14. Stack

The stack functions manipulate a simple LIFO stack of pointers to objects but the underlying array will grow and shrink as storage requirements change.

14.1. Memory management functions

These functions should be used to create and destroy stack objects.

The stack_init function
Synopsis


  #include <mba/stack.h>
  int stack_init(struct stack *s, unsigned int max_size, struct allocator *al);

Description
The stack_init function initializes the stack s and saving a pointer to the allocator(3m) al which will be used to allocate memory for susequent stack operations. The stack will accept no more than max data pointers. If max is 0, INT_MAX elements may be pushed onto the stack.
Returns
The stack_init function returns -1 if s is a null pointer. Otherwise 0 is returned.

The stack_deinit function
Synopsis


  #include <mba/stack.h>
  int stack_deinit(struct stack *s, del_fn data_del, void *context)

Description
The stack_deinit function deinitializes the stack s. If the data_del function is not NULL, it will be called with the context parameter and each element on the stack.
Returns
The stack_deinit function returns 0 if the stack was successfully deinitialized or -1 if the data_del function returned anything other than 0 or if an error occured attempting to free the memory backing the stack.

The stack_new function
Synopsis


  #include <mba/stack.h>
  struct stack *stack_new(unsigned int max_size, struct allocator *al);

Description
Create a new stack(3) object that will accept no more than max_size data pointers. If max_size is 0, the stack will accept at most INT_MAX elements.
Returns
The stack_new function returns a new stack object or NULL of memory could not be allocated in which case errno will be set to ENOMEM.

The stack_del function
Synopsis


  #include <mba/stack.h>
  int stack_del(struct stack *s, del_fn data_del, void *context);

Description
The stack_del function deletes the stack object s. If the data_del function is not NULL, it will be called with each remaining element before deallocating the stack s itself.

The stack_clear function
Synopsis


  #include <mba/stack.h>
  int stack_clear(struct stack *s, del_fn data_del, void *context)

Description
The stack_clear function will remove all elements on the stack. If the data_del function is not NULL it will be called with each remaining element.

The stack_clean function
Synopsis


  #include <mba/stack.h>
  int stack_clean(struct stack *s)

Description
The stack_clean function reallocates the array backing the stack to be exactly the number of elements necessary. A stack(3m) will automatically shrink at an appropriate point but this function might be called by an allocator(3m) reclaim_fn function.

14.2. Stack functions

The stack_push function
Synopsis


  #include <mba/stack.h>
  int stack_push(struct stack *s, void *data);

Description
The stack_push function pushes the element data onto the stack identified by s;
Returns
The stack_push function returns -1 and sets errno to an appropriate value if the operation failed or 0 if the data pointer was successfully pushed onto the stack (e.g. ERANGE if the stack is full).

The stack_pop function
Synopsis


  #include <mba/stack.h>
  void *stack_pop(struct stack *s);

Description
The stack_pop function removes the last element pushed onto the stack s.
Returns
The stack_pop function returns the data pointer popped off the stack.

The stack_is_empty function
Synopsis


  #include <mba/stack.h>
  int stack_is_empty(const struct stack *s);

Description
Returns non-zero if the stack s has no elements and 0 otherwise.

The stack_size function
Synopsis


  #include <mba/stack.h>
  unsigned int stack_size(const struct stack *s);

Description
The stack_size function returns the number of elements currently on the stack.

The stack_iterate function
Synopsis


  #include <mba/stack.h>
  void stack_iterate(void *s, iter_t *iter);

Description
Enumerate each element on the stack. Call stack_iterate to initialize the iter object to point to the bottom of the stack (the first element pushed onto the stack) and call stack_next to retrieve each data pointer. When the top of the stack has been reached, stack_next will return NULL.

The stack_next function
Synopsis


  #include <mba/stack.h>
  void *stack_next(void *s, iter_t *iter);

Returns
The stack_next function returns the next data pointer on the stack or NULL if the top of the stack has been exceeded.

The stack_peek function
Synopsis


  #include <mba/stack.h>
  void *stack_peek(struct stack *s);

Description
The stack_peek function returns the element at the top of the stack s or NULL of the stack is empty. The data pointer is not removed.