*
* It is used to find data streams for files in the WIM.
*
- * The lookup_table_entry for a given dentry in the WIM is found using the SHA1
- * message digest field.
+ * Metadata resources and reparse point data buffers will also have lookup table
+ * entries associated with the data.
+ *
+ * The lookup_table_entry for a given dentry or alternate stream entry in the
+ * WIM is found using the SHA1 message digest field.
*/
struct lookup_table_entry {
/* List of lookup table entries in this hash bucket */
struct hlist_node hash_list;
- /* @resource_entry is read from the lookup table in the WIM
- * file; it says where to find the file resource in the WIM
- * file, and whether it is compressed or not. */
+ /* Location and size of the stream in the WIM, whether it is compressed
+ * or not, and whether it's a metadata resource or not. This is an
+ * on-disk field. */
struct resource_entry resource_entry;
- /* Currently ignored; set to 1 in new lookup table entries. */
+ /* Specifies which part of the split WIM the resource is located in.
+ * This is on on-disk field.
+ *
+ * In stand-alone WIMs, this must be 1.
+ *
+ * In split WIMs, every split WIM part has its own lookup table, and in
+ * read_lookup_table() it's currently expected that the part number of
+ * each lookup table entry in a split WIM part's lookup table is the
+ * same as the part number of that split WIM part. So this makes this
+ * field redundant since we store a pointer to the corresponding
+ * WIMStruct in the lookup table entry anyway.
+ */
u16 part_number;
- /* If %true, this lookup table entry corresponds to a symbolic link
- * reparse buffer. @symlink_reparse_data_buf will give the target of
- * the symbolic link. */
+ /* An enumerated type that identifies where the stream corresponding to
+ * this lookup table entry is actually located.
+ *
+ * Obviously if we open a WIM and read its lookup table, the location is
+ * set to RESOURCE_IN_WIM since all the streams will initially be
+ * located in the WIM. However, to deal with problems such as image
+ * capture and image mount, we allow the actual location of the stream
+ * to be somewhere else, such as an external file.
+ */
enum {
+ /* The lookup table entry does not correspond to a stream (this
+ * state should exist only temporarily) */
RESOURCE_NONEXISTENT = 0,
+
+ /* The stream resource is located in a WIM file. The WIMStruct
+ * for the WIM file will be pointed to by the @wim member. */
RESOURCE_IN_WIM,
+
+ /* The stream resource is located in an external file. The
+ * name of the file will be provided by @file_on_disk member.
+ * In addition, if @file_on_disk_fp is not NULL, it will be an
+ * open FILE * to the file. */
RESOURCE_IN_FILE_ON_DISK,
+
+ /* The stream resource is located in an external file in the
+ * staging directory for a read-write mount. */
RESOURCE_IN_STAGING_FILE,
+
+ /* The stream resource is directly attached in an in-memory
+ * buffer pointed to by @attached_buffer. */
RESOURCE_IN_ATTACHED_BUFFER,
+
+ /* The stream resource is located in an NTFS volume. It is
+ * identified by volume, filename, data stream name, and by
+ * whether it is a reparse point or not. @ntfs_loc points to a
+ * structure containing this information. */
RESOURCE_IN_NTFS_VOLUME,
} resource_location;
- /* Number of times this lookup table entry is referenced by dentries. */
+ /* (On-disk field)
+ * Number of times this lookup table entry is referenced by dentries.
+ * Unfortunately, this field is not always set correctly in Microsoft's
+ * WIMs, so we have no choice but to fix it if more references to the
+ * lookup table entry are found than stated here. */
u32 refcnt;
union {
- /* SHA1 hash of the file resource pointed to by this lookup
- * table entry */
+ /* (On-disk field) SHA1 message digest of the stream referenced
+ * by this lookup table entry */
u8 hash[SHA1_HASH_SIZE];
- /* First 4 or 8 bytes of the SHA1 hash, used for inserting the
- * entry into the hash table. Since the SHA1 hashes can be
- * considered random, we don't really need the full 20 byte hash
- * just to insert the entry in a hash table. */
+ /* First 4 or 8 bytes of the SHA1 message digest, used for
+ * inserting the entry into the hash table. Since the SHA1
+ * message digest can be considered random, we don't really need
+ * the full 20 byte hash just to insert the entry in a hash
+ * table. */
size_t hash_short;
};
- /* If @file_on_disk != NULL, the file resource indicated by this lookup
- * table entry is not in the WIM file, but rather a file on disk; this
- * occurs for files that are added to the WIM. In that case,
- * file_on_disk is the name of the file in the outside filesystem.
- * It will not be compressed, and its size will be given by
- * resource_entry.size and resource_entry.original_size. */
+ /* Pointers to somewhere where the stream is actually located. See the
+ * comments for the @resource_location field above. */
union {
WIMStruct *wim;
char *file_on_disk;
#endif
};
union {
+ /* Temporary field for creating a singly linked list. Shouldn't
+ * really be here */
struct lookup_table_entry *next_lte_in_swm;
+
+ /* @file_on_disk_fp and @attr are both used to cache file/stream
+ * handles so we don't have re-open them on every read */
FILE *file_on_disk_fp;
#ifdef WITH_NTFS_3G
struct _ntfs_attr *attr;
#endif
};
#ifdef WITH_FUSE
- /* File descriptors table for this data stream */
+ /* File descriptors table for this data stream. This is used if the WIM
+ * is mounted. Basically, each time a file is open()ed, a new file
+ * descriptor is added here, and each time a file is close()ed, the file
+ * descriptor is gotten rid of. If the stream is opened for writing, it
+ * will be extracted to the staging directory and there will be an
+ * actual native file descriptor associated with each "wimlib file
+ * descriptor". */
u16 num_opened_fds;
u16 num_allocated_fds;
struct wimlib_fd **fds;
/* When a WIM file is written, out_refcnt starts at 0 and is incremented
* whenever the file resource pointed to by this lookup table entry
- * needs to be written. Naturally, the file resource only need to be
- * written when out_refcnt is 0. Incrementing it further is needed to
- * find the correct reference count to write to the lookup table in the
- * output file, which may be less than the regular refcnt if not all
- * images in the WIM file are written.
- *
- * output_resource_entry is the struct resource_entry for the position of the
- * file resource when written to the output file. */
+ * needs to be written. The file resource only need to be written when
+ * out_refcnt is nonzero, since otherwise it is not referenced by any
+ * dentries. */
u32 out_refcnt;
+
union {
+ /* When a WIM file is written, @output_resource_entry is filled
+ * in with the resource entry for the output WIM. This will not
+ * necessarily be the same as the @resource_entry since:
+ * - The stream may have a different offset in the new WIM
+ * - The stream may have a different compressed size in the
+ * new WIM if the compression type changed
+ */
struct resource_entry output_resource_entry;
+
+ /* This field is used for the special hardlink or symlink image
+ * application mode. In these mode, all identical files are
+ * linked together, and @extracted_file will be set to the
+ * filename of the first extracted file containing this stream.
+ * */
char *extracted_file;
};
/* Circular linked list of streams that share the same lookup table
- * entry
+ * entry.
*
* This list of streams may include streams from different hard link
* sets that happen to be the same. */
git://wimlib.net / wimlib / blobdiff