ntfs-3g/libntfs/dir.c

/*
 * dir.c - Directory handling code. Part of the Linux-NTFS project.
 *
 * Copyright (c) 2002-2003 Anton Altaparmakov
 *
 * This program/include file 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 2 of the License, or
 * (at your option) any later version.
 *
 * This program/include file 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 this program (in the main directory of the Linux-NTFS
 * distribution in the file COPYING); if not, write to the Free Software
 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <stdlib.h>
#include <errno.h>
#include <string.h>

#include "types.h"
#include "debug.h"
#include "attrib.h"
#include "inode.h"
#include "dir.h"
#include "volume.h"

/*
 * The little endian Unicode string "$I30" as a global constant.
 */
uchar_t I30[5] = { const_cpu_to_le16('$'), const_cpu_to_le16('I'),
		   const_cpu_to_le16('3'), const_cpu_to_le16('0'),
		   const_cpu_to_le16('\0') };

/**
 * ntfs_inode_lookup_by_name - find an inode in a directory given its name
 * @dir_ni:	ntfs inode of the directory in which to search for the name
 * @uname:	Unicode name for which to search in the directory
 * @uname_len:	length of the name @uname in Unicode characters
 *
 * Look for an inode with name @uname in the directory with inode @dir_ni.
 * ntfs_inode_lookup_by_name() walks the contents of the directory looking for
 * the Unicode name. If the name is found in the directory, the corresponding
 * inode number (>= 0) is returned as a mft reference in cpu format, i.e. it
 * is a 64-bit number containing the sequence number.
 *
 * On error, return -1 with errno set to the error code. If the inode is is not
 * found errno is ENOENT.
 *
 * Note, @uname_len does not include the (optional) terminating NULL character.
 *
 * Note, we look for a case sensitive match first but we also look for a case
 * insensitive match at the same time. If we find a case insensitive match, we
 * save that for the case that we don't find an exact match, where we return
 * the mft reference of the case insensitive match.
 *
 * If the volume is mounted with the case sensitive flag set, then we only
 * allow exact matches.
 */
u64 ntfs_inode_lookup_by_name(ntfs_inode *dir_ni, const uchar_t *uname,
		const int uname_len)
{
	VCN vcn;
	u64 mref = 0;
	s64 br;
	ntfs_volume *vol = dir_ni->vol;
	ntfs_attr_search_ctx *ctx;
	INDEX_ROOT *ir;
	INDEX_ENTRY *ie;
	INDEX_ALLOCATION *ia;
	u8 *index_end;
	ntfs_attr *ia_na;
	int eo, rc;
	u32 index_block_size, index_vcn_size;
	u8 index_vcn_size_bits;

	if (!dir_ni || !dir_ni->mrec || !uname || uname_len <= 0) {
		errno = EINVAL;
		return -1;
	}

	ctx = ntfs_attr_get_search_ctx(dir_ni, NULL);
	if (!ctx)
		return -1;

