]> wimlib.net Git - wimlib/blobdiff - src/dentry.c
Rearrange struct wim_inode and improve comments
[wimlib] / src / dentry.c
index d7f189900ef545107156bd06710d24ccbe95409d..d6eb8a5c737f3942e80d4b753ea47a314ff697ce 100644 (file)
@@ -72,18 +72,107 @@ struct wim_ads_entry_on_disk {
 
 #define WIM_ADS_ENTRY_DISK_SIZE 38
 
-/* WIM directory entry (on-disk format) */
+/* On-disk format of a WIM dentry (directory entry), located in the metadata
+ * resource for a WIM image.  */
 struct wim_dentry_on_disk {
+
+       /* Length of this directory entry in bytes, not including any alternate
+        * data stream entries.  Should be a multiple of 8 so that the following
+        * dentry or alternate data stream entry is aligned on an 8-byte
+        * boundary.  (If not, wimlib will round it up.)  It must be at least as
+        * long as the fixed-length fields of the dentry (WIM_DENTRY_DISK_SIZE),
+        * plus the lengths of the file name and/or short name if present.
+        *
+        * It is also possible for this field to be 0.  This situation, which is
+        * undocumented, indicates the end of a list of sibling nodes in a
+        * directory.  It also means the real length is 8, because the dentry
+        * included only the length field, but that takes up 8 bytes.  */
        le64 length;
+
+       /* Attributes of the file or directory.  This is a bitwise OR of the
+        * FILE_ATTRIBUTE_* constants and should correspond to the value
+        * retrieved by GetFileAttributes() on Windows. */
        le32 attributes;
+
+       /* A value that specifies the security descriptor for this file or
+        * directory.  If -1, the file or directory has no security descriptor.
+        * Otherwise, it is a 0-based index into the WIM image's table of
+        * security descriptors (see: `struct wim_security_data') */
        sle32 security_id;
+
+       /* Offset, in bytes, from the start of the uncompressed metadata
+        * resource of this directory's child directory entries, or 0 if this
+        * directory entry does not correspond to a directory or otherwise does
+        * not have any children. */
        le64 subdir_offset;
+
+       /* Reserved fields */
        le64 unused_1;
        le64 unused_2;
+
+
+       /* Creation time, last access time, and last write time, in
+        * 100-nanosecond intervals since 12:00 a.m UTC January 1, 1601.  They
+        * should correspond to the times gotten by calling GetFileTime() on
+        * Windows. */
        le64 creation_time;
        le64 last_access_time;
        le64 last_write_time;
+
+       /* Vaguely, the SHA-1 message digest ("hash") of the file's contents.
+        * More specifically, this is for the "unnamed data stream" rather than
+        * any "alternate data streams".  This hash value is used to look up the
+        * corresponding entry in the WIM's stream lookup table to actually find
+        * the file contents within the WIM.
+        *
+        * If the file has no unnamed data stream (e.g. is a directory), then
+        * this field will be all zeroes.  If the unnamed data stream is empty
+        * (i.e. an "empty file"), then this field is also expected to be all
+        * zeroes.  (It will be if wimlib created the WIM image, at least;
+        * otherwise it can't be ruled out that the SHA-1 message digest of 0
+        * bytes of data is given explicitly.)
+        *
+        * If the file has reparse data, then this field will instead specify
+        * the SHA-1 message digest of the reparse data.  If it is somehow
+        * possible for a file to have both an unnamed data stream and reparse
+        * data, then this is not handled by wimlib.
+        *
+        * As a further special case, if this field is all zeroes but there is
+        * an alternate data stream entry with no name and a nonzero SHA-1
+        * message digest field, then that hash must be used instead of this
+        * one.  (wimlib does not use this quirk on WIM images it creates.)
+        */
        u8 unnamed_stream_hash[SHA1_HASH_SIZE];
+
+       /* The format of the following data is not yet completely known and they
+        * do not correspond to Microsoft's documentation.
+        *
+        * If this directory entry is for a reparse point (has
+        * FILE_ATTRIBUTE_REPARSE_POINT set in the attributes field), then the
+        * version of the following fields containing the reparse tag is valid.
+        * Furthermore, the field notated as not_rpfixed, as far as I can tell,
+        * is supposed to be set to 1 if reparse point fixups (a.k.a. fixing the
+        * targets of absolute symbolic links) were *not* done, and otherwise 0.
+        *
+        * If this directory entry is not for a reparse point, then the version
+        * of the following fields containing the hard_link_group_id is valid.
+        * All MS says about this field is that "If this file is part of a hard
+        * link set, all the directory entries in the set will share the same
+        * value in this field.".  However, more specifically I have observed
+        * the following:
+        *    - If the file is part of a hard link set of size 1, then the
+        *    hard_link_group_id should be set to either 0, which is treated
+        *    specially as indicating "not hardlinked", or any unique value.
+        *    - The specific nonzero values used to identity hard link sets do
+        *    not matter, as long as they are unique.
+        *    - However, due to bugs in Microsoft's software, it is actually NOT
+        *    guaranteed that directory entries that share the same hard link
+        *    group ID are actually hard linked to each either.  We have to
+        *    handle this by using special code to use distinguishing features
+        *    (which is possible because some information about the underlying
+        *    inode is repeated in each dentry) to split up these fake hard link
+        *    groups into what they actually are supposed to be.
+        */
        union {
                struct {
                        le32 rp_unknown_1;
@@ -96,14 +185,28 @@ struct wim_dentry_on_disk {
                        le64 hard_link_group_id;
                } _packed_attribute nonreparse;
        };
+
+       /* Number of alternate data stream entries that directly follow this
+        * dentry on-disk. */
        le16 num_alternate_data_streams;
+
+       /* Length of this file's UTF-16LE encoded short name (8.3 DOS-compatible
+        * name), if present, in bytes, excluding the null terminator.  If this
+        * file has no short name, then this field should be 0.  */
        le16 short_name_nbytes;
+
+       /* Length of this file's UTF-16LE encoded "long" name, excluding the
+        * null terminator.  If this file has no short name, then this field
+        * should be 0.  It's expected that only the root dentry has this field
+        * set to 0.  */
        le16 file_name_nbytes;
 
