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