]> wimlib.net Git - wimlib/blobdiff - src/dentry.c
wimlib.h: C++ compatibility
[wimlib] / src / dentry.c
index abe5095c2f7f0ce0a1597bdf54803060e1f3afa2..7762e702caac6df5d8b975c64c4d5677255297d5 100644 (file)
@@ -38,6 +38,7 @@
 #include "wimlib/lookup_table.h"
 #include "wimlib/metadata.h"
 #include "wimlib/resource.h"
+#include "wimlib/security.h"
 #include "wimlib/sha1.h"
 #include "wimlib/timestamp.h"
 
@@ -72,18 +73,107 @@ 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 +186,28 @@ 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[];
+       /* Followed 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 +453,8 @@ 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 +498,7 @@ 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,
@@ -479,9 +584,8 @@ calculate_subdir_offsets(struct wim_dentry *dentry, u64 *subdir_offset_p)
        }
 }
 
-/* UNIX: Case-sensitive UTF-16LE dentry or stream name comparison.  We call this
- * on Windows as well to distinguish true duplicates from names differing by
- * case only. */
+/* Case-sensitive UTF-16LE dentry or stream name comparison.  Used on both UNIX
+ * (always) and Windows (sometimes) */
 static int
 compare_utf16le_names_case_sensitive(const utf16lechar *name1, size_t nbytes1,
                                     const utf16lechar *name2, size_t nbytes2)
@@ -573,15 +677,29 @@ 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);
@@ -648,12 +766,13 @@ 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,
@@ -672,8 +791,12 @@ get_dentry_utf16le(WIMStruct *wim, const utf16lechar *path)
        return cur_dentry;
 }
 
-/* Returns the dentry corresponding to the @path, or NULL if there is no such
- * dentry. */
+/*
+ * Returns the dentry in the currently selected WIM image named by @path
+ * starting from the root of the WIM image, or NULL if there is no such dentry.
+ *
+ * On Windows, the search is done case-insensitively.
+ */
 struct wim_dentry *
 get_dentry(WIMStruct *wim, const tchar *path)
 {
@@ -712,11 +835,11 @@ 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');
 }
@@ -865,13 +988,6 @@ new_timeless_inode(void)
                inode->i_next_stream_id = 1;
                inode->i_not_rpfixed = 1;
                INIT_LIST_HEAD(&inode->i_list);
-       #ifdef WITH_FUSE
-               if (pthread_mutex_init(&inode->i_mutex, NULL) != 0) {
-                       ERROR_WITH_ERRNO("Error initializing mutex");
-                       FREE(inode);
-                       return NULL;
-               }
-       #endif
                INIT_LIST_HEAD(&inode->i_dentry);
        }
        return inode;
@@ -970,6 +1086,19 @@ new_filler_directory(const tchar *name, struct wim_dentry **dentry_ret)
        return 0;
 }
 
+static int
+dentry_clear_inode_visited(struct wim_dentry *dentry, void *_ignore)
+{
+       dentry->d_inode->i_visited = 0;
+       return 0;
+}
+
+void
+dentry_tree_clear_inode_visited(struct wim_dentry *root)
+{
+       for_dentry_in_tree(root, dentry_clear_inode_visited, NULL);
+}
+
 static int
 init_ads_entry(struct wim_ads_entry *ads_entry, const void *name,
               size_t name_nbytes, bool is_utf16le)
@@ -1010,15 +1139,10 @@ free_inode(struct wim_inode *inode)
                                destroy_ads_entry(&inode->i_ads_entries[i]);
                        FREE(inode->i_ads_entries);
                }
-       #ifdef WITH_FUSE
-               wimlib_assert(inode->i_num_opened_fds == 0);
-               FREE(inode->i_fds);
-               pthread_mutex_destroy(&inode->i_mutex);
-       #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);
        }
 }
@@ -1081,11 +1205,13 @@ do_free_dentry(struct wim_dentry *dentry, void *_lookup_table)
 /*
  * Unlinks and frees a dentry tree.
  *
- * @root:              The root of the tree.
- * @lookup_table:      The lookup table for dentries.  If non-NULL, the
- *                     reference counts in the lookup table for the lookup
- *                     table entries corresponding to the dentries will be
- *                     decremented.
+ * @root:
+ *     The root of the tree.
+ *
+ * @lookup_table:
+ *     The lookup table for dentries.  If non-NULL, the reference counts in the
+ *     lookup table for the lookup table entries corresponding to the dentries
+ *     will be decremented.
  */
 void
 free_dentry_tree(struct wim_dentry *root, struct wim_lookup_table *lookup_table)
@@ -1093,6 +1219,45 @@ 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.
  *
@@ -1136,31 +1301,17 @@ 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;
 }
@@ -1169,14 +1320,31 @@ 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
 }
 