-       /* Follewed by variable length file name, if file_name_nbytes != 0 */
-       utf16lechar file_name[];
+       /* Follewed by variable length file name, in UTF16-LE, if
+        * file_name_nbytes != 0.  Includes null terminator. */
+       /*utf16lechar file_name[];*/
 
-       /* Followed by variable length short name, if short_name_nbytes != 0 */
+       /* Followed by variable length short name, in UTF16-LE, if
+        * short_name_nbytes != 0.  Includes null terminator. */
        /*utf16lechar short_name[];*/
 } _packed_attribute;
 
@@ -349,7 +452,8 @@ calculate_dentry_full_path(struct wim_dentry *dentry)
                return 0;
 
        if (dentry_is_root(dentry)) {
-               full_path = TSTRDUP(T("/"));
+               static const tchar _root_path[] = {WIM_PATH_SEPARATOR, T('\0')};
+               full_path = TSTRDUP(_root_path);
                if (!full_path)
                        return WIMLIB_ERR_NOMEM;
                full_path_nbytes = 1 * sizeof(tchar);
@@ -393,7 +497,7 @@ calculate_dentry_full_path(struct wim_dentry *dentry)
                if (!full_path)
                        return WIMLIB_ERR_NOMEM;
                memcpy(full_path, parent_full_path, parent_full_path_nbytes);
-               full_path[parent_full_path_nbytes / sizeof(tchar)] = T('/');
+               full_path[parent_full_path_nbytes / sizeof(tchar)] = WIM_PATH_SEPARATOR;
        #if TCHAR_IS_UTF16LE
                memcpy(&full_path[parent_full_path_nbytes / sizeof(tchar) + 1],
                       dentry->file_name,
@@ -572,15 +676,29 @@ ads_entry_has_name(const struct wim_ads_entry *entry,
                                      entry->stream_name_nbytes);
 }
 
