[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 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"
#include <errno.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_nbytes, u16 short_name_nbytes)
{
        u64 length = WIM_DENTRY_DISK_SIZE;
        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_unaligned(const struct wim_dentry *dentry)
{
        return __dentry_correct_length_unaligned(dentry->file_name_nbytes,
                                                 dentry->short_name_nbytes);
}

/* 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 wim_dentry *dentry)
{
        return (dentry_correct_length_unaligned(dentry) + 7) & ~7;
}

/* Return %true iff the alternate data stream entry @entry has the UTF-16LE
 * stream name @name that has length @name_nbytes bytes. */
static inline bool
ads_entry_has_name(const struct wim_ads_entry *entry,
                   const utf16lechar *name, size_t name_nbytes)
{
        return entry->stream_name_nbytes == name_nbytes &&
               memcmp(entry->stream_name, name, name_nbytes) == 0;
}

/* Duplicates a multibyte string into a UTF-16LE string and returns the string
 * and its length, in bytes, in the pointer arguments.  Frees any existing
 * string at the return location before overwriting it. */
static int
get_utf16le_name(const mbchar *name, utf16lechar **name_utf16le_ret,
                 u16 *name_utf16le_nbytes_ret)
{
        utf16lechar *name_utf16le;
        size_t name_utf16le_nbytes;
        int ret;

        ret = mbs_to_utf16le(name, strlen(name), &name_utf16le,
                             &name_utf16le_nbytes);
        if (name_utf16le_nbytes > 0xffff) {
                FREE(name_utf16le);
                ERROR("Multibyte string \"%s\" is too long!", name);
                ret = WIMLIB_ERR_INVALID_UTF8_STRING;
        }
        if (ret == 0) {
                FREE(*name_utf16le_ret);
                *name_utf16le_ret = name_utf16le;
                *name_utf16le_nbytes_ret = name_utf16le_nbytes;
        }
        return ret;
}

/* Sets the name of a WIM dentry from a multibyte string. */
int
set_dentry_name(struct wim_dentry *dentry, const mbchar *new_name)
{
        int ret;
        ret = get_utf16le_name(new_name, &dentry->file_name,
                               &dentry->file_name_nbytes);
        if (ret == 0) {
                /* Clear the short name and recalculate the dentry length */
                if (dentry->short_name_nbytes) {
                        FREE(dentry->short_name);
                        dentry->short_name = NULL;
                        dentry->short_name_nbytes = 0;
                }
                dentry->length = dentry_correct_length(dentry);
        }
        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 = WIM_ADS_ENTRY_DISK_SIZE;
        if (entry->stream_name_nbytes)
                len += entry->stream_name_nbytes + 2;
        return (len + 7) & ~7;
}


static u64
__dentry_total_length(const struct wim_dentry *dentry, u64 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;
}

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

int
for_dentry_in_rbtree(struct rb_node *root,
                     int (*visitor)(struct wim_dentry *, void *),
                     void *arg)
{
        int ret;
        struct rb_node *node = root;
        LIST_HEAD(stack);
        while (1) {
                if (node) {
                        list_add(&rbnode_dentry(node)->tmp_list, &stack);
                        node = node->rb_left;
                } else {
                        struct list_head *next;
                        struct wim_dentry *dentry;

                        next = stack.next;
                        if (next == &stack)
                                return 0;
                        dentry = container_of(next, struct wim_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 wim_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;
}

static int
for_dentry_tree_in_rbtree(struct rb_node *node,
                          int (*visitor)(struct wim_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;
}

/* 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)
{
        int ret = visitor(root, arg);
        if (ret == 0) {
                ret = for_dentry_tree_in_rbtree(root->d_inode->i_children.rb_node,
                                                visitor,
                                                arg);
        }
        return ret;
}

/* 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)
{
        int ret;
        ret = for_dentry_tree_in_rbtree_depth(root->d_inode->i_children.rb_node,
                                              visitor, arg);
        if (ret == 0)
                ret = visitor(root, arg);
        return ret;
}