 /*
@@ -1291,7 +1459,7 @@ add_stream_from_data_buffer(const void *buffer, size_t size,
        struct wim_lookup_table_entry *lte, *existing_lte;
 
        sha1_buffer(buffer, size, hash);
-       existing_lte = __lookup_resource(lookup_table, hash);
+       existing_lte = lookup_resource(lookup_table, hash);
        if (existing_lte) {
                wimlib_assert(wim_resource_size(existing_lte) == size);
                lte = existing_lte;
@@ -1338,6 +1506,15 @@ inode_add_ads_with_data(struct wim_inode *inode, const tchar *name,
        return 0;
 }
 
+bool
+inode_has_named_stream(const struct wim_inode *inode)
+{
+       for (u16 i = 0; i < inode->i_num_ads; i++)
+               if (ads_entry_is_named_stream(&inode->i_ads_entries[i]))
+                       return true;
+       return false;
+}
+
 /* Set the unnamed stream of a WIM inode, given a data buffer containing the
  * stream contents. */
 int
@@ -1378,6 +1555,15 @@ inode_remove_ads(struct wim_inode *inode, u16 idx,
        inode->i_num_ads--;
 }
 
+bool
+inode_has_unix_data(const struct wim_inode *inode)
+{
+       for (u16 i = 0; i < inode->i_num_ads; i++)
+               if (ads_entry_is_unix_data(&inode->i_ads_entries[i]))
+                       return true;
+       return false;
+}
+
 #ifndef __WIN32__
 int
 inode_get_unix_data(const struct wim_inode *inode,
@@ -1453,19 +1639,24 @@ inode_set_unix_data(struct wim_inode *inode, uid_t uid, gid_t gid, mode_t mode,
 /*
  * Reads the alternate data stream entries of a WIM dentry.
  *
- * @p: Pointer to buffer that starts with the first alternate stream entry.
+ * @p:
+ *     Pointer to buffer that starts with the first alternate stream entry.
  *
- * @inode:     Inode to load the alternate data streams into.
- *             @inode->i_num_ads must have been set to the number of
- *             alternate data streams that are expected.
+ * @inode:
+ *     Inode to load the alternate data streams into.  @inode->i_num_ads must
+ *     have been set to the number of alternate data streams that are expected.
  *
- * @remaining_size:    Number of bytes of data remaining in the buffer pointed
- *                     to by @p.
+ * @remaining_size:
+ *     Number of bytes of data remaining in the buffer pointed to by @p.
  *
+ * On success, inode->i_ads_entries is set to an array of `struct
+ * wim_ads_entry's of length inode->i_num_ads.  On failure, @inode is not
+ * modified.
  *
- * Return 0 on success or nonzero on failure.  On success, inode->i_ads_entries
- * is set to an array of `struct wim_ads_entry's of length inode->i_num_ads.  On
- * failure, @inode is not modified.
+ * Return values:
+ *     WIMLIB_ERR_SUCCESS (0)
+ *     WIMLIB_ERR_INVALID_METADATA_RESOURCE
+ *     WIMLIB_ERR_NOMEM
  */
 static int
 read_ads_entries(const u8 * restrict p, struct wim_inode * restrict inode,
@@ -1569,7 +1760,7 @@ out_of_memory:
        goto out_free_ads_entries;
 out_invalid:
        ERROR("An alternate data stream entry is invalid");
-       ret = WIMLIB_ERR_INVALID_DENTRY;
+       ret = WIMLIB_ERR_INVALID_METADATA_RESOURCE;
 out_free_ads_entries:
        if (ads_entries) {
                for (u16 i = 0; i < num_ads; i++)
@@ -1590,7 +1781,7 @@ out:
  * @metadata_resource_len:
  *             Length of the metadata resource buffer, in bytes.
  *
- * @offset:    Offset of the dentry within the metadata resource.
+ * @offset:    Offset of the dentry within the metadata resource.
  *
  * @dentry:    A `struct wim_dentry' that will be filled in by this function.
  *
@@ -1600,9 +1791,10 @@ out:
  * this was a special "end of directory" dentry and not a real dentry.  If
  * nonzero, this was a real dentry.
  *
- * Possible errors include:
- *     WIMLIB_ERR_NOMEM
- *     WIMLIB_ERR_INVALID_DENTRY
+ * Return values:
+ *     WIMLIB_ERR_SUCCESS (0)
+ *     WIMLIB_ERR_INVALID_METADATA_RESOURCE
+ *     WIMLIB_ERR_NOMEM
  */
 int
 read_dentry(const u8 * restrict metadata_resource, u64 metadata_resource_len,
@@ -1636,7 +1828,7 @@ read_dentry(const u8 * restrict metadata_resource, u64 metadata_resource_len,
                ERROR("Directory entry starting at %"PRIu64" ends past the "
                      "end of the metadata resource (size %"PRIu64")",
                      offset, metadata_resource_len);
-               return WIMLIB_ERR_INVALID_DENTRY;
+               return WIMLIB_ERR_INVALID_METADATA_RESOURCE;
        }
        dentry->length = le64_to_cpu(disk_dentry->length);
 