+/* Given a UTF-16LE filename and a directory, look up the dentry for the file.
+ * Return it if found, otherwise NULL.  This is case-sensitive on UNIX and
+ * case-insensitive on Windows. */
 struct wim_dentry *
 get_dentry_child_with_utf16le_name(const struct wim_dentry *dentry,
                                   const utf16lechar *name,
                                   size_t name_nbytes)
 {
-       struct rb_node *node = dentry->d_inode->i_children.rb_node;
+       struct rb_node *node;
+
+#ifdef __WIN32__
+       node = dentry->d_inode->i_children_case_insensitive.rb_node;
+#else
+       node = dentry->d_inode->i_children.rb_node;
+#endif
+
        struct wim_dentry *child;
        while (node) {
+       #ifdef __WIN32__
+               child = rb_entry(node, struct wim_dentry, rb_node_case_insensitive);
+       #else
                child = rbnode_dentry(node);
+       #endif
                int result = compare_utf16le_names(name, name_nbytes,
                                                   child->file_name,
                                                   child->file_name_nbytes);
@@ -647,12 +765,13 @@ get_dentry_utf16le(WIMStruct *wim, const utf16lechar *path)
        }
        p = path;
        while (1) {
-               while (*p == cpu_to_le16('/'))
+               while (*p == cpu_to_le16(WIM_PATH_SEPARATOR))
                        p++;
                if (*p == cpu_to_le16('\0'))
                        break;
                pp = p;
-               while (*pp != cpu_to_le16('/') && *pp != cpu_to_le16('\0'))
+               while (*pp != cpu_to_le16(WIM_PATH_SEPARATOR) &&
+                      *pp != cpu_to_le16('\0'))
                        pp++;
 
                cur_dentry = get_dentry_child_with_utf16le_name(parent_dentry, p,
@@ -711,11 +830,11 @@ static void
 to_parent_name(tchar *buf, size_t len)
 {
        ssize_t i = (ssize_t)len - 1;
-       while (i >= 0 && buf[i] == T('/'))
+       while (i >= 0 && buf[i] == WIM_PATH_SEPARATOR)
                i--;
-       while (i >= 0 && buf[i] != T('/'))
+       while (i >= 0 && buf[i] != WIM_PATH_SEPARATOR)
                i--;
-       while (i >= 0 && buf[i] == T('/'))
+       while (i >= 0 && buf[i] == WIM_PATH_SEPARATOR)
                i--;
        buf[i + 1] = T('\0');
 }
@@ -1016,8 +1135,8 @@ free_inode(struct wim_inode *inode)
        #endif
                /* HACK: This may instead delete the inode from i_list, but the
                 * hlist_del() behaves the same as list_del(). */
-               hlist_del(&inode->i_hlist);
-               FREE(inode->i_extracted_file);
+               if (!hlist_unhashed(&inode->i_hlist))
+                       hlist_del(&inode->i_hlist);
                FREE(inode);
        }
 }
@@ -1092,6 +1211,45 @@ free_dentry_tree(struct wim_dentry *root, struct wim_lookup_table *lookup_table)
        for_dentry_in_tree_depth(root, do_free_dentry, lookup_table);
 }
 
