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