avl_tree: Optimize first iteration of insertion rebalance loop

[wimlib] / src / dentry.c

/*
 * dentry.c
 *
 * In the WIM file format, the dentries are stored in the "metadata resource"
 * section right after the security data.  Each image in the WIM file has its
 * own metadata resource with its own security data and dentry tree.  Dentries
 * in different images may share file resources by referring to the same lookup
 * table entries.
 */

/*
 * Copyright (C) 2012, 2013, 2014 Eric Biggers
 *
 * This file is part of wimlib, a library for working with WIM files.
 *
 * wimlib is free software; you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 3 of the License, or (at your option) any later
 * version.
 *
 * wimlib is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * wimlib; if not, see http://www.gnu.org/licenses/.
 */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include "wimlib.h"
#include "wimlib/case.h"
#include "wimlib/dentry.h"
#include "wimlib/encoding.h"
#include "wimlib/endianness.h"
#include "wimlib/error.h"
#include "wimlib/lookup_table.h"
#include "wimlib/metadata.h"
#include "wimlib/paths.h"
#include "wimlib/resource.h"
#include "wimlib/security.h"
#include "wimlib/sha1.h"
#include "wimlib/timestamp.h"

#include <errno.h>

/* 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.  In fact, when named data streams are present, some versions of
         * Windows PE contain a bug where they only look in the alternate data
         * stream entries for the unnamed data stream, not here.
         */
        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;
                        le32 reparse_tag;
                        le16 rp_unknown_2;
                        le16 not_rpfixed;
                } _packed_attribute reparse;
                struct {
                        le32 rp_unknown_1;
                        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;

        /* 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, in UTF16-LE, if
         * short_name_nbytes != 0.  Includes null terminator. */
        /*utf16lechar short_name[];*/
} _packed_attribute;

/* Calculates the unaligned length, in bytes, of an on-disk WIM dentry that has
 * a file name and short name that take the specified numbers of bytes.  This
 * excludes any alternate data stream entries that may follow the dentry. */
static u64
dentry_correct_length_unaligned(u16 file_name_nbytes, u16 short_name_nbytes)
{
        u64 length = sizeof(struct wim_dentry_on_disk);
        if (file_name_nbytes)
                length += file_name_nbytes + 2;
        if (short_name_nbytes)
                length += short_name_nbytes + 2;
        return length;
}

/* Calculates the unaligned length, in bytes, of an on-disk WIM dentry, based on
 * the file name length and short name length.  Note that dentry->length is
 * ignored; also, this excludes any alternate data stream entries that may
 * follow the dentry. */
static u64
dentry_correct_length_aligned(const struct wim_dentry *dentry)
{
        u64 len;

        len = dentry_correct_length_unaligned(dentry->file_name_nbytes,
                                              dentry->short_name_nbytes);
        return (len + 7) & ~7;
}

/* Sets the name of a WIM dentry from a multibyte string.
 * Only use this on dentries not inserted into the tree.  Use rename_wim_path()
 * to do a real rename.  */
int
dentry_set_name(struct wim_dentry *dentry, const tchar *new_name)
{
        int ret;
        ret = get_utf16le_string(new_name, &dentry->file_name,
                                 &dentry->file_name_nbytes);
        if (ret == 0) {
                /* Clear the short name and recalculate the dentry length */
                if (dentry_has_short_name(dentry)) {
                        FREE(dentry->short_name);
                        dentry->short_name = NULL;
                        dentry->short_name_nbytes = 0;
                }
        }
        return ret;
}

/* Returns the total length of a WIM alternate data stream entry on-disk,
 * including the stream name, the null terminator, AND the padding after the
 * entry to align the next ADS entry or dentry on an 8-byte boundary. */
static u64
ads_entry_total_length(const struct wim_ads_entry *entry)
{
        u64 len = sizeof(struct wim_ads_entry_on_disk);
        if (entry->stream_name_nbytes)
                len += entry->stream_name_nbytes + 2;
        return (len + 7) & ~7;
}

/*
 * Determine whether to include a "dummy" stream when writing a WIM dentry:
 *
 * Some versions of Microsoft's WIM software (the boot driver(s) in WinPE 3.0,
 * for example) contain a bug where they assume the first alternate data stream
 * (ADS) entry of a dentry with a nonzero ADS count specifies the unnamed
 * stream, even if it has a name and the unnamed stream is already specified in
 * the hash field of the dentry itself.
 *
 * wimlib has to work around this behavior by carefully emulating the behavior
 * of (most versions of) ImageX/WIMGAPI, which move the unnamed stream reference
 * into the alternate stream entries whenever there are named data streams, even
 * though there is already a field in the dentry itself for the unnamed stream
 * reference, which then goes to waste.
 */
static inline bool
inode_needs_dummy_stream(const struct wim_inode *inode)
{
        return (inode->i_num_ads > 0 &&
                inode->i_num_ads < 0xffff && /* overflow check */
                inode->i_canonical_streams); /* assume the dentry is okay if it
                                                already had an unnamed ADS entry
                                                when it was read in  */
}

/* Calculate the total number of bytes that will be consumed when a WIM dentry
 * is written.  This includes base dentry and name fields as well as all
 * alternate data stream entries and alignment bytes.  */
u64
dentry_out_total_length(const struct wim_dentry *dentry)
{
        u64 length = dentry_correct_length_aligned(dentry);
        const struct wim_inode *inode = dentry->d_inode;

        if (inode_needs_dummy_stream(inode))
                length += ads_entry_total_length(&(struct wim_ads_entry){});

        for (u16 i = 0; i < inode->i_num_ads; i++)
                length += ads_entry_total_length(&inode->i_ads_entries[i]);

        return length;
}

/* Calculate the aligned, total length of a dentry, including all alternate data
 * stream entries.  Uses dentry->length.  */
static u64
dentry_in_total_length(const struct wim_dentry *dentry)
{
        u64 length = dentry->length;
        const struct wim_inode *inode = dentry->d_inode;
        for (u16 i = 0; i < inode->i_num_ads; i++)
                length += ads_entry_total_length(&inode->i_ads_entries[i]);
        return (length + 7) & ~7;
}

static int
do_for_dentry_in_tree(struct wim_dentry *dentry,
                      int (*visitor)(struct wim_dentry *, void *), void *arg)
{
        int ret;
        struct wim_dentry *child;

        ret = (*visitor)(dentry, arg);
        if (unlikely(ret))
                return ret;

        for_dentry_child(child, dentry) {
                ret = for_dentry_in_tree(child, visitor, arg);
                if (unlikely(ret))
                        return ret;
        }
        return 0;
}


static int
do_for_dentry_in_tree_depth(struct wim_dentry *dentry,
                            int (*visitor)(struct wim_dentry *, void *), void *arg)
{
        int ret;
        struct wim_dentry *child;

        for_dentry_child_postorder(child, dentry) {
                ret = for_dentry_in_tree_depth(child, visitor, arg);
                if (unlikely(ret))
                        return ret;
        }
        return unlikely((*visitor)(dentry, arg));
}

