1  // SPDX-License-Identifier: GPL-2.0
2  /*
3   * Simple pointer stack
4   *
5   * (c) 2010 Arnaldo Carvalho de Melo <acme@redhat.com>
6   */
7  
8  #include "pstack.h"
9  #include "debug.h"
10  #include <linux/kernel.h>
11  #include <linux/zalloc.h>
12  #include <stdlib.h>
13  #include <string.h>
14  
15  struct pstack {
16  	unsigned short	top;
17  	unsigned short	max_nr_entries;
18  	void		*entries[];
19  };
20  
pstack__new(unsigned short max_nr_entries)21  struct pstack *pstack__new(unsigned short max_nr_entries)
22  {
23  	struct pstack *pstack = zalloc((sizeof(*pstack) +
24  				       max_nr_entries * sizeof(void *)));
25  	if (pstack != NULL)
26  		pstack->max_nr_entries = max_nr_entries;
27  	return pstack;
28  }
29  
pstack__delete(struct pstack * pstack)30  void pstack__delete(struct pstack *pstack)
31  {
32  	free(pstack);
33  }
34  
pstack__empty(const struct pstack * pstack)35  bool pstack__empty(const struct pstack *pstack)
36  {
37  	return pstack->top == 0;
38  }
39  
pstack__remove(struct pstack * pstack,void * key)40  void pstack__remove(struct pstack *pstack, void *key)
41  {
42  	unsigned short i = pstack->top, last_index = pstack->top - 1;
43  
44  	while (i-- != 0) {
45  		if (pstack->entries[i] == key) {
46  			if (i < last_index)
47  				memmove(pstack->entries + i,
48  					pstack->entries + i + 1,
49  					(last_index - i) * sizeof(void *));
50  			--pstack->top;
51  			return;
52  		}
53  	}
54  	pr_err("%s: %p not on the pstack!\n", __func__, key);
55  }
56  
pstack__push(struct pstack * pstack,void * key)57  void pstack__push(struct pstack *pstack, void *key)
58  {
59  	if (pstack->top == pstack->max_nr_entries) {
60  		pr_err("%s: top=%d, overflow!\n", __func__, pstack->top);
61  		return;
62  	}
63  	pstack->entries[pstack->top++] = key;
64  }
65  
pstack__pop(struct pstack * pstack)66  void *pstack__pop(struct pstack *pstack)
67  {
68  	void *ret;
69  
70  	if (pstack->top == 0) {
71  		pr_err("%s: underflow!\n", __func__);
72  		return NULL;
73  	}
74  
75  	ret = pstack->entries[--pstack->top];
76  	pstack->entries[pstack->top] = NULL;
77  	return ret;
78  }
79  
pstack__peek(struct pstack * pstack)80  void *pstack__peek(struct pstack *pstack)
81  {
82  	if (pstack->top == 0)
83  		return NULL;
84  	return pstack->entries[pstack->top - 1];
85  }
86