Version 1.2.1

[wimlib] / src / dentry.c

/*
 * dentry.c
 *
 * A dentry (directory entry) contains the metadata for a file.  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 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/.
 */

#include "buffer_io.h"
#include "dentry.h"
#include "lookup_table.h"
#include "timestamp.h"
#include "wimlib_internal.h"

/* 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_len,
                                             u16 short_name_len)
{
        u64 length = WIM_DENTRY_DISK_SIZE;
        if (file_name_len)
                length += file_name_len + 2;
        if (short_name_len)
                length += short_name_len + 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_unaligned(const struct dentry *dentry)
{
        return __dentry_correct_length_unaligned(dentry->file_name_len,
                                                 dentry->short_name_len);
}

/* Return the "correct" value to write in the length field of a WIM dentry,
 * based on the file name length and short name length. */
static u64 dentry_correct_length(const struct dentry *dentry)
{
        return (dentry_correct_length_unaligned(dentry) + 7) & ~7;
}

/* Return %true iff the alternate data stream entry @entry has the UTF-8 stream
 * name @name that has length @name_len bytes. */
static inline bool ads_entry_has_name(const struct ads_entry *entry,
                                      const char *name, size_t name_len)
{
        if (entry->stream_name_utf8_len != name_len)
                return false;
        return memcmp(entry->stream_name_utf8, name, name_len) == 0;
}

/* Duplicates a UTF-8 name into UTF-8 and UTF-16 strings and returns the strings
 * and their lengths in the pointer arguments */
int get_names(char **name_utf16_ret, char **name_utf8_ret,
              u16 *name_utf16_len_ret, u16 *name_utf8_len_ret,
              const char *name)
{
        size_t utf8_len;
        size_t utf16_len;
        char *name_utf16, *name_utf8;
        int ret;

        utf8_len = strlen(name);
        ret = utf8_to_utf16(name, utf8_len, &name_utf16, &utf16_len);
        if (ret != 0)
                return ret;

        name_utf8 = MALLOC(utf8_len + 1);
        if (!name_utf8) {
                FREE(name_utf8);
                return WIMLIB_ERR_NOMEM;
        }
        memcpy(name_utf8, name, utf8_len + 1);
        FREE(*name_utf8_ret);
        FREE(*name_utf16_ret);
        *name_utf8_ret      = name_utf8;
        *name_utf16_ret     = name_utf16;
        *name_utf8_len_ret  = utf8_len;
        *name_utf16_len_ret = utf16_len;
        return 0;
}

/* Changes the name of a dentry to @new_name.  Only changes the file_name and
 * file_name_utf8 fields; does not change the short_name, short_name_utf8, or
 * full_path_utf8 fields.  Also recalculates its length. */
static int change_dentry_name(struct dentry *dentry, const char *new_name)
{
        int ret;

        ret = get_names(&dentry->file_name, &dentry->file_name_utf8,
                        &dentry->file_name_len, &dentry->file_name_utf8_len,
                        new_name);
        if (ret == 0) {
                if (dentry->short_name_len) {
                        FREE(dentry->short_name);
                        dentry->short_name_len = 0;
                }
                dentry->length = dentry_correct_length(dentry);
        }
        return ret;
}

/*
 * Changes the name of an alternate data stream */
static int change_ads_name(struct ads_entry *entry, const char *new_name)
{
        return get_names(&entry->stream_name, &entry->stream_name_utf8,
                         &entry->stream_name_len,
                         &entry->stream_name_utf8_len,
                         new_name);
}

/* 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 one (or the next dentry) on an 8-byte boundary. */
static u64 ads_entry_total_length(const struct ads_entry *entry)
{
        u64 len = WIM_ADS_ENTRY_DISK_SIZE;
        if (entry->stream_name_len)
                len += entry->stream_name_len + 2;
        return (len + 7) & ~7;
}


static u64 __dentry_total_length(const struct dentry *dentry, u64 length)
{
        const struct inode *inode = dentry->d_inode;
        for (u16 i = 0; i < inode->num_ads; i++)
                length += ads_entry_total_length(&inode->ads_entries[i]);
        return (length + 7) & ~7;
}

/* Calculate the aligned *total* length of an on-disk WIM dentry.  This includes
 * all alternate data streams. */
u64 dentry_correct_total_length(const struct dentry *dentry)
{
        return __dentry_total_length(dentry,
                                     dentry_correct_length_unaligned(dentry));
}

/* Like dentry_correct_total_length(), but use the existing dentry->length field
 * instead of calculating its "correct" value. */
static u64 dentry_total_length(const struct dentry *dentry)
{
        return __dentry_total_length(dentry, dentry->length);
}

int for_dentry_in_rbtree(struct rb_node *root,
                         int (*visitor)(struct dentry *, void *),
                         void *arg)
{
        int ret;
        struct rb_node *node = root;
        LIST_HEAD(stack);
        while (true) {
                if (node) {
                        list_add(&rbnode_dentry(node)->tmp_list, &stack);
                        node = node->rb_left;
                } else {
                        struct list_head *next;
                        struct dentry *dentry;

                        next = stack.next;
                        if (next == &stack)
                                return 0;
                        dentry = container_of(next, struct dentry, tmp_list);
                        list_del(next);
                        ret = visitor(dentry, arg);
                        if (ret != 0)
                                return ret;
                        node = dentry->rb_node.rb_right;
                }
        }
}

static int for_dentry_tree_in_rbtree_depth(struct rb_node *node,
                                           int (*visitor)(struct dentry*, void*),
                                           void *arg)
{
        int ret;
        if (node) {
                ret = for_dentry_tree_in_rbtree_depth(node->rb_left,
                                                      visitor, arg);
                if (ret != 0)
                        return ret;
                ret = for_dentry_tree_in_rbtree_depth(node->rb_right,
                                                      visitor, arg);
                if (ret != 0)
                        return ret;
                ret = for_dentry_in_tree_depth(rbnode_dentry(node), visitor, arg);
                if (ret != 0)
                        return ret;
        }
        return 0;
}

/*#define RECURSIVE_FOR_DENTRY_IN_TREE*/

#ifdef RECURSIVE_FOR_DENTRY_IN_TREE
static int for_dentry_tree_in_rbtree(struct rb_node *node,
                                     int (*visitor)(struct dentry*, void*),
                                     void *arg)
{
        int ret;
        if (node) {
                ret = for_dentry_tree_in_rbtree(node->rb_left, visitor, arg);
                if (ret != 0)
                        return ret;
                ret = for_dentry_in_tree(rbnode_dentry(node), visitor, arg);
                if (ret != 0)
                        return ret;
                ret = for_dentry_tree_in_rbtree(node->rb_right, visitor, arg);
                if (ret != 0)
                        return ret;
        }
        return 0;
}
#endif