	/* Find the index root attribute in the mft record. */
	if (ntfs_attr_lookup(AT_INDEX_ROOT, I30, 4, CASE_SENSITIVE, 0, NULL,
			0, ctx)) {
		Dprintf("Index root attribute missing in directory inode "
				"0x%llx: %s\n",
				(unsigned long long)dir_ni->mft_no,
				strerror(errno));
		goto put_err_out;
	}
	/* Get to the index root value. */
	ir = (INDEX_ROOT*)((u8*)ctx->attr +
			le16_to_cpu(ctx->attr->value_offset));
	index_block_size = le32_to_cpu(ir->index_block_size);
	if (index_block_size < NTFS_SECTOR_SIZE ||
			index_block_size & (index_block_size - 1)) {
		Dprintf("Index block size %u is invalid.\n", index_block_size);
		goto put_err_out;
	}
	index_end = (u8*)&ir->index + le32_to_cpu(ir->index.index_length);
	/* The first index entry. */
	ie = (INDEX_ENTRY*)((u8*)&ir->index +
			le32_to_cpu(ir->index.entries_offset));
	/*
	 * Loop until we exceed valid memory (corruption case) or until we
	 * reach the last entry.
	 */
	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
		/* Bounds checks. */
		if ((u8*)ie < (u8*)ctx->mrec || (u8*)ie +
				sizeof(INDEX_ENTRY_HEADER) > index_end ||
				(u8*)ie + le16_to_cpu(ie->key_length) >
				index_end)
			goto put_err_out;
		/*
		 * The last entry cannot contain a name. It can however contain
		 * a pointer to a child node in the B+tree so we just break out.
		 */
		if (ie->flags & INDEX_ENTRY_END)
			break;
		/*
		 * We perform a case sensitive comparison and if that matches
		 * we are done and return the mft reference of the inode (i.e.
		 * the inode number together with the sequence number for
		 * consistency checking). We convert it to cpu format before
		 * returning.
		 */
		if (ntfs_names_are_equal(uname, uname_len,
				(uchar_t*)&ie->key.file_name.file_name,
				ie->key.file_name.file_name_length,
				CASE_SENSITIVE, vol->upcase, vol->upcase_len)) {
found_it:
			/*
			 * We have a perfect match, so we don't need to care
			 * about having matched imperfectly before.
			 */
			mref = le64_to_cpu(ie->indexed_file);
			ntfs_attr_put_search_ctx(ctx);
			return mref;
		}
		/*
		 * For a case insensitive mount, we also perform a case
		 * insensitive comparison (provided the file name is not in the
		 * POSIX namespace). If the comparison matches, we cache the
		 * mft reference in mref.
		 */
		if (!NVolCaseSensitive(vol) &&
				ie->key.file_name.file_name_type &&
				ntfs_names_are_equal(uname, uname_len,
				(uchar_t*)&ie->key.file_name.file_name,
				ie->key.file_name.file_name_length,
				IGNORE_CASE, vol->upcase, vol->upcase_len)) {
			/* Only one case insensitive matching name allowed. */
			if (mref) {
				Dputs("Found already cached mft reference in "
						"phase 1. Please run chkdsk "
						"and if that doesn't find any "
						"errors please report you saw "
						"this message to "
						"linux-ntfs-dev@lists.sf.net.");
				goto put_err_out;
			}
			mref = le64_to_cpu(ie->indexed_file);
		}
		/*
		 * Not a perfect match, need to do full blown collation so we
		 * know which way in the B+tree we have to go.
		 */
		rc = ntfs_names_collate(uname, uname_len,
				(uchar_t*)&ie->key.file_name.file_name,
				ie->key.file_name.file_name_length, 1,
				IGNORE_CASE, vol->upcase, vol->upcase_len);
		/*
		 * If uname collates before the name of the current entry, there
		 * is definitely no such name in this index but we might need to
		 * descend into the B+tree so we just break out of the loop.
		 */
		if (rc == -1)
			break;
		/* The names are not equal, continue the search. */
		if (rc)
			continue;
		/*
		 * Names match with case insensitive comparison, now try the
		 * case sensitive comparison, which is required for proper
		 * collation.
		 */
		rc = ntfs_names_collate(uname, uname_len,
				(uchar_t*)&ie->key.file_name.file_name,
				ie->key.file_name.file_name_length, 1,
				CASE_SENSITIVE, vol->upcase, vol->upcase_len);
		if (rc == -1)
			break;
		if (rc)
			continue;
		/*
		 * Perfect match, this will never happen as the
		 * ntfs_are_names_equal() call will have gotten a match but we
		 * still treat it correctly.
		 */
		goto found_it;
	}
	/*
	 * We have finished with this index without success. Check for the
	 * presence of a child node and if not present return error code
	 * ENOENT, unless we have got the mft reference of a matching name
	 * cached in mref in which case return mref.
	 */
	if (!(ie->flags & INDEX_ENTRY_NODE)) {
		ntfs_attr_put_search_ctx(ctx);
		if (mref)
			return mref;
		Dputs("Entry not found.");
		errno = ENOENT;
		return -1;
	} /* Child node present, descend into it. */

	/* Open the index allocation attribute. */
	ia_na = ntfs_attr_open(dir_ni, AT_INDEX_ALLOCATION, I30, 4);
	if (!ia_na) {
		Dprintf("Failed to open index allocation attribute. Directory "
				"inode 0x%llx is corrupt or driver bug: %s\n",
				(unsigned long long)dir_ni->mft_no,
				strerror(errno));
		goto put_err_out;
	}

	/* Allocate a buffer for the current index block. */
	ia = (INDEX_ALLOCATION*)malloc(index_block_size);
	if (!ia) {
		Dperror("Failed to allocate buffer for index block");
		ntfs_attr_close(ia_na);
		goto put_err_out;
	}

