libexfat/lookup.c

   1 /*
   2  *  lookup.c
   3  *  exFAT file system implementation library.
   4  *
   5  *  Created by Andrew Nayenko on 02.09.09.
   6  *  This software is distributed under the GNU General Public License
   7  *  version 3 or any later.
   8  */
   9
  10 #include "exfat.h"
  11 #include <string.h>
  12 #include <errno.h>
  13 #include <inttypes.h>
  14
  15 void exfat_opendir(struct exfat_node* node, struct exfat_iterator* it)
  16 {
  17         if (!(node->flags & EXFAT_ATTRIB_DIR))
  18                 exfat_bug("`%s' is not a directory", node->name);
  19         it->cluster = node->start_cluster;
  20         it->offset = 0;
  21         it->contiguous = IS_CONTIGUOUS(*node);
  22         it->chunk = NULL;
  23 }
  24
  25 void exfat_closedir(struct exfat_iterator* it)
  26 {
  27         it->cluster = 0;
  28         it->offset = 0;
  29         it->contiguous = 0;
  30         free(it->chunk);
  31         it->chunk = NULL;
  32 }
  33
  34 /*
  35  * Reads one entry in directory at position pointed by iterator and fills
  36  * node structure.
  37  */
  38 int exfat_readdir(struct exfat* ef, struct exfat_node* node,
  39                 struct exfat_iterator* it)
  40 {
  41         const struct exfat_entry* entry;
  42         const struct exfat_file* file;
  43         const struct exfat_file_info* file_info;
  44         const struct exfat_file_name* file_name;
  45         const struct exfat_upcase* upcase;
  46         uint8_t continuations = 0;
  47         le16_t* namep = NULL;
  48
  49         if (it->chunk == NULL)
  50         {
  51                 it->chunk = malloc(CLUSTER_SIZE(*ef->sb));
  52                 if (it->chunk == NULL)
  53                 {
  54                         exfat_error("out of memory");
  55                         return -ENOMEM;
  56                 }
  57                 exfat_read_raw(it->chunk, CLUSTER_SIZE(*ef->sb),
  58                                 exfat_c2o(ef, it->cluster), ef->fd);
  59         }
  60
  61         for (;;)
  62         {
  63                 /* every directory (even empty one) occupies at least one cluster and
  64                    must contain EOD entry */
  65                 entry = (const struct exfat_entry*)
  66                                 (it->chunk + it->offset % CLUSTER_SIZE(*ef->sb));
  67                 /* move iterator to the next entry in the directory */
  68                 it->offset += sizeof(struct exfat_entry);
  69
  70                 switch (entry->type)
  71                 {
  72                 case EXFAT_ENTRY_EOD:
  73                         if (continuations != 0)
  74                         {
  75                                 exfat_error("expected %hhu continuations before EOD",
  76                                                 continuations);
  77                                 return -EIO;
  78                         }
  79                         return -ENOENT; /* that's OK, means end of directory */
  80
  81                 case EXFAT_ENTRY_FILE:
  82                         if (continuations != 0)
  83                         {
  84                                 exfat_error("expected %hhu continuations before new entry",
  85                                                 continuations);
  86                                 return -EIO;
  87                         }
  88                         memset(node, 0, sizeof(struct exfat_node));
  89                         file = (const struct exfat_file*) entry;
  90                         node->flags = le16_to_cpu(file->attrib);
  91                         node->mtime = exfat_exfat2unix(file->mdate, file->mtime);
  92                         node->atime = exfat_exfat2unix(file->adate, file->atime);
  93                         namep = node->name;
  94                         continuations = file->continuations;
  95                         /* each file entry must have at least 2 continuations:
  96                            info and name */
  97                         if (continuations < 2)
  98                         {
  99                                 exfat_error("too few continuations (%hhu)", continuations);
 100                                 return -EIO;
 101                         }
 102                         break;
 103
 104                 case EXFAT_ENTRY_FILE_INFO:
 105                         if (continuations < 2)
 106                         {
 107                                 exfat_error("unexpected continuation (%hhu)",
 108                                                 continuations);
 109                                 return -EIO;
 110                         }
 111                         file_info = (const struct exfat_file_info*) entry;
 112                         node->size = le64_to_cpu(file_info->size);
 113                         node->start_cluster = le32_to_cpu(file_info->start_cluster);
 114                         if (file_info->flag == EXFAT_FLAG_CONTIGUOUS)
 115                                 node->flags |= EXFAT_ATTRIB_CONTIGUOUS;
 116                         --continuations;
 117                         break;
 118
 119                 case EXFAT_ENTRY_FILE_NAME:
 120                         if (continuations == 0)
 121                         {
 122                                 exfat_error("unexpected continuation");
 123                                 return -EIO;
 124                         }
 125                         file_name = (const struct exfat_file_name*) entry;
 126                         memcpy(namep, file_name->name, EXFAT_ENAME_MAX * sizeof(le16_t));
 127                         namep += EXFAT_ENAME_MAX;
 128                         if (--continuations == 0)
 129                                 return 0; /* entry completed */
 130                         break;
 131
 132                 case EXFAT_ENTRY_UPCASE:
 133                         if (ef->upcase != NULL)
