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/*
 * 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
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @file stack.h
 * 
 * Default stack memory allocation implementation.
 * 
 * @author Mike Becker
 * @author Olaf Wintermann
 */

#ifndef UCX_STACK_H
#define	UCX_STACK_H

#include "ucx.h"
#include "allocator.h"

#ifdef	__cplusplus
extern "C" {
#endif


/**
 * UCX stack structure.
 */
typedef struct {
    /** UcxAllocator based on this stack */
    UcxAllocator allocator;
    
    /** Stack size. */
    size_t size;
    
    /** Pointer to the bottom of the stack */
    char *space;
    
    /** Pointer to the top of the stack */
    char *top;
} UcxStack;

/**
 * Metadata for each UCX stack element.
 */
struct ucx_stack_metadata {
    /**
     * Location of the previous element (<code>NULL</code> if this is the first)
     */
    char *prev;
    
    /** Size of this element */
    size_t size;
};

/**
 * Initializes UcxStack structure with memory.
 * 
 * @param stack a pointer to an uninitialized stack structure
 * @param space the memory area that shall be managed
 * @param size size of the memory area
 * @return a new UcxStack structure
 */
void ucx_stack_init(UcxStack *stack, char* space, size_t size);

/**
 * Allocates stack memory.
 * 
 * @param stack a pointer to the stack
 * @param n amount of memory to allocate
 * @return a pointer to the allocated memory
 * @see ucx_allocator_malloc()
 */
void *ucx_stack_malloc(UcxStack *stack, size_t n);

/**
 * Alias for #ucx_stack_malloc().
 * @param stack a pointer to the stack
 * @param n amount of memory to allocate
 * @return a pointer to the allocated memory
 * @see ucx_stack_malloc
 */
#define ucx_stack_push(stack, n) ucx_stack_malloc(stack, n)

/**
 * Allocates an array of stack memory
 * 
 * The content of the allocated memory is set to zero.
 * 
 * @param stack a pointer to the stack
 * @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_stack_calloc(UcxStack *stack, size_t nelem, size_t elsize);

/**
 * Alias for #ucx_stack_calloc().
 * 
 * @param stack a pointer to the stack
 * @param n amount of elements to allocate
 * @param elsize amount of memory per element
 * @return a pointer to the allocated memory
 * @see ucx_stack_calloc
 */
#define ucx_stack_pusharr(stack,n,elsize) ucx_stack_calloc(stack,n,elssize)

/**
 * Reallocates memory on the stack.
 * 
 * Shrinking memory is always safe. Extending memory can be very expensive. 
 * 
 * @param stack the stack
 * @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_stack_realloc(UcxStack *stack, void *ptr, size_t n);

/**
 * Frees memory on the stack.
 * 
 * Freeing stack memory behaves in a special way.
 * 
 * If the element, that should be freed, is the top most element of the stack,
 * it is removed from the stack. Otherwise it is marked as freed. Marked
 * elements are removed, when they become the top most elements of the stack.
 * 
 * @param stack a pointer to the stack
 * @param ptr a pointer to the memory that shall be freed
 */
void ucx_stack_free(UcxStack *stack, void *ptr);


/**
 * Returns the size of the top most element.
 * @param stack a pointer to the stack
 * @return the size of the top most element
 */
#define ucx_stack_topsize(stack) ((stack)->top ? ((struct ucx_stack_metadata*)\
                                  (stack)->top - 1)->size : 0)

/**
 * Removes the top most element from the stack and copies the content to <code>
 * dest</code>, if specified.
 * 
 * Use #ucx_stack_topsize()# to get the amount of memory that must be available
 * at the location of <code>dest</code>.
 * 
 * @param stack a pointer to the stack
 * @param dest the location where the contents shall be written to, or <code>
 * NULL</code>, if the element shall only be removed.
 * @see ucx_stack_free
 * @see ucx_stack_popn
 */
#define ucx_stack_pop(stack, dest) ucx_stack_popn(stack, dest, (size_t)-1)

/**
 * Removes the top most element from the stack and copies the content to <code>
 * dest</code>.
 * 
 * In contrast to #ucx_stack_pop() the <code>dest</code> pointer <code>MUST
 * NOT</code> be <code>NULL</code>.
 * 
 * @param stack a pointer to the stack
 * @param dest the location where the contents shall be written to
 * @param n copies at most n elements to <code>dest</code>
 * @see ucx_stack_pop
 */
void ucx_stack_popn(UcxStack *stack, void *dest, size_t n);

/**
 * Returns the remaining available memory on the specified stack.
 * 
 * @param stack a pointer to the stack
 * @return the remaining available memory
 */
size_t ucx_stack_avail(UcxStack *stack);

/**
 * Checks, if the stack is empty.
 * 
 * @param stack a pointer to the stack
 * @return nonzero, if the stack is empty, zero otherwise
 */
#define ucx_stack_empty(stack) (!(stack)->top)

/**
 * Computes a recommended size for the stack memory area. Note, that
 * reallocations have not been taken into account, so you might need to reserve
 * twice as much memory to allow many reallocations.
 * 
 * @param size the approximate payload
 * @param elems the approximate count of element allocations
 * @return a recommended size for the stack space based on the information
 * provided
 */
#define ucx_stack_dim(size, elems) (size+sizeof(struct ucx_stack_metadata) * \
                                    (elems + 1))


#ifdef	__cplusplus
}
#endif

#endif	/* UCX_STACK_H */