	/* Determine the size of a vcn in the directory index. */
	if (vol->cluster_size <= index_block_size) {
		index_vcn_size = vol->cluster_size;
		index_vcn_size_bits = vol->cluster_size_bits;
	} else {
		index_vcn_size = vol->sector_size;
		index_vcn_size_bits = vol->sector_size_bits;
	}

	/* Get the starting vcn of the index_block holding the child node. */
	vcn = sle64_to_cpup((u8*)ie + le16_to_cpu(ie->length) - 8);

descend_into_child_node:

	/* Read the index block starting at vcn. */
	br = ntfs_attr_mst_pread(ia_na, vcn << index_vcn_size_bits, 1,
			index_block_size, ia);
	if (br != 1) {
		if (br != -1)
			errno = EIO;
		Dprintf("Failed to read vcn 0x%llx: %s\n", vcn, strerror(errno));
		goto close_err_out;
	}

	if (sle64_to_cpu(ia->index_block_vcn) != vcn) {
		Dprintf("Actual VCN (0x%llx) of index buffer is different from "
				"expected VCN (0x%llx).\n",
				(long long)sle64_to_cpu(ia->index_block_vcn),
				(long long)vcn);
		errno = EIO;
		goto close_err_out;
	}
	if (le32_to_cpu(ia->index.allocated_size) + 0x18 != index_block_size) {
		Dprintf("Index buffer (VCN 0x%llx) of directory inode 0x%llx "
				"has a size (%u) differing from the directory "
				"specified size (%u).\n", (long long)vcn,
				(unsigned long long)dir_ni->mft_no,
				le32_to_cpu(ia->index.allocated_size) + 0x18,
				index_block_size);
		errno = EIO;
		goto close_err_out;
	}
	index_end = (u8*)&ia->index + le32_to_cpu(ia->index.index_length);
	if (index_end > (u8*)ia + index_block_size) {
		Dprintf("Size of index buffer (VCN 0x%llx) of directory inode "
				"0x%llx exceeds maximum size.\n", (long long)vcn,
				(unsigned long long)dir_ni->mft_no);
		errno = EIO;
		goto close_err_out;
	}