/* Calls a function on all directory entries in a WIM dentry tree.  Logically,
 * this is a pre-order traversal (the function is called on a parent dentry
 * before its children), but sibling dentries will be visited in order as well.
 * */
int
for_dentry_in_tree(struct wim_dentry *root,
                   int (*visitor)(struct wim_dentry *, void *), void *arg)
{
        if (unlikely(!root))
                return 0;
        return do_for_dentry_in_tree(root, visitor, arg);
}

/* Like for_dentry_in_tree(), but the visitor function is always called on a
 * dentry's children before on itself. */
int
for_dentry_in_tree_depth(struct wim_dentry *root,
                         int (*visitor)(struct wim_dentry *, void *), void *arg)
{
        if (unlikely(!root))
                return 0;
        return do_for_dentry_in_tree_depth(root, visitor, arg);
}

/* Calculate the full path of @dentry.  The full path of its parent must have
 * already been calculated, or it must be the root dentry. */
int
calculate_dentry_full_path(struct wim_dentry *dentry)
{
        tchar *full_path;
        u32 full_path_nbytes;
        int ret;

        if (dentry->_full_path)
                return 0;

        if (dentry_is_root(dentry)) {
                static const tchar _root_path[] = {WIM_PATH_SEPARATOR, T('\0')};
                full_path = TSTRDUP(_root_path);
                if (full_path == NULL)
                        return WIMLIB_ERR_NOMEM;
                full_path_nbytes = 1 * sizeof(tchar);
        } else {
                struct wim_dentry *parent;
                tchar *parent_full_path;
                u32 parent_full_path_nbytes;
                size_t filename_nbytes;

                parent = dentry->parent;
                if (dentry_is_root(parent)) {
                        parent_full_path = T("");
                        parent_full_path_nbytes = 0;
                } else {
                        if (parent->_full_path == NULL) {
                                ret = calculate_dentry_full_path(parent);
                                if (ret)
                                        return ret;
                        }
                        parent_full_path = parent->_full_path;
                        parent_full_path_nbytes = parent->full_path_nbytes;
                }

                /* Append this dentry's name as a tchar string to the full path
                 * of the parent followed by the path separator */
        #if TCHAR_IS_UTF16LE
                filename_nbytes = dentry->file_name_nbytes;
        #else
                {
                        int ret = utf16le_to_tstr_nbytes(dentry->file_name,
                                                         dentry->file_name_nbytes,
                                                         &filename_nbytes);
                        if (ret)
                                return ret;
                }
        #endif

                full_path_nbytes = parent_full_path_nbytes + sizeof(tchar) +
                                   filename_nbytes;
                full_path = MALLOC(full_path_nbytes + sizeof(tchar));
                if (full_path == NULL)
                        return WIMLIB_ERR_NOMEM;
                memcpy(full_path, parent_full_path, parent_full_path_nbytes);
                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,
                       filename_nbytes + sizeof(tchar));
        #else
                utf16le_to_tstr_buf(dentry->file_name,
                                    dentry->file_name_nbytes,
                                    &full_path[parent_full_path_nbytes /
                                               sizeof(tchar) + 1]);
        #endif
        }
        dentry->_full_path = full_path;
        dentry->full_path_nbytes= full_path_nbytes;
        return 0;
}

static int
do_calculate_dentry_full_path(struct wim_dentry *dentry, void *_ignore)
{
        return calculate_dentry_full_path(dentry);
}

int
calculate_dentry_tree_full_paths(struct wim_dentry *root)
{
        return for_dentry_in_tree(root, do_calculate_dentry_full_path, NULL);
}

tchar *
dentry_full_path(struct wim_dentry *dentry)
{
        calculate_dentry_full_path(dentry);
        return dentry->_full_path;
}

static int
dentry_calculate_subdir_offset(struct wim_dentry *dentry, void *_subdir_offset_p)
{

        if (dentry_is_directory(dentry)) {
                u64 *subdir_offset_p = _subdir_offset_p;
                struct wim_dentry *child;

                /* Set offset of directory's child dentries  */
                dentry->subdir_offset = *subdir_offset_p;

                /* Account for child dentries  */
                for_dentry_child(child, dentry)
                        *subdir_offset_p += dentry_out_total_length(child);

                /* Account for end-of-directory entry  */
                *subdir_offset_p += 8;
        } else {
                /* Not a directory; set subdir_offset to 0  */
                dentry->subdir_offset = 0;
        }
        return 0;
}

/*
 * Calculates the subdir offsets for a directory tree.
 */
void
calculate_subdir_offsets(struct wim_dentry *root, u64 *subdir_offset_p)
{
        for_dentry_in_tree(root, dentry_calculate_subdir_offset, subdir_offset_p);
}

/* Compare the UTF-16LE long filenames of two dentries case insensitively.  */
static int
dentry_compare_names_case_insensitive(const struct wim_dentry *d1,
                                      const struct wim_dentry *d2)
{
        return cmp_utf16le_strings(d1->file_name,
                                   d1->file_name_nbytes / 2,
                                   d2->file_name,
                                   d2->file_name_nbytes / 2,
                                   true);
}

/* Compare the UTF-16LE long filenames of two dentries case sensitively.  */
static int
dentry_compare_names_case_sensitive(const struct wim_dentry *d1,
                                    const struct wim_dentry *d2)
{
        return cmp_utf16le_strings(d1->file_name,
                                   d1->file_name_nbytes / 2,
                                   d2->file_name,
                                   d2->file_name_nbytes / 2,
                                   false);
}

static int
_avl_dentry_compare_names_ci(const struct avl_tree_node *n1,
                             const struct avl_tree_node *n2)
{
        const struct wim_dentry *d1, *d2;

        d1 = avl_tree_entry(n1, struct wim_dentry, d_index_node_ci);
        d2 = avl_tree_entry(n2, struct wim_dentry, d_index_node_ci);
        return dentry_compare_names_case_insensitive(d1, d2);
}

static int
_avl_dentry_compare_names(const struct avl_tree_node *n1,
                          const struct avl_tree_node *n2)
{
        const struct wim_dentry *d1, *d2;

        d1 = avl_tree_entry(n1, struct wim_dentry, d_index_node);
        d2 = avl_tree_entry(n2, struct wim_dentry, d_index_node);
        return dentry_compare_names_case_sensitive(d1, d2);
}

/* Default case sensitivity behavior for searches with
 * WIMLIB_CASE_PLATFORM_DEFAULT specified.  This can be modified by
 * wimlib_global_init().  */
bool default_ignore_case =
#ifdef __WIN32__
        true
#else
        false
#endif
;

