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view doorbelld/src/dynarr.c @ 7:dc4018af3a40
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| author | John Tsiombikas <nuclear@member.fsf.org> |
|---|---|
| date | Wed, 16 Mar 2016 02:50:30 +0200 |
| parents | |
| children |
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1 /* dynarr - dynamic resizable C array data structure
2 * author: John Tsiombikas <nuclear@member.fsf.org>
3 * license: public domain
4 */
5 #include <stdio.h>
6 #include <stdlib.h>
7 #include <string.h>
8 #include "dynarr.h"
10 /* The array descriptor keeps auxilliary information needed to manipulate
11 * the dynamic array. It's allocated adjacent to the array buffer.
12 */
13 struct arrdesc {
14 int nelem, szelem;
15 int max_elem;
16 int bufsz; /* not including the descriptor */
17 };
19 #define DESC(x) ((struct arrdesc*)((char*)(x) - sizeof(struct arrdesc)))
21 void *dynarr_alloc(int elem, int szelem)
22 {
23 struct arrdesc *desc;
25 if(!(desc = malloc(elem * szelem + sizeof *desc))) {
26 return 0;
27 }
28 desc->nelem = desc->max_elem = elem;
29 desc->szelem = szelem;
30 desc->bufsz = elem * szelem;
31 return (char*)desc + sizeof *desc;
32 }
34 void dynarr_free(void *da)
35 {
36 if(da) {
37 free(DESC(da));
38 }
39 }
41 void *dynarr_resize(void *da, int elem)
42 {
43 int newsz;
44 void *tmp;
45 struct arrdesc *desc;
47 if(!da) return 0;
48 desc = DESC(da);
50 newsz = desc->szelem * elem;
52 if(!(tmp = realloc(desc, newsz + sizeof *desc))) {
53 return 0;
54 }
55 desc = tmp;
57 desc->nelem = desc->max_elem = elem;
58 desc->bufsz = newsz;
59 return (char*)desc + sizeof *desc;
60 }
62 int dynarr_empty(void *da)
63 {
64 return DESC(da)->nelem ? 0 : 1;
65 }
67 int dynarr_size(void *da)
68 {
69 return DESC(da)->nelem;
70 }
73 /* stack semantics */
74 void *dynarr_push(void *da, void *item)
75 {
76 struct arrdesc *desc;
77 int nelem;
79 desc = DESC(da);
80 nelem = desc->nelem;
82 if(nelem >= desc->max_elem) {
83 /* need to resize */
84 struct arrdesc *tmp;
85 int newsz = desc->max_elem ? desc->max_elem * 2 : 1;
87 if(!(tmp = dynarr_resize(da, newsz))) {
88 fprintf(stderr, "failed to resize\n");
89 return da;
90 }
91 da = tmp;
92 desc = DESC(da);
93 desc->nelem = nelem;
94 }
96 if(item) {
97 memcpy((char*)da + desc->nelem++ * desc->szelem, item, desc->szelem);
98 }
99 return da;
100 }
102 void *dynarr_pop(void *da)
103 {
104 struct arrdesc *desc;
105 int nelem;
107 desc = DESC(da);
108 nelem = desc->nelem;
110 if(!nelem) return da;
112 if(nelem <= desc->max_elem / 3) {
113 /* reclaim space */
114 struct arrdesc *tmp;
115 int newsz = desc->max_elem / 2;
117 if(!(tmp = dynarr_resize(da, newsz))) {
118 fprintf(stderr, "failed to resize\n");
119 return da;
120 }
121 da = tmp;
122 desc = DESC(da);
123 desc->nelem = nelem;
124 }
125 desc->nelem--;
127 return da;
128 }