/* Calculate the full path of @dentry.  The full path of its parent must have
 * already been calculated. */
int
calculate_dentry_full_path(struct wim_dentry *dentry, void *ignore)
{
        char *full_path;
        u32 full_path_nbytes;

        wimlib_assert(dentry_is_root(dentry) ||
                      dentry->parent->full_path != NULL);

        if (dentry_is_root(dentry)) {
                full_path = MALLOC(2);
                if (!full_path)
                        return WIMLIB_ERR_NOMEM;
                full_path[0] = '/';
                full_path[1] = '\0';
                full_path_nbytes = 1;
        } else {
                char *parent_full_path;
                u32 parent_full_path_nbytes;
                const struct wim_dentry *parent;
                char *name_mbs;
                size_t name_mbs_nbytes;
                int ret;

                ret = utf16le_to_mbs_nbytes(dentry->file_name,
                                            dentry->file_name_nbytes,
                                            &name_mbs_nbytes);
                if (ret)
                        return ret;
                parent = dentry->parent;
                if (dentry_is_root(parent)) {
                        parent_full_path = "";
                        parent_full_path_nbytes = 0;
                } else {
                        parent_full_path = parent->full_path;
                        parent_full_path_nbytes = parent->full_path_nbytes;
                }
                full_path_nbytes = parent_full_path_nbytes + 1 +
                                   name_mbs_nbytes;
                full_path = MALLOC(full_path_nbytes + 1);
                if (!full_path)
                        return WIMLIB_ERR_NOMEM;
                memcpy(full_path, parent_full_path, parent_full_path_nbytes);
                full_path[parent_full_path_nbytes] = '/';

                utf16le_to_mbs_buf(dentry->file_name,
                                   dentry->file_name_nbytes,
                                   &full_path[parent_full_path_nbytes + 1]);
        }
        FREE(dentry->full_path);
        dentry->full_path = full_path;
        dentry->full_path_nbytes= full_path_nbytes;
        return 0;
}

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

static int
call_calculate_subdir_offsets(struct wim_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 wim_dentry *dentry, u64 *subdir_offset_p)
{
        struct rb_node *node;

        dentry->subdir_offset = *subdir_offset_p;
        node = dentry->d_inode->i_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
dentry_compare_names(const struct wim_dentry *d1, const struct wim_dentry *d2)
{
        int result = memcmp(d1->file_name, d2->file_name,
                            min(d1->file_name_nbytes, d2->file_name_nbytes));
        if (result)
                return result;
        else
                return d1->file_name_nbytes - d2->file_name_nbytes;
}


struct wim_dentry *
get_dentry_child_with_utf16le_name(const struct wim_dentry *dentry,
                                   const utf16lechar *name)
{
        struct rb_node *node = dentry->d_inode->i_children.rb_node;
        while (node) {
                struct wim_dentry *child = rbnode_dentry(node);
                int result = dentry_compare_names(dentry, child);
                if (result < 0)
                        node = node->rb_left;
                else if (result > 0)
                        node = node->rb_right;
                else
                        return child;
        }
        return NULL;
}

/* 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 mbchar *name)
{
        utf16lechar *utf16le_name;
        size_t utf16le_name_nbytes;
        int ret;
        struct wim_dentry *child;

        ret = mbs_to_utf16le(name, strlen(name),
                             &utf16le_name, &utf16le_name_nbytes);
        if (ret) {
                child = NULL;
        } else {
                child = get_dentry_child_with_utf16le_name(dentry,
                                                           utf16le_name);
                FREE(utf16le_name);
        }
        return child;
}