/*
 * 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.
 *
 * In reality, the data structures are more complicated than the above might
 * suggest because there is a separate red-black tree for each dentry that
 * contains its direct children.
 */
int for_dentry_in_tree(struct dentry *root,
                       int (*visitor)(struct dentry*, void*), void *arg)
{
#ifdef RECURSIVE_FOR_DENTRY_IN_TREE
        int ret = visitor(root, arg);
        if (ret != 0)
                return ret;
        return for_dentry_tree_in_rbtree(root->d_inode->children.rb_node, visitor, arg);
#else
        int ret;
        struct list_head main_stack;
        struct list_head sibling_stack;
        struct list_head *sibling_stack_bottom;
        struct dentry *main_dentry;
        struct rb_node *node;
        struct list_head *next_sibling;
        struct dentry *dentry;

        ret = visitor(root, arg);
        if (ret != 0)
                return ret;

        main_dentry = root;
        sibling_stack_bottom = &sibling_stack;
        INIT_LIST_HEAD(&main_stack);
        INIT_LIST_HEAD(&sibling_stack);

        list_add(&root->tmp_list, &main_stack);
        node = root->d_inode->children.rb_node;

        while (1) {
                // Prepare for non-recursive in-order traversal of the red-black
                // tree of this dentry's children

                while (node) {
                        // Push this node to the sibling stack and examine the
                        // left neighbor, if any
                        list_add(&rbnode_dentry(node)->tmp_list, &sibling_stack);
                        node = node->rb_left;
                }

                next_sibling = sibling_stack.next;
                if (next_sibling == sibling_stack_bottom) {
                        // Done with all siblings.  Pop the main dentry to move
                        // back up one level.
                        main_dentry = container_of(main_stack.next,
                                                   struct dentry,
                                                   tmp_list);
                        list_del(&main_dentry->tmp_list);

                        if (main_dentry == root)
                                goto out;

                        // Restore sibling stack bottom from the previous level
                        sibling_stack_bottom = (void*)main_dentry->parent;

                        // Restore the just-popped main dentry's parent
                        main_dentry->parent = container_of(main_stack.next,
                                                           struct dentry,
                                                           tmp_list);

                        // The next sibling to traverse in the previous level,
                        // in the in-order traversal of the red-black tree, is
                        // the one to the right.
                        node = main_dentry->rb_node.rb_right;
                } else {
                        // The sibling stack is not empty, so there are more to
                        // go!

                        // Pop a sibling from the stack.
                        list_del(next_sibling);
                        dentry = container_of(next_sibling, struct dentry, tmp_list);

                        // Visit the sibling.
                        ret = visitor(dentry, arg);
                        if (ret != 0) {
                                // Failed.  Restore parent pointers for the
                                // dentries in the main stack
                                list_for_each_entry(dentry, &main_stack, tmp_list) {
                                        dentry->parent = container_of(dentry->tmp_list.next,
                                                                      struct dentry,
                                                                      tmp_list);
                                }
                                goto out;
                        }

                        // We'd like to recursively visit the dentry tree rooted
                        // at this sibling.  To do this, add it to the main
                        // stack, save the bottom of this level's sibling stack
                        // in the dentry->parent field, re-set the bottom of the
                        // sibling stack to be its current height, and set
                        // main_dentry to the sibling so it becomes the parent
                        // dentry in the next iteration through the outer loop.
                        if (inode_has_children(dentry->d_inode)) {
                                list_add(&dentry->tmp_list, &main_stack);
                                dentry->parent = (void*)sibling_stack_bottom;
                                sibling_stack_bottom = sibling_stack.next;

                                main_dentry = dentry;
                                node = main_dentry->d_inode->children.rb_node;
                        } else {
                                node = dentry->rb_node.rb_right;
                        }
                }
        }
out:
        root->parent = root;
        return ret;
#endif
}

/*
 * 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 dentry *root,
                             int (*visitor)(struct dentry*, void*), void *arg)
{
#if 1
        int ret;
        ret = for_dentry_tree_in_rbtree_depth(root->d_inode->children.rb_node,
                                              visitor, arg);
        if (ret != 0)
                return ret;
        return visitor(root, arg);

#else
        int ret;
        struct list_head main_stack;
        struct list_head sibling_stack;
        struct list_head *sibling_stack_bottom;
        struct dentry *main_dentry;
        struct rb_node *node;
        struct list_head *next_sibling;
        struct dentry *dentry;

        main_dentry = root;
        sibling_stack_bottom = &sibling_stack;
        INIT_LIST_HEAD(&main_stack);
        INIT_LIST_HEAD(&sibling_stack);

        list_add(&main_dentry->tmp_list, &main_stack);

        while (1) {
                node = main_dentry->d_inode->children.rb_node;

                while (1) {
                        if (node->rb_left) {
                                list_add(&rbnode_dentry(node)->tmp_list, &sibling_stack);
                                node = node->rb_left;
                                continue;
                        }
                        if (node->rb_right) {
                                list_add(&rbnode_dentry(node)->tmp_list, &sibling_stack);
                                node = node->rb_right;
                                continue;
                        }
                        list_add(&rbnode_dentry(node)->tmp_list, &sibling_stack);
                }

        pop_sibling:
                next_sibling = sibling_stack.next;
                if (next_sibling == sibling_stack_bottom) {
                        main_dentry = container_of(main_stack.next,
                                                   struct dentry,
                                                   tmp_list);
                        list_del(&main_dentry->tmp_list);


                        sibling_stack_bottom = (void*)main_dentry->parent;

                        if (main_dentry == root) {
                                main_dentry->parent = main_dentry;
                                ret = visitor(dentry, arg);
                                return ret;
                        } else {
                                main_dentry->parent = container_of(main_stack.next,
                                                                   struct dentry,
                                                                   tmp_list);
                        }

                        ret = visitor(main_dentry, arg);

                        if (ret != 0) {
                                list_del(&root->tmp_list);
                                list_for_each_entry(dentry, &main_stack, tmp_list) {
                                        dentry->parent = container_of(dentry->tmp_list.next,
                                                                      struct dentry,
                                                                      tmp_list);
                                }
                                root->parent = root;
                                return ret;
                        }
                        goto pop_sibling;
                } else {

                        list_del(next_sibling);
                        dentry = container_of(next_sibling, struct dentry, tmp_list);


                        list_add(&dentry->tmp_list, &main_stack);
                        dentry->parent = (void*)sibling_stack_bottom;
                        sibling_stack_bottom = sibling_stack.next;