 134                                 break;
 135                         upcase = (const struct exfat_upcase*) entry;
 136                         if (CLUSTER_INVALID(le32_to_cpu(upcase->start_cluster)))
 137                         {
 138                                 exfat_error("invalid cluster in upcase table");
 139                                 return -EIO;
 140                         }
 141                         if (le64_to_cpu(upcase->size) == 0 ||
 142                                 le64_to_cpu(upcase->size) > 0xffff * sizeof(uint16_t) ||
 143                                 le64_to_cpu(upcase->size) % sizeof(uint16_t) != 0)
 144                         {
 145                                 exfat_error("bad upcase table size (%"PRIu64" bytes)",
 146                                                 le64_to_cpu(upcase->size));
 147                                 return -EIO;
 148                         }
 149                         ef->upcase = malloc(le64_to_cpu(upcase->size));
 150                         ef->upcase_chars = le64_to_cpu(upcase->size) / sizeof(le16_t);
 151
 152                         /* set up a few fields in node just to satisfy exfat_read() */
 153                         memset(node, 0, sizeof(struct exfat_node));
 154                         node->start_cluster = le32_to_cpu(upcase->start_cluster);
 155                         node->flags = EXFAT_ATTRIB_CONTIGUOUS;
 156                         node->size = le64_to_cpu(upcase->size);
 157                         if (exfat_read(ef, node, ef->upcase, node->size, 0) != node->size)
 158                                 return -EIO;
 159                         break;
 160                 }
 161
 162                 /* fetch the next cluster if needed */
 163                 if ((it->offset & (CLUSTER_SIZE(*ef->sb) - 1)) == 0)
 164                 {
 165                         it->cluster = exfat_next_cluster(ef, it->cluster, it->contiguous);
 166                         if (CLUSTER_INVALID(it->cluster))
 167                         {
 168                                 exfat_error("invalid cluster while reading directory");
 169                                 return -EIO;
 170                         }
 171                         exfat_read_raw(it->chunk, CLUSTER_SIZE(*ef->sb),
 172                                         exfat_c2o(ef, it->cluster), ef->fd);
 173                 }
 174         }
 175         /* we never reach here */
 176 }
 177
 178 static int compare_char(struct exfat* ef, uint16_t a, uint16_t b)
 179 {
 180         if (a >= ef->upcase_chars || b >= ef->upcase_chars)
 181                 return a - b;
 182         else
 183                 return le16_to_cpu(ef->upcase[a]) - le16_to_cpu(ef->upcase[b]);
 184 }
 185
 186 static int compare_name(struct exfat* ef, const le16_t* a, const le16_t* b)
 187 {
 188         while (le16_to_cpu(*a) && le16_to_cpu(*b))
 189         {
 190                 if (compare_char(ef, le16_to_cpu(*a), le16_to_cpu(*b)) != 0)
 191                         break;
 192                 a++;
 193                 b++;
 194         }
 195         return le16_to_cpu(*a) - le16_to_cpu(*b);
 196 }
 197
 198 static int lookup_name(struct exfat* ef, struct exfat_node* node,
 199                 const le16_t* name)
 200 {
 201         struct exfat_iterator it;
 202
 203         exfat_opendir(node, &it);
 204         while (exfat_readdir(ef, node, &it) == 0)
 205         {
 206                 if (compare_name(ef, name, node->name) == 0)
 207                 {
 208                         exfat_closedir(&it);
 209                         return 0;
 210                 }
 211         }
 212         exfat_closedir(&it);
 213         return -ENOENT;
 214 }
 215
 216 int exfat_lookup(struct exfat* ef, struct exfat_node* node,
 217                 const char* path)
 218 {
 219         le16_t buffer[EXFAT_NAME_MAX + 1];
 220         int rc;
 221         le16_t* p;
 222         le16_t* subpath;
 223
 224         if (strlen(path) > EXFAT_NAME_MAX)
 225         {
 226                 exfat_error("file name `%s' is too long", path);
 227                 return -ENAMETOOLONG;
 228         }
 229
 230         rc = utf8_to_utf16(buffer, path, EXFAT_NAME_MAX, strlen(path));
 231         if (rc != 0)
 232                 return rc;
 233
 234         /* start from the root directory */
 235         node->flags = EXFAT_ATTRIB_DIR;
 236         node->size = 0;
 237         node->start_cluster = le32_to_cpu(ef->sb->rootdir_cluster);
 238         node->name[0] = cpu_to_le16('\0');
 239         /* exFAT does not have time attributes for the root directory */
 240         node->mtime = ef->mount_time;
 241         node->atime = ef->mount_time;
 242
 243         for (subpath = p = buffer; p; subpath = p + 1)
 244         {
 245                 while (le16_to_cpu(*subpath) == '/')
 246                         subpath++;              /* skip leading slashes */
 247                 for (p = subpath; ; p++)
 248                 {
 249                         if (le16_to_cpu(*p) == '\0')
 250                         {
 251                                 p = NULL;
 252                                 break;
 253                         }
 254                         if (le16_to_cpu(*p) == '/')
 255                         {
 256                                 *p = cpu_to_le16('\0');
 257                                 break;
 258                         }
 259                 }
 260                 if (le16_to_cpu(*subpath) == '\0')
 261                         break;                  /* skip trailing slashes */
 262                 if (le16_to_cpu(subpath[0]) == '.' && le16_to_cpu(subpath[1]) == '\0')
 263                         continue;               /* skip "." component */
 264                 if (lookup_name(ef, node, subpath) != 0)
 265                         return -ENOENT;
 266         }
 267         return 0;
 268 }