/* Returns the dentry corresponding to the @path, or NULL if there is no such
 * dentry. */
struct wim_dentry *
get_dentry(WIMStruct *w, const mbchar *path)
{
        utf16lechar *path_utf16le;
        size_t path_utf16le_nbytes;
        int ret;
        struct wim_dentry *cur_dentry, *parent_dentry;
        utf16lechar *p, *pp;
        utf16lechar save;

        ret = mbs_to_utf16le(path, strlen(path), &path_utf16le,
                             &path_utf16le_nbytes);
        if (ret) {
                errno = ENOMEM;
                return NULL;
        }

        parent_dentry = wim_root_dentry(w);
        p = path_utf16le;

        while (1) {
                while (*p == '/')
                        p++;
                cur_dentry = parent_dentry;
                if (*p == '\0')
                        break;
                pp = p;
                while (*pp != '/' && *pp != '\0')
                        pp++;

                save = *pp;
                *pp = '\0';
                cur_dentry = get_dentry_child_with_utf16le_name(parent_dentry, p);
                if (cur_dentry == NULL)
                        break;
                *pp = save;
                p = pp;
        }
        FREE(path_utf16le);
        if (cur_dentry == NULL) {
                if (dentry_is_directory(parent_dentry))
                        errno = ENOENT;
                else
                        errno = ENOTDIR;
        }
        return cur_dentry;
}

struct wim_inode *
wim_pathname_to_inode(WIMStruct *w, const mbchar *path)
{
        struct wim_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 wim_dentry *get_parent_dentry(WIMStruct *w, const mbchar *path)
{
        size_t path_len = strlen(path);
        mbchar 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 wim_dentry *dentry, void *ignore)
{
        if (dentry->full_path)
                puts(dentry->full_path);
        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 wim_dentry *dentry, void *lookup_table)
{
        const u8 *hash;
        struct wim_lookup_table_entry *lte;
        const struct wim_inode *inode = dentry->d_inode;
        char buf[50];

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

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

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

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

        printf("Reparse Tag       = 0x%"PRIx32"\n", inode->i_reparse_tag);
        printf("Hard Link Group   = 0x%"PRIx64"\n", inode->i_ino);
        printf("Hard Link Group Size = %"PRIu32"\n", inode->i_nlink);
        printf("Number of Alternate Data Streams = %hu\n", inode->i_num_ads);
        wimlib_printf("Filename = \"%W\"\n", dentry->file_name);
        wimlib_printf("Short Name \"%W\"\n", dentry->short_name);
        printf("Full Path = \"%s\"\n", dentry->full_path);

        lte = inode_stream_lte(dentry->d_inode, 0, lookup_table);
        if (lte) {
                print_lookup_table_entry(lte, stdout);
        } 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->i_num_ads; i++) {
                printf("[Alternate Stream Entry %u]\n", i);
                wimlib_printf("Name = \"%W\"\n", inode->i_ads_entries[i].stream_name);
                printf("Name Length (UTF16) = %u\n",
                       inode->i_ads_entries[i].stream_name_nbytes);
                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),
                                         stdout);
        }
        return 0;
}

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

static struct wim_inode *new_timeless_inode()
{
        struct wim_inode *inode = CALLOC(1, sizeof(struct wim_inode));
        if (inode) {
                inode->i_security_id = -1;
                inode->i_nlink = 1;
        #ifdef WITH_FUSE
                inode->i_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->i_dentry);
        }
        return inode;
}

static struct wim_inode *new_inode()
{
        struct wim_inode *inode = new_timeless_inode();
        if (inode) {
                u64 now = get_wim_timestamp();
                inode->i_creation_time = now;
                inode->i_last_access_time = now;
                inode->i_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.
 */
struct wim_dentry *new_dentry(const mbchar *name)
{
        struct wim_dentry *dentry;

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

        dentry_common_init(dentry);
        if (set_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 wim_dentry *
__new_dentry_with_inode(const mbchar *name, bool timeless)
{
        struct wim_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 wim_dentry *
new_dentry_with_timeless_inode(const mbchar *name)
{
        return __new_dentry_with_inode(name, true);
}

struct wim_dentry *
new_dentry_with_inode(const mbchar *name)
{
        return __new_dentry_with_inode(name, false);
}


static int
init_ads_entry(struct wim_ads_entry *ads_entry, const mbchar *name)
{
        int ret = 0;
        memset(ads_entry, 0, sizeof(*ads_entry));
        if (name && *name) {
                ret = get_utf16le_name(name, &ads_entry->stream_name,
                                       &ads_entry->stream_name_nbytes);
        }
        return ret;
}

