/* vi: set sw=4 ts=4: */
/*
 * namei.c --- ext2fs directory lookup operations
 *
 * Copyright (C) 1993, 1994, 1994, 1995 Theodore Ts'o.
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Public
 * License.
 * %End-Header%
 */

#include <stdio.h>
#include <string.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif

/* #define NAMEI_DEBUG */

#include "ext2_fs.h"
#include "ext2fs.h"

static errcode_t open_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t base,
                            const char *pathname, size_t pathlen, int follow,
                            int link_count, char *buf, ext2_ino_t *res_inode);

static errcode_t follow_link(ext2_filsys fs, ext2_ino_t root, ext2_ino_t dir,
                             ext2_ino_t inode, int link_count,
                             char *buf, ext2_ino_t *res_inode)
{
        char *pathname;
        char *buffer = 0;
        errcode_t retval;
        struct ext2_inode ei;

#ifdef NAMEI_DEBUG
        printf("follow_link: root=%lu, dir=%lu, inode=%lu, lc=%d\n",
               root, dir, inode, link_count);

#endif
        retval = ext2fs_read_inode (fs, inode, &ei);
        if (retval) return retval;
        if (!LINUX_S_ISLNK (ei.i_mode)) {
                *res_inode = inode;
                return 0;
        }
        if (link_count++ > 5) {
                return EXT2_ET_SYMLINK_LOOP;
        }
        if (ext2fs_inode_data_blocks(fs,&ei)) {
                retval = ext2fs_get_mem(fs->blocksize, &buffer);
                if (retval)
                        return retval;
                retval = io_channel_read_blk(fs->io, ei.i_block[0], 1, buffer);
                if (retval) {
                        ext2fs_free_mem(&buffer);
                        return retval;
                }
                pathname = buffer;
        } else
                pathname = (char *)&(ei.i_block[0]);
        retval = open_namei(fs, root, dir, pathname, ei.i_size, 1,
                            link_count, buf, res_inode);
        ext2fs_free_mem(&buffer);
        return retval;
}

/*
 * This routine interprets a pathname in the context of the current
 * directory and the root directory, and returns the inode of the
 * containing directory, and a pointer to the filename of the file
 * (pointing into the pathname) and the length of the filename.
 */
static errcode_t dir_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t dir,
                           const char *pathname, int pathlen,
                           int link_count, char *buf,
                           const char **name, int *namelen,
                           ext2_ino_t *res_inode)
{
        char c;
        const char *thisname;
        int len;
        ext2_ino_t inode;
        errcode_t retval;

        if ((c = *pathname) == '/') {
                dir = root;
                pathname++;
                pathlen--;
        }
        while (1) {
                thisname = pathname;
                for (len=0; --pathlen >= 0;len++) {
                        c = *(pathname++);
                        if (c == '/')
                                break;
                }
                if (pathlen < 0)
                        break;
                retval = ext2fs_lookup (fs, dir, thisname, len, buf, &inode);
                if (retval) return retval;
                retval = follow_link (fs, root, dir, inode,
                                      link_count, buf, &dir);
                if (retval) return retval;
        }
        *name = thisname;
        *namelen = len;
        *res_inode = dir;
        return 0;
}

static errcode_t open_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t base,
                            const char *pathname, size_t pathlen, int follow,
                            int link_count, char *buf, ext2_ino_t *res_inode)
{
        const char *basename;
        int namelen;
        ext2_ino_t dir, inode;
        errcode_t retval;

#ifdef NAMEI_DEBUG
        printf("open_namei: root=%lu, dir=%lu, path=%*s, lc=%d\n",
               root, base, pathlen, pathname, link_count);
#endif
        retval = dir_namei(fs, root, base, pathname, pathlen,
                           link_count, buf, &basename, &namelen, &dir);
        if (retval) return retval;
        if (!namelen) {                     /* special case: '/usr/' etc */
                *res_inode=dir;
                return 0;
        }
        retval = ext2fs_lookup (fs, dir, basename, namelen, buf, &inode);
        if (retval)
                return retval;
        if (follow) {
                retval = follow_link(fs, root, dir, inode, link_count,
                                     buf, &inode);
                if (retval)
                        return retval;
        }
#ifdef NAMEI_DEBUG
        printf("open_namei: (link_count=%d) returns %lu\n",
               link_count, inode);
#endif
        *res_inode = inode;
        return 0;
}

errcode_t ext2fs_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
                       const char *name, ext2_ino_t *inode)
{
        char *buf;
        errcode_t retval;

        EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

        retval = ext2fs_get_mem(fs->blocksize, &buf);
        if (retval)
                return retval;

        retval = open_namei(fs, root, cwd, name, strlen(name), 0, 0,
                            buf, inode);

        ext2fs_free_mem(&buf);
        return retval;
}

errcode_t ext2fs_namei_follow(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
                              const char *name, ext2_ino_t *inode)
{
        char *buf;
        errcode_t retval;

        EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

        retval = ext2fs_get_mem(fs->blocksize, &buf);
        if (retval)
                return retval;

        retval = open_namei(fs, root, cwd, name, strlen(name), 1, 0,
                            buf, inode);

        ext2fs_free_mem(&buf);
        return retval;
}

errcode_t ext2fs_follow_link(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
                        ext2_ino_t inode, ext2_ino_t *res_inode)
{
        char *buf;
        errcode_t retval;

        EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

        retval = ext2fs_get_mem(fs->blocksize, &buf);
        if (retval)
                return retval;

        retval = follow_link(fs, root, cwd, inode, 0, buf, res_inode);

        ext2fs_free_mem(&buf);
        return retval;
}