attrib.c

添加linux下对NTFS格式文件系统访问支持的源代码ntfs-3g

/**
 * ntfs_attr_close - free an ntfs attribute structure
 * @na:		ntfs attribute structure to free
 *
 * Release all memory associated with the ntfs attribute @na and then release
 * @na itself.
 */
void ntfs_attr_close(ntfs_attr *na)
{
	if (!na)
		return;
	if (NAttrNonResident(na) && na->rl)
		free(na->rl);
	/* Don't release if using an internal constant. */
	if (na->name != AT_UNNAMED && na->name != NTFS_INDEX_I30)
		free(na->name);
	free(na);
}

/**
 * ntfs_attr_map_runlist - map (a part of) a runlist of an ntfs attribute
 * @na:		ntfs attribute for which to map (part of) a runlist
 * @vcn:	map runlist part containing this vcn
 *
 * Map the part of a runlist containing the @vcn of an the ntfs attribute @na.
 *
 * Return 0 on success and -1 on error with errno set to the error code.
 */
int ntfs_attr_map_runlist(ntfs_attr *na, VCN vcn)
{
	LCN lcn;
	ntfs_attr_search_ctx *ctx;

	ntfs_log_trace("Entering for inode 0x%llx, attr 0x%x, vcn 0x%llx.\n",
		(unsigned long long)na->ni->mft_no, na->type, (long long)vcn);

	lcn = ntfs_rl_vcn_to_lcn(na->rl, vcn);
	if (lcn >= 0 || lcn == LCN_HOLE || lcn == LCN_ENOENT)
		return 0;

	ctx = ntfs_attr_get_search_ctx(na->ni, NULL);
	if (!ctx)
		return -1;

	/* Find the attribute in the mft record. */
	if (!ntfs_attr_lookup(na->type, na->name, na->name_len, CASE_SENSITIVE,
			vcn, NULL, 0, ctx)) {
		runlist_element *rl;

		/* Decode the runlist. */
		rl = ntfs_mapping_pairs_decompress(na->ni->vol, ctx->attr,
				na->rl);
		if (rl) {
			na->rl = rl;
			ntfs_attr_put_search_ctx(ctx);
			return 0;
		}
	}
	
	ntfs_attr_put_search_ctx(ctx);
	return -1;
}

/**
 * ntfs_attr_map_whole_runlist - map the whole runlist of an ntfs attribute
 * @na:		ntfs attribute for which to map the runlist
 *
 * Map the whole runlist of an the ntfs attribute @na.  For an attribute made
 * up of only one attribute extent this is the same as calling
 * ntfs_attr_map_runlist(na, 0) but for an attribute with multiple extents this
 * will map the runlist fragments from each of the extents thus giving access
 * to the entirety of the disk allocation of an attribute.
 *
 * Return 0 on success and -1 on error with errno set to the error code.
 */
int ntfs_attr_map_whole_runlist(ntfs_attr *na)
{
	VCN next_vcn, last_vcn, highest_vcn;
	ntfs_attr_search_ctx *ctx;
	ntfs_volume *vol = na->ni->vol;
	ATTR_RECORD *a;
	int err;

	ntfs_log_trace("Entering for inode 0x%llx, attr 0x%x.\n",
			(unsigned long long)na->ni->mft_no, na->type);

	ctx = ntfs_attr_get_search_ctx(na->ni, NULL);
	if (!ctx)
		return -1;

	/* Map all attribute extents one by one. */
	next_vcn = last_vcn = highest_vcn = 0;
	a = NULL;
	while (1) {
		runlist_element *rl;

		int not_mapped = 0;
		if (ntfs_rl_vcn_to_lcn(na->rl, next_vcn) == LCN_RL_NOT_MAPPED)
			not_mapped = 1;

		if (ntfs_attr_lookup(na->type, na->name, na->name_len,
				CASE_SENSITIVE, next_vcn, NULL, 0, ctx))
			break;

		a = ctx->attr;

		if (not_mapped) {
			/* Decode the runlist. */
			rl = ntfs_mapping_pairs_decompress(na->ni->vol,
								a, na->rl);
			if (!rl)
				goto err_out;
			na->rl = rl;
		}

		/* Are we in the first extent? */
		if (!next_vcn) {
			 if (a->lowest_vcn) {
				 errno = EIO;
				 ntfs_log_perror("Attribute first extent has "
						 "non-zero lowest_vcn");
				 goto err_out;
			}
			/* Get the last vcn in the attribute. */
			last_vcn = sle64_to_cpu(a->allocated_size) >>
					vol->cluster_size_bits;
		}

		/* Get the lowest vcn for the next extent. */
		highest_vcn = sle64_to_cpu(a->highest_vcn);
		next_vcn = highest_vcn + 1;

		/* Only one extent or error, which we catch below. */
		if (next_vcn <= 0) {
			errno = ENOENT;
			break;
		}