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

/* Frees an inode. */
void free_inode(struct wim_inode *inode)
{
        if (inode) {
                if (inode->i_ads_entries) {
                        for (u16 i = 0; i < inode->i_num_ads; i++)
                                destroy_ads_entry(&inode->i_ads_entries[i]);
                        FREE(inode->i_ads_entries);
                }
        #ifdef WITH_FUSE
                wimlib_assert(inode->i_num_opened_fds == 0);
                FREE(inode->i_fds);
                pthread_mutex_destroy(&inode->i_mutex);
                if (inode->i_hlist.pprev)
                        hlist_del(&inode->i_hlist);
        #endif
                FREE(inode->i_extracted_file);
                FREE(inode);
        }
}

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

/* 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)
{
        FREE(dentry->file_name);
        FREE(dentry->short_name);
        FREE(dentry->full_path);
        if (dentry->d_inode)
                put_inode(dentry->d_inode);
        FREE(dentry);
}

void put_dentry(struct wim_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. */
static int do_free_dentry(struct wim_dentry *dentry, void *__lookup_table)
{
        struct wim_lookup_table *lookup_table = __lookup_table;
        unsigned i;

        if (lookup_table) {
                struct wim_lookup_table_entry *lte;
                struct wim_inode *inode = dentry->d_inode;
                wimlib_assert(inode->i_nlink != 0);
                for (i = 0; i <= inode->i_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 wim_dentry *root, struct wim_lookup_table *lookup_table)
{
        if (root)
                for_dentry_in_tree_depth(root, do_free_dentry, lookup_table);
}

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

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

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

        while (*new) {
                struct wim_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;
}

/* Unlink a WIM dentry from the directory entry tree. */
void
unlink_dentry(struct wim_dentry *dentry)
{
        struct wim_dentry *parent = dentry->parent;
        if (parent == dentry)
                return;
        rb_erase(&dentry->rb_node, &parent->d_inode->i_children);
}

/*
 * Returns the alternate data stream entry belonging to @inode that has the
 * stream name @stream_name.
 */
struct wim_ads_entry *
inode_get_ads_entry(struct wim_inode *inode, const mbchar *stream_name,
                    u16 *idx_ret)
{
        if (inode->i_num_ads == 0) {
                return NULL;
        } else {
                int ret;
                utf16lechar *stream_name_utf16le;
                size_t stream_name_utf16le_nbytes;
                u16 i;
                struct wim_ads_entry *result;

                ret = mbs_to_utf16le(stream_name, strlen(stream_name),
                                     &stream_name_utf16le,
                                     &stream_name_utf16le_nbytes);
                if (ret)
                        return NULL;

                i = 0;
                result = NULL;
                do {
                        if (ads_entry_has_name(&inode->i_ads_entries[i],
                                               stream_name_utf16le,
                                               stream_name_utf16le_nbytes))
                        {
                                if (idx_ret)
                                        *idx_ret = i;
                                result = &inode->i_ads_entries[i];
                                break;
                        }
                } while (++i != inode->i_num_ads);
                FREE(stream_name_utf16le);
                return result;
        }
}

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

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

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

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

int
inode_add_ads_with_data(struct wim_inode *inode, const mbchar *name,
                        const void *value, size_t size,
                        struct wim_lookup_table *lookup_table)
{
        int ret = WIMLIB_ERR_NOMEM;
        struct wim_ads_entry *new_ads_entry;
        struct wim_lookup_table_entry *existing_lte;
        struct wim_lookup_table_entry *lte;
        u8 value_hash[SHA1_HASH_SIZE];

