75 lines
2.1 KiB
C
75 lines
2.1 KiB
C
/* $OpenBSD: seekdir.c,v 1.13 2015/09/12 13:34:22 guenther Exp $ */
|
|
/*
|
|
* Copyright (c) 2013 Ingo Schwarze <schwarze@openbsd.org>
|
|
*
|
|
* Permission to use, copy, modify, and distribute this software for any
|
|
* purpose with or without fee is hereby granted, provided that the above
|
|
* copyright notice and this permission notice appear in all copies.
|
|
*
|
|
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
|
|
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
|
|
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
|
|
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
|
|
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
|
|
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
|
|
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
|
|
*/
|
|
|
|
#include <dirent.h>
|
|
#include <unistd.h>
|
|
|
|
#include "thread_private.h"
|
|
#include "telldir.h"
|
|
|
|
/*
|
|
* Seek to an entry in a directory.
|
|
* Only values returned by "telldir" should be passed to seekdir.
|
|
*/
|
|
void
|
|
seekdir(DIR *dirp, long loc)
|
|
{
|
|
struct dirent *dp;
|
|
|
|
/*
|
|
* First check whether the directory entry to seek for
|
|
* is still buffered in the directory structure in memory.
|
|
*/
|
|
|
|
_MUTEX_LOCK(&dirp->dd_lock);
|
|
if (dirp->dd_size && dirp->dd_bufpos == loc) {
|
|
dirp->dd_loc = 0;
|
|
dirp->dd_curpos = loc;
|
|
_MUTEX_UNLOCK(&dirp->dd_lock);
|
|
return;
|
|
}
|
|
|
|
for (dirp->dd_loc = 0;
|
|
dirp->dd_loc < dirp->dd_size;
|
|
dirp->dd_loc += dp->d_reclen) {
|
|
dp = (struct dirent *)(dirp->dd_buf + dirp->dd_loc);
|
|
if (dp->d_off != loc)
|
|
continue;
|
|
|
|
/*
|
|
* Entry found in the buffer, use it. If readdir(3)
|
|
* follows, this will save us a getdents(2) syscall.
|
|
* Note that d_off is the offset of the _next_ entry,
|
|
* so advance dd_loc.
|
|
*/
|
|
|
|
dirp->dd_loc += dp->d_reclen;
|
|
dirp->dd_curpos = loc;
|
|
_MUTEX_UNLOCK(&dirp->dd_lock);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* The entry is not in the buffer, prepare a call to getdents(2).
|
|
* In particular, invalidate dd_loc.
|
|
*/
|
|
|
|
dirp->dd_loc = dirp->dd_size;
|
|
dirp->dd_bufpos = dirp->dd_curpos = lseek(dirp->dd_fd, loc, SEEK_SET);
|
|
_MUTEX_UNLOCK(&dirp->dd_lock);
|
|
}
|
|
DEF_WEAK(seekdir);
|