2 * Copyright (c) 1983, 1993
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33 * $FreeBSD: src/lib/libc/gen/telldir.c,v 1.4.12.1 2001/03/05 09:39:59 obrien Exp $
34 * $DragonFly: src/lib/libc/gen/telldir.c,v 1.7 2008/05/03 22:07:37 dillon Exp $
36 * @(#)telldir.c 8.1 (Berkeley) 6/4/93
39 #include "namespace.h"
40 #include <sys/param.h>
45 #include "un-namespace.h"
47 #include "libc_private.h"
50 * One of these structures is malloced to describe the current directory
51 * position each time telldir is called. It records the current magic
52 * cookie returned by getdirentries and the offset within the buffer
53 * associated with that return value.
56 struct ddloc
*loc_next
;/* next structure in list */
57 long loc_index
; /* key associated with structure */
58 off_t loc_seek
; /* magic cookie returned by getdirentries */
59 long loc_loc
; /* offset of entry in buffer */
60 const DIR* loc_dirp
; /* directory which used this entry */
63 #define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */
64 #define LOCHASH(i) ((i)&(NDIRHASH-1))
66 static long dd_loccnt
; /* Index of entry for sequential readdir's */
67 static struct ddloc
*dd_hash
[NDIRHASH
]; /* Hash list heads for ddlocs */
68 static pthread_mutex_t dd_hash_lock
;
71 * return a pointer into a directory
74 telldir(const DIR *dirp
)
80 _pthread_mutex_lock((pthread_mutex_t
*)&dirp
->dd_lock
);
81 _pthread_mutex_lock(&dd_hash_lock
);
85 * Reduce memory use by reusing a ddloc that might already exist
88 for (lp
= dd_hash
[LOCHASH(dirp
->dd_lastseek
)]; lp
; lp
= lp
->loc_next
) {
89 if (lp
->loc_dirp
== dirp
&& lp
->loc_seek
== dirp
->dd_seek
&&
90 lp
->loc_loc
== dirp
->dd_loc
) {
91 index
= lp
->loc_index
;
96 if ((lp
= (struct ddloc
*)malloc(sizeof(struct ddloc
))) == NULL
) {
101 lp
->loc_index
= index
;
102 lp
->loc_seek
= dirp
->dd_seek
;
103 lp
->loc_loc
= dirp
->dd_loc
;
106 lp
->loc_next
= dd_hash
[LOCHASH(index
)];
107 dd_hash
[LOCHASH(index
)] = lp
;
111 _pthread_mutex_unlock(&dd_hash_lock
);
112 _pthread_mutex_unlock((pthread_mutex_t
*)&dirp
->dd_lock
);
118 * seek to an entry in a directory.
119 * Only values returned by "telldir" should be passed to seekdir.
122 _seekdir(DIR *dirp
, long loc
)
125 struct ddloc
**prevlp
;
129 _pthread_mutex_lock(&dd_hash_lock
);
130 for (lp
= dd_hash
[LOCHASH(loc
)]; lp
; lp
= lp
->loc_next
) {
131 if (lp
->loc_dirp
== dirp
&& lp
->loc_index
== loc
)
135 _pthread_mutex_unlock(&dd_hash_lock
);
138 if (lp
->loc_loc
== dirp
->dd_loc
&& lp
->loc_seek
== dirp
->dd_seek
)
140 lseek(dirp
->dd_fd
, lp
->loc_seek
, SEEK_SET
);
141 dirp
->dd_seek
= lp
->loc_seek
;
143 dirp
->dd_lastseek
= loc
;
146 * Scan the buffer until we find dd_loc. If the directory
147 * changed between the tell and seek it is possible to
148 * load a new buffer or for dd_loc to not match directly.
150 while (dirp
->dd_loc
< lp
->loc_loc
&& dirp
->dd_seek
== lp
->loc_seek
) {
151 dp
= _readdir_unlocked(dirp
, 0);
158 * Reclaim memory for telldir cookies which weren't used.
161 _reclaim_telldir(DIR *dirp
)
164 struct ddloc
**prevlp
;
168 _pthread_mutex_lock(&dd_hash_lock
);
169 for (i
= 0; i
< NDIRHASH
; i
++) {
170 prevlp
= &dd_hash
[i
];
173 if (lp
->loc_dirp
== dirp
) {
174 *prevlp
= lp
->loc_next
;
179 prevlp
= &lp
->loc_next
;
184 _pthread_mutex_unlock(&dd_hash_lock
);