lib/ext2fs/link.c

   1 /*
   2  * link.c --- create or delete links in a ext2fs directory
   3  *
   4  * Copyright (C) 1993 Theodore Ts'o.  This file may be redistributed
   5  * under the terms of the GNU Public License.
   6  */
   7
   8 #include <stdio.h>
   9 #include <string.h>
  10 #include <unistd.h>
  11 #include <stdlib.h>
  12 #include <linux/fs.h>
  13 #include <linux/ext2_fs.h>
  14
  15 #include "ext2fs.h"
  16
  17 struct link_struct  {
  18         const char      *name;
  19         int             namelen;
  20         ino_t           inode;
  21         int             flags;
  22         int             done;
  23 };
  24
  25 static int link_proc(struct ext2_dir_entry *dirent,
  26                      int        offset,
  27                      int        blocksize,
  28                      char       *buf,
  29                      void       *private)
  30 {
  31         struct link_struct *ls = (struct link_struct *) private;
  32         struct ext2_dir_entry *next;
  33         int rec_len;
  34         int ret = 0;
  35
  36         rec_len = EXT2_DIR_REC_LEN(ls->namelen);
  37
  38         /*
  39          * See if the following directory entry (if any) is unused;
  40          * if so, absorb it into this one.
  41          */
  42         next = (struct ext2_dir_entry *) (buf + offset + dirent->rec_len);
  43         if ((offset + dirent->rec_len < blocksize - 8) &&
  44             (next->inode == 0) &&
  45             (offset + dirent->rec_len + next->rec_len <= blocksize)) {
  46                 dirent->rec_len += next->rec_len;
  47                 ret = DIRENT_CHANGED;
  48         }
  49
  50         /*
  51          * If the directory entry is used, see if we can split the
  52          * directory entry to make room for the new name.  If so,
  53          * truncate it and return.
  54          */
  55         if (dirent->inode) {
  56                 if (dirent->rec_len < (EXT2_DIR_REC_LEN(dirent->name_len) +
  57                                        rec_len))
  58                         return ret;
  59                 rec_len = dirent->rec_len - EXT2_DIR_REC_LEN(dirent->name_len);
  60                 dirent->rec_len = EXT2_DIR_REC_LEN(dirent->name_len);
  61                 next = (struct ext2_dir_entry *) (buf + offset +
  62                                                   dirent->rec_len);
  63                 next->inode = 0;
  64                 next->name_len = 0;
  65                 next->rec_len = rec_len;
  66                 return DIRENT_CHANGED;
  67         }
  68
  69         /*
  70          * If we get this far, then the directory entry is not used.
  71          * See if we can fit the request entry in.  If so, do it.
  72          */
  73         if (dirent->rec_len < rec_len)
  74                 return ret;
  75         dirent->inode = ls->inode;
  76         dirent->name_len = ls->namelen;
  77         strncpy(dirent->name, ls->name, ls->namelen);
  78
  79         ls->done++;
  80         return DIRENT_ABORT|DIRENT_CHANGED;
  81 }
  82
  83 errcode_t ext2fs_link(ext2_filsys fs, ino_t dir, const char *name, ino_t ino,
  84                       int flags)
  85 {
  86         errcode_t       retval;
  87         struct link_struct ls;
  88
  89         if (!(fs->flags & EXT2_FLAG_RW))
  90                 return EXT2_ET_RO_FILSYS;
  91
  92         ls.name = name;
  93         ls.namelen = name ? strlen(name) : 0;
  94         ls.inode = ino;
  95         ls.flags = 0;
  96         ls.done = 0;
  97
  98         retval = ext2fs_dir_iterate(fs, dir, DIRENT_FLAG_INCLUDE_EMPTY,
  99                                     0, link_proc, &ls);
 100         if (retval)
 101                 return retval;
 102
 103         return (ls.done) ? 0 : EXT2_ET_DIR_NO_SPACE;
 104 }
 105
 106 static int unlink_proc(struct ext2_dir_entry *dirent,
 107                      int        offset,
 108                      int        blocksize,
 109                      char       *buf,
 110                      void       *private)
 111 {
 112         struct link_struct *ls = (struct link_struct *) private;
 113
 114         if (ls->name && (dirent->name_len != ls->namelen))
 115                 return 0;
 116         if (ls->name && strncmp(ls->name, dirent->name, dirent->name_len))
 117                 return 0;
 118         if (ls->inode && (dirent->inode != ls->inode))
 119                 return 0;
 120
 121         dirent->inode = 0;
 122         ls->done++;
 123         return DIRENT_ABORT|DIRENT_CHANGED;
 124 }
 125
 126 errcode_t ext2fs_unlink(ext2_filsys fs, ino_t dir, const char *name, ino_t ino,
 127                         int flags)
 128 {
 129         errcode_t       retval;
 130         struct link_struct ls;
 131
 132         if (!(fs->flags & EXT2_FLAG_RW))
 133                 return EXT2_ET_RO_FILSYS;
 134
 135         ls.name = name;
 136         ls.namelen = name ? strlen(name) : 0;
 137         ls.inode = ino;
 138         ls.flags = 0;
 139         ls.done = 0;
 140
 141         retval = ext2fs_dir_iterate(fs, dir, 0, 0, unlink_proc, &ls);
 142         if (retval)
 143                 return retval;
 144
 145         return (ls.done) ? 0 : EXT2_ET_DIR_NO_SPACE;
 146 }
 147