attrib.c

LINUX下读写NTFS分区的工具。 已经集成了通过LIBCONV库支持中文的代码。

	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;
					ntfs_log_perror("%s: Failed to find VCN #2",
							__FUNCTION__);
				}
				goto rl_err_out;
			}
			/* Needed for case when runs merged. */
			ofs = pos + total - (rl->vcn << vol->cluster_size_bits);
		}
		if (!rl->length) {
			errno = EIO;
			ntfs_log_perror("%s: Zero run length", __FUNCTION__);
			goto rl_err_out;
		}
		if (rl->lcn < (LCN)0) {
			if (rl->lcn != (LCN)LCN_HOLE) {
				ntfs_log_perror("%s: Bad run (%lld)", 
						__FUNCTION__,
						(long long)rl->lcn);
				goto rl_err_out;
			}
			/* It is a hole, just zero the matching @b range. */
			to_read = min(count, (rl->length <<
					vol->cluster_size_bits) - ofs);
			memset(b, 0, to_read);
			/* Update progress counters. */
			total += to_read;
			count -= to_read;
			b = (u8*)b + to_read;
			continue;
		}
		/* It is a real lcn, read it into @dst. */
		to_read = min(count, (rl->length << vol->cluster_size_bits) -
				ofs);
retry:
		ntfs_log_trace("Reading 0x%llx bytes from vcn 0x%llx, lcn 0x%llx, "
				"ofs 0x%llx.\n", to_read, rl->vcn, rl->lcn, ofs);
		br = ntfs_pread(vol->dev, (rl->lcn << vol->cluster_size_bits) +
				ofs, to_read, b);
		/* If everything ok, update progress counters and continue. */
		if (br > 0) {
			total += br;
			count -= br;
			b = (u8*)b + br;
			continue;
		}
		/* If the syscall was interrupted, try again. */
		if (br == (s64)-1 && errno == EINTR)
			goto retry;
		if (total)
			return total;
		if (!br)
			errno = EIO;
		ntfs_log_perror("%s: ntfs_pread failed", __FUNCTION__);
		return -1;
	}
	/* Finally, return the number of bytes read. */
	return total + total2;
rl_err_out:
	if (total)
		return total;
	errno = EIO;
	return -1;
}

/**
 * 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)
{
	int ret;
	
	if (!na || !na->ni || !na->ni->vol || !b || pos < 0 || count < 0) {
		errno = EINVAL;
		ntfs_log_perror("%s: na=%p  b=%p  pos=%lld  count=%lld",
				__FUNCTION__, na, b, (long long)pos,
				(long long)count);
		return -1;
	}
	
	ntfs_log_enter("Entering for inode %lld attr 0x%x pos %lld count "
		       "%lld\n", (unsigned long long)na->ni->mft_no,
		       na->type, (long long)pos, (long long)count);

	ret = ntfs_attr_pread_i(na, pos, count, b);
	
	ntfs_log_leave("\n");
	return ret;
}

static int ntfs_attr_fill_zero(ntfs_attr *na, s64 pos, s64 count)
{
	char *buf;
	s64 written, size, end = pos + count;
	int ret = -1;

	ntfs_log_trace("pos %lld, count %lld\n", (long long)pos, 
		       (long long)count);
	
	if (!na || pos < 0 || count < 0) {
		errno = EINVAL;
		goto err_out;
	}
	
	buf = ntfs_calloc(NTFS_BUF_SIZE);
	if (!buf)
		goto err_out;
	
	while (pos < end) {
		size = min(end - pos, NTFS_BUF_SIZE);
		written = ntfs_rl_pwrite(na->ni->vol, na->rl, pos, size, buf);
		if (written <= 0) {
			ntfs_log_perror("Failed to zero space");
			goto err_free;
		}
		pos += written;
	}
	
	ret = 0;
err_free:	
	free(buf);
err_out:
	return ret;	
}

static int ntfs_attr_fill_hole(ntfs_attr *na, s64 count, s64 *ofs, 
			       runlist_element **rl, VCN *update_from)
{
	s64 to_write;
	ntfs_volume *vol = na->ni->vol;
	int eo, ret = -1;
	runlist *rlc;
	LCN lcn_seek_from = -1;
	VCN cur_vcn, from_vcn;

	to_write = min(count, ((*rl)->length << vol->cluster_size_bits) - *ofs);
	
	cur_vcn = (*rl)->vcn;
	from_vcn = (*rl)->vcn + (*ofs >> vol->cluster_size_bits);
	
	ntfs_log_trace("count: %lld, cur_vcn: %lld, from: %lld, to: %lld, ofs: "
		       "%lld\n", count, cur_vcn, from_vcn, to_write, *ofs);
	 
