/*
   * Simple pointer stack
   *
   * (c) 2010 Arnaldo Carvalho de Melo <acme@redhat.com>
   */
  
  #include "util.h"
  #include "pstack.h"

  #include "debug.h"

  #include <linux/kernel.h>
  #include <stdlib.h>
  
  struct pstack {
  	unsigned short	top;
  	unsigned short	max_nr_entries;
  	void		*entries[0];
  };
  
  struct pstack *pstack__new(unsigned short max_nr_entries)
  {

  	struct pstack *pstack = zalloc((sizeof(*pstack) +
  				       max_nr_entries * sizeof(void *)));
  	if (pstack != NULL)
  		pstack->max_nr_entries = max_nr_entries;
  	return pstack;

  }

  void pstack__delete(struct pstack *pstack)

  {

  	free(pstack);

  }

  bool pstack__empty(const struct pstack *pstack)

  {

  	return pstack->top == 0;

  }

  void pstack__remove(struct pstack *pstack, void *key)

  {

  	unsigned short i = pstack->top, last_index = pstack->top - 1;

  
  	while (i-- != 0) {

  		if (pstack->entries[i] == key) {

  			if (i < last_index)

  				memmove(pstack->entries + i,
  					pstack->entries + i + 1,

  					(last_index - i) * sizeof(void *));

  			--pstack->top;

  			return;
  		}
  	}
  	pr_err("%s: %p not on the pstack!
  ", __func__, key);
  }

  void pstack__push(struct pstack *pstack, void *key)

  {

  	if (pstack->top == pstack->max_nr_entries) {
  		pr_err("%s: top=%d, overflow!
  ", __func__, pstack->top);

  		return;
  	}

  	pstack->entries[pstack->top++] = key;

  }

  void *pstack__pop(struct pstack *pstack)

  {
  	void *ret;

  	if (pstack->top == 0) {

  		pr_err("%s: underflow!
  ", __func__);
  		return NULL;
  	}

  	ret = pstack->entries[--pstack->top];
  	pstack->entries[pstack->top] = NULL;

  	return ret;
  }

  
  void *pstack__peek(struct pstack *pstack)
  {
  	if (pstack->top == 0)
  		return NULL;
  	return pstack->entries[pstack->top - 1];
  }