/* Case-sensitive dentry lookup.  Only @file_name and @file_name_nbytes of
 * @dummy must be valid.  */
static struct wim_dentry *
dir_lookup(const struct wim_inode *dir, const struct wim_dentry *dummy)
{
        struct avl_tree_node *node;

        node = avl_tree_lookup_node(dir->i_children,
                                    &dummy->d_index_node,
                                    _avl_dentry_compare_names);
        if (!node)
                return NULL;
        return avl_tree_entry(node, struct wim_dentry, d_index_node);
}

/* Case-insensitive dentry lookup.  Only @file_name and @file_name_nbytes of
 * @dummy must be valid.  */
static struct wim_dentry *
dir_lookup_ci(const struct wim_inode *dir, const struct wim_dentry *dummy)
{
        struct avl_tree_node *node;

        node = avl_tree_lookup_node(dir->i_children_ci,
                                    &dummy->d_index_node_ci,
                                    _avl_dentry_compare_names_ci);
        if (!node)
                return NULL;
        return avl_tree_entry(node, struct wim_dentry, d_index_node_ci);
}

/* 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,
                                   CASE_SENSITIVITY_TYPE case_ctype)
{
        const struct wim_inode *dir = dentry->d_inode;
        bool ignore_case = will_ignore_case(case_ctype);
        struct wim_dentry dummy;
        struct wim_dentry *child;

        dummy.file_name = (utf16lechar*)name;
        dummy.file_name_nbytes = name_nbytes;

        if (!ignore_case)
                /* Case-sensitive lookup.  */
                return dir_lookup(dir, &dummy);

        /* Case-insensitive lookup.  */

        child = dir_lookup_ci(dir, &dummy);
        if (!child)
                return NULL;

        if (likely(list_empty(&child->d_ci_conflict_list)))
                /* Only one dentry has this case-insensitive name; return it */
                return child;

        /* Multiple dentries have the same case-insensitive name.  Choose the
         * dentry with the same case-sensitive name, if one exists; otherwise
         * print a warning and choose one of the possible dentries arbitrarily.
         */
        struct wim_dentry *alt = child;
        size_t num_alts = 0;

        do {
                num_alts++;
                if (!dentry_compare_names_case_sensitive(&dummy, alt))
                        return alt;
                alt = list_entry(alt->d_ci_conflict_list.next,
                                 struct wim_dentry, d_ci_conflict_list);
        } while (alt != child);

        WARNING("Result of case-insensitive lookup is ambiguous\n"
                "          (returning \"%"TS"\" of %zu "
                "possible files, including \"%"TS"\")",
                dentry_full_path(child),
                num_alts,
                dentry_full_path(list_entry(child->d_ci_conflict_list.next,
                                            struct wim_dentry,
                                            d_ci_conflict_list)));
        return child;
}

/* Returns the child of @dentry that has the file name @name.  Returns NULL if
 * no child has the name. */
struct wim_dentry *
get_dentry_child_with_name(const struct wim_dentry *dentry, const tchar *name,
                           CASE_SENSITIVITY_TYPE case_type)
{
#if TCHAR_IS_UTF16LE
        return get_dentry_child_with_utf16le_name(dentry, name,
                                                  tstrlen(name) * sizeof(tchar),
                                                  case_type);
#else
        utf16lechar *utf16le_name;
        size_t utf16le_name_nbytes;
        int ret;
        struct wim_dentry *child;

        ret = tstr_to_utf16le(name, tstrlen(name) * sizeof(tchar),
                              &utf16le_name, &utf16le_name_nbytes);
        if (ret) {
                child = NULL;
        } else {
                child = get_dentry_child_with_utf16le_name(dentry,
                                                           utf16le_name,
                                                           utf16le_name_nbytes,
                                                           case_type);
                FREE(utf16le_name);
        }
        return child;
#endif
}

static struct wim_dentry *
get_dentry_utf16le(WIMStruct *wim, const utf16lechar *path,
                   CASE_SENSITIVITY_TYPE case_type)
{
        struct wim_dentry *cur_dentry;
        const utf16lechar *name_start, *name_end;

        /* Start with the root directory of the image.  Note: this will be NULL
         * if an image has been added directly with wimlib_add_empty_image() but
         * no files have been added yet; in that case we fail with ENOENT.  */
        cur_dentry = wim_root_dentry(wim);

        name_start = path;
        for (;;) {
                if (cur_dentry == NULL) {
                        errno = ENOENT;
                        return NULL;
                }

                if (*name_start && !dentry_is_directory(cur_dentry)) {
                        errno = ENOTDIR;
                        return NULL;
                }

                while (*name_start == cpu_to_le16(WIM_PATH_SEPARATOR))
                        name_start++;

                if (!*name_start)
                        return cur_dentry;

                name_end = name_start;
                do {
                        ++name_end;
                } while (*name_end != cpu_to_le16(WIM_PATH_SEPARATOR) && *name_end);

                cur_dentry = get_dentry_child_with_utf16le_name(cur_dentry,
                                                                name_start,
                                                                (u8*)name_end - (u8*)name_start,
                                                                case_type);
                name_start = name_end;
        }
}

/*
 * WIM path lookup: translate a path in the currently selected WIM image to the
 * corresponding dentry, if it exists.
 *
 * @wim
 *      The WIMStruct for the WIM.  The search takes place in the currently
 *      selected image.
 *
 * @path
 *      The path to look up, given relative to the root of the WIM image.
 *      Characters with value WIM_PATH_SEPARATOR are taken to be path
 *      separators.  Leading path separators are ignored, whereas one or more
 *      trailing path separators cause the path to only match a directory.
 *
 * @case_type
 *      The case-sensitivity behavior of this function, as one of the following
 *      constants:
 *
 *    - WIMLIB_CASE_SENSITIVE:  Perform the search case sensitively.  This means
 *      that names must match exactly.
 *
 *    - WIMLIB_CASE_INSENSITIVE:  Perform the search case insensitively.  This
 *      means that names are considered to match if they are equal when
 *      transformed to upper case.  If a path component matches multiple names
 *      case-insensitively, the name that matches the path component
 *      case-sensitively is chosen, if existent; otherwise one
 *      case-insensitively matching name is chosen arbitrarily.
 *
 *    - WIMLIB_CASE_PLATFORM_DEFAULT:  Perform either case-sensitive or
 *      case-insensitive search, depending on the value of the global variable
 *      default_ignore_case.
 *
 *    In any case, no Unicode normalization is done before comparing strings.
 *
 * Returns a pointer to the dentry that is the result of the lookup, or NULL if
 * no such dentry exists.  If NULL is returned, errno is set to one of the
 * following values:
 *
 *      ENOTDIR if one of the path components used as a directory existed but
 *      was not, in fact, a directory.
 *
 *      ENOENT otherwise.
 *
 * Additional notes:
 *
 *    - This function does not consider a reparse point to be a directory, even
 *      if it has FILE_ATTRIBUTE_DIRECTORY set.
 *
 *    - This function does not dereference symbolic links or junction points
 *      when performing the search.
 *
 *    - Since this function ignores leading slashes, the empty path is valid and
 *      names the root directory of the WIM image.
 *
 *    - An image added with wimlib_add_empty_image() does not have a root
 *      directory yet, and this function will fail with ENOENT for any path on
 *      such an image.
 */
struct wim_dentry *
get_dentry(WIMStruct *wim, const tchar *path, CASE_SENSITIVITY_TYPE case_type)
{
#if TCHAR_IS_UTF16LE
        return get_dentry_utf16le(wim, path, case_type);
#else
        utf16lechar *path_utf16le;
        size_t path_utf16le_nbytes;
        int ret;
        struct wim_dentry *dentry;

        ret = tstr_to_utf16le(path, tstrlen(path) * sizeof(tchar),
                              &path_utf16le, &path_utf16le_nbytes);
        if (ret)
                return NULL;
        dentry = get_dentry_utf16le(wim, path_utf16le, case_type);
        FREE(path_utf16le);
        return dentry;
#endif
}