	/* The first index entry. */
	ie = (INDEX_ENTRY*)((u8*)&ia->index +
			le32_to_cpu(ia->index.entries_offset));
	/*
	 * Iterate similar to above big loop but applied to index buffer, thus
	 * loop until we exceed valid memory (corruption case) or until we
	 * reach the last entry.
	 */
	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
		/* Bounds check. */
		if ((u8*)ie < (u8*)ia || (u8*)ie +
				sizeof(INDEX_ENTRY_HEADER) > index_end ||
				(u8*)ie + le16_to_cpu(ie->key_length) >
				index_end) {
			Dprintf("Index entry out of bounds in directory inode "
					"0x%llx.\n",
					(unsigned long long)dir_ni->mft_no);
			errno = EIO;
			goto close_err_out;
		}
		/*
		 * The last entry cannot contain a name. It can however contain
		 * a pointer to a child node in the B+tree so we just break out.
		 */
		if (ie->flags & INDEX_ENTRY_END)
			break;
		/*
		 * We perform a case sensitive comparison and if that matches
		 * we are done and return the mft reference of the inode (i.e.
		 * the inode number together with the sequence number for
		 * consistency checking). We convert it to cpu format before
		 * returning.
		 */
		if (ntfs_names_are_equal(uname, uname_len,
				(uchar_t*)&ie->key.file_name.file_name,
				ie->key.file_name.file_name_length,
				CASE_SENSITIVE, vol->upcase, vol->upcase_len)) {
found_it2:
			/*
			 * We have a perfect match, so we don't need to care
			 * about having matched imperfectly before.
			 */
			mref = le64_to_cpu(ie->indexed_file);
			free(ia);
			ntfs_attr_close(ia_na);
			ntfs_attr_put_search_ctx(ctx);
			return mref;
		}
		/*
		 * For a case insensitive mount, we also perform a case
		 * insensitive comparison (provided the file name is not in the
		 * POSIX namespace). If the comparison matches, we cache the
		 * mft reference in mref.
		 */
		if (!NVolCaseSensitive(vol) &&
				ie->key.file_name.file_name_type &&
				ntfs_names_are_equal(uname, uname_len,
				(uchar_t*)&ie->key.file_name.file_name,
				ie->key.file_name.file_name_length,
				IGNORE_CASE, vol->upcase, vol->upcase_len)) {
			/* Only one case insensitive matching name allowed. */
			if (mref) {
				Dputs("Found already cached mft reference in "
						"phase 2. Please run chkdsk "
						"and if that doesn't find any "
						"errors please report you saw "
						"this message to "
						"linux-ntfs-dev@lists.sf.net.");
				goto close_err_out;
			}
			mref = le64_to_cpu(ie->indexed_file);
		}
		/*
		 * Not a perfect match, need to do full blown collation so we
		 * know which way in the B+tree we have to go.
		 */
		rc = ntfs_names_collate(uname, uname_len,
				(uchar_t*)&ie->key.file_name.file_name,
				ie->key.file_name.file_name_length, 1,
				IGNORE_CASE, vol->upcase, vol->upcase_len);
		/*
		 * If uname collates before the name of the current entry, there
		 * is definitely no such name in this index but we might need to
		 * descend into the B+tree so we just break out of the loop.
		 */
		if (rc == -1)
			break;
		/* The names are not equal, continue the search. */
		if (rc)
			continue;
		/*
		 * Names match with case insensitive comparison, now try the
		 * case sensitive comparison, which is required for proper
		 * collation.
		 */
		rc = ntfs_names_collate(uname, uname_len,
				(uchar_t*)&ie->key.file_name.file_name,
				ie->key.file_name.file_name_length, 1,
				CASE_SENSITIVE, vol->upcase, vol->upcase_len);
		if (rc == -1)
			break;
		if (rc)
			continue;
		/*
		 * Perfect match, this will never happen as the
		 * ntfs_are_names_equal() call will have gotten a match but we
		 * still treat it correctly.
		 */
		goto found_it2;
	}
	/*
	 * We have finished with this index buffer without success. Check for
	 * the presence of a child node.
	 */
	if (ie->flags & INDEX_ENTRY_NODE) {
		if ((ia->index.flags & NODE_MASK) == LEAF_NODE) {
			Dprintf("Index entry with child node found in a leaf "
					"node in directory inode 0x%llx.\n",
					(unsigned long long)dir_ni->mft_no);
			errno = EIO;
			goto close_err_out;
		}
		/* Child node present, descend into it. */
		vcn = sle64_to_cpup((u8*)ie + le16_to_cpu(ie->length) - 8);
		if (vcn >= 0)
			goto descend_into_child_node;
		Dprintf("Negative child node vcn in directory inode 0x%llx.\n",
				(unsigned long long)dir_ni->mft_no);
		errno = EIO;
		goto close_err_out;
	}
	free(ia);
	ntfs_attr_close(ia_na);
	ntfs_attr_put_search_ctx(ctx);
	/*
	 * No child node present, return error code ENOENT, unless we have got
	 * the mft reference of a matching name cached in mref in which case
	 * return mref.
	 */
	if (mref)
		return mref;
	Dputs("Entry not found.");
	errno = ENOENT;
	return -1;
put_err_out:
	eo = EIO;
	Dputs("Corrupt directory. Aborting lookup.");
eo_put_err_out:
	ntfs_attr_put_search_ctx(ctx);
	errno = eo;
	return -1;
close_err_out:
	eo = errno;
	free(ia);
	ntfs_attr_close(ia_na);
	goto eo_put_err_out;
}

/*
 * The little endian Unicode string ".." for ntfs_readdir().
 */
static const uchar_t dotdot[3] = { const_cpu_to_le16('.'),
				   const_cpu_to_le16('.'),
				   const_cpu_to_le16('\0') };

/*
 * More helpers for ntfs_readdir().
 */
typedef union {
	INDEX_ROOT *ir;
	INDEX_ALLOCATION *ia;
} index_union __attribute__ ((__transparent_union__));

typedef enum {
	INDEX_TYPE_ROOT,	/* index root */
	INDEX_TYPE_ALLOCATION,	/* index allocation */
} INDEX_TYPE;

/**
 * Internal:
 *
 * ntfs_filldir - ntfs specific filldir method
 * @dir_ni:	ntfs inode of current directory
 * @pos:	current position in directory
 * @ivcn_bits:	log(2) of index vcn size
 * @index_type:	specifies whether @iu is an index root or an index allocation
 * @iu:		index root or index block to which @ie belongs
 * @ie:		current index entry
 * @dirent:	context for filldir callback supplied by the caller
 * @filldir:	filldir callback supplied by the caller
 *
 * Pass information specifying the current directory entry @ie to the @filldir
 * callback.
 */
static inline int ntfs_filldir(ntfs_inode *dir_ni, s64 *pos, u8 ivcn_bits,
		const INDEX_TYPE index_type, index_union iu, INDEX_ENTRY *ie,
		void *dirent, ntfs_filldir_t filldir)
{
	FILE_NAME_ATTR *fn = &ie->key.file_name;
	unsigned dt_type;