@@ -1658,7 +1850,7 @@ read_dentry(const u8 * restrict metadata_resource, u64 metadata_resource_len,
                      "%"PRIu64" ends past the end of the metadata resource "
                      "(size %"PRIu64")",
                      offset, dentry->length, metadata_resource_len);
-               return WIMLIB_ERR_INVALID_DENTRY;
+               return WIMLIB_ERR_INVALID_METADATA_RESOURCE;
        }
 
        /* Make sure the dentry length is at least as large as the number of
@@ -1666,7 +1858,7 @@ read_dentry(const u8 * restrict metadata_resource, u64 metadata_resource_len,
        if (dentry->length < sizeof(struct wim_dentry_on_disk)) {
                ERROR("Directory entry has invalid length of %"PRIu64" bytes",
                      dentry->length);
-               return WIMLIB_ERR_INVALID_DENTRY;
+               return WIMLIB_ERR_INVALID_METADATA_RESOURCE;
        }
 
        /* Allocate a `struct wim_inode' for this `struct wim_dentry'. */
@@ -1712,7 +1904,7 @@ read_dentry(const u8 * restrict metadata_resource, u64 metadata_resource_len,
        if ((short_name_nbytes & 1) | (file_name_nbytes & 1))
        {
                ERROR("Dentry name is not valid UTF-16LE (odd number of bytes)!");
-               ret = WIMLIB_ERR_INVALID_DENTRY;
+               ret = WIMLIB_ERR_INVALID_METADATA_RESOURCE;
                goto out_free_inode;
        }
 
@@ -1729,7 +1921,7 @@ read_dentry(const u8 * restrict metadata_resource, u64 metadata_resource_len,
                ERROR("Unexpected end of directory entry! (Expected "
                      "at least %"PRIu64" bytes, got %"PRIu64" bytes.)",
                      calculated_size, dentry->length);
-               ret = WIMLIB_ERR_INVALID_DENTRY;
+               ret = WIMLIB_ERR_INVALID_METADATA_RESOURCE;
                goto out_free_inode;
        }
 
@@ -1783,7 +1975,7 @@ read_dentry(const u8 * restrict metadata_resource, u64 metadata_resource_len,
         * be included in the dentry->length field for some reason.
         */
        if (inode->i_num_ads != 0) {
-               ret = WIMLIB_ERR_INVALID_DENTRY;
+               ret = WIMLIB_ERR_INVALID_METADATA_RESOURCE;
                if (offset + dentry->length > metadata_resource_len ||
                    (ret = read_ads_entries(&metadata_resource[offset + dentry->length],
                                            inode,
@@ -1828,26 +2020,32 @@ dentry_get_file_type_string(const struct wim_dentry *dentry)
 /* Reads the children of a dentry, and all their children, ..., etc. from the
  * metadata resource and into the dentry tree.
  *
- * @metadata_resource: An array that contains the uncompressed metadata
- *                     resource for the WIM file.
+ * @metadata_resource:
+ *     An array that contains the uncompressed metadata resource for the WIM
+ *     file.
  *
- * @metadata_resource_len:  The length of the uncompressed metadata resource, in
- *                         bytes.
+ * @metadata_resource_len:
+ *     The length of the uncompressed metadata resource, in bytes.
  *
- * @dentry:    A pointer to a `struct wim_dentry' that is the root of the directory
- *             tree and has already been read from the metadata resource.  It
- *             does not need to be the real root because this procedure is
- *             called recursively.
+ * @dentry:
+ *     A pointer to a `struct wim_dentry' that is the root of the directory
+ *     tree and has already been read from the metadata resource.  It does not
+ *     need to be the real root because this procedure is called recursively.
  *
- * Returns zero on success; nonzero on failure.
+ * Return values:
+ *     WIMLIB_ERR_SUCCESS (0)
+ *     WIMLIB_ERR_INVALID_METADATA_RESOURCE
+ *     WIMLIB_ERR_NOMEM
  */
 int
-read_dentry_tree(const u8 metadata_resource[], u64 metadata_resource_len,
-                struct wim_dentry *dentry)
+read_dentry_tree(const u8 * restrict metadata_resource,
+                u64 metadata_resource_len,
+                struct wim_dentry * restrict dentry)
 {
        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;
 