+#ifdef __WIN32__
+
+/* Insert a dentry into the case insensitive index for a directory.
+ *
+ * This is a red-black tree, but when multiple dentries share the same
+ * case-insensitive name, only one is inserted into the tree itself; the rest
+ * are connected in a list.
+ */
+static struct wim_dentry *
+dentry_add_child_case_insensitive(struct wim_dentry *parent,
+                                 struct wim_dentry *child)
+{
+       struct rb_root *root;
+       struct rb_node **new;
+       struct rb_node *rb_parent;
+
+       root = &parent->d_inode->i_children_case_insensitive;
+       new = &root->rb_node;
+       rb_parent = NULL;
+       while (*new) {
+               struct wim_dentry *this = container_of(*new, struct wim_dentry,
+                                                      rb_node_case_insensitive);
+               int result = dentry_compare_names_case_insensitive(child, this);
+
+               rb_parent = *new;
+
+               if (result < 0)
+                       new = &((*new)->rb_left);
+               else if (result > 0)
+                       new = &((*new)->rb_right);
+               else
+                       return this;
+       }
+       rb_link_node(&child->rb_node_case_insensitive, rb_parent, new);
+       rb_insert_color(&child->rb_node_case_insensitive, root);
+       return NULL;
+}
+#endif
+
 /*
  * Links a dentry into the directory tree.
  *
@@ -1135,31 +1293,17 @@ dentry_add_child(struct wim_dentry * restrict parent,
        rb_insert_color(&child->rb_node, root);
 
 #ifdef __WIN32__
-       /* Case insensitive child dentry index */
-       root = &parent->d_inode->i_children_case_insensitive;
-       new = &root->rb_node;
-       rb_parent = NULL;
-       while (*new) {
-               struct wim_dentry *this = container_of(*new, struct wim_dentry,
-                                                      rb_node_case_insensitive);
-               int result = dentry_compare_names_case_insensitive(child, this);
-
-               rb_parent = *new;
-
-               if (result < 0)
-                       new = &((*new)->rb_left);
-               else if (result > 0)
-                       new = &((*new)->rb_right);
-               else {
+       {
+               struct wim_dentry *existing;
+               existing = dentry_add_child_case_insensitive(parent, child);
+               if (existing) {
                        list_add(&child->case_insensitive_conflict_list,
-                                &this->case_insensitive_conflict_list);
-                       return NULL;
-
+                                &existing->case_insensitive_conflict_list);
+                       child->rb_node_case_insensitive.__rb_parent_color = 0;
+               } else {
+                       INIT_LIST_HEAD(&child->case_insensitive_conflict_list);
                }
        }
-       rb_link_node(&child->rb_node_case_insensitive, rb_parent, new);
-       rb_insert_color(&child->rb_node_case_insensitive, root);
-       INIT_LIST_HEAD(&child->case_insensitive_conflict_list);
 #endif
        return NULL;
 }
@@ -1168,14 +1312,31 @@ dentry_add_child(struct wim_dentry * restrict parent,
 void
 unlink_dentry(struct wim_dentry *dentry)
 {
-       if (!dentry_is_root(dentry)) {
-               rb_erase(&dentry->rb_node, &dentry->parent->d_inode->i_children);
-       #ifdef __WIN32__
+       struct wim_dentry *parent = dentry->parent;
+
+       if (parent == dentry)
+               return;
+       rb_erase(&dentry->rb_node, &parent->d_inode->i_children);
+#ifdef __WIN32__
+       if (dentry->rb_node_case_insensitive.__rb_parent_color) {
+               /* This dentry was in the case-insensitive red-black tree. */
                rb_erase(&dentry->rb_node_case_insensitive,
-                        &dentry->parent->d_inode->i_children_case_insensitive);
-               list_del(&dentry->case_insensitive_conflict_list);
-       #endif
+                        &parent->d_inode->i_children_case_insensitive);
+               if (!list_empty(&dentry->case_insensitive_conflict_list)) {
+                       /* Make a different case-insensitively-the-same dentry
+                        * be the "representative" in the red-black tree. */
+                       struct list_head *next;
+                       struct wim_dentry *other;
+                       struct wim_dentry *existing;
+
+                       next = dentry->case_insensitive_conflict_list.next;
+                       other = list_entry(next, struct wim_dentry, case_insensitive_conflict_list);
+                       existing = dentry_add_child_case_insensitive(parent, other);
+                       wimlib_assert(existing == NULL);
+               }
        }
+       list_del(&dentry->case_insensitive_conflict_list);
+#endif
 }
 