	/* Advance the position even if going to skip the entry. */
	if (index_type == INDEX_TYPE_ALLOCATION)
		*pos = (u8*)ie - (u8*)iu.ia + (sle64_to_cpu(
				iu.ia->index_block_vcn) << ivcn_bits) +
				dir_ni->vol->mft_record_size;
	else /* if (index_type == INDEX_TYPE_ROOT) */
		*pos = (u8*)ie - (u8*)iu.ir;
	/* Skip root directory self reference entry. */
	if (MREF_LE(ie->indexed_file) == FILE_root)
		return 0;
	if (ie->key.file_name.file_attributes &
			FILE_ATTR_DUP_FILE_NAME_INDEX_PRESENT)
		dt_type = NTFS_DT_DIR;
	else
		dt_type = NTFS_DT_REG;
	return filldir(dirent, fn->file_name, fn->file_name_length,
			fn->file_name_type, *pos,
			le64_to_cpu(ie->indexed_file), dt_type);
}

/**
 * Internal:
 *
 * ntfs_mft_get_parent_ref - find mft reference of parent directory of an inode
 * @ni:		ntfs inode whose parent directory to find
 *
 * Find the parent directory of the ntfs inode @ni. To do this, find the first
 * file name attribute in the mft record of @ni and return the parent mft
 * reference from that.
 *
 * Note this only makes sense for directories, since files can be hard linked
 * from multiple directories and there is no way for us to tell which one is
 * being looked for.
 *
 * Technically directories can have hard links, too, but we consider that as
 * illegal as Linux/UNIX do not support directory hard links.
 *
 * Return the mft reference of the parent directory on success or -1 on error
 * with errno set to the error code.
 */
static MFT_REF ntfs_mft_get_parent_ref(ntfs_inode *ni)
{
	MFT_REF mref;
	ntfs_attr_search_ctx *ctx;
	FILE_NAME_ATTR *fn;
	int eo;

	if (!ni) {
		errno = EINVAL;
		return ERR_MREF(-1);
	}

	ctx = ntfs_attr_get_search_ctx(ni, NULL);
	if (!ctx)
		return ERR_MREF(-1);
	if (ntfs_attr_lookup(AT_FILE_NAME, AT_UNNAMED, 0, 0, 0, NULL, 0, ctx)) {
		Dprintf("No file name found in inode 0x%llx. Corrupt inode.\n",
				(unsigned long long)ni->mft_no);
		goto err_out;
	}
	if (ctx->attr->non_resident) {
		Dprintf("File name attribute must be resident. Corrupt inode "
				"0x%llx.\n", (unsigned long long)ni->mft_no);
		goto io_err_out;
	}
	fn = (FILE_NAME_ATTR*)((u8*)ctx->attr +
			le16_to_cpu(ctx->attr->value_offset));
	if ((u8*)fn +	le32_to_cpu(ctx->attr->value_length) >
			(u8*)ctx->attr + le32_to_cpu(ctx->attr->length)) {
		Dprintf("Corrupt file name attribute in inode 0x%llx.\n",
				(unsigned long long)ni->mft_no);
		goto io_err_out;
	}
	mref = le64_to_cpu(fn->parent_directory);
	ntfs_attr_put_search_ctx(ctx);
	return mref;
io_err_out:
	errno = EIO;
err_out:
	eo = errno;
	ntfs_attr_put_search_ctx(ctx);
	errno = eo;
	return ERR_MREF(-1);
}