                        main_dentry = dentry;
                }
        }
#endif
}

/*
 * Calculate the full path of @dentry, based on its parent's full path and on
 * its UTF-8 file name.
 */
int calculate_dentry_full_path(struct dentry *dentry, void *ignore)
{
        char *full_path;
        u32 full_path_len;
        if (dentry_is_root(dentry)) {
                full_path = MALLOC(2);
                if (!full_path)
                        goto oom;
                full_path[0] = '/';
                full_path[1] = '\0';
                full_path_len = 1;
        } else {
                char *parent_full_path;
                u32 parent_full_path_len;
                const struct dentry *parent = dentry->parent;

                if (dentry_is_root(parent)) {
                        parent_full_path = "";
                        parent_full_path_len = 0;
                } else {
                        parent_full_path = parent->full_path_utf8;
                        parent_full_path_len = parent->full_path_utf8_len;
                }

                full_path_len = parent_full_path_len + 1 +
                                dentry->file_name_utf8_len;
                full_path = MALLOC(full_path_len + 1);
                if (!full_path)
                        goto oom;

                memcpy(full_path, parent_full_path, parent_full_path_len);
                full_path[parent_full_path_len] = '/';
                memcpy(full_path + parent_full_path_len + 1,
                       dentry->file_name_utf8,
                       dentry->file_name_utf8_len);
                full_path[full_path_len] = '\0';
        }
        FREE(dentry->full_path_utf8);
        dentry->full_path_utf8 = full_path;
        dentry->full_path_utf8_len = full_path_len;
        return 0;
oom:
        ERROR("Out of memory while calculating dentry full path");
        return WIMLIB_ERR_NOMEM;
}

static int increment_subdir_offset(struct dentry *dentry, void *subdir_offset_p)
{
        *(u64*)subdir_offset_p += dentry_correct_total_length(dentry);
        return 0;
}

static int call_calculate_subdir_offsets(struct dentry *dentry,
                                         void *subdir_offset_p)
{
        calculate_subdir_offsets(dentry, subdir_offset_p);
        return 0;
}

/*
 * Recursively calculates the subdir offsets for a directory tree.
 *
 * @dentry:  The root of the directory tree.
 * @subdir_offset_p:  The current subdirectory offset; i.e., the subdirectory
 *                    offset for @dentry.
 */
void calculate_subdir_offsets(struct dentry *dentry, u64 *subdir_offset_p)
{
        struct rb_node *node;

        dentry->subdir_offset = *subdir_offset_p;
        node = dentry->d_inode->children.rb_node;
        if (node) {
                /* Advance the subdir offset by the amount of space the children
                 * of this dentry take up. */
                for_dentry_in_rbtree(node, increment_subdir_offset, subdir_offset_p);

                /* End-of-directory dentry on disk. */
                *subdir_offset_p += 8;

                /* Recursively call calculate_subdir_offsets() on all the
                 * children. */
                for_dentry_in_rbtree(node, call_calculate_subdir_offsets, subdir_offset_p);
        } else {
                /* On disk, childless directories have a valid subdir_offset
                 * that points to an 8-byte end-of-directory dentry.  Regular
                 * files or reparse points have a subdir_offset of 0. */
                if (dentry_is_directory(dentry))
                        *subdir_offset_p += 8;
                else
                        dentry->subdir_offset = 0;
        }
}

static int compare_names(const char *name_1, u16 len_1,
                         const char *name_2, u16 len_2)
{
        int result = strncasecmp(name_1, name_2, min(len_1, len_2));
        if (result) {
                return result;
        } else {
                return (int)len_1 - (int)len_2;
        }
}

static int dentry_compare_names(const struct dentry *d1, const struct dentry *d2)
{
        return compare_names(d1->file_name_utf8, d1->file_name_utf8_len,
                             d2->file_name_utf8, d2->file_name_utf8_len);
}


static struct dentry *
get_rbtree_child_with_name(const struct rb_node *node,
                           const char *name, size_t name_len)
{
        do {
                struct dentry *child = rbnode_dentry(node);
                int result = compare_names(name, name_len,
                                           child->file_name_utf8,
                                           child->file_name_utf8_len);
                if (result < 0)
                        node = node->rb_left;
                else if (result > 0)
                        node = node->rb_right;
                else
                        return child;
        } while (node);
        return NULL;
}

/* Returns the child of @dentry that has the file name @name.
 * Returns NULL if no child has the name. */
struct dentry *get_dentry_child_with_name(const struct dentry *dentry,
                                          const char *name)
{
        struct rb_node *node = dentry->d_inode->children.rb_node;
        if (node)
                return get_rbtree_child_with_name(node, name, strlen(name));
        else
                return NULL;
}

/* Retrieves the dentry that has the UTF-8 @path relative to the dentry
 * @cur_dentry.  Returns NULL if no dentry having the path is found. */
static struct dentry *get_dentry_relative_path(struct dentry *cur_dentry,
                                               const char *path)
{
        if (*path == '\0')
                return cur_dentry;

        struct rb_node *node = cur_dentry->d_inode->children.rb_node;
        if (node) {
                struct dentry *child;
                size_t base_len;
                const char *new_path;

                new_path = path_next_part(path, &base_len);

                child = get_rbtree_child_with_name(node, path, base_len);
                if (child)
                        return get_dentry_relative_path(child, new_path);
        }
        return NULL;
}

/* Returns the dentry corresponding to the UTF-8 @path, or NULL if there is no
 * such dentry. */
struct dentry *get_dentry(WIMStruct *w, const char *path)
{
        struct dentry *root = wim_root_dentry(w);
        while (*path == '/')
                path++;
        return get_dentry_relative_path(root, path);
}

struct inode *wim_pathname_to_inode(WIMStruct *w, const char *path)
{
        struct dentry *dentry;
        dentry = get_dentry(w, path);
        if (dentry)
                return dentry->d_inode;
        else
                return NULL;
}

/* Returns the dentry that corresponds to the parent directory of @path, or NULL
 * if the dentry is not found. */
struct dentry *get_parent_dentry(WIMStruct *w, const char *path)
{
        size_t path_len = strlen(path);
        char buf[path_len + 1];

        memcpy(buf, path, path_len + 1);

        to_parent_name(buf, path_len);

        return get_dentry(w, buf);
}

/* Prints the full path of a dentry. */
int print_dentry_full_path(struct dentry *dentry, void *ignore)
{
        if (dentry->full_path_utf8)
                puts(dentry->full_path_utf8);
        return 0;
}

/* We want to be able to show the names of the file attribute flags that are
 * set. */
struct file_attr_flag {
        u32 flag;
        const char *name;
};
struct file_attr_flag file_attr_flags[] = {
        {FILE_ATTRIBUTE_READONLY,           "READONLY"},
        {FILE_ATTRIBUTE_HIDDEN,             "HIDDEN"},
        {FILE_ATTRIBUTE_SYSTEM,             "SYSTEM"},
        {FILE_ATTRIBUTE_DIRECTORY,          "DIRECTORY"},
        {FILE_ATTRIBUTE_ARCHIVE,            "ARCHIVE"},
        {FILE_ATTRIBUTE_DEVICE,             "DEVICE"},
        {FILE_ATTRIBUTE_NORMAL,             "NORMAL"},
        {FILE_ATTRIBUTE_TEMPORARY,          "TEMPORARY"},
        {FILE_ATTRIBUTE_SPARSE_FILE,        "SPARSE_FILE"},
        {FILE_ATTRIBUTE_REPARSE_POINT,      "REPARSE_POINT"},
        {FILE_ATTRIBUTE_COMPRESSED,         "COMPRESSED"},
        {FILE_ATTRIBUTE_OFFLINE,            "OFFLINE"},
        {FILE_ATTRIBUTE_NOT_CONTENT_INDEXED,"NOT_CONTENT_INDEXED"},
        {FILE_ATTRIBUTE_ENCRYPTED,          "ENCRYPTED"},
        {FILE_ATTRIBUTE_VIRTUAL,            "VIRTUAL"},
};