/* Takes in a path of length @len in @buf, and transforms it into a string for
 * the path of its parent directory. */
static void
to_parent_name(tchar *buf, size_t len)
{
        ssize_t i = (ssize_t)len - 1;
        while (i >= 0 && buf[i] == WIM_PATH_SEPARATOR)
                i--;
        while (i >= 0 && buf[i] != WIM_PATH_SEPARATOR)
                i--;
        while (i >= 0 && buf[i] == WIM_PATH_SEPARATOR)
                i--;
        buf[i + 1] = T('\0');
}

/* Similar to get_dentry(), but returns the dentry named by @path with the last
 * component stripped off.
 *
 * Note: The returned dentry is NOT guaranteed to be a directory.  */
struct wim_dentry *
get_parent_dentry(WIMStruct *wim, const tchar *path,
                  CASE_SENSITIVITY_TYPE case_type)
{
        size_t path_len = tstrlen(path);
        tchar buf[path_len + 1];

        tmemcpy(buf, path, path_len + 1);
        to_parent_name(buf, path_len);
        return get_dentry(wim, buf, case_type);
}

#ifdef WITH_FUSE
/* Finds the dentry, lookup table entry, and stream index for a WIM file stream,
 * given a path name.
 *
 * Currently, lookups of this type are only needed if FUSE is enabled.  */
int
wim_pathname_to_stream(WIMStruct *wim,
                       const tchar *path,
                       int lookup_flags,
                       struct wim_dentry **dentry_ret,
                       struct wim_lookup_table_entry **lte_ret,
                       u16 *stream_idx_ret)
{
        struct wim_dentry *dentry;
        struct wim_lookup_table_entry *lte;
        u16 stream_idx;
        const tchar *stream_name = NULL;
        struct wim_inode *inode;
        tchar *p = NULL;

        if (lookup_flags & LOOKUP_FLAG_ADS_OK) {
                stream_name = path_stream_name(path);
                if (stream_name) {
                        p = (tchar*)stream_name - 1;
                        *p = T('\0');
                }
        }

        dentry = get_dentry(wim, path, WIMLIB_CASE_SENSITIVE);
        if (p)
                *p = T(':');
        if (!dentry)
                return -errno;

        inode = dentry->d_inode;

        if (!inode->i_resolved)
                if (inode_resolve_streams(inode, wim->lookup_table, false))
                        return -EIO;

        if (!(lookup_flags & LOOKUP_FLAG_DIRECTORY_OK)
              && inode_is_directory(inode))
                return -EISDIR;

        if (stream_name) {
                struct wim_ads_entry *ads_entry;
                u16 ads_idx;
                ads_entry = inode_get_ads_entry(inode, stream_name,
                                                &ads_idx);
                if (ads_entry) {
                        stream_idx = ads_idx + 1;
                        lte = ads_entry->lte;
                        goto out;
                } else {
                        return -ENOENT;
                }
        } else {
                lte = inode_unnamed_stream_resolved(inode, &stream_idx);
        }
out:
        if (dentry_ret)
                *dentry_ret = dentry;
        if (lte_ret)
                *lte_ret = lte;
        if (stream_idx_ret)
                *stream_idx_ret = stream_idx;
        return 0;
}
#endif /* WITH_FUSE  */

/* Initializations done on every `struct wim_dentry'. */
static void
dentry_common_init(struct wim_dentry *dentry)
{
        memset(dentry, 0, sizeof(struct wim_dentry));
}

/* Creates an unlinked directory entry. */
int
new_dentry(const tchar *name, struct wim_dentry **dentry_ret)
{
        struct wim_dentry *dentry;
        int ret;

        dentry = MALLOC(sizeof(struct wim_dentry));
        if (dentry == NULL)
                return WIMLIB_ERR_NOMEM;

        dentry_common_init(dentry);
        if (*name) {
                ret = dentry_set_name(dentry, name);
                if (ret) {
                        FREE(dentry);
                        ERROR("Failed to set name on new dentry with name \"%"TS"\"",
                              name);
                        return ret;
                }
        }
        dentry->parent = dentry;
        *dentry_ret = dentry;
        return 0;
}

static int
_new_dentry_with_inode(const tchar *name, struct wim_dentry **dentry_ret,
                        bool timeless)
{
        struct wim_dentry *dentry;
        int ret;

        ret = new_dentry(name, &dentry);
        if (ret)
                return ret;

        if (timeless)
                dentry->d_inode = new_timeless_inode();
        else
                dentry->d_inode = new_inode();
        if (dentry->d_inode == NULL) {
                free_dentry(dentry);
                return WIMLIB_ERR_NOMEM;
        }

        inode_add_dentry(dentry, dentry->d_inode);
        *dentry_ret = dentry;
        return 0;
}

int
new_dentry_with_timeless_inode(const tchar *name, struct wim_dentry **dentry_ret)
{
        return _new_dentry_with_inode(name, dentry_ret, true);
}

int
new_dentry_with_inode(const tchar *name, struct wim_dentry **dentry_ret)
{
        return _new_dentry_with_inode(name, dentry_ret, false);
}

int
new_filler_directory(const tchar *name, struct wim_dentry **dentry_ret)
{
        int ret;
        struct wim_dentry *dentry;

        DEBUG("Creating filler directory \"%"TS"\"", name);
        ret = new_dentry_with_inode(name, &dentry);
        if (ret)
                return ret;
        /* Leave the inode number as 0; this is allowed for non
         * hard-linked files. */
        dentry->d_inode->i_resolved = 1;
        dentry->d_inode->i_attributes = FILE_ATTRIBUTE_DIRECTORY;
        *dentry_ret = dentry;
        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);
}

/* Frees a WIM dentry.
 *
 * The corresponding inode (if any) is freed only if its link count is
 * decremented to 0.  */
void
free_dentry(struct wim_dentry *dentry)
{
        if (dentry) {
                FREE(dentry->file_name);
                FREE(dentry->short_name);
                FREE(dentry->_full_path);
                if (dentry->d_inode)
                        put_inode(dentry->d_inode);
                FREE(dentry);
        }
}

