/*
 * Copyright (c) 1983, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * %sccs.include.redist.c%
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)opendir.c	8.6 (Berkeley) 08/14/94";
#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>
#include <sys/mount.h>

#include <dirent.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>

/*
 * Open a directory.
 */
DIR *
opendir(name)
	const char *name;
{

	return (__opendir2(name, DTF_HIDEW|DTF_NODUP));
}

DIR *
__opendir2(name, flags)
	const char *name;
	int flags;
{
	DIR *dirp;
	int fd;
	int incr;
	int unionstack;

	if ((fd = open(name, O_RDONLY)) == -1)
		return (NULL);
	if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1 ||
	    (dirp = (DIR *)malloc(sizeof(DIR))) == NULL) {
		close(fd);
		return (NULL);
	}

	/*
	 * If CLBYTES is an exact multiple of DIRBLKSIZ, use a CLBYTES
	 * 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 ((CLBYTES % DIRBLKSIZ) == 0)
		incr = CLBYTES;
	else
		incr = DIRBLKSIZ;

	/*
	 * Determine whether this directory is the top of a union stack.
	 */
	if (flags & DTF_NODUP) {
		struct statfs sfb;

		if (fstatfs(fd, &sfb) < 0) {
			free(dirp);
			close(fd);
			return (NULL);
		}
		unionstack = (sfb.f_type == MOUNT_UNION);
	} else {
		unionstack = 0;
	}

	if (unionstack) {
		int len = 0;
		int space = 0;
		char *buf = 0;
		char *ddptr = 0;
		int n;
		struct dirent **dpv;

		/*
		 * The strategy here is to read all the directory
		 * entries into a buffer, sort the buffer, and
		 * remove duplicate entries by setting the inode
		 * number to zero.
		 */

		do {
			/*
			 * Always make at least DIRBLKSIZ bytes
			 * available to getdirentries
			 */
			if (space < DIRBLKSIZ) {
				space += incr;
				len += incr;
				buf = realloc(buf, len);
				if (buf == NULL) {
					free(dirp);
					close(fd);
					return (NULL);
				}
				ddptr = buf + (len - space);
			}

			n = getdirentries(fd, ddptr, space, &dirp->dd_seek);
			if (n > 0) {
				ddptr += n;
				space -= n;
			}
		} while (n > 0);

		flags |= __DTF_READALL;

		/*
		 * Re-open the directory.
		 * This has the effect of rewinding back to the
		 * top of the union stack and is needed by
		 * programs which plan to fchdir to a descriptor
		 * which has also been read -- see fts.c.
		 */
		if (flags & DTF_REWIND) {
			(void) close(fd);
			if ((fd = open(name, O_RDONLY)) == -1) {
				free(buf);
				free(dirp);
				return (NULL);
			}
		}

		/*
		 * There is now a buffer full of (possibly) duplicate
		 * names.
		 */
		dirp->dd_buf = buf;

		/*
		 * Go round this loop twice...
		 *
		 * Scan through the buffer, counting entries.
		 * On the second pass, save pointers to each one.
		 * Then sort the pointers and remove duplicate names.
		 */
		for (dpv = 0;;) {
			n = 0;
			ddptr = buf;
			while (ddptr < buf + len) {
				struct dirent *dp;

				dp = (struct dirent *) ddptr;
				if ((int)dp & 03)
					break;
				if ((dp->d_reclen <= 0) ||
				    (dp->d_reclen > (buf + len + 1 - ddptr)))
					break;
				ddptr += dp->d_reclen;
				if (dp->d_fileno) {
					if (dpv)
						dpv[n] = dp;
					n++;
				}
			}

			if (dpv) {
				struct dirent *xp;

				/*
				 * This sort must be stable.
				 */
				mergesort(dpv, n, sizeof(*dpv), alphasort);

				dpv[n] = NULL;
				xp = NULL;

				/*
				 * Scan through the buffer in sort order,
				 * zapping the inode number of any
				 * duplicate names.
				 */
				for (n = 0; dpv[n]; n++) {
					struct dirent *dp = dpv[n];

					if ((xp == NULL) ||
					    strcmp(dp->d_name, xp->d_name)) {
						xp = dp;
					} else {
						dp->d_fileno = 0;
					}
					if (dp->d_type == DT_WHT &&
					    (flags & DTF_HIDEW))
						dp->d_fileno = 0;
				}

				free(dpv);
				break;
			} else {
				dpv = malloc((n+1) * sizeof(struct dirent *));
				if (dpv == NULL)
					break;
			}
		}

		dirp->dd_len = len;
		dirp->dd_size = ddptr - dirp->dd_buf;
	} else {
		dirp->dd_len = incr;
		dirp->dd_buf = malloc(dirp->dd_len);
		if (dirp->dd_buf == NULL) {
			free(dirp);
			close (fd);
			return (NULL);
		}
		dirp->dd_seek = 0;
		flags &= ~DTF_REWIND;
	}

	dirp->dd_loc = 0;
	dirp->dd_fd = fd;
	dirp->dd_flags = flags;

	/*
	 * Set up seek point for rewinddir.
	 */
	dirp->dd_rewind = telldir(dirp);

	return (dirp);
}