        wimlib_assert(inode->i_resolved);
        new_ads_entry = inode_add_ads(inode, name);
        if (!new_ads_entry)
                goto out;
        sha1_buffer((const u8*)value, size, value_hash);
        existing_lte = __lookup_resource(lookup_table, value_hash);
        if (existing_lte) {
                lte = existing_lte;
                lte->refcnt++;
        } else {
                u8 *value_copy;
                lte = new_lookup_table_entry();
                if (!lte)
                        goto out_free_ads_entry;
                value_copy = MALLOC(size);
                if (!value_copy) {
                        FREE(lte);
                        goto out_free_ads_entry;
                }
                memcpy(value_copy, value, size);
                lte->resource_location            = RESOURCE_IN_ATTACHED_BUFFER;
                lte->attached_buffer              = value_copy;
                lte->resource_entry.original_size = size;
                lte->resource_entry.size          = size;
                lte->resource_entry.flags         = 0;
                copy_hash(lte->hash, value_hash);
                lookup_table_insert(lookup_table, lte);
        }
        new_ads_entry->lte = lte;
        ret = 0;
        goto out;
out_free_ads_entry:
        inode_remove_ads(inode, new_ads_entry - inode->i_ads_entries,
                         lookup_table);
out:
        return ret;
}

/* Remove an alternate data stream from a WIM inode  */
void
inode_remove_ads(struct wim_inode *inode, u16 idx,
                 struct wim_lookup_table *lookup_table)
{
        struct wim_ads_entry *ads_entry;
        struct wim_lookup_table_entry *lte;

        wimlib_assert(idx < inode->i_num_ads);
        wimlib_assert(inode->i_resolved);

        ads_entry = &inode->i_ads_entries[idx];

        DEBUG("Remove alternate data stream \"%W\"", ads_entry->stream_name);

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

        destroy_ads_entry(ads_entry);

        memmove(&inode->i_ads_entries[idx],
                &inode->i_ads_entries[idx + 1],
                (inode->i_num_ads - idx - 1) * sizeof(inode->i_ads_entries[0]));
        inode->i_num_ads--;
}

#ifndef __WIN32__
int
inode_get_unix_data(const struct wim_inode *inode,
                    struct wimlib_unix_data *unix_data,
                    u16 *stream_idx_ret)
{
        const struct wim_ads_entry *ads_entry;
        const struct wim_lookup_table_entry *lte;
        size_t size;
        int ret;

        wimlib_assert(inode->i_resolved);

        ads_entry = inode_get_ads_entry((struct wim_inode*)inode,
                                        WIMLIB_UNIX_DATA_TAG, NULL);
        if (!ads_entry)
                return NO_UNIX_DATA;

        if (stream_idx_ret)
                *stream_idx_ret = ads_entry - inode->i_ads_entries;

        lte = ads_entry->lte;
        if (!lte)
                return NO_UNIX_DATA;

        size = wim_resource_size(lte);
        if (size != sizeof(struct wimlib_unix_data))
                return BAD_UNIX_DATA;

        ret = read_full_wim_resource(lte, (u8*)unix_data, 0);
        if (ret)
                return ret;

        if (unix_data->version != 0)
                return BAD_UNIX_DATA;
        return 0;
}

int
inode_set_unix_data(struct wim_inode *inode, uid_t uid, gid_t gid, mode_t mode,
                    struct wim_lookup_table *lookup_table, int which)
{
        struct wimlib_unix_data unix_data;
        int ret;
        bool have_good_unix_data = false;
        bool have_unix_data = false;
        u16 stream_idx;

        if (!(which & UNIX_DATA_CREATE)) {
                ret = inode_get_unix_data(inode, &unix_data, &stream_idx);
                if (ret == 0 || ret == BAD_UNIX_DATA || ret > 0)
                        have_unix_data = true;
                if (ret == 0)
                        have_good_unix_data = true;
        }
        unix_data.version = 0;
        if (which & UNIX_DATA_UID || !have_good_unix_data)
                unix_data.uid = uid;
        if (which & UNIX_DATA_GID || !have_good_unix_data)
                unix_data.gid = gid;
        if (which & UNIX_DATA_MODE || !have_good_unix_data)
                unix_data.mode = mode;
        ret = inode_add_ads_with_data(inode, WIMLIB_UNIX_DATA_TAG,
                                      (const u8*)&unix_data,
                                      sizeof(struct wimlib_unix_data),
                                      lookup_table);
        if (ret == 0 && have_unix_data)
                inode_remove_ads(inode, stream_idx, lookup_table);
        return ret;
}
#endif /* !__WIN32__ */