/* This function is passed as an argument to for_dentry_in_tree_depth() in order
 * to free a directory tree. */
static int
do_free_dentry(struct wim_dentry *dentry, void *_lookup_table)
{
        struct wim_lookup_table *lookup_table = _lookup_table;

        if (lookup_table) {
                struct wim_inode *inode = dentry->d_inode;
                for (unsigned i = 0; i <= inode->i_num_ads; i++) {
                        struct wim_lookup_table_entry *lte;

                        lte = inode_stream_lte(inode, i, lookup_table);
                        if (lte)
                                lte_decrement_refcnt(lte, lookup_table);
                }
        }
        free_dentry(dentry);
        return 0;
}

/*
 * 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.
 */
void
free_dentry_tree(struct wim_dentry *root, struct wim_lookup_table *lookup_table)
{
        for_dentry_in_tree_depth(root, do_free_dentry, lookup_table);
}

/* Insert the @child dentry into the case sensitive index of the @dir directory.
 * Return NULL if successfully inserted, otherwise a pointer to the
 * already-inserted duplicate.  */
static struct wim_dentry *
dir_index_child(struct wim_inode *dir, struct wim_dentry *child)
{
        struct avl_tree_node *duplicate;

        duplicate = avl_tree_insert(&dir->i_children,
                                    &child->d_index_node,
                                    _avl_dentry_compare_names);
        if (!duplicate)
                return NULL;
        return avl_tree_entry(duplicate, struct wim_dentry, d_index_node);
}

/* Insert the @child dentry into the case insensitive index of the @dir
 * directory.  Return NULL if successfully inserted, otherwise a pointer to the
 * already-inserted duplicate.  */
static struct wim_dentry *
dir_index_child_ci(struct wim_inode *dir, struct wim_dentry *child)
{
        struct avl_tree_node *duplicate;

        duplicate = avl_tree_insert(&dir->i_children_ci,
                                    &child->d_index_node_ci,
                                    _avl_dentry_compare_names_ci);
        if (!duplicate)
                return NULL;
        return avl_tree_entry(duplicate, struct wim_dentry, d_index_node_ci);
}

/* Removes the specified dentry from its directory's case-sensitive index.  */
static void
dir_unindex_child(struct wim_inode *dir, struct wim_dentry *child)
{
        avl_tree_remove(&dir->i_children, &child->d_index_node);
}

/* Removes the specified dentry from its directory's case-insensitive index.  */
static void
dir_unindex_child_ci(struct wim_inode *dir, struct wim_dentry *child)
{
        avl_tree_remove(&dir->i_children_ci, &child->d_index_node_ci);
}

/* Returns true iff the specified dentry is in its parent directory's
 * case-insensitive index.  */
static bool
dentry_in_ci_index(const struct wim_dentry *dentry)
{
        return !avl_tree_node_is_unlinked(&dentry->d_index_node_ci);
}

/*
 * Links a dentry into the directory tree.
 *
 * @parent: The dentry that will be the parent of @child.
 * @child: The dentry to link.
 *
 * Returns NULL if successful.  If @parent already contains a dentry with the
 * same case-sensitive name as @child, returns a pointer to this duplicate
 * dentry.
 */
struct wim_dentry *
dentry_add_child(struct wim_dentry *parent, struct wim_dentry *child)
{
        struct wim_dentry *duplicate;
        struct wim_inode *dir;

        wimlib_assert(parent != child);

        dir = parent->d_inode;

        wimlib_assert(inode_is_directory(dir));

        duplicate = dir_index_child(dir, child);
        if (duplicate)
                return duplicate;

        duplicate = dir_index_child_ci(dir, child);
        if (duplicate) {
                list_add(&child->d_ci_conflict_list, &duplicate->d_ci_conflict_list);
                avl_tree_node_set_unlinked(&child->d_index_node_ci);
        } else {
                INIT_LIST_HEAD(&child->d_ci_conflict_list);
        }
        child->parent = parent;
        return NULL;
}

/* Unlink a WIM dentry from the directory entry tree.  */
void
unlink_dentry(struct wim_dentry *dentry)
{
        struct wim_inode *dir;

        if (dentry_is_root(dentry))
                return;

        dir = dentry->parent->d_inode;

        dir_unindex_child(dir, dentry);

        if (dentry_in_ci_index(dentry)) {

                dir_unindex_child_ci(dir, dentry);

                if (!list_empty(&dentry->d_ci_conflict_list)) {
                        /* Make a different case-insensitively-the-same dentry
                         * be the "representative" in the search index. */
                        struct list_head *next;
                        struct wim_dentry *other;
                        struct wim_dentry *existing;

                        next = dentry->d_ci_conflict_list.next;
                        other = list_entry(next, struct wim_dentry, d_ci_conflict_list);
                        existing = dir_index_child_ci(dir, other);
                        wimlib_assert(existing == NULL);
                }
        }
        list_del(&dentry->d_ci_conflict_list);
}

static int
free_dentry_full_path(struct wim_dentry *dentry, void *_ignore)
{
        FREE(dentry->_full_path);
        dentry->_full_path = NULL;
        return 0;
}

/* Rename a file or directory in the WIM.  */
int
rename_wim_path(WIMStruct *wim, const tchar *from, const tchar *to,
                CASE_SENSITIVITY_TYPE case_type)
{
        struct wim_dentry *src;
        struct wim_dentry *dst;
        struct wim_dentry *parent_of_dst;
        int ret;

        /* This rename() implementation currently only supports actual files
         * (not alternate data streams) */

        src = get_dentry(wim, from, case_type);
        if (!src)
                return -errno;

        dst = get_dentry(wim, to, case_type);

        if (dst) {
                /* Destination file exists */

                if (src == dst) /* Same file */
                        return 0;

                if (!dentry_is_directory(src)) {
                        /* Cannot rename non-directory to directory. */
                        if (dentry_is_directory(dst))
                                return -EISDIR;
                } else {
                        /* Cannot rename directory to a non-directory or a non-empty
                         * directory */
                        if (!dentry_is_directory(dst))
                                return -ENOTDIR;
                        if (dentry_has_children(dst))
                                return -ENOTEMPTY;
                }
                parent_of_dst = dst->parent;
        } else {
                /* Destination does not exist */
                parent_of_dst = get_parent_dentry(wim, to, case_type);
                if (!parent_of_dst)
                        return -errno;

                if (!dentry_is_directory(parent_of_dst))
                        return -ENOTDIR;
        }

        ret = dentry_set_name(src, path_basename(to));
        if (ret)
                return -ENOMEM;
        if (dst) {
                unlink_dentry(dst);
                free_dentry_tree(dst, wim->lookup_table);
        }
        unlink_dentry(src);
        dentry_add_child(parent_of_dst, src);
        if (src->_full_path)
                for_dentry_in_tree(src, free_dentry_full_path, NULL);
        return 0;
}