/* Prints a directory entry.  @lookup_table is a pointer to the lookup table, if
 * available.  If the dentry is unresolved and the lookup table is NULL, the
 * lookup table entries will not be printed.  Otherwise, they will be. */
int print_dentry(struct dentry *dentry, void *lookup_table)
{
        const u8 *hash;
        struct lookup_table_entry *lte;
        const struct inode *inode = dentry->d_inode;
        char buf[50];

        printf("[DENTRY]\n");
        printf("Length            = %"PRIu64"\n", dentry->length);
        printf("Attributes        = 0x%x\n", inode->attributes);
        for (size_t i = 0; i < ARRAY_LEN(file_attr_flags); i++)
                if (file_attr_flags[i].flag & inode->attributes)
                        printf("    FILE_ATTRIBUTE_%s is set\n",
                                file_attr_flags[i].name);
        printf("Security ID       = %d\n", inode->security_id);
        printf("Subdir offset     = %"PRIu64"\n", dentry->subdir_offset);

        wim_timestamp_to_str(inode->creation_time, buf, sizeof(buf));
        printf("Creation Time     = %s\n", buf);

        wim_timestamp_to_str(inode->last_access_time, buf, sizeof(buf));
        printf("Last Access Time  = %s\n", buf);

        wim_timestamp_to_str(inode->last_write_time, buf, sizeof(buf));
        printf("Last Write Time   = %s\n", buf);

        printf("Reparse Tag       = 0x%"PRIx32"\n", inode->reparse_tag);
        printf("Hard Link Group   = 0x%"PRIx64"\n", inode->ino);
        printf("Hard Link Group Size = %"PRIu32"\n", inode->link_count);
        printf("Number of Alternate Data Streams = %hu\n", inode->num_ads);
        printf("Filename (UTF-8)  = \"%s\"\n", dentry->file_name_utf8);
        /*printf("Filename (UTF-8) Length = %hu\n", dentry->file_name_utf8_len);*/
        printf("Short Name (UTF-16LE) = \"");
        print_string(dentry->short_name, dentry->short_name_len);
        puts("\"");
        /*printf("Short Name Length = %hu\n", dentry->short_name_len);*/
        printf("Full Path (UTF-8) = \"%s\"\n", dentry->full_path_utf8);
        lte = inode_stream_lte(dentry->d_inode, 0, lookup_table);
        if (lte) {
                print_lookup_table_entry(lte);
        } else {
                hash = inode_stream_hash(inode, 0);
                if (hash) {
                        printf("Hash              = 0x");
                        print_hash(hash);
                        putchar('\n');
                        putchar('\n');
                }
        }
        for (u16 i = 0; i < inode->num_ads; i++) {
                printf("[Alternate Stream Entry %u]\n", i);
                printf("Name = \"%s\"\n", inode->ads_entries[i].stream_name_utf8);
                printf("Name Length (UTF-16) = %u\n",
                        inode->ads_entries[i].stream_name_len);
                hash = inode_stream_hash(inode, i + 1);
                if (hash) {
                        printf("Hash              = 0x");
                        print_hash(hash);
                        putchar('\n');
                }
                print_lookup_table_entry(inode_stream_lte(inode, i + 1,
                                                          lookup_table));
        }
        return 0;
}

/* Initializations done on every `struct dentry'. */
static void dentry_common_init(struct dentry *dentry)
{
        memset(dentry, 0, sizeof(struct dentry));
        dentry->refcnt = 1;
}

static struct inode *new_timeless_inode()
{
        struct inode *inode = CALLOC(1, sizeof(struct inode));
        if (inode) {
                inode->security_id = -1;
                inode->link_count = 1;
        #ifdef WITH_FUSE
                inode->next_stream_id = 1;
                if (pthread_mutex_init(&inode->i_mutex, NULL) != 0) {
                        ERROR_WITH_ERRNO("Error initializing mutex");
                        FREE(inode);
                        return NULL;
                }
        #endif
                INIT_LIST_HEAD(&inode->dentry_list);
        }
        return inode;
}

static struct inode *new_inode()
{
        struct inode *inode = new_timeless_inode();
        if (inode) {
                u64 now = get_wim_timestamp();
                inode->creation_time = now;
                inode->last_access_time = now;
                inode->last_write_time = now;
        }
        return inode;
}

/*
 * Creates an unlinked directory entry.
 *
 * @name:  The UTF-8 filename of the new dentry.
 *
 * Returns a pointer to the new dentry, or NULL if out of memory.
 */
#ifndef WITH_FUSE
static
#endif
struct dentry *new_dentry(const char *name)
{
        struct dentry *dentry;

        dentry = MALLOC(sizeof(struct dentry));
        if (!dentry)
                goto err;

        dentry_common_init(dentry);
        if (change_dentry_name(dentry, name) != 0)
                goto err;

        dentry->parent = dentry;

        return dentry;
err:
        FREE(dentry);
        ERROR_WITH_ERRNO("Failed to create new dentry with name \"%s\"", name);
        return NULL;
}


static struct dentry *__new_dentry_with_inode(const char *name, bool timeless)
{
        struct dentry *dentry;
        dentry = new_dentry(name);
        if (dentry) {
                if (timeless)
                        dentry->d_inode = new_timeless_inode();
                else
                        dentry->d_inode = new_inode();
                if (dentry->d_inode) {
                        inode_add_dentry(dentry, dentry->d_inode);
                } else {
                        free_dentry(dentry);
                        dentry = NULL;
                }
        }
        return dentry;
}

struct dentry *new_dentry_with_timeless_inode(const char *name)
{
        return __new_dentry_with_inode(name, true);
}

struct dentry *new_dentry_with_inode(const char *name)
{
        return __new_dentry_with_inode(name, false);
}


static int init_ads_entry(struct ads_entry *ads_entry, const char *name)
{
        int ret = 0;
        memset(ads_entry, 0, sizeof(*ads_entry));
        if (name && *name)
                ret = change_ads_name(ads_entry, name);
        return ret;
}

static void destroy_ads_entry(struct ads_entry *ads_entry)
{
        FREE(ads_entry->stream_name);
        FREE(ads_entry->stream_name_utf8);
}


/* Frees an inode. */
void free_inode(struct inode *inode)
{
        if (inode) {
                if (inode->ads_entries) {
                        for (u16 i = 0; i < inode->num_ads; i++)
                                destroy_ads_entry(&inode->ads_entries[i]);
                        FREE(inode->ads_entries);
                }
        #ifdef WITH_FUSE
                wimlib_assert(inode->num_opened_fds == 0);
                FREE(inode->fds);
                pthread_mutex_destroy(&inode->i_mutex);
                if (inode->hlist.pprev)
                        hlist_safe_del(&inode->hlist);
        #endif
                FREE(inode->extracted_file);
                FREE(inode);
        }
}

