cxFree(CxAllocator allocator, void *mem);

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

#endif /* UCX_ALLOCATOR_H */