/* Reads a WIM directory entry, including all alternate data stream entries that
 * follow it, from the WIM image's metadata resource.  */
static int
read_dentry(const u8 * restrict buf, size_t buf_len,
            u64 offset, struct wim_dentry **dentry_ret)
{
        u64 length;
        const u8 *p;
        const struct wim_dentry_on_disk *disk_dentry;
        struct wim_dentry *dentry;
        struct wim_inode *inode;
        u16 short_name_nbytes;
        u16 file_name_nbytes;
        u64 calculated_size;
        int ret;

        BUILD_BUG_ON(sizeof(struct wim_dentry_on_disk) != WIM_DENTRY_DISK_SIZE);

        /* Before reading the whole dentry, we need to read just the length.
         * This is because a dentry of length 8 (that is, just the length field)
         * terminates the list of sibling directory entries. */

        /* Check for buffer overrun.  */
        if (unlikely(offset + sizeof(u64) > buf_len ||
                     offset + sizeof(u64) < offset))
        {
                ERROR("Directory entry starting at %"PRIu64" ends past the "
                      "end of the metadata resource (size %zu)",
                      offset, buf_len);
                return WIMLIB_ERR_INVALID_METADATA_RESOURCE;
        }

        /* Get pointer to the dentry data.  */
        p = &buf[offset];
        disk_dentry = (const struct wim_dentry_on_disk*)p;

        if (unlikely((uintptr_t)p & 7))
                WARNING("WIM dentry is not 8-byte aligned");

        /* Get dentry length.  */
        length = le64_to_cpu(disk_dentry->length);

        /* Check for end-of-directory.  */
        if (length <= 8) {
                *dentry_ret = NULL;
                return 0;
        }

        /* Validate dentry length.  */
        if (unlikely(length < sizeof(struct wim_dentry_on_disk))) {
                ERROR("Directory entry has invalid length of %"PRIu64" bytes",
                      length);
                return WIMLIB_ERR_INVALID_METADATA_RESOURCE;
        }

        /* Check for buffer overrun.  */
        if (unlikely(offset + length > buf_len ||
                     offset + length < offset))
        {
                ERROR("Directory entry at offset %"PRIu64" and with size "
                      "%"PRIu64" ends past the end of the metadata resource "
                      "(size %zu)", offset, length, buf_len);
                return WIMLIB_ERR_INVALID_METADATA_RESOURCE;
        }

        /* Allocate new dentry structure, along with a preliminary inode.  */
        ret = new_dentry_with_timeless_inode(T(""), &dentry);
        if (ret)
                return ret;

        dentry->length = length;
        inode = dentry->d_inode;

        /* Read more fields: some into the dentry, and some into the inode.  */
        inode->i_attributes = le32_to_cpu(disk_dentry->attributes);
        inode->i_security_id = le32_to_cpu(disk_dentry->security_id);
        dentry->subdir_offset = le64_to_cpu(disk_dentry->subdir_offset);
        inode->i_creation_time = le64_to_cpu(disk_dentry->creation_time);
        inode->i_last_access_time = le64_to_cpu(disk_dentry->last_access_time);
        inode->i_last_write_time = le64_to_cpu(disk_dentry->last_write_time);
        copy_hash(inode->i_hash, disk_dentry->unnamed_stream_hash);

        /* I don't know what's going on here.  It seems like M$ screwed up the
         * reparse points, then put the fields in the same place and didn't
         * document it.  So we have some fields we read for reparse points, and
         * some fields in the same place for non-reparse-points.  */
        if (inode->i_attributes & FILE_ATTRIBUTE_REPARSE_POINT) {
                inode->i_rp_unknown_1 = le32_to_cpu(disk_dentry->reparse.rp_unknown_1);
                inode->i_reparse_tag = le32_to_cpu(disk_dentry->reparse.reparse_tag);
                inode->i_rp_unknown_2 = le16_to_cpu(disk_dentry->reparse.rp_unknown_2);
                inode->i_not_rpfixed = le16_to_cpu(disk_dentry->reparse.not_rpfixed);
                /* Leave inode->i_ino at 0.  Note that this means the WIM file
                 * cannot archive hard-linked reparse points.  Such a thing
                 * doesn't really make sense anyway, although I believe it's
                 * theoretically possible to have them on NTFS.  */
        } else {
                inode->i_rp_unknown_1 = le32_to_cpu(disk_dentry->nonreparse.rp_unknown_1);
                inode->i_ino = le64_to_cpu(disk_dentry->nonreparse.hard_link_group_id);
        }
        inode->i_num_ads = le16_to_cpu(disk_dentry->num_alternate_data_streams);

        /* Now onto reading the names.  There are two of them: the (long) file
         * name, and the short name.  */

        short_name_nbytes = le16_to_cpu(disk_dentry->short_name_nbytes);
        file_name_nbytes = le16_to_cpu(disk_dentry->file_name_nbytes);

        if (unlikely((short_name_nbytes & 1) | (file_name_nbytes & 1))) {
                ERROR("Dentry name is not valid UTF-16 (odd number of bytes)!");
                ret = WIMLIB_ERR_INVALID_METADATA_RESOURCE;
                goto err_free_dentry;
        }

        /* We now know the length of the file name and short name.  Make sure
         * the length of the dentry is large enough to actually hold them.
         *
         * The calculated length here is unaligned to allow for the possibility
         * that the dentry->length names an unaligned length, although this
         * would be unexpected.  */
        calculated_size = dentry_correct_length_unaligned(file_name_nbytes,
                                                          short_name_nbytes);

        if (unlikely(dentry->length < calculated_size)) {
                ERROR("Unexpected end of directory entry! (Expected "
                      "at least %"PRIu64" bytes, got %"PRIu64" bytes.)",
                      calculated_size, dentry->length);
                ret = WIMLIB_ERR_INVALID_METADATA_RESOURCE;
                goto err_free_dentry;
        }

        /* Advance p to point past the base dentry, to the first name.  */
        p += sizeof(struct wim_dentry_on_disk);

        /* Read the filename if present.  Note: if the filename is empty, there
         * is no null terminator following it.  */
        if (file_name_nbytes) {
                dentry->file_name = MALLOC(file_name_nbytes + 2);
                if (dentry->file_name == NULL) {
                        ret = WIMLIB_ERR_NOMEM;
                        goto err_free_dentry;
                }
                dentry->file_name_nbytes = file_name_nbytes;
                memcpy(dentry->file_name, p, file_name_nbytes);
                p += file_name_nbytes + 2;
                dentry->file_name[file_name_nbytes / 2] = cpu_to_le16(0);
        }

