lib/libc/gen/directory.c

/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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 BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)closedir.c  5.9 (Berkeley) 2/23/91";
#endif /* LIBC_SCCS and not lint */

/*
 * 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 */
};

static long     dd_loccnt = 0;  /* Index of entry for sequential telldir's */

#include <sys/types.h>
#include <sys/param.h>
#include <dirent.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

/*
 * close a directory.
 */
int
closedir(dirp)
        register DIR *dirp;
{
        struct ddloc *ptr, *nextptr;
        int fd;

        fd = dirp->dd_fd;
        dirp->dd_fd = -1;
        dirp->dd_loc = 0;
        for (ptr = (struct ddloc*)dirp->dd_ddloc; ptr; ptr = nextptr) {
                nextptr = ptr->loc_next;
                free((void *)ptr);
        }
        free((void *)dirp->dd_buf);
        free((void *)dirp);
        return(close(fd));
}

/*
 * open a directory.
 */
DIR *
opendir(name)
        const char *name;
{
        register DIR *dirp;
        register int fd;

        if ((fd = open(name, 0)) == -1)
                return NULL;
        if (fcntl(fd, F_SETFD, 1) == -1 ||
            (dirp = (DIR *)malloc(sizeof(DIR))) == NULL) {
                close (fd);
                return NULL;
        }
        /*
         * If CLSIZE is an exact multiple of DIRBLKSIZ, use a CLSIZE
         * buffer that it cluster boundary aligned.
         * Hopefully this can be a big win someday by allowing page trades
         * to user space to be done by getdirentries()
         */
        if ((CLSIZE % DIRBLKSIZ) == 0) {
                dirp->dd_buf = malloc(CLSIZE);
                dirp->dd_len = CLSIZE;
        } else {
                dirp->dd_buf = malloc(DIRBLKSIZ);
                dirp->dd_len = DIRBLKSIZ;
        }
        if (dirp->dd_buf == NULL) {
                close (fd);
                free(dirp);
                return NULL;
        }
        dirp->dd_fd = fd;
        dirp->dd_loc = 0;
        dirp->dd_seek = 0;
        dirp->dd_ddloc = NULL;

        return dirp;
}

/*
 * get next entry in a directory.
 */
struct dirent *
readdir(dirp)
        register DIR *dirp;
{
        register struct dirent *dp;

        for (;;) {
                if (dirp->dd_loc == 0) {
                        dirp->dd_size = getdirentries(dirp->dd_fd,
                            dirp->dd_buf, dirp->dd_len, &dirp->dd_seek);
                        if (dirp->dd_size <= 0)
                                return NULL;
                }
                if (dirp->dd_loc >= dirp->dd_size) {
                        dirp->dd_loc = 0;
                        continue;
                }
                dp = (struct dirent *)(dirp->dd_buf + dirp->dd_loc);
                if ((int)dp & 03)       /* bogus pointer check */
                        return NULL;
                if (dp->d_reclen <= 0 ||
                    dp->d_reclen > dirp->dd_len + 1 - dirp->dd_loc)
                        return NULL;
                dirp->dd_loc += dp->d_reclen;
                if (dp->d_ino == 0)
                        continue;
                return (dp);
        }
}

void
rewinddir(dirp)
        DIR *dirp;
{
        (void)lseek(dirp->dd_fd, 0, 0);
        dirp->dd_seek = 0;
        dirp->dd_loc = 0;
}

/*
 * Seek to an entry in a directory.
 * _seekdir is in telldir.c so that it can share opaque data structures.
 */
void
seekdir(dirp, loc)
        DIR *dirp;
        long loc;
{
        register struct ddloc **prevlp;
        register struct ddloc *lp;
        struct dirent *dp;
        extern long lseek();

        prevlp = (struct ddloc **)&(dirp->dd_ddloc);
        lp = *prevlp;
        while (lp != NULL) {
                if (lp->loc_index == loc)
                        break;
                prevlp = &lp->loc_next;
                lp = lp->loc_next;
        }
        if (lp) {
                if (lp->loc_seek != dirp->dd_seek) {
                        if (lseek(dirp->dd_fd, lp->loc_seek, 0) == -1) {
                                *prevlp = lp->loc_next;
                                free(lp);
                                return;
                        }
                        dirp->dd_seek = lp->loc_seek;
                        dirp->dd_loc = 0;
                        while (dirp->dd_loc < lp->loc_loc) {
                                if (!(dp = readdir(dirp))) {
                                        *prevlp = lp->loc_next;
                                        free(lp);
                                        return;
                                }
                        }
                }
        }
}

/*
 * return a pointer into a directory
 */
long
telldir(dirp)
        const DIR *dirp;
{
        register struct ddloc *lp, **fakeout;

        if (lp = (struct ddloc *)malloc(sizeof(struct ddloc))) {
                lp->loc_index = dd_loccnt++;
                lp->loc_seek = dirp->dd_seek;
                lp->loc_loc = dirp->dd_loc;
                lp->loc_next = dirp->dd_ddloc;

                /* Compiler won't let us change anything pointed to by db directly */
                /* So we fake to the left and do it anyway */
                /* Wonder if the compile optomizes it to the correct solution */
                fakeout = (struct ddloc **)&(dirp->dd_ddloc);
                *fakeout = lp;

                return (lp->loc_index);
        }
        return (-1);
}