@@ -1860,6 +2058,18 @@ 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_METADATA_RESOURCE;
+               }
+       }
+
        /* Find and read all the children of @dentry. */
        for (;;) {
 
@@ -1889,8 +2099,16 @@ 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);
@@ -1899,23 +2117,24 @@ 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;
@@ -1941,7 +2160,7 @@ write_dentry(const struct wim_dentry * restrict dentry, u8 * restrict p)
        wimlib_assert(((uintptr_t)p & 7) == 0); /* 8 byte aligned */
        orig_p = p;
 
-       inode = dentry->d_inode;
+       inode = dentry->d_inode;
        disk_dentry = (struct wim_dentry_on_disk*)p;
 
        disk_dentry->attributes = cpu_to_le32(inode->i_attributes);
@@ -1969,6 +2188,8 @@ 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);
 
@@ -2065,7 +2286,7 @@ write_dentry_tree_recursive(const struct wim_dentry *parent, u8 *p)
  * Returns pointer to the byte after the last byte we wrote.
  */
 u8 *
-write_dentry_tree(const struct wim_dentry *root, u8 *p)
+write_dentry_tree(const struct wim_dentry * restrict root, u8 * restrict p)
 {
        DEBUG("Writing dentry tree.");
        wimlib_assert(dentry_is_root(root));
@@ -2082,3 +2303,407 @@ write_dentry_tree(const struct wim_dentry *root, u8 *p)
        /* Recursively write the rest of the dentry tree. */
        return write_dentry_tree_recursive(root, p);
 }
+
+
+static int
+init_wimlib_dentry(struct wimlib_dir_entry *wdentry,
+                  struct wim_dentry *dentry,
+                  const WIMStruct *wim)
+{
+       int ret;
+       size_t dummy;
+       const struct wim_inode *inode = dentry->d_inode;
+       struct wim_lookup_table_entry *lte;
+
+#if TCHAR_IS_UTF16LE
+       wdentry->filename = dentry->file_name;
+       wdentry->dos_name = dentry->short_name;
+#else
+       if (dentry_has_long_name(dentry)) {
+               ret = utf16le_to_tstr(dentry->file_name,
+                                     dentry->file_name_nbytes,
+                                     (tchar**)&wdentry->filename,
+                                     &dummy);
+               if (ret)
+                       return ret;
+       }
+       if (dentry_has_short_name(dentry)) {
+               ret = utf16le_to_tstr(dentry->short_name,
+                                     dentry->short_name_nbytes,
+                                     (tchar**)&wdentry->dos_name,
+                                     &dummy);
+               if (ret)
+                       return ret;
+       }
+#endif
+       ret = calculate_dentry_full_path(dentry);
+       if (ret)
+               return ret;
+       wdentry->full_path = dentry->_full_path;
+
+       for (struct wim_dentry *d = dentry; !dentry_is_root(d); d = d->parent)
+               wdentry->depth++;
+
+       if (inode->i_security_id >= 0) {
+               const struct wim_security_data *sd = wim_const_security_data(wim);
+               wdentry->security_descriptor = sd->descriptors[inode->i_security_id];
+               wdentry->security_descriptor_size = sd->sizes[inode->i_security_id];
+       }
+       wdentry->reparse_tag = inode->i_reparse_tag;
+       wdentry->num_links = inode->i_nlink;
+       wdentry->attributes = inode->i_attributes;
+       wdentry->hard_link_group_id = inode->i_ino;
+       wdentry->creation_time = wim_timestamp_to_timespec(inode->i_creation_time);
+       wdentry->last_write_time = wim_timestamp_to_timespec(inode->i_last_write_time);
+       wdentry->last_access_time = wim_timestamp_to_timespec(inode->i_last_access_time);
+
+       lte = inode_unnamed_lte(inode, wim->lookup_table);
+       if (lte)
+               lte_to_wimlib_resource_entry(lte, &wdentry->streams[0].resource);
+
+       for (unsigned i = 0; i < inode->i_num_ads; i++) {
+               if (inode->i_ads_entries[i].stream_name == NULL)
+                       continue;
+               lte = inode_stream_lte(inode, i + 1, wim->lookup_table);
+               wdentry->num_named_streams++;
+               if (lte) {
+                       lte_to_wimlib_resource_entry(lte, &wdentry->streams[