/**
 * ntfs_readdir - read the contents of an ntfs directory
 * @dir_ni:	ntfs inode of current directory
 * @pos:	current position in directory
 * @dirent:	context for filldir callback supplied by the caller
 * @filldir:	filldir callback supplied by the caller
 *
 * Parse the index root and the index blocks that are marked in use in the
 * index bitmap and hand each found directory entry to the @filldir callback
 * supplied by the caller.
 *
 * Return 0 on success or -1 on error with errno set to the error code.
 *
 * Note: Index blocks are parsed in ascending vcn order, from which follows
 * that the directory entries are not returned sorted.
 */
int ntfs_readdir(ntfs_inode *dir_ni, s64 *pos,
		void *dirent, ntfs_filldir_t filldir)
{
	s64 i_size, br, ia_pos, bmp_pos, ia_start;
	ntfs_volume *vol;
	ntfs_attr *ia_na, *bmp_na = NULL;
	ntfs_attr_search_ctx *ctx = NULL;
	u8 *index_end, *bmp = NULL;
	INDEX_ROOT *ir;
	INDEX_ENTRY *ie;
	INDEX_ALLOCATION *ia = NULL;
	int rc, ir_pos, bmp_buf_size, bmp_buf_pos, eo;
	u32 index_block_size, index_vcn_size;
	u8 index_block_size_bits, index_vcn_size_bits;

	if (!dir_ni || !pos || !filldir) {
		errno = EINVAL;
		return -1;
	}

	if (!(dir_ni->mrec->flags & MFT_RECORD_IS_DIRECTORY)) {
		errno = ENOTDIR;
		return -1;
	}

	vol = dir_ni->vol;

	Dprintf("Entering for inode 0x%llx, *pos 0x%llx.\n",
			(unsigned long long)dir_ni->mft_no, (long long)*pos);

	/* Open the index allocation attribute. */
	ia_na = ntfs_attr_open(dir_ni, AT_INDEX_ALLOCATION, I30, 4);
	if (!ia_na) {
		if (errno != ENOENT) {
			Dprintf("Failed to open index allocation attribute. "
					"Directory inode 0x%llx is corrupt or "
					"bug: %s\n",
					(unsigned long long)dir_ni->mft_no,
					strerror(errno));
			return -1;
		}
		i_size = 0;
	} else
		i_size = ia_na->data_size;

	rc = 0;

	/* Are we at end of dir yet? */
	if (*pos >= i_size + vol->mft_record_size)
		goto done;

	/* Emulate . and .. for all directories. */
	if (!*pos) {
		rc = filldir(dirent, dotdot, 1, FILE_NAME_POSIX, *pos,
				MK_MREF(dir_ni->mft_no,
				le16_to_cpu(dir_ni->mrec->sequence_number)),
				NTFS_DT_DIR);
		if (rc)
			goto done;
		++*pos;
	}
	if (*pos == 1) {
		MFT_REF parent_mref;

		parent_mref = ntfs_mft_get_parent_ref(dir_ni);
		if (parent_mref == ERR_MREF(-1)) {
			Dprintf("Parent directory not found: %s\n", errno);
			goto dir_err_out;
		}

		rc = filldir(dirent, dotdot, 2, FILE_NAME_POSIX, *pos,
				parent_mref, NTFS_DT_DIR);
		if (rc)
			goto done;
		++*pos;
	}

	ctx = ntfs_attr_get_search_ctx(dir_ni, NULL);
	if (!ctx)
		goto err_out;

	/* Get the offset into the index root attribute. */
	ir_pos = (int)*pos;
	/* Find the index root attribute in the mft record. */
	if (ntfs_attr_lookup(AT_INDEX_ROOT, I30, 4, CASE_SENSITIVE, 0, NULL,
			0, ctx)) {
		Dprintf("Index root attribute missing in directory inode "
				"0x%llx.\n", (unsigned long long)dir_ni->mft_no);
		goto dir_err_out;
	}
	/* Get to the index root value. */
	ir = (INDEX_ROOT*)((u8*)ctx->attr +
			le16_to_cpu(ctx->attr->value_offset));

	/* Determine the size of a vcn in the directory index. */
	index_block_size = le32_to_cpu(ir->index_block_size);
	if (index_block_size < NTFS_SECTOR_SIZE ||
			index_block_size & (index_block_size - 1)) {
		Dprintf("Index block size %u is invalid.\n", index_block_size);
		goto dir_err_out;
	}
	index_block_size_bits = ffs(index_block_size) - 1;
	if (vol->cluster_size <= index_block_size) {
		index_vcn_size = vol->cluster_size;
		index_vcn_size_bits = vol->cluster_size_bits;
	} else {
		index_vcn_size = vol->sector_size;
		index_vcn_size_bits = vol->sector_size_bits;
	}