        /* Read the short filename if present.  Note: if there is no short
         * filename, there is no null terminator following it. */
        if (short_name_nbytes) {
                dentry->short_name = MALLOC(short_name_nbytes + 2);
                if (dentry->short_name == NULL) {
                        ret = WIMLIB_ERR_NOMEM;
                        goto err_free_dentry;
                }
                dentry->short_name_nbytes = short_name_nbytes;
                memcpy(dentry->short_name, p, short_name_nbytes);
                p += short_name_nbytes + 2;
                dentry->short_name[short_name_nbytes / 2] = cpu_to_le16(0);
        }

        /* Align the dentry length.  */
        dentry->length = (dentry->length + 7) & ~7;

        /* Read the alternate data streams, if present.  inode->i_num_ads tells
         * us how many they are, and they will directly follow the dentry in the
         * metadata resource buffer.
         *
         * Note that each alternate data stream entry begins on an 8-byte
         * aligned boundary, and the alternate data stream entries seem to NOT
         * be included in the dentry->length field for some reason.  */
        if (unlikely(inode->i_num_ads != 0)) {
                ret = WIMLIB_ERR_INVALID_METADATA_RESOURCE;
                if (offset + dentry->length > buf_len ||
                    (ret = read_ads_entries(&buf[offset + dentry->length],
                                            inode,
                                            buf_len - offset - dentry->length)))
                {
                        ERROR("Failed to read alternate data stream "
                              "entries of WIM dentry \"%"WS"\"",
                              dentry->file_name);
                        goto err_free_dentry;
                }
        }

        *dentry_ret = dentry;
        return 0;

err_free_dentry:
        free_dentry(dentry);
        return ret;
}

static const tchar *
dentry_get_file_type_string(const struct wim_dentry *dentry)
{
        const struct wim_inode *inode = dentry->d_inode;
        if (inode_is_directory(inode))
                return T("directory");
        else if (inode_is_symlink(inode))
                return T("symbolic link");
        else
                return T("file");
}

static bool
dentry_is_dot_or_dotdot(const struct wim_dentry *dentry)
{
        if (dentry->file_name_nbytes <= 4) {
                if (dentry->file_name_nbytes == 4) {
                        if (dentry->file_name[0] == cpu_to_le16('.') &&
                            dentry->file_name[1] == cpu_to_le16('.'))
                                return true;
                } else if (dentry->file_name_nbytes == 2) {
                        if (dentry->file_name[0] == cpu_to_le16('.'))
                                return true;
                }
        }
        return false;
}

static int
read_dentry_tree_recursive(const u8 * restrict buf, size_t buf_len,
                           struct wim_dentry * restrict dir)
{
        u64 cur_offset = dir->subdir_offset;

        /* Check for cyclic directory structure, which would cause infinite
         * recursion if not handled.  */
        for (struct wim_dentry *d = dir->parent;
             !dentry_is_root(d); d = d->parent)
        {
                if (unlikely(d->subdir_offset == cur_offset)) {
                        ERROR("Cyclic directory structure detected: children "
                              "of \"%"TS"\" coincide with children of \"%"TS"\"",
                              dentry_full_path(dir), dentry_full_path(d));
                        return WIMLIB_ERR_INVALID_METADATA_RESOURCE;
                }
        }

        for (;;) {
                struct wim_dentry *child;
                struct wim_dentry *duplicate;
                int ret;

                /* Read next child of @dir.  */
                ret = read_dentry(buf, buf_len, cur_offset, &child);
                if (ret)
                        return ret;

                /* Check for end of directory.  */
                if (child == NULL)
                        return 0;

                /* Advance to the offset of the next child.  Note: We need to
                 * advance by the TOTAL length of the dentry, not by the length
                 * child->length, which although it does take into account the
                 * padding, it DOES NOT take into account alternate stream
                 * entries.  */
                cur_offset += dentry_in_total_length(child);

                /* All dentries except the root should be named.  */
                if (unlikely(!dentry_has_long_name(child))) {
                        WARNING("Ignoring unnamed dentry in "
                                "directory \"%"TS"\"", dentry_full_path(dir));
                        free_dentry(child);
                        continue;
                }

                /* Don't allow files named "." or "..".  */
                if (unlikely(dentry_is_dot_or_dotdot(child))) {
                        WARNING("Ignoring file named \".\" or \"..\"; "
                                "potentially malicious archive!!!");
                        free_dentry(child);
                        continue;
                }

                /* Link the child into the directory.  */
                duplicate = dentry_add_child(dir, child);
                if (unlikely(duplicate)) {
                        /* We already found a dentry with this same
                         * case-sensitive long name.  Only keep the first one.
                         */
                        const tchar *child_type, *duplicate_type;
                        child_type = dentry_get_file_type_string(child);
                        duplicate_type = dentry_get_file_type_string(duplicate);
                        WARNING("Ignoring duplicate %"TS" \"%"TS"\" "
                                "(the WIM image already contains a %"TS" "
                                "at that path with the exact same name)",
                                child_type, dentry_full_path(duplicate),
                                duplicate_type);
                        free_dentry(child);
                        continue;
                }

                /* If this child is a directory that itself has children, call
                 * this procedure recursively.  */
                if (child->subdir_offset != 0) {
                        if (likely(dentry_is_directory(child))) {
                                ret = read_dentry_tree_recursive(buf,
                                                                 buf_len,
                                                                 child);
                                if (ret)
                                        return ret;
                        } else {
                                WARNING("Ignoring children of "
                                        "non-directory file \"%"TS"\"",
                                        dentry_full_path(child));
                        }
                }
        }
}

/*
 * Read a tree of dentries (directory entries) from a WIM metadata resource.
 *
 * @buf:
 *      Buffer containing an uncompressed WIM metadata resource.
 *
 * @buf_len:
 *      Length of the uncompressed metadata resource, in bytes.
 *
 * @root_offset
 *      Offset in the metadata resource of the root of the dentry tree.
 *
 * @root_ret:
 *      On success, either NULL or a pointer to the root dentry is written to
 *      this location.  The former case only occurs in the unexpected case that
 *      the tree began with an end-of-directory entry.
 *
 * Return values:
 *      WIMLIB_ERR_SUCCESS (0)
 *      WIMLIB_ERR_INVALID_METADATA_RESOURCE
 *      WIMLIB_ERR_NOMEM
 */
int
read_dentry_tree(const u8 *buf, size_t buf_len,
                 u64 root_offset, struct wim_dentry **root_ret)
{
        int ret;
        struct wim_dentry *root;

        DEBUG("Reading dentry tree (root_offset=%"PRIu64")", root_offset);

        ret = read_dentry(buf, buf_len, root_offset, &root);
        if (ret)
                return ret;

        if (likely(root != NULL)) {
                if (unlikely(dentry_has_long_name(root) ||
                             dentry_has_short_name(root)))
                {
                        WARNING("The root directory has a nonempty name; "
                                "removing it.");
                        FREE(root->file_name);
                        FREE(root->short_name);
                        root->file_name = NULL;
                        root->short_name = NULL;
                        root->file_name_nbytes = 0;
                        root->short_name_nbytes = 0;
                }

                if (unlikely(!dentry_is_directory(root))) {
                        ERROR("The root of the WIM image is not a directory!");
                        ret = WIMLIB_ERR_INVALID_METADATA_RESOURCE;
                        goto err_free_dentry_tree;
                }

                if (likely(root->subdir_offset != 0)) {
                        ret = read_dentry_tree_recursive(buf, buf_len, root);
                        if (ret)
                                goto err_free_dentry_tree;
                }
        } else {
                WARNING("The metadata resource has no directory entries; "
                        "treating as an empty image.");
        }
        *root_ret = root;
        return 0;

err_free_dentry_tree:
        free_dentry_tree(root, NULL);
        return ret;
}