/* Decrements link count on an inode and frees it if the link count reaches 0.
 * */
static void put_inode(struct inode *inode)
{
        wimlib_assert(inode->link_count != 0);
        if (--inode->link_count == 0) {
        #ifdef WITH_FUSE
                if (inode->num_opened_fds == 0)
        #endif
                {
                        free_inode(inode);
                }
        }
}

/* Frees a WIM dentry.
 *
 * The inode is freed only if its link count is decremented to 0.
 */
void free_dentry(struct dentry *dentry)
{
        FREE(dentry->file_name);
        FREE(dentry->file_name_utf8);
        FREE(dentry->short_name);
        FREE(dentry->full_path_utf8);
        if (dentry->d_inode)
                put_inode(dentry->d_inode);
        FREE(dentry);
}

void put_dentry(struct dentry *dentry)
{
        wimlib_assert(dentry->refcnt != 0);
        if (--dentry->refcnt == 0)
                free_dentry(dentry);
}

/*
 * This function is passed as an argument to for_dentry_in_tree_depth() in order
 * to free a directory tree.  __args is a pointer to a `struct free_dentry_args'.
 */
static int do_free_dentry(struct dentry *dentry, void *__lookup_table)
{
        struct lookup_table *lookup_table = __lookup_table;
        unsigned i;

        if (lookup_table) {
                struct lookup_table_entry *lte;
                struct inode *inode = dentry->d_inode;
                wimlib_assert(inode->link_count != 0);
                for (i = 0; i <= inode->num_ads; i++) {
                        lte = inode_stream_lte(inode, i, lookup_table);
                        if (lte)
                                lte_decrement_refcnt(lte, lookup_table);
                }
        }

        put_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 dentry *root, struct lookup_table *lookup_table)
{
        if (root)
                for_dentry_in_tree_depth(root, do_free_dentry, lookup_table);
}

int increment_dentry_refcnt(struct dentry *dentry, void *ignore)
{
        dentry->refcnt++;
        return 0;
}

/*
 * Links a dentry into the directory tree.
 *
 * @dentry: The dentry to link.
 * @parent: The dentry that will be the parent of @dentry.
 */
bool dentry_add_child(struct dentry * restrict parent,
                      struct dentry * restrict child)
{
        wimlib_assert(dentry_is_directory(parent));

        struct rb_root *root = &parent->d_inode->children;
        struct rb_node **new = &(root->rb_node);
        struct rb_node *rb_parent = NULL;

        while (*new) {
                struct dentry *this = rbnode_dentry(*new);
                int result = dentry_compare_names(child, this);

                rb_parent = *new;

                if (result < 0)
                        new = &((*new)->rb_left);
                else if (result > 0)
                        new = &((*new)->rb_right);
                else
                        return false;
        }
        child->parent = parent;
        rb_link_node(&child->rb_node, rb_parent, new);
        rb_insert_color(&child->rb_node, root);
        return true;
}

#ifdef WITH_FUSE
/*
 * Unlink a dentry from the directory tree.
 *
 * Note: This merely removes it from the in-memory tree structure.
 */
void unlink_dentry(struct dentry *dentry)
{
        struct dentry *parent = dentry->parent;
        if (parent == dentry)
                return;
        rb_erase(&dentry->rb_node, &parent->d_inode->children);
}
#endif

#ifdef WITH_FUSE
/* Returns the alternate data stream entry belonging to @inode that has the
 * stream name @stream_name. */
struct ads_entry *inode_get_ads_entry(struct inode *inode,
                                      const char *stream_name,
                                      u16 *idx_ret)
{
        size_t stream_name_len;
        if (!stream_name)
                return NULL;
        if (inode->num_ads) {
                u16 i = 0;
                stream_name_len = strlen(stream_name);
                do {
                        if (ads_entry_has_name(&inode->ads_entries[i],
                                               stream_name, stream_name_len))
                        {
                                if (idx_ret)
                                        *idx_ret = i;
                                return &inode->ads_entries[i];
                        }
                } while (++i != inode->num_ads);
        }
        return NULL;
}
#endif

#if defined(WITH_FUSE) || defined(WITH_NTFS_3G)
/*
 * Add an alternate stream entry to an inode and return a pointer to it, or NULL
 * if memory could not be allocated.
 */
struct ads_entry *inode_add_ads(struct inode *inode, const char *stream_name)
{
        u16 num_ads;
        struct ads_entry *ads_entries;
        struct ads_entry *new_entry;

        DEBUG("Add alternate data stream \"%s\"", stream_name);

        if (inode->num_ads >= 0xfffe) {
                ERROR("Too many alternate data streams in one inode!");
                return NULL;
        }
        num_ads = inode->num_ads + 1;
        ads_entries = REALLOC(inode->ads_entries,
                              num_ads * sizeof(inode->ads_entries[0]));
        if (!ads_entries) {
                ERROR("Failed to allocate memory for new alternate data stream");
                return NULL;
        }
        inode->ads_entries = ads_entries;

        new_entry = &inode->ads_entries[num_ads - 1];
        if (init_ads_entry(new_entry, stream_name) != 0)
                return NULL;
#ifdef WITH_FUSE
        new_entry->stream_id = inode->next_stream_id++;
#endif
        inode->num_ads = num_ads;
        return new_entry;
}
#endif

#ifdef WITH_FUSE
/* Remove an alternate data stream from the inode  */
void inode_remove_ads(struct inode *inode, u16 idx,
                      struct lookup_table *lookup_table)
{
        struct ads_entry *ads_entry;
        struct lookup_table_entry *lte;

        wimlib_assert(idx < inode->num_ads);
        wimlib_assert(inode->resolved);

        ads_entry = &inode->ads_entries[idx];

        DEBUG("Remove alternate data stream \"%s\"", ads_entry->stream_name_utf8);

        lte = ads_entry->lte;
        if (lte)
                lte_decrement_refcnt(lte, lookup_table);

        destroy_ads_entry(ads_entry);

        memcpy(&inode->ads_entries[idx],
               &inode->ads_entries[idx + 1],
               (inode->num_ads - idx - 1) * sizeof(inode->ads_entries[0]));
        inode->num_ads--;
}
#endif