	/* Are we jumping straight into the index allocation attribute? */
	if (*pos >= vol->mft_record_size) {
		ntfs_attr_put_search_ctx(ctx);
		ctx = NULL;
		goto skip_index_root;
	}

	index_end = (u8*)&ir->index + le32_to_cpu(ir->index.index_length);
	/* The first index entry. */
	ie = (INDEX_ENTRY*)((u8*)&ir->index +
			le32_to_cpu(ir->index.entries_offset));
	/*
	 * Loop until we exceed valid memory (corruption case) or until we
	 * reach the last entry or until filldir tells us it has had enough
	 * or signals an error (both covered by the rc test).
	 */
	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
		Dprintf("In index root, offset 0x%x.\n", (u8*)ie - (u8*)ir);
		/* Bounds checks. */
		if ((u8*)ie < (u8*)ctx->mrec || (u8*)ie +
				sizeof(INDEX_ENTRY_HEADER) > index_end ||
				(u8*)ie + le16_to_cpu(ie->key_length) >
				index_end)
			goto dir_err_out;
		/* The last entry cannot contain a name. */
		if (ie->flags & INDEX_ENTRY_END)
			break;
		/* Skip index root entry if continuing previous readdir. */
		if (ir_pos > (u8*)ie - (u8*)ir)
			continue;
		/*
		 * Submit the directory entry to ntfs_filldir(), which will
		 * invoke the filldir() callback as appropriate.
		 */
		rc = ntfs_filldir(dir_ni, pos, index_vcn_size_bits,
				INDEX_TYPE_ROOT, ir, ie, dirent, filldir);
		if (rc) {
			ntfs_attr_put_search_ctx(ctx);
			ctx = NULL;
			goto done;
		}
	}
	ntfs_attr_put_search_ctx(ctx);
	ctx = NULL;

	/* If there is no index allocation attribute we are finished. */
	if (!ia_na)
		goto EOD;

	/* Advance *pos to the beginning of the index allocation. */
	*pos = vol->mft_record_size;

skip_index_root:

	if (!ia_na)
		goto done;

	/* Allocate a buffer for the current index block. */
	ia = (INDEX_ALLOCATION*)malloc(index_block_size);
	if (!ia) {
		Dperror("Failed to allocate buffer for index block");
		goto err_out;
	}

	bmp_na = ntfs_attr_open(dir_ni, AT_BITMAP, I30, 4);
	if (!bmp_na) {
		Dperror("Failed to open index bitmap attribute");
		goto dir_err_out;
	}

	/* Get the offset into the index allocation attribute. */
	ia_pos = *pos - vol->mft_record_size;

	bmp_pos = ia_pos >> index_block_size_bits;
	if (bmp_pos >> 3 >= bmp_na->data_size) {
		Dputs("Current index position exceeds index bitmap size.");
		goto dir_err_out;
	}

	bmp_buf_size = min(bmp_na->data_size - (bmp_pos >> 3), 4096);
	bmp = (u8*)malloc(bmp_buf_size);
	if (!bmp) {
		Dperror("Failed to allocate bitmap buffer");
		goto err_out;
	}

	br = ntfs_attr_pread(bmp_na, bmp_pos >> 3, bmp_buf_size, bmp);
	if (br != bmp_buf_size) {
		if (br != -1)
			errno = EIO;
		Dperror("Failed to read from inde bitmap attribute");
		goto err_out;
	}

	bmp_buf_pos = 0;
	/* If the index block is not in use find the next one that is. */
	while (!(bmp[bmp_buf_pos >> 3] & (1 << (bmp_buf_pos & 7)))) {
find_next_index_buffer:
		bmp_pos++;
		bmp_buf_pos++;
		/* If we have reached the end of the bitmap, we are done. */
		if (bmp_pos >> 3 >= bmp_na->data_size)
			goto EOD;
		ia_pos = bmp_pos << index_block_size_bits;
		if (bmp_buf_pos >> 3 < bmp_buf_size)
			continue;
		/* Read next chunk from the index bitmap. */
		if ((bmp_pos >> 3) + bmp_buf_size > bmp_na->data_size)
			bmp_buf_size = bmp_na->data_size - (bmp_pos >> 3);
		br = ntfs_attr_pread(bmp_na, bmp_pos >> 3, bmp_buf_size, bmp);
		if (br != bmp_buf_size) {
			if (br != -1)
				errno = EIO;
			Dperror("Failed to read from inde bitmap attribute");
			goto err_out;
		}
	}

	Dprintf("Handling index block 0x%llx.", (long long)bmp_pos);

