X-Git-Url: https://wimlib.net/git/?p=wimlib;a=blobdiff_plain;f=src%2Flookup_table.h;h=6fc5ae50c3f5f37439ca191f01d4fc3ef3ba0105;hp=f0ee25b78f2d89761352afaa4860a39e1f783312;hb=6f841e85af6215e88bce12a34a00548664fba6ea;hpb=1cfb17b5e36ad9b6148a14a5bcc8a68689ec10ec diff --git a/src/lookup_table.h b/src/lookup_table.h index f0ee25b7..6fc5ae50 100644 --- a/src/lookup_table.h +++ b/src/lookup_table.h @@ -41,55 +41,97 @@ struct ntfs_location { * * 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; @@ -100,14 +142,25 @@ struct lookup_table_entry { #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; @@ -115,22 +168,31 @@ struct lookup_table_entry { /* 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. */