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 14 struct pstack { 15 unsigned short top; 16 unsigned short max_nr_entries; 17 void *entries[0]; 18 }; 19 20 struct pstack *pstack__new(unsigned short max_nr_entries) 21 { 22 struct pstack *pstack = zalloc((sizeof(*pstack) + 23 max_nr_entries * sizeof(void *))); 24 if (pstack != NULL) 25 pstack->max_nr_entries = max_nr_entries; 26 return pstack; 27 } 28 29 void pstack__delete(struct pstack *pstack) 30 { 31 free(pstack); 32 } 33 34 bool pstack__empty(const struct pstack *pstack) 35 { 36 return pstack->top == 0; 37 } 38 39 void pstack__remove(struct pstack *pstack, void *key) 40 { 41 unsigned short i = pstack->top, last_index = pstack->top - 1; 42 43 while (i-- != 0) { 44 if (pstack->entries[i] == key) { 45 if (i < last_index) 46 memmove(pstack->entries + i, 47 pstack->entries + i + 1, 48 (last_index - i) * sizeof(void *)); 49 --pstack->top; 50 return; 51 } 52 } 53 pr_err("%s: %p not on the pstack!\n", __func__, key); 54 } 55 56 void pstack__push(struct pstack *pstack, void *key) 57 { 58 if (pstack->top == pstack->max_nr_entries) { 59 pr_err("%s: top=%d, overflow!\n", __func__, pstack->top); 60 return; 61 } 62 pstack->entries[pstack->top++] = key; 63 } 64 65 void *pstack__pop(struct pstack *pstack) 66 { 67 void *ret; 68 69 if (pstack->top == 0) { 70 pr_err("%s: underflow!\n", __func__); 71 return NULL; 72 } 73 74 ret = pstack->entries[--pstack->top]; 75 pstack->entries[pstack->top] = NULL; 76 return ret; 77 } 78 79 void *pstack__peek(struct pstack *pstack) 80 { 81 if (pstack->top == 0) 82 return NULL; 83 return pstack->entries[pstack->top - 1]; 84 } 85