+                                                               wdentry->num_named_streams].resource);
+               }
+       #if TCHAR_IS_UTF16LE
+               wdentry->streams[wdentry->num_named_streams].stream_name =
+                               inode->i_ads_entries[i].stream_name;
+       #else
+               size_t dummy;
+
+               ret = utf16le_to_tstr(inode->i_ads_entries[i].stream_name,
+                                     inode->i_ads_entries[i].stream_name_nbytes,
+                                     (tchar**)&wdentry->streams[
+                                               wdentry->num_named_streams].stream_name,
+                                     &dummy);
+               if (ret)
+                       return ret;
+       #endif
+       }
+       return 0;
+}
+
+static void
+free_wimlib_dentry(struct wimlib_dir_entry *wdentry)
+{
+#if !TCHAR_IS_UTF16LE
+       FREE((tchar*)wdentry->filename);
+       FREE((tchar*)wdentry->dos_name);
+       for (unsigned i = 1; i <= wdentry->num_named_streams; i++)
+               FREE((tchar*)wdentry->streams[i].stream_name);
+#endif
+       FREE(wdentry);
+}
+
+struct iterate_dir_tree_ctx {
+       WIMStruct *wim;
+       int flags;
+       wimlib_iterate_dir_tree_callback_t cb;
+       void *user_ctx;
+};
+
+static int
+do_iterate_dir_tree(WIMStruct *wim,
+                   struct wim_dentry *dentry, int flags,
+                   wimlib_iterate_dir_tree_callback_t cb,
+                   void *user_ctx);
+
+static int
+call_do_iterate_dir_tree(struct wim_dentry *dentry, void *_ctx)
+{
+       struct iterate_dir_tree_ctx *ctx = _ctx;
+       return do_iterate_dir_tree(ctx->wim, dentry, ctx->flags,
+                                  ctx->cb, ctx->user_ctx);
+}
+
+static int
+do_iterate_dir_tree(WIMStruct *wim,
+                   struct wim_dentry *dentry, int flags,
+                   wimlib_iterate_dir_tree_callback_t cb,
+                   void *user_ctx)
+{
+       struct wimlib_dir_entry *wdentry;
+       int ret = WIMLIB_ERR_NOMEM;
+
+
+       wdentry = CALLOC(1, sizeof(struct wimlib_dir_entry) +
+                                 (1 + dentry->d_inode->i_num_ads) *
+                                       sizeof(struct wimlib_stream_entry));
+       if (!wdentry)
+               goto out;
+
+       ret = init_wimlib_dentry(wdentry, dentry, wim);
+       if (ret)
+               goto out_free_wimlib_dentry;
+
+       if (!(flags & WIMLIB_ITERATE_DIR_TREE_FLAG_CHILDREN)) {
+               ret = (*cb)(wdentry, user_ctx);
+               if (ret)
+                       goto out_free_wimlib_dentry;
+       }
+
+       if (flags & (WIMLIB_ITERATE_DIR_TREE_FLAG_RECURSIVE |
+                    WIMLIB_ITERATE_DIR_TREE_FLAG_CHILDREN))
+       {
+               struct iterate_dir_tree_ctx ctx = {
+                       .wim      = wim,
+                       .flags    = flags &= ~WIMLIB_ITERATE_DIR_TREE_FLAG_CHILDREN,
+                       .cb       = cb,
+                       .user_ctx = user_ctx,
+               };
+               ret = for_dentry_child(dentry, call_do_iterate_dir_tree, &ctx);
+       }
+out_free_wimlib_dentry:
+       free_wimlib_dentry(wdentry);
+out:
+       return ret;
+}
+
+struct image_iterate_dir_tree_ctx {
+       const tchar *path;
+       int flags;
+       wimlib_iterate_dir_tree_callback_t cb;
+       void *user_ctx;
+};
+
+
+static int
+image_do_iterate_dir_tree(WIMStruct *wim)
+{
+       struct image_iterate_dir_tree_ctx *ctx = wim->private;
+       struct wim_dentry *dentry;
+
+       dentry = get_dentry(wim, ctx->path);
+       if (!dentry)
+               return WIMLIB_ERR_PATH_DOES_NOT_EXIST;
+       return do_iterate_dir_tree(wim, dentry, ctx->flags, ctx->cb, ctx->user_ctx);
+}
+
+/* API function documented in wimlib.h  */
+WIMLIBAPI int
+wimlib_iterate_dir_tree(WIMStruct *wim, int image, const tchar *path,
+                       int flags,
+                       wimlib_iterate_dir_tree_callback_t cb, void *user_ctx)
+{
+       struct image_iterate_dir_tree_ctx ctx = {
+               .path = path,
+               .flags = flags,
+               .cb = cb,
+               .user_ctx = user_ctx,
+       };