		/* Avoid endless loops due to corruption. */
		if (next_vcn < sle64_to_cpu(a->lowest_vcn)) {
			errno = EIO;
			ntfs_log_perror("Inode has corrupt attribute list");
			goto err_out;
		}
	}
	if (!a) {
		ntfs_log_perror("Couldn't find attribute for runlist mapping");
		goto err_out;
	}
	if (highest_vcn && highest_vcn != last_vcn - 1) {
		errno = EIO;
		ntfs_log_perror("Couldn't load full runlist: "
				"highest_vcn = 0x%llx, last_vcn = 0x%llx",
				(long long)highest_vcn, (long long)last_vcn);
		goto err_out;
	}
	err = errno;
	ntfs_attr_put_search_ctx(ctx);
	if (err == ENOENT)
		return 0;
out_now:
	errno = err;
	return -1;
err_out:
	err = errno;
	ntfs_attr_put_search_ctx(ctx);
	goto out_now;
}

/**
 * ntfs_attr_vcn_to_lcn - convert a vcn into a lcn given an ntfs attribute
 * @na:		ntfs attribute whose runlist to use for conversion
 * @vcn:	vcn to convert
 *
 * Convert the virtual cluster number @vcn of an attribute into a logical
 * cluster number (lcn) of a device using the runlist @na->rl to map vcns to
 * their corresponding lcns.
 *
 * If the @vcn is not mapped yet, attempt to map the attribute extent
 * containing the @vcn and retry the vcn to lcn conversion.
 *
 * Since lcns must be >= 0, we use negative return values with special meaning:
 *
 * Return value		Meaning / Description
 * ==========================================
 *  -1 = LCN_HOLE	Hole / not allocated on disk.
 *  -3 = LCN_ENOENT	There is no such vcn in the attribute.
 *  -4 = LCN_EINVAL	Input parameter error.
 *  -5 = LCN_EIO	Corrupt fs, disk i/o error, or not enough memory.
 */
LCN ntfs_attr_vcn_to_lcn(ntfs_attr *na, const VCN vcn)
{
	LCN lcn;
	BOOL is_retry = FALSE;

	if (!na || !NAttrNonResident(na) || vcn < 0)
		return (LCN)LCN_EINVAL;

	ntfs_log_trace("Entering for inode 0x%llx, attr 0x%x.\n", (unsigned long
			long)na->ni->mft_no, na->type);
retry:
	/* Convert vcn to lcn. If that fails map the runlist and retry once. */
	lcn = ntfs_rl_vcn_to_lcn(na->rl, vcn);
	if (lcn >= 0)
		return lcn;
	if (!is_retry && !ntfs_attr_map_runlist(na, vcn)) {
		is_retry = TRUE;
		goto retry;
	}
	/*
	 * If the attempt to map the runlist failed, or we are getting
	 * LCN_RL_NOT_MAPPED despite having mapped the attribute extent
	 * successfully, something is really badly wrong...
	 */
	if (!is_retry || lcn == (LCN)LCN_RL_NOT_MAPPED)
		return (LCN)LCN_EIO;
	/* lcn contains the appropriate error code. */
	return lcn;
}

/**
 * ntfs_attr_find_vcn - find a vcn in the runlist of an ntfs attribute
 * @na:		ntfs attribute whose runlist to search
 * @vcn:	vcn to find
 *
 * Find the virtual cluster number @vcn in the runlist of the ntfs attribute
 * @na and return the the address of the runlist element containing the @vcn.
 *
 * Note you need to distinguish between the lcn of the returned runlist
 * element being >= 0 and LCN_HOLE. In the later case you have to return zeroes
 * on read and allocate clusters on write. You need to update the runlist, the
 * attribute itself as well as write the modified mft record to disk.
 *
 * If there is an error return NULL with errno set to the error code. The
 * following error codes are defined:
 *	EINVAL		Input parameter error.
 *	ENOENT		There is no such vcn in the runlist.
 *	ENOMEM		Not enough memory.
 *	EIO		I/O error or corrupt metadata.
 */
runlist_element *ntfs_attr_find_vcn(ntfs_attr *na, const VCN vcn)
{
	runlist_element *rl;
	BOOL is_retry = FALSE;

	if (!na || !NAttrNonResident(na) || vcn < 0) {
		errno = EINVAL;
		return NULL;
	}

	ntfs_log_trace("Entering for inode 0x%llx, attr 0x%x, vcn %llx\n",
		       (unsigned long long)na->ni->mft_no, na->type,
		       (long long)vcn);
retry:
	rl = na->rl;
	if (!rl)
		goto map_rl;
	if (vcn < rl[0].vcn)
		goto map_rl;
	while (rl->length) {
		if (vcn < rl[1].vcn) {
			if (rl->lcn >= (LCN)LCN_HOLE)
				return rl;
			break;
		}
		rl++;
	}
	switch (rl->lcn) {
	case (LCN)LCN_RL_NOT_MAPPED:
		goto map_rl;
	case (LCN)LCN_ENOENT:
		errno = ENOENT;
		break;
	case (LCN)LCN_EINVAL:
		errno = EINVAL;
		break;
	default:
		errno = EIO;
		break;
	}
	return NULL;
map_rl:
	/* The @vcn is in an unmapped region, map the runlist and retry. */
	if (!is_retry && !ntfs_attr_map_runlist(na, vcn)) {
		is_retry = TRUE;
		goto retry;
	}
	/*
	 * If we already retried or the mapping attempt failed something has
	 * gone badly wrong. EINVAL and ENOENT coming from a failed mapping
	 * attempt are equivalent to errors for us as they should not happen
	 * in our code paths.
	 */
	if (is_retry || errno == EINVAL || errno == ENOENT)
		errno = EIO;
	return NULL;
}

