1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Manage a cache of file names' existence */
3 #include <pthread.h>
4 #include <stdlib.h>
5 #include <string.h>
6 #include <unistd.h>
7 #include <linux/compiler.h>
8 #include "fncache.h"
9 #include "hashmap.h"
10
11 static struct hashmap *fncache;
12
fncache__hash(long key,void * ctx __maybe_unused)13 static size_t fncache__hash(long key, void *ctx __maybe_unused)
14 {
15 return str_hash((const char *)key);
16 }
17
fncache__equal(long key1,long key2,void * ctx __maybe_unused)18 static bool fncache__equal(long key1, long key2, void *ctx __maybe_unused)
19 {
20 return strcmp((const char *)key1, (const char *)key2) == 0;
21 }
22
fncache__init(void)23 static void fncache__init(void)
24 {
25 fncache = hashmap__new(fncache__hash, fncache__equal, /*ctx=*/NULL);
26 }
27
fncache__get(void)28 static struct hashmap *fncache__get(void)
29 {
30 static pthread_once_t fncache_once = PTHREAD_ONCE_INIT;
31
32 pthread_once(&fncache_once, fncache__init);
33
34 return fncache;
35 }
36
lookup_fncache(const char * name,bool * res)37 static bool lookup_fncache(const char *name, bool *res)
38 {
39 long val;
40
41 if (!hashmap__find(fncache__get(), name, &val))
42 return false;
43
44 *res = (val != 0);
45 return true;
46 }
47
update_fncache(const char * name,bool res)48 static void update_fncache(const char *name, bool res)
49 {
50 char *old_key = NULL, *key = strdup(name);
51
52 if (key) {
53 hashmap__set(fncache__get(), key, res, &old_key, /*old_value*/NULL);
54 free(old_key);
55 }
56 }
57
58 /* No LRU, only use when bounded in some other way. */
file_available(const char * name)59 bool file_available(const char *name)
60 {
61 bool res;
62
63 if (lookup_fncache(name, &res))
64 return res;
65 res = access(name, R_OK) == 0;
66 update_fncache(name, res);
67 return res;
68 }
69