1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
|
// SPDX-License-Identifier: GPL-2.0-only
/* Manage a cache of file names' existence */
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <linux/list.h>
#include "fncache.h"
struct fncache {
struct hlist_node nd;
bool res;
char name[];
};
#define FNHSIZE 61
static struct hlist_head fncache_hash[FNHSIZE];
unsigned shash(const unsigned char *s)
{
unsigned h = 0;
while (*s)
h = 65599 * h + *s++;
return h ^ (h >> 16);
}
static bool lookup_fncache(const char *name, bool *res)
{
int h = shash((const unsigned char *)name) % FNHSIZE;
struct fncache *n;
hlist_for_each_entry(n, &fncache_hash[h], nd) {
if (!strcmp(n->name, name)) {
*res = n->res;
return true;
}
}
return false;
}
static void update_fncache(const char *name, bool res)
{
struct fncache *n = malloc(sizeof(struct fncache) + strlen(name) + 1);
int h = shash((const unsigned char *)name) % FNHSIZE;
if (!n)
return;
strcpy(n->name, name);
n->res = res;
hlist_add_head(&n->nd, &fncache_hash[h]);
}
/* No LRU, only use when bounded in some other way. */
bool file_available(const char *name)
{
bool res;
if (lookup_fncache(name, &res))
return res;
res = access(name, R_OK) == 0;
update_fncache(name, res);
return res;
}
|