/*
 * Writes a WIM alternate data stream (ADS) entry to an output buffer.
 *
 * @ads_entry:  The ADS entry structure.
 * @hash:       The hash field to use (instead of the one in the ADS entry).
 * @p:          The memory location to write the data to.
 *
 * Returns a pointer to the byte after the last byte written.
 */
static u8 *
write_ads_entry(const struct wim_ads_entry *ads_entry,
                const u8 *hash, u8 * restrict p)
{
        struct wim_ads_entry_on_disk *disk_ads_entry =
                        (struct wim_ads_entry_on_disk*)p;
        u8 *orig_p = p;

        disk_ads_entry->reserved = cpu_to_le64(ads_entry->reserved);
        copy_hash(disk_ads_entry->hash, hash);
        disk_ads_entry->stream_name_nbytes = cpu_to_le16(ads_entry->stream_name_nbytes);
        p += sizeof(struct wim_ads_entry_on_disk);
        if (ads_entry->stream_name_nbytes) {
                p = mempcpy(p, ads_entry->stream_name,
                            ads_entry->stream_name_nbytes + 2);
        }
        /* Align to 8-byte boundary */
        while ((uintptr_t)p & 7)
                *p++ = 0;
        disk_ads_entry->length = cpu_to_le64(p - orig_p);
        return p;
}

/*
 * Writes a WIM dentry to an output buffer.
 *
 * @dentry:  The dentry structure.
 * @p:       The memory location to write the data to.
 *
 * Returns the pointer to the byte after the last byte we wrote as part of the
 * dentry, including any alternate data stream entries.
 */
static u8 *
write_dentry(const struct wim_dentry * restrict dentry, u8 * restrict p)
{
        const struct wim_inode *inode;
        struct wim_dentry_on_disk *disk_dentry;
        const u8 *orig_p;
        const u8 *hash;
        bool use_dummy_stream;
        u16 num_ads;

        wimlib_assert(((uintptr_t)p & 7) == 0); /* 8 byte aligned */
        orig_p = p;

        inode = dentry->d_inode;
        use_dummy_stream = inode_needs_dummy_stream(inode);
        disk_dentry = (struct wim_dentry_on_disk*)p;

        disk_dentry->attributes = cpu_to_le32(inode->i_attributes);
        disk_dentry->security_id = cpu_to_le32(inode->i_security_id);
        disk_dentry->subdir_offset = cpu_to_le64(dentry->subdir_offset);
        disk_dentry->unused_1 = cpu_to_le64(0);
        disk_dentry->unused_2 = cpu_to_le64(0);
        disk_dentry->creation_time = cpu_to_le64(inode->i_creation_time);
        disk_dentry->last_access_time = cpu_to_le64(inode->i_last_access_time);
        disk_dentry->last_write_time = cpu_to_le64(inode->i_last_write_time);
        if (use_dummy_stream)
                hash = zero_hash;
        else
                hash = inode_stream_hash(inode, 0);
        copy_hash(disk_dentry->unnamed_stream_hash, hash);
        if (inode->i_attributes & FILE_ATTRIBUTE_REPARSE_POINT) {
                disk_dentry->reparse.rp_unknown_1 = cpu_to_le32(inode->i_rp_unknown_1);
                disk_dentry->reparse.reparse_tag = cpu_to_le32(inode->i_reparse_tag);
                disk_dentry->reparse.rp_unknown_2 = cpu_to_le16(inode->i_rp_unknown_2);
                disk_dentry->reparse.not_rpfixed = cpu_to_le16(inode->i_not_rpfixed);
        } else {
                disk_dentry->nonreparse.rp_unknown_1 = cpu_to_le32(inode->i_rp_unknown_1);
                disk_dentry->nonreparse.hard_link_group_id =
                        cpu_to_le64((inode->i_nlink == 1) ? 0 : inode->i_ino);
        }
        num_ads = inode->i_num_ads;
        if (use_dummy_stream)
                num_ads++;
        disk_dentry->num_alternate_data_streams = cpu_to_le16(num_ads);
        disk_dentry->short_name_nbytes = cpu_to_le16(dentry->short_name_nbytes);
        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);

        if (dentry_has_short_name(dentry))
                p = mempcpy(p, dentry->short_name, dentry->short_name_nbytes + 2);

        /* Align to 8-byte boundary */
        while ((uintptr_t)p & 7)
                *p++ = 0;

        /* We calculate the correct length of the dentry ourselves because the
         * dentry->length field may been set to an unexpected value from when we
         * read the dentry in (for example, there may have been unknown data
         * appended to the end of the dentry...).  Furthermore, the dentry may
         * have been renamed, thus changing its needed length. */
        disk_dentry->length = cpu_to_le64(p - orig_p);

        if (use_dummy_stream) {
                hash = inode_unnamed_stream_hash(inode);
                p = write_ads_entry(&(struct wim_ads_entry){}, hash, p);
        }

        /* Write the alternate data streams entries, if any. */
        for (u16 i = 0; i < inode->i_num_ads; i++) {
                hash = inode_stream_hash(inode, i + 1);
                p = write_ads_entry(&inode->i_ads_entries[i], hash, p);
        }

        return p;
}

static int
write_dir_dentries(struct wim_dentry *dir, void *_pp)
{
        if (dentry_is_directory(dir)) {
                u8 **pp = _pp;
                u8 *p = *pp;
                struct wim_dentry *child;

                /* write child dentries */
                for_dentry_child(child, dir)
                        p = write_dentry(child, p);

                /* write end of directory entry */
                *(u64*)p = 0;
                p += 8;
                *pp = p;
        }
        return 0;
}

/* Writes a directory tree to the metadata resource.
 *
 * @root:       Root of the dentry tree.
 * @p:          Pointer to a buffer with enough space for the dentry tree.
 *
 * Returns pointer to the byte after the last byte we wrote.
 */
u8 *
write_dentry_tree(struct wim_dentry *root, u8 *p)
{
        DEBUG("Writing dentry tree.");
        wimlib_assert(dentry_is_root(root));

        /* write root dentry and end-of-directory entry following it */
        p = write_dentry(root, p);
        *(u64*)p = 0;
        p += 8;

        /* write the rest of the dentry tree */
        for_dentry_in_tree(root, write_dir_dentries, &p);

        return p;
}