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tar: cache [ug]id->username/groupname mappings. Cuts down amount

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of open/read/close of /etc/passwd and /etc/group
dramatically (we were rereading those for each untarred file!!!)
This commit is contained in:
Denis Vlasenko
2006-11-24 14:57:31 +00:00
parent 4fbb584a0e
commit c50f370f98
3 changed files with 52 additions and 24 deletions
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66
libbb/procps.c
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@@ -11,32 +11,62 @@
#include "libbb.h"
typedef struct {
uid_t uid;
char username[12];
} user_map_t;
typedef struct unsigned_to_name_map_t {
unsigned id;
char name[12];
} unsigned_to_name_map_t;
static user_map_t *username_cache;
static int username_cache_size;
typedef struct cache_t {
unsigned_to_name_map_t *cache;
int size;
} cache_t;
static cache_t username, groupname;
static void clear_cache(cache_t *cp)
{
free(cp->cache);
cp->cache = NULL;
cp->size = 0;
}
void clear_username_cache(void)
{
free(username_cache);
username_cache = NULL;
username_cache_size = 0;
clear_cache(&username);
clear_cache(&groupname);
}
const char* get_cached_username(uid_t uid)
/* Returns -N-1 if not found. */
/* cp->cache[N] is allocated and must be filled in this case */
static int get_cached(cache_t *cp, unsigned id)
{
int i;
for (i = 0; i < username_cache_size; i++)
if (username_cache[i].uid == uid)
return username_cache[i].username;
i = username_cache_size++;
username_cache = xrealloc(username_cache, username_cache_size * sizeof(*username_cache));
username_cache[i].uid = uid;
bb_getpwuid(username_cache[i].username, uid, sizeof(username_cache[i].username));
return username_cache[i].username;
for (i = 0; i < cp->size; i++)
if (cp->cache[i].id == id)
return i;
i = cp->size++;
cp->cache = xrealloc(cp->cache, cp->size * sizeof(*cp->cache));
cp->cache[i++].id = id;
return -i;
}
const char* get_cached_username(uid_t uid)
{
int i = get_cached(&username, uid);
if (i < 0) {
i = -i - 1;
bb_getpwuid(username.cache[i].name, uid,
sizeof(username.cache[i].name));
}
return username.cache[i].name;
}
const char* get_cached_groupname(uid_t uid)
{
int i = get_cached(&groupname, uid);
if (i < 0) {
i = -i - 1;
bb_getgrgid(groupname.cache[i].name, uid,
sizeof(groupname.cache[i].name));
}
return username.cache[i].name;
}