/*
 * Reads the alternate data stream entries of a WIM dentry.
 *
 * @p:  Pointer to buffer that starts with the first alternate stream entry.
 *
 * @inode:      Inode to load the alternate data streams into.
 *                      @inode->i_num_ads must have been set to the number of
 *                      alternate data streams that are expected.
 *
 * @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 wim_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->i_ads_entries
 * is set to an array of `struct wim_ads_entry's of length inode->i_num_ads.  On
 * failure, @inode is not modified.
 */
static int
read_ads_entries(const u8 *p, struct wim_inode *inode, u64 remaining_size)
{
        u16 num_ads;
        struct wim_ads_entry *ads_entries;
        int ret;

        num_ads = inode->i_num_ads;
        ads_entries = CALLOC(num_ads, sizeof(inode->i_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 wim_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_nbytes);

                cur_entry->stream_name = NULL;

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

                /* 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_nbytes) {
                        cur_entry->stream_name = MALLOC((size_t)
                                                        cur_entry->stream_name_nbytes + 2);
                        if (!cur_entry->stream_name) {
                                ret = WIMLIB_ERR_NOMEM;
                                goto out_free_ads_entries;
                        }
                        get_bytes(p, cur_entry->stream_name_nbytes,
                                  cur_entry->stream_name);
                        cur_entry->stream_name[cur_entry->stream_name_nbytes / 2] = 0;
                }
                /* 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->i_ads_entries = ads_entries;
#ifdef WITH_FUSE
        inode->i_next_stream_id = inode->i_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 WIM 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 wim_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 wim_dentry *dentry)
{
        const u8 *p;
        u64 calculated_size;
        utf16lechar *file_name = NULL;
        utf16lechar *short_name = NULL;
        u16 short_name_nbytes;
        u16 file_name_nbytes;
        int ret;
        struct wim_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->i_attributes);
        p = get_u32(p, (u32*)&inode->i_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->i_creation_time);
        p = get_u64(p, &inode->i_last_access_time);
        p = get_u64(p, &inode->i_last_write_time);

        p = get_bytes(p, SHA1_HASH_SIZE, inode->i_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->i_attributes & FILE_ATTRIBUTE_REPARSE_POINT) {
                /* ??? */
                p += 4;
                p = get_u32(p, &inode->i_reparse_tag);
                p += 4;
        } else {
                p = get_u32(p, &inode->i_reparse_tag);
                p = get_u64(p, &inode->i_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->i_num_ads);

        p = get_u16(p, &short_name_nbytes);
        p = get_u16(p, &file_name_nbytes);

        /* 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 (dentry->length < calculated_size) {
                ERROR("Unexpected end of directory entry! (Expected "
                      "at least %"PRIu64" bytes, got %"PRIu64" bytes. "
                      "short_name_nbytes = %hu, file_name_nbytes = %hu)",
                      calculated_size, dentry->length,
                      short_name_nbytes, file_name_nbytes);
                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_nbytes) {
                file_name = MALLOC((size_t)file_name_nbytes + 2);
                if (!file_name) {
                        ERROR("Failed to allocate %zu bytes for dentry file name",
                              (size_t)file_name_nbytes + 2);
                        ret = WIMLIB_ERR_NOMEM;
                        goto out_free_inode;
                }
                p = get_bytes(p, (size_t)file_name_nbytes + 2, file_name);
                if (file_name[file_name_nbytes / 2] != 0) {
                        file_name[file_name_nbytes / 2] = 0;
                        WARNING("File name in WIM dentry \"%W\" is not "
                                "null-terminated!", file_name);
                }
        }

