archie/prospero/lib/pcompat/telldir.c
2024-05-27 16:13:40 +02:00

130 lines
3.7 KiB
C

/*
* Derived from Berkeley source code. Those parts are
* Copyright (c) 1983 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that: (1) source distributions retain this entire copyright
* notice and comment, and (2) distributions including binaries display
* the following acknowledgement: ``This product includes software
* developed by the University of California, Berkeley and its contributors''
* in the documentation or other materials provided with the distribution
* and in all advertising materials mentioning features or use of this
* software. Neither the name of the University nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)telldir.c 5.8 (Berkeley) 6/1/90";
#endif /* LIBC_SCCS and not lint */
#include <sys/param.h>
#include <pmachine.h>
#include <stdlib.h> /* For malloc and free */
#ifdef USE_SYS_DIR_H
#include <sys/dir.h>
#else
#include <dirent.h>
#endif
#if defined(AIX) && defined(__GNUC__) /* lucb */
#define dd_bsize dd_size
#endif
/*
* The option SINGLEUSE may be defined to say that a telldir
* cookie may be used only once before it is freed. This option
* is used to avoid having memory usage grow without bound.
*/
#define SINGLEUSE
/*
* One of these structures is malloced to describe the current directory
* position each time telldir is called. It records the current magic
* cookie returned by getdirentries and the offset within the buffer
* associated with that return value.
*/
struct ddloc {
struct ddloc *loc_next;/* next structure in list */
long loc_index; /* key associated with structure */
long loc_seek; /* magic cookie returned by getdirentries */
long loc_loc; /* offset of entry in buffer */
};
#define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */
#define LOCHASH(i) ((i)&(NDIRHASH-1))
static long dd_loccnt; /* Index of entry for sequential readdir's */
static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */
/*
* return a pointer into a directory
*/
long
telldir(dirp)
DIR *dirp;
{
register int index;
register struct ddloc *lp;
if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL)
return (-1);
index = dd_loccnt++;
lp->loc_index = index;
lp->loc_seek = dirp->dd_bbase;
lp->loc_loc = dirp->dd_loc;
lp->loc_next = dd_hash[LOCHASH(index)];
dd_hash[LOCHASH(index)] = lp;
return (index);
}
/*
* seek to an entry in a directory.
* Only values returned by "telldir" should be passed to seekdir.
*/
void
p__seekdir(register DIR *dirp, long loc)
{
register struct ddloc *lp;
register struct ddloc **prevlp;
struct dirent *dp;
extern long lseek();
prevlp = &dd_hash[LOCHASH(loc)];
lp = *prevlp;
while (lp != NULL) {
if (lp->loc_index == loc)
break;
prevlp = &lp->loc_next;
lp = lp->loc_next;
}
if (lp == NULL)
return;
if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_bbase)
goto found;
if(dirp->dd_fd < 0)
p__seekvdir(dirp->dd_fd,lp->loc_seek);
else
(void) lseek(dirp->dd_fd, lp->loc_seek, 0);
dirp->dd_bbase = lp->loc_seek;
dirp->dd_loc = 0;
while (dirp->dd_loc < lp->loc_loc) {
assert(P_IS_THIS_THREAD_MASTER()); /*SOLARIS: readdir MT-Unsafe */
dp = readdir(dirp);
if (dp == NULL)
break;
}
found:
#ifdef SINGLEUSE
*prevlp = lp->loc_next;
free((caddr_t)lp);
#endif
}