/*
 * Reads the alternate data stream entries for a dentry.
 *
 * @p:  Pointer to buffer that starts with the first alternate stream entry.
 *
 * @inode:      Inode to load the alternate data streams into.
 *                      @inode->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.
 *
 * The format of the on-disk alternate stream entries is as follows:
 *
 * struct ads_entry_on_disk {
 *      u64  length;          // Length of the entry, in bytes.  This includes
 *                                  all fields (including the stream name and
 *                                  null terminator if present, AND the padding!).
 *      u64  reserved;        // Seems to be unused
 *      u8   hash[20];        // SHA1 message digest of the uncompressed stream
 *      u16  stream_name_len; // Length of the stream name, in bytes
 *      char stream_name[];   // Stream name in UTF-16LE, @stream_name_len bytes long,
 *                                  not including null terminator
 *      u16  zero;            // UTF-16 null terminator for the stream name, NOT
 *                                  included in @stream_name_len.  Based on what
 *                                  I've observed from filenames in dentries,
 *                                  this field should not exist when
 *                                  (@stream_name_len == 0), but you can't
 *                                  actually tell because of the padding anyway
 *                                  (provided that the padding is zeroed, which
 *                                  it always seems to be).
 *      char padding[];       // Padding to make the size a multiple of 8 bytes.
 * };
 *
 * In addition, the entries are 8-byte aligned.
 *
 * Return 0 on success or nonzero on failure.  On success, inode->ads_entries
 * is set to an array of `struct ads_entry's of length inode->num_ads.  On
 * failure, @inode is not modified.
 */
static int read_ads_entries(const u8 *p, struct inode *inode,
                            u64 remaining_size)
{
        u16 num_ads;
        struct ads_entry *ads_entries;
        int ret;

        num_ads = inode->num_ads;
        ads_entries = CALLOC(num_ads, sizeof(inode->ads_entries[0]));
        if (!ads_entries) {
                ERROR("Could not allocate memory for %"PRIu16" "
                      "alternate data stream entries", num_ads);
                return WIMLIB_ERR_NOMEM;
        }

        for (u16 i = 0; i < num_ads; i++) {
                struct ads_entry *cur_entry;
                u64 length;
                u64 length_no_padding;
                u64 total_length;
                size_t utf8_len;
                const u8 *p_save = p;

                cur_entry = &ads_entries[i];

        #ifdef WITH_FUSE
                ads_entries[i].stream_id = i + 1;
        #endif

                /* Read the base stream entry, excluding the stream name. */
                if (remaining_size < WIM_ADS_ENTRY_DISK_SIZE) {
                        ERROR("Stream entries go past end of metadata resource");
                        ERROR("(remaining_size = %"PRIu64")", remaining_size);
                        ret = WIMLIB_ERR_INVALID_DENTRY;
                        goto out_free_ads_entries;
                }

                p = get_u64(p, &length);
                p += 8; /* Skip the reserved field */
                p = get_bytes(p, SHA1_HASH_SIZE, (u8*)cur_entry->hash);
                p = get_u16(p, &cur_entry->stream_name_len);

                cur_entry->stream_name = NULL;
                cur_entry->stream_name_utf8 = NULL;

                /* Length including neither the null terminator nor the padding
                 * */
                length_no_padding = WIM_ADS_ENTRY_DISK_SIZE +
                                    cur_entry->stream_name_len;

                /* Length including the null terminator and the padding */
                total_length = ((length_no_padding + 2) + 7) & ~7;

                wimlib_assert(total_length == ads_entry_total_length(cur_entry));

                if (remaining_size < length_no_padding) {
                        ERROR("Stream entries go past end of metadata resource");
                        ERROR("(remaining_size = %"PRIu64" bytes, "
                              "length_no_padding = %"PRIu64" bytes)",
                              remaining_size, length_no_padding);
                        ret = WIMLIB_ERR_INVALID_DENTRY;
                        goto out_free_ads_entries;
                }

                /* The @length field in the on-disk ADS entry is expected to be
                 * equal to @total_length, which includes all of the entry and
                 * the padding that follows it to align the next ADS entry to an
                 * 8-byte boundary.  However, to be safe, we'll accept the
                 * length field as long as it's not less than the un-padded
                 * total length and not more than the padded total length. */
                if (length < length_no_padding || length > total_length) {
                        ERROR("Stream entry has unexpected length "
                              "field (length field = %"PRIu64", "
                              "unpadded total length = %"PRIu64", "
                              "padded total length = %"PRIu64")",
                              length, length_no_padding, total_length);
                        ret = WIMLIB_ERR_INVALID_DENTRY;
                        goto out_free_ads_entries;
                }

                if (cur_entry->stream_name_len) {
                        cur_entry->stream_name = MALLOC(cur_entry->stream_name_len);
                        if (!cur_entry->stream_name) {
                                ret = WIMLIB_ERR_NOMEM;
                                goto out_free_ads_entries;
                        }
                        get_bytes(p, cur_entry->stream_name_len,
                                  (u8*)cur_entry->stream_name);

                        ret = utf16_to_utf8(cur_entry->stream_name,
                                            cur_entry->stream_name_len,
                                            &cur_entry->stream_name_utf8,
                                            &utf8_len);
                        if (ret != 0)
                                goto out_free_ads_entries;
                        cur_entry->stream_name_utf8_len = utf8_len;
                }
                /* It's expected that the size of every ADS entry is a multiple
                 * of 8.  However, to be safe, I'm allowing the possibility of
                 * an ADS entry at the very end of the metadata resource ending
                 * un-aligned.  So although we still need to increment the input
                 * pointer by @total_length to reach the next ADS entry, it's
                 * possible that less than @total_length is actually remaining
                 * in the metadata resource. We should set the remaining size to
                 * 0 bytes if this happens. */
                p = p_save + total_length;
                if (remaining_size < total_length)
                        remaining_size = 0;
                else
                        remaining_size -= total_length;
        }
        inode->ads_entries = ads_entries;
#ifdef WITH_FUSE
        inode->next_stream_id = inode->num_ads + 1;
#endif
        return 0;
out_free_ads_entries:
        for (u16 i = 0; i < num_ads; i++)
                destroy_ads_entry(&ads_entries[i]);
        FREE(ads_entries);
        return ret;
}

/*
 * Reads a directory entry, including all alternate data stream entries that
 * follow it, from the WIM image's metadata resource.
 *
 * @metadata_resource:  Buffer containing the uncompressed metadata resource.
 * @metadata_resource_len:   Length of the metadata resource.
 * @offset:     Offset of this directory entry in the metadata resource.
 * @dentry:     A `struct dentry' that will be filled in by this function.
 *
 * Return 0 on success or nonzero on failure.  On failure, @dentry will have
 * been modified, but it will not be left with pointers to any allocated
 * buffers.  On success, the dentry->length field must be examined.  If zero,
 * this was a special "end of directory" dentry and not a real dentry.  If
 * nonzero, this was a real dentry.
 */
int read_dentry(const u8 metadata_resource[], u64 metadata_resource_len,
                u64 offset, struct dentry *dentry)
{
        const u8 *p;
        u64 calculated_size;
        char *file_name = NULL;
        char *file_name_utf8 = NULL;
        char *short_name = NULL;
        u16 short_name_len;
        u16 file_name_len;
        size_t file_name_utf8_len = 0;
        int ret;
        struct inode *inode = NULL;

        dentry_common_init(dentry);

        /*Make sure the dentry really fits into the metadata resource.*/
        if (offset + 8 > metadata_resource_len || offset + 8 < offset) {
                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;
        }

        /* 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. */

        p = get_u64(&metadata_resource[offset], &dentry->length);

        /* A zero length field (really a length of 8, since that's how big the
         * directory entry is...) indicates that this is the end of directory
         * dentry.  We do not read it into memory as an actual dentry, so just
         * return successfully in that case. */
        if (dentry->length == 0)
                return 0;