 /*
@@ -1847,6 +2008,7 @@ read_dentry_tree(const u8 metadata_resource[], u64 metadata_resource_len,
        u64 cur_offset = dentry->subdir_offset;
        struct wim_dentry *child;
        struct wim_dentry *duplicate;
+       struct wim_dentry *parent;
        struct wim_dentry cur_child;
        int ret;
 
@@ -1859,6 +2021,18 @@ read_dentry_tree(const u8 metadata_resource[], u64 metadata_resource_len,
        if (cur_offset == 0)
                return 0;
 
+       /* Check for cyclic directory structure */
+       for (parent = dentry->parent; !dentry_is_root(parent); parent = parent->parent)
+       {
+               if (unlikely(parent->subdir_offset == cur_offset)) {
+                       ERROR("Cyclic directory structure directed: children "
+                             "of \"%"TS"\" coincide with children of \"%"TS"\"",
+                             dentry_full_path(dentry),
+                             dentry_full_path(parent));
+                       return WIMLIB_ERR_INVALID_DENTRY;
+               }
+       }
+
        /* Find and read all the children of @dentry. */
        for (;;) {
 
@@ -1888,8 +2062,16 @@ read_dentry_tree(const u8 metadata_resource[], u64 metadata_resource_len,
                 * entries. */
                cur_offset += dentry_total_length(child);
 
+               if (unlikely(!dentry_has_long_name(child))) {
+                       WARNING("Ignoring unnamed dentry in "
+                               "directory \"%"TS"\"",
+                               dentry_full_path(dentry));
+                       free_dentry(child);
+                       continue;
+               }
+
                duplicate = dentry_add_child(dentry, child);
-               if (duplicate) {
+               if (unlikely(duplicate)) {
                        const tchar *child_type, *duplicate_type;
                        child_type = dentry_get_file_type_string(child);
                        duplicate_type = dentry_get_file_type_string(duplicate);
@@ -1898,23 +2080,24 @@ read_dentry_tree(const u8 metadata_resource[], u64 metadata_resource_len,
                                "at that path with the exact same name)",
                                child_type, dentry_full_path(duplicate),
                                duplicate_type);
-               } else {
-                       inode_add_dentry(child, child->d_inode);
-                       /* If there are children of this child, call this
-                        * procedure recursively. */
-                       if (child->subdir_offset != 0) {
-                               if (dentry_is_directory(child)) {
-                                       ret = read_dentry_tree(metadata_resource,
-                                                              metadata_resource_len,
-                                                              child);
-                                       if (ret)
-                                               break;
-                               } else {
-                                       WARNING("Ignoring children of non-directory \"%"TS"\"",
-                                               dentry_full_path(child));
-                               }
-                       }
+                       free_dentry(child);
+                       continue;
+               }
 
+               inode_add_dentry(child, child->d_inode);
+               /* If there are children of this child, call this
+                * procedure recursively. */
+               if (child->subdir_offset != 0) {
+                       if (likely(dentry_is_directory(child))) {
+                               ret = read_dentry_tree(metadata_resource,
+                                                      metadata_resource_len,
+                                                      child);
+                               if (ret)
+                                       break;
+                       } else {
+                               WARNING("Ignoring children of non-directory \"%"TS"\"",
+                                       dentry_full_path(child));
+                       }
                }
        }
        return ret;
@@ -1968,6 +2151,8 @@ write_dentry(const struct wim_dentry * restrict dentry, u8 * restrict p)
        disk_dentry->file_name_nbytes = cpu_to_le16(dentry->file_name_nbytes);
        p += sizeof(struct wim_dentry_on_disk);
 
+       wimlib_assert(dentry_is_root(dentry) != dentry_has_long_name(dentry));
+
        if (dentry_has_long_name(dentry))
                p = mempcpy(p, dentry->file_name, dentry->file_name_nbytes + 2);