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 /*

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

  *

  * Copyright 2017 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

  * 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 or <code>NULL</code> on stack

  * overflow

  * @see ucx_allocator_malloc()

  */

 void *ucx_stack_malloc(UcxStack *stack, size_t n);

 /**

  * Allocates memory with #ucx_stack_malloc() and copies the specified data if

  * the allocation was successful.

  * 

  * @param stack a pointer to the stack

  * @param n amount of memory to allocate

  * @param data a pointer to the data to copy

  * @return a pointer to the allocated memory

  * @see ucx_stack_malloc

  */

 void *ucx_stack_push(UcxStack *stack, size_t n, const void *data);

 /**

  * 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);

 /**

  * Allocates memory with #ucx_stack_calloc() and copies the specified data if

  * the allocation was successful.

  * 

  * @param stack a pointer to the stack

  * @param nelem amount of elements to allocate

  * @param elsize amount of memory per element

  * @param data a pointer to the data

  * @return a pointer to the allocated memory

  * @see ucx_stack_calloc

  */

 void *ucx_stack_pusharr(UcxStack *stack,

         size_t nelem, size_t elsize, const void *data);

 /**

  * 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>.

  * 

  * This function copies at most <code>n</code> bytes to the destination, but

  * the element is always freed as a whole.

  * If the element was larger than <code>n</code>, the remaining data is lost.

  * 

  * @param stack a pointer to the stack

  * @param dest the location where the contents shall be written to

  * @param n copies at most n bytes 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 */