	/* Read the index block starting at bmp_pos. */
	br = ntfs_attr_mst_pread(ia_na, bmp_pos << index_block_size_bits, 1,
			index_block_size, ia);
	if (br != 1) {
		if (br != -1)
			errno = EIO;
		Dperror("Failed to read index block");
		goto err_out;
	}

	ia_start = ia_pos & ~(s64)(index_block_size - 1);
	if (sle64_to_cpu(ia->index_block_vcn) != ia_start >>
			index_vcn_size_bits) {
		Dprintf("Actual VCN (0x%llx) of index buffer is different from "
				"expected VCN (0x%llx) in inode 0x%llx.\n",
				(long long)sle64_to_cpu(ia->index_block_vcn),
				(long long)ia_start >> index_vcn_size_bits,
				(unsigned long long)dir_ni->mft_no);
		goto dir_err_out;
	}
	if (le32_to_cpu(ia->index.allocated_size) + 0x18 != index_block_size) {
		Dprintf("Index buffer (VCN 0x%llx) of directory inode 0x%llx "
				"has a size (%u) differing from the directory "
				"specified size (%u).\n",
				(long long)ia_start >> index_vcn_size_bits,
				(unsigned long long)dir_ni->mft_no,
				le32_to_cpu(ia->index.allocated_size) + 0x18,
				index_block_size);
		goto dir_err_out;
	}
	index_end = (u8*)&ia->index + le32_to_cpu(ia->index.index_length);
	if (index_end > (u8*)ia + index_block_size) {
		Dprintf("Size of index buffer (VCN 0x%llx) of directory inode "
				"0x%llx exceeds maximum size.\n",
				(long long)ia_start >> index_vcn_size_bits,
				(unsigned long long)dir_ni->mft_no);
		goto dir_err_out;
	}
	/* The first index entry. */
	ie = (INDEX_ENTRY*)((u8*)&ia->index +
			le32_to_cpu(ia->index.entries_offset));
	/*
	 * Loop until we exceed valid memory (corruption case) or until we
	 * reach the last entry or until ntfs_filldir tells us it has had
	 * enough or signals an error (both covered by the rc test).
	 */
	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
		Dprintf("In index allocation, offset 0x%llx.\n",
				(long long)ia_start + ((u8*)ie - (u8*)ia));
		/* Bounds checks. */
		if ((u8*)ie < (u8*)ia || (u8*)ie +
				sizeof(INDEX_ENTRY_HEADER) > index_end ||
				(u8*)ie + le16_to_cpu(ie->key_length) >
				index_end) {
			Dprintf("Index entry out of bounds in directory inode "
					"0x%llx.\n",
					(unsigned long long)dir_ni->mft_no);
			goto dir_err_out;
		}
		/* The last entry cannot contain a name. */
		if (ie->flags & INDEX_ENTRY_END)
			break;
		/* Skip index entry if continuing previous readdir. */
		if (ia_pos - ia_start > (u8*)ie - (u8*)ia)
			continue;
		/*
		 * Submit the directory entry to ntfs_filldir(), which will
		 * invoke the filldir() callback as appropriate.
		 */
		rc = ntfs_filldir(dir_ni, pos, index_vcn_size_bits,
				INDEX_TYPE_ALLOCATION, ia, ie, dirent, filldir);
		if (rc)
			goto done;
	}
	goto find_next_index_buffer;
EOD:
	/* We are finished, set *pos to EOD. */
	*pos = i_size + vol->mft_record_size;
done:
	if (ia)
		free(ia);
	if (bmp)
		free(bmp);
	if (bmp_na)
		ntfs_attr_close(bmp_na);
	if (ia_na)
		ntfs_attr_close(ia_na);
#ifdef DEBUG
	if (!rc)
		Dprintf("EOD, *pos 0x%llx, returning 0.\n", (long long)*pos);
	else
		Dprintf("filldir returned %i, *pos 0x%llx, returning 0.\n",
				rc, (long long)*pos);
#endif
	return 0;
dir_err_out:
	errno = EIO;
err_out:
	eo = errno;
	Dprintf("%s() failed.\n", __FUNCTION__);
	if (ctx)
		ntfs_attr_put_search_ctx(ctx);
	if (ia)
		free(ia);
	if (bmp)
		free(bmp);
	if (bmp_na)
		ntfs_attr_close(bmp_na);
	if (ia_na)
		ntfs_attr_close(ia_na);
	errno = eo;
	return -1;
}