+       wim->private = &ctx;
+       return for_image(wim, image, image_do_iterate_dir_tree);
+}
+
+/* Returns %true iff the metadata of @inode and @template_inode are reasonably
+ * consistent with them being the same, unmodified file.  */
+static bool
+inode_metadata_consistent(const struct wim_inode *inode,
+                         const struct wim_inode *template_inode,
+                         const struct wim_lookup_table *template_lookup_table)
+{
+       /* Must have exact same creation time and last write time.  */
+       if (inode->i_creation_time != template_inode->i_creation_time ||
+           inode->i_last_write_time != template_inode->i_last_write_time)
+               return false;
+
+       /* Last access time may have stayed the same or increased, but certainly
+        * shouldn't have decreased.  */
+       if (inode->i_last_access_time < template_inode->i_last_access_time)
+               return false;
+
+       /* Must have same number of alternate data stream entries.  */
+       if (inode->i_num_ads != template_inode->i_num_ads)
+               return false;
+
+       /* If the stream entries for the inode are for some reason not resolved,
+        * then the hashes are already available and the point of this function
+        * is defeated.  */
+       if (!inode->i_resolved)
+               return false;
+
+       /* Iterate through each stream and do some more checks.  */
+       for (unsigned i = 0; i <= inode->i_num_ads; i++) {
+               const struct wim_lookup_table_entry *lte, *template_lte;
+
+               lte = inode_stream_lte_resolved(inode, i);
+               template_lte = inode_stream_lte(template_inode, i,
+                                               template_lookup_table);
+
+               /* Compare stream sizes.  */
+               if (lte && template_lte) {
+                       if (wim_resource_size(lte) != wim_resource_size(template_lte))
+                               return false;
+
+                       /* If hash happens to be available, compare with template.  */
+                       if (!lte->unhashed && !template_lte->unhashed &&
+                           !hashes_equal(lte->hash, template_lte->hash))
+                               return false;
+
+               } else if (lte && wim_resource_size(lte)) {
+                       return false;
+               } else if (template_lte && wim_resource_size(template_lte)) {
+                       return false;
+               }
+       }
+
+       /* All right, barring a full checksum and given that the inodes share a
+        * path and the user isn't trying to trick us, these inodes most likely
+        * refer to the same file.  */
+       return true;
+}
+
+/**
+ * Given an inode @inode that has been determined to be "the same" as another
+ * inode @template_inode in either the same WIM or another WIM, retrieve some
+ * useful stream information (e.g. checksums) from @template_inode.
+ *
+ * This assumes that the streams for @inode have been resolved (to point
+ * directly to the appropriate `struct wim_lookup_table_entry's)  but do not
+ * necessarily have checksum information filled in.
+ */
+static int
+inode_copy_checksums(struct wim_inode *inode,
+                    struct wim_inode *template_inode,
+                    WIMStruct *wim,
+                    WIMStruct *template_wim)
+{
+       for (unsigned i = 0; i <= inode->i_num_ads; i++) {
+               struct wim_lookup_table_entry *lte, *template_lte;
+               struct wim_lookup_table_entry *replace_lte;
+
+               lte = inode_stream_lte_resolved(inode, i);
+               template_lte = inode_stream_lte(template_inode, i,
+                                               template_wim->lookup_table);
+
+               /* Only take action if both entries exist, the entry for @inode
+                * has no checksum calculated, but the entry for @template_inode
+                * does.  */
+               if (!lte || !template_lte ||
+                   !lte->unhashed || template_lte->unhashed)
+                       continue;
+
+               wimlib_assert(lte->refcnt == inode->i_nlink);