/**
 * ntfs_attr_pread - read from an attribute specified by an ntfs_attr structure
 * @na:		ntfs attribute to read from
 * @pos:	byte position in the attribute to begin reading from
 * @count:	number of bytes to read
 * @b:		output data buffer
 *
 * This function will read @count bytes starting at offset @pos from the ntfs
 * attribute @na into the data buffer @b.
 *
 * On success, return the number of successfully read bytes. If this number is
 * lower than @count this means that the read reached end of file or that an
 * error was encountered during the read so that the read is partial. 0 means
 * end of file or nothing was read (also return 0 when @count is 0).
 *
 * On error and nothing has been read, return -1 with errno set appropriately
 * to the return code of ntfs_pread(), or to EINVAL in case of invalid
 * arguments.
 */
s64 ntfs_attr_pread(ntfs_attr *na, const s64 pos, s64 count, void *b)
{
	s64 br, to_read, ofs, total, total2;
	ntfs_volume *vol;
	runlist_element *rl;

	ntfs_log_trace("Entering for inode 0x%llx, attr 0x%x, pos 0x%llx, count "
			"0x%llx.\n", (unsigned long long)na->ni->mft_no,
			na->type, (long long)pos, (long long)count);
	if (!na || !na->ni || !na->ni->vol || !b || pos < 0 || count < 0) {
		errno = EINVAL;
		return -1;
	}
	/*
	 * If this is a compressed attribute it needs special treatment, but
	 * only if it is non-resident.
	 */
	if (NAttrCompressed(na) && NAttrNonResident(na))
		return ntfs_compressed_attr_pread(na, pos, count, b);
	/*
	 * Encrypted non-resident attributes are not supported.  We return
	 * access denied, which is what Windows NT4 does, too.
	 */
	if (NAttrEncrypted(na) && NAttrNonResident(na)) {
		errno = EACCES;
		return -1;
	}
	vol = na->ni->vol;
	/* Update access time if needed. */
	if (na->type == AT_DATA || na->type == AT_INDEX_ROOT ||
			na->type == AT_INDEX_ALLOCATION)
		ntfs_inode_update_atime(na->ni);
	if (!count)
		return 0;
	/* Truncate reads beyond end of attribute. */
	if (pos + count > na->data_size) {
		if (pos >= na->data_size)
			return 0;
		count = na->data_size - pos;
	}
	/* If it is a resident attribute, get the value from the mft record. */
	if (!NAttrNonResident(na)) {
		ntfs_attr_search_ctx *ctx;
		char *val;

		ctx = ntfs_attr_get_search_ctx(na->ni, NULL);
		if (!ctx)
			return -1;
		if (ntfs_attr_lookup(na->type, na->name, na->name_len, 0,
				0, NULL, 0, ctx)) {
res_err_out:
			ntfs_attr_put_search_ctx(ctx);
			return -1;
		}
		val = (char*)ctx->attr + le16_to_cpu(ctx->attr->value_offset);
		if (val < (char*)ctx->attr || val +
				le32_to_cpu(ctx->attr->value_length) >
				(char*)ctx->mrec + vol->mft_record_size) {
			errno = EIO;
			goto res_err_out;
		}
		memcpy(b, val + pos, count);
		ntfs_attr_put_search_ctx(ctx);
		return count;
	}
	total = total2 = 0;
	/* Zero out reads beyond initialized size. */
	if (pos + count > na->initialized_size) {
		if (pos >= na->initialized_size) {
			memset(b, 0, count);
			return count;
		}
		total2 = pos + count - na->initialized_size;
		count -= total2;
		memset((u8*)b + count, 0, total2);
	}
	/* Find the runlist element containing the vcn. */
	rl = ntfs_attr_find_vcn(na, pos >> vol->cluster_size_bits);
	if (!rl) {
		/*
		 * If the vcn is not present it is an out of bounds read.
		 * However, we already truncated the read to the data_size,
		 * so getting this here is an error.
		 */
		if (errno == ENOENT)
			errno = EIO;
		return -1;
	}
	/*
	 * Gather the requested data into the linear destination buffer. Note,
	 * a partial final vcn is taken care of by the @count capping of read
	 * length.
	 */
	ofs = pos - (rl->vcn << vol->cluster_size_bits);
	for (; count; rl++, ofs = 0) {
		if (rl->lcn == LCN_RL_NOT_MAPPED) {
			rl = ntfs_attr_find_vcn(na, rl->vcn);
			if (!rl) {
				if (errno == ENOENT)
					errno = EIO;
				goto rl_err_out;
			}
			/* Needed for case when runs merged. */
			ofs = pos + total - (rl->vcn << vol->cluster_size_bits);
		}
		if (!rl->length)
			goto rl_err_out;
		if (rl->lcn < (LCN)0) {