        /* If the dentry does not overflow the metadata resource buffer and is
         * not too short, read the rest of it (excluding the alternate data
         * streams, but including the file name and short name variable-length
         * fields) into memory. */
        if (offset + dentry->length >= metadata_resource_len
            || offset + dentry->length < offset)
        {
                ERROR("Directory entry at offset %"PRIu64" and with size "
                      "%"PRIu64" ends past the end of the metadata resource "
                      "(size %"PRIu64")",
                      offset, dentry->length, metadata_resource_len);
                return WIMLIB_ERR_INVALID_DENTRY;
        }

        if (dentry->length < WIM_DENTRY_DISK_SIZE) {
                ERROR("Directory entry has invalid length of %"PRIu64" bytes",
                      dentry->length);
                return WIMLIB_ERR_INVALID_DENTRY;
        }

        inode = new_timeless_inode();
        if (!inode)
                return WIMLIB_ERR_NOMEM;

        p = get_u32(p, &inode->attributes);
        p = get_u32(p, (u32*)&inode->security_id);
        p = get_u64(p, &dentry->subdir_offset);

        /* 2 unused fields */
        p += 2 * sizeof(u64);
        /*p = get_u64(p, &dentry->unused1);*/
        /*p = get_u64(p, &dentry->unused2);*/

        p = get_u64(p, &inode->creation_time);
        p = get_u64(p, &inode->last_access_time);
        p = get_u64(p, &inode->last_write_time);

        p = get_bytes(p, SHA1_HASH_SIZE, inode->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.  The WIM_HDR_FLAG_RP_FIX flag in the WIM header might
         * have something to do with this, but it's not documented.
         */
        if (inode->attributes & FILE_ATTRIBUTE_REPARSE_POINT) {
                /* ??? */
                p += 4;
                p = get_u32(p, &inode->reparse_tag);
                p += 4;
        } else {
                p = get_u32(p, &inode->reparse_tag);
                p = get_u64(p, &inode->ino);
        }

        /* By the way, the reparse_reserved field does not actually exist (at
         * least when the file is not a reparse point) */

        p = get_u16(p, &inode->num_ads);

        p = get_u16(p, &short_name_len);
        p = get_u16(p, &file_name_len);

        /* 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_len,
                                                            short_name_len);

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

        /* Read the filename if present.  Note: if the filename is empty, there
         * is no null terminator following it. */
        if (file_name_len) {
                file_name = MALLOC(file_name_len);
                if (!file_name) {
                        ERROR("Failed to allocate %hu bytes for dentry file name",
                              file_name_len);
                        ret = WIMLIB_ERR_NOMEM;
                        goto out_free_inode;
                }
                p = get_bytes(p, file_name_len, file_name);

                /* Convert filename to UTF-8. */
                ret = utf16_to_utf8(file_name, file_name_len, &file_name_utf8,
                                    &file_name_utf8_len);
                if (ret != 0)
                        goto out_free_file_name;
                if (*(u16*)p)
                        WARNING("Expected two zero bytes following the file name "
                                "`%s', but found non-zero bytes", file_name_utf8);
                p += 2;
        }

        /* Align the calculated size */
        calculated_size = (calculated_size + 7) & ~7;

        if (dentry->length > calculated_size) {
                /* Weird; the dentry says it's longer than it should be.  Note
                 * that the length field does NOT include the size of the
                 * alternate stream entries. */

                /* Strangely, some directory entries inexplicably have a little
                 * over 70 bytes of extra data.  The exact amount of data seems
                 * to be 72 bytes, but it is aligned on the next 8-byte
                 * boundary.  It does NOT seem to be alternate data stream
                 * entries.  Here's an example of the aligned data:
                 *
                 * 01000000 40000000 6c786bba c58ede11 b0bb0026 1870892a b6adb76f
                 * e63a3e46 8fca8653 0d2effa1 6c786bba c58ede11 b0bb0026 1870892a
                 * 00000000 00000000 00000000 00000000
                 *
                 * Here's one interpretation of how the data is laid out.
                 *
                 * struct unknown {
                 *      u32 field1; (always 0x00000001)
                 *      u32 field2; (always 0x40000000)
                 *      u8  data[48]; (???)
                 *      u64 reserved1; (always 0)
                 *      u64 reserved2; (always 0)
                 * };*/
                DEBUG("Dentry for file or directory `%s' has %zu extra "
                      "bytes of data",
                      file_name_utf8, dentry->length - calculated_size);
        }

        /* Read the short filename if present.  Note: if there is no short
         * filename, there is no null terminator following it. */
        if (short_name_len) {
                short_name = MALLOC(short_name_len);
                if (!short_name) {
                        ERROR("Failed to allocate %hu bytes for short filename",
                              short_name_len);
                        ret = WIMLIB_ERR_NOMEM;
                        goto out_free_file_name_utf8;
                }

                p = get_bytes(p, short_name_len, short_name);
                if (*(u16*)p)
                        WARNING("Expected two zero bytes following the short name of "
                                "`%s', but found non-zero bytes", file_name_utf8);
                p += 2;
        }

        /*
         * Read the alternate data streams, if present.  dentry->num_ads tells
         * us how many they are, and they will directly follow the dentry
         * on-disk.
         *
         * Note that each alternate data stream entry begins on an 8-byte
         * aligned boundary, and the alternate data stream entries are NOT
         * included in the dentry->length field for some reason.
         */
        if (inode->num_ads != 0) {

                /* Trying different lengths is just a hack to make sure we have
                 * a chance of reading the ADS entries correctly despite the
                 * poor documentation. */

                if (calculated_size != dentry->length) {
                        WARNING("Trying calculated dentry length (%"PRIu64") "
                                "instead of dentry->length field (%"PRIu64") "
                                "to read ADS entries",
                                calculated_size, dentry->length);
                }
                u64 lengths_to_try[3] = {calculated_size,
                                         (dentry->length + 7) & ~7,
                                         dentry->length};
                ret = WIMLIB_ERR_INVALID_DENTRY;
                for (size_t i = 0; i < ARRAY_LEN(lengths_to_try); i++) {
                        if (lengths_to_try[i] > metadata_resource_len - offset)
                                continue;
                        ret = read_ads_entries(&metadata_resource[offset + lengths_to_try[i]],
                                               inode,
                                               metadata_resource_len - offset - lengths_to_try[i]);
                        if (ret == 0)
                                goto out;
                }
                ERROR("Failed to read alternate data stream "
                      "entries of `%s'", dentry->file_name_utf8);
                goto out_free_short_name;
        }
out:

        /* We've read all the data for this dentry.  Set the names and their
         * lengths, and we've done. */
        dentry->d_inode            = inode;
        dentry->file_name          = file_name;
        dentry->file_name_utf8     = file_name_utf8;
        dentry->short_name         = short_name;
        dentry->file_name_len      = file_name_len;
        dentry->file_name_utf8_len = file_name_utf8_len;
        dentry->short_name_len     = short_name_len;
        return 0;
out_free_short_name:
        FREE(short_name);
out_free_file_name_utf8:
        FREE(file_name_utf8);
out_free_file_name:
        FREE(file_name);
out_free_inode:
        free_inode(inode);
        return ret;
}