+
+               /* If the WIM of the template image is the same as the WIM of
+                * the new image, then @template_lte can be used directly.
+                *
+                * Otherwise, look for a stream with the same hash in the WIM of
+                * the new image.  If found, use it; otherwise re-use the entry
+                * being discarded, filling in the hash.  */
+
+               if (wim == template_wim)
+                       replace_lte = template_lte;
+               else
+                       replace_lte = lookup_resource(wim->lookup_table,
+                                                     template_lte->hash);
+
+               list_del(&lte->unhashed_list);
+               if (replace_lte) {
+                       free_lookup_table_entry(lte);
+               } else {
+                       copy_hash(lte->hash, template_lte->hash);
+                       lte->unhashed = 0;
+                       lookup_table_insert(wim->lookup_table, lte);
+                       lte->refcnt = 0;
+                       replace_lte = lte;
+               }
+
+               if (i == 0)
+                       inode->i_lte = replace_lte;
+               else
+                       inode->i_ads_entries[i - 1].lte = replace_lte;
+
+               replace_lte->refcnt += inode->i_nlink;
+       }
+       return 0;
+}
+
+struct reference_template_args {
+       WIMStruct *wim;
+       WIMStruct *template_wim;
+};
+
+static int
+dentry_reference_template(struct wim_dentry *dentry, void *_args)
+{
+       int ret;
+       struct wim_dentry *template_dentry;
+       struct wim_inode *inode, *template_inode;
+       struct reference_template_args *args = _args;
+       WIMStruct *wim = args->wim;
+       WIMStruct *template_wim = args->template_wim;
+
+       if (dentry->d_inode->i_visited)
+               return 0;
+
+       ret = calculate_dentry_full_path(dentry);
+       if (ret)
+               return ret;
+
+       template_dentry = get_dentry(template_wim, dentry->_full_path);
+       if (!template_dentry) {
+               DEBUG("\"%"TS"\": newly added file", dentry->_full_path);
+               return 0;
+       }
+
+       inode = dentry->d_inode;
+       template_inode = template_dentry->d_inode;
+
+       if (inode_metadata_consistent(inode, template_inode,
+                                     template_wim->lookup_table)) {
+               /*DEBUG("\"%"TS"\": No change detected", dentry->_full_path);*/
+               ret = inode_copy_checksums(inode, template_inode,
+                                          wim, template_wim);
+               inode->i_visited = 1;
+       } else {
+               DEBUG("\"%"TS"\": change detected!", dentry->_full_path);
+               ret = 0;
+       }
+       return ret;
+}
+
+/* API function documented in wimlib.h  */
+WIMLIBAPI int
+wimlib_reference_template_image(WIMStruct *wim, int new_image,
+                               WIMStruct *template_wim, int template_image,
+                               int flags, wimlib_progress_func_t progress_func)
+{
+       int ret;
+       struct wim_image_metadata *new_imd;
+
+       if (wim == NULL || template_wim == NULL)
+               return WIMLIB_ERR_INVALID_PARAM;
+
+       if (wim == template_wim && new_image == template_image)
+               return WIMLIB_ERR_INVALID_PARAM;
+
+       if (new_image < 1 || new_image > wim->hdr.image_count)
+               return WIMLIB_ERR_INVALID_IMAGE;
+
+       if (!wim_has_metadata(wim))
+               return WIMLIB_ERR_METADATA_NOT_FOUND;
+
+       new_imd = wim->image_metadata[new_image - 1];
+       if (!new_imd->modified)
+               return WIMLIB_ERR_INVALID_PARAM;
+
+       ret = select_wim_image(template_wim, template_image);
+       if (ret)
+               return ret;
+
+       struct reference_template_args args = {
+               .wim = wim,
+               .template_wim = template_wim,
+       };
+
+       ret = for_dentry_in_tree(new_imd->root_dentry,
+                                dentry_reference_template, &args);
+       dentry_tree_clear_inode_visited(new_imd->root_dentry);
+       return ret;
+}