        /* 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 %"PRIu64" 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_nbytes) {
                short_name = MALLOC((size_t)short_name_nbytes + 2);
                if (!short_name) {
                        ERROR("Failed to allocate %zu bytes for dentry short name",
                              (size_t)short_name_nbytes + 2);
                        ret = WIMLIB_ERR_NOMEM;
                        goto out_free_file_name;
                }
                p = get_bytes(p, (size_t)short_name_nbytes + 2, short_name);
                if (short_name[short_name_nbytes / 2] != 0) {
                        short_name[short_name_nbytes / 2] = 0;
                        WARNING("Short name in WIM dentry \"%W\" is not "
                                "null-terminated!", file_name);
                }
        }

        /*
         * 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->i_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 WIM dentry \"%W\"", file_name);
                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->short_name        = short_name;
        dentry->file_name_nbytes  = file_name_nbytes;
        dentry->short_name_nbytes = short_name_nbytes;
        return 0;
out_free_short_name:
        FREE(short_name);
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 wim_dentry' that is the root of the directory
 *              tree and has already been read from the metadata resource.  It
 *              does not need to be the real root because this procedure is
 *              called recursively.
 *
 * Returns zero on success; nonzero on failure.
 */
int
read_dentry_tree(const u8 metadata_resource[], u64 metadata_resource_len,
                 struct wim_dentry *dentry)
{
        u64 cur_offset = dentry->subdir_offset;
        struct wim_dentry *child;
        struct wim_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 wim_dentry));
                if (!child) {
                        ERROR("Failed to allocate %zu bytes for new dentry",
                              sizeof(struct wim_dentry));
                        ret = WIMLIB_ERR_NOMEM;
                        break;
                }
                memcpy(child, &cur_child, sizeof(struct wim_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 wim_dentry *dentry, u8 *p)
{
        u8 *orig_p = p;
        const u8 *hash;
        const struct wim_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->i_attributes);
        p = put_u32(p, inode->i_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->i_creation_time);
        p = put_u64(p, inode->i_last_access_time);
        p = put_u64(p, inode->i_last_write_time);
        hash = inode_stream_hash(inode, 0);
        p = put_bytes(p, SHA1_HASH_SIZE, hash);
        if (inode->i_attributes & FILE_ATTRIBUTE_REPARSE_POINT) {
                p = put_zeroes(p, 4);
                p = put_u32(p, inode->i_reparse_tag);
                p = put_zeroes(p, 4);
        } else {
                u64 link_group_id;
                p = put_u32(p, 0);
                if (inode->i_nlink == 1)
                        link_group_id = 0;
                else
                        link_group_id = inode->i_ino;
                p = put_u64(p, link_group_id);
        }
        p = put_u16(p, inode->i_num_ads);
        p = put_u16(p, dentry->short_name_nbytes);
        p = put_u16(p, dentry->file_name_nbytes);
        if (dentry->file_name_nbytes) {
                p = put_bytes(p, dentry->file_name_nbytes + 2,
                              dentry->file_name);
        }
        if (dentry->short_name_nbytes) {
                p = put_bytes(p, dentry->short_name_nbytes + 2,
                              dentry->short_name);
        }

        /* 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->i_num_ads; i++) {
                p = put_u64(p, ads_entry_total_length(&inode->i_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->i_ads_entries[i].stream_name_nbytes);
                if (inode->i_ads_entries[i].stream_name_nbytes) {
                        p = put_bytes(p,
                                      inode->i_ads_entries[i].stream_name_nbytes + 2,
                                      inode->i_ads_entries[i].stream_name);
                }
                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 wim_dentry *dentry, void *_p)
{
        u8 **p = _p;
        *p = write_dentry(dentry, *p);
        return 0;
}

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

static int
write_dentry_tree_recursive_cb(struct wim_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 wim_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_child(parent, write_dentry_cb, &p);

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

        /* Recurse on children. */
        for_dentry_child(parent, 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 wim_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);
}