/* 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_len:  The length of the uncompressed metadata resource, in
 *                          bytes.
 *
 * @dentry:     A pointer to a `struct 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.
 *
 * @return:     Zero on success, nonzero on failure.
 */
int read_dentry_tree(const u8 metadata_resource[], u64 metadata_resource_len,
                     struct dentry *dentry)
{
        u64 cur_offset = dentry->subdir_offset;
        struct dentry *child;
        struct dentry cur_child;
        int ret;

        /*
         * If @dentry has no child dentries, nothing more needs to be done for
         * this branch.  This is the case for regular files, symbolic links, and
         * *possibly* empty directories (although an empty directory may also
         * have one child dentry that is the special end-of-directory dentry)
         */
        if (cur_offset == 0)
                return 0;

        /* Find and read all the children of @dentry. */
        while (1) {

                /* Read next child of @dentry into @cur_child. */
                ret = read_dentry(metadata_resource, metadata_resource_len,
                                  cur_offset, &cur_child);
                if (ret != 0)
                        break;

                /* Check for end of directory. */
                if (cur_child.length == 0)
                        break;

                /* Not end of directory.  Allocate this child permanently and
                 * link it to the parent and previous child. */
                child = MALLOC(sizeof(struct dentry));
                if (!child) {
                        ERROR("Failed to allocate %zu bytes for new dentry",
                              sizeof(struct dentry));
                        ret = WIMLIB_ERR_NOMEM;
                        break;
                }
                memcpy(child, &cur_child, sizeof(struct dentry));
                dentry_add_child(dentry, child);
                inode_add_dentry(child, child->d_inode);

                /* If there are children of this child, call this procedure
                 * recursively. */
                if (child->subdir_offset != 0) {
                        ret = read_dentry_tree(metadata_resource,
                                               metadata_resource_len, child);
                        if (ret != 0)
                                break;
                }

                /* 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_total_length(child);
        }
        return ret;
}

/*
 * Writes a WIM dentry to an output buffer.
 *
 * @dentry:  The dentry structure.
 * @p:       The memory location to write the data to.
 * @return:  Pointer to the byte after the last byte we wrote as part of the
 *              dentry.
 */
static u8 *write_dentry(const struct dentry *dentry, u8 *p)
{
        u8 *orig_p = p;
        const u8 *hash;
        const struct inode *inode = dentry->d_inode;

        /* 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...) */
        u64 length = dentry_correct_length(dentry);

        p = put_u64(p, length);
        p = put_u32(p, inode->attributes);
        p = put_u32(p, inode->security_id);
        p = put_u64(p, dentry->subdir_offset);
        p = put_u64(p, 0); /* unused1 */
        p = put_u64(p, 0); /* unused2 */
        p = put_u64(p, inode->creation_time);
        p = put_u64(p, inode->last_access_time);
        p = put_u64(p, inode->last_write_time);
        hash = inode_stream_hash(inode, 0);
        p = put_bytes(p, SHA1_HASH_SIZE, hash);
        if (inode->attributes & FILE_ATTRIBUTE_REPARSE_POINT) {
                p = put_zeroes(p, 4);
                p = put_u32(p, inode->reparse_tag);
                p = put_zeroes(p, 4);
        } else {
                u64 link_group_id;
                p = put_u32(p, 0);
                if (inode->link_count == 1)
                        link_group_id = 0;
                else
                        link_group_id = inode->ino;
                p = put_u64(p, link_group_id);
        }
        p = put_u16(p, inode->num_ads);
        p = put_u16(p, dentry->short_name_len);
        p = put_u16(p, dentry->file_name_len);
        if (dentry->file_name_len) {
                p = put_bytes(p, dentry->file_name_len, (u8*)dentry->file_name);
                p = put_u16(p, 0); /* filename padding, 2 bytes. */
        }
        if (dentry->short_name) {
                p = put_bytes(p, dentry->short_name_len, (u8*)dentry->short_name);
                p = put_u16(p, 0); /* short name padding, 2 bytes */
        }

        /* Align to 8-byte boundary */
        wimlib_assert(length >= (p - orig_p) && length - (p - orig_p) <= 7);
        p = put_zeroes(p, length - (p - orig_p));

        /* Write the alternate data streams, if there are any.  Please see
         * read_ads_entries() for comments about the format of the on-disk
         * alternate data stream entries. */
        for (u16 i = 0; i < inode->num_ads; i++) {
                p = put_u64(p, ads_entry_total_length(&inode->ads_entries[i]));
                p = put_u64(p, 0); /* Unused */
                hash = inode_stream_hash(inode, i + 1);
                p = put_bytes(p, SHA1_HASH_SIZE, hash);
                p = put_u16(p, inode->ads_entries[i].stream_name_len);
                if (inode->ads_entries[i].stream_name_len) {
                        p = put_bytes(p, inode->ads_entries[i].stream_name_len,
                                         (u8*)inode->ads_entries[i].stream_name);
                        p = put_u16(p, 0);
                }
                p = put_zeroes(p, (8 - (p - orig_p) % 8) % 8);
        }
        wimlib_assert(p - orig_p == __dentry_total_length(dentry, length));
        return p;
}

static int write_dentry_cb(struct dentry *dentry, void *_p)
{
        u8 **p = _p;
        *p = write_dentry(dentry, *p);
        return 0;
}

static u8 *write_dentry_tree_recursive(const struct dentry *parent, u8 *p);

static int write_dentry_tree_recursive_cb(struct dentry *dentry, void *_p)
{
        u8 **p = _p;
        *p = write_dentry_tree_recursive(dentry, *p);
        return 0;
}

/* Recursive function that writes a dentry tree rooted at @parent, not including
 * @parent itself, which has already been written. */
static u8 *write_dentry_tree_recursive(const struct dentry *parent, u8 *p)
{
        /* Nothing to do if this dentry has no children. */
        if (parent->subdir_offset == 0)
                return p;

        /* Write child dentries and end-of-directory entry.
         *
         * Note: we need to write all of this dentry's children before
         * recursively writing the directory trees rooted at each of the child
         * dentries, since the on-disk dentries for a dentry's children are
         * always located at consecutive positions in the metadata resource! */
        for_dentry_in_rbtree(parent->d_inode->children.rb_node, write_dentry_cb, &p);

        /* write end of directory entry */
        p = put_u64(p, 0);

        /* Recurse on children. */
        for_dentry_in_rbtree(parent->d_inode->children.rb_node,
                             write_dentry_tree_recursive_cb, &p);
        return p;
}

/* 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(const struct dentry *root, u8 *p)
{
        DEBUG("Writing dentry tree.");
        wimlib_assert(dentry_is_root(root));

        /* If we're the root dentry, we have no parent that already
         * wrote us, so we need to write ourselves. */
        p = write_dentry(root, p);

        /* Write end of directory entry after the root dentry just to be safe;
         * however the root dentry obviously cannot have any siblings. */
        p = put_u64(p, 0);

        /* Recursively write the rest of the dentry tree. */
        return write_dentry_tree_recursive(root, p);
}