	/* Map whole runlist to be able update mapping pairs later. */
	if (ntfs_attr_map_whole_runlist(na))
		goto err_out;
	 
	/* Restore @*rl, it probably get lost during runlist mapping. */
	*rl = ntfs_attr_find_vcn(na, cur_vcn);
	if (!*rl) {
		ntfs_log_error("Failed to find run after mapping runlist. "
			       "Please report to %s.\n", NTFS_DEV_LIST);
		errno = EIO;
		goto err_out;
	}
	
	/* Search backwards to find the best lcn to start seek from. */
	rlc = *rl;
	while (rlc->vcn) {
		rlc--;
		if (rlc->lcn >= 0) {
			lcn_seek_from = rlc->lcn + (from_vcn - rlc->vcn);
			break;
		}
	}
	if (lcn_seek_from == -1) {
		/* Backwards search failed, search forwards. */
		rlc = *rl;
		while (rlc->length) {
			rlc++;
			if (rlc->lcn >= 0) {
				lcn_seek_from = rlc->lcn - (rlc->vcn - from_vcn);
				if (lcn_seek_from < -1)
					lcn_seek_from = -1;
				break;
			}
		}
	}
	
	rlc = ntfs_cluster_alloc(vol, from_vcn,
				((*ofs + to_write - 1) >> vol->cluster_size_bits)
				 + 1 + (*rl)->vcn - from_vcn, 
				 lcn_seek_from, DATA_ZONE);
	if (!rlc)
		goto err_out;
	
	*rl = ntfs_runlists_merge(na->rl, rlc);
	if (!*rl) {
		eo = errno;
		ntfs_log_perror("Failed to merge runlists");
		if (ntfs_cluster_free_from_rl(vol, rlc)) {
			ntfs_log_perror("Failed to free hot clusters. "
					"Please run chkdsk /f");
		}
		errno = eo;
		goto err_out;
	}
	na->rl = *rl;
	if (*update_from == -1)
		*update_from = from_vcn;
	*rl = ntfs_attr_find_vcn(na, cur_vcn);
	if (!*rl) {
		/*
		 * It's definitely a BUG, if we failed to find @cur_vcn, because
		 * we missed it during instantiating of the hole.
		 */
		ntfs_log_error("Failed to find run after hole instantiation. "
			       "Please report to %s.\n", NTFS_DEV_LIST);
		errno = EIO;
		goto err_out;
	}
	/* If leaved part of the hole go to the next run. */
	if ((*rl)->lcn < 0)
		(*rl)++;
	/* Now LCN shoudn't be less than 0. */
	if ((*rl)->lcn < 0) {
		ntfs_log_error("BUG! LCN is lesser than 0. "
			       "Please report to the %s.\n", NTFS_DEV_LIST);
		errno = EIO;
		goto err_out;
	}
	if (*ofs) {
		/* Clear non-sparse region from @cur_vcn to @*ofs. */
		if (ntfs_attr_fill_zero(na, cur_vcn << vol->cluster_size_bits,
					*ofs))
			goto err_out;
	}
	if ((*rl)->vcn < cur_vcn) {
		/*
		 * Clusters that replaced hole are merged with
		 * previous run, so we need to update offset.
		 */
		*ofs += (cur_vcn - (*rl)->vcn) << vol->cluster_size_bits;
	}
	if ((*rl)->vcn > cur_vcn) {
		/*
		 * We left part of the hole, so we need to update offset
		 */
		*ofs -= ((*rl)->vcn - cur_vcn) << vol->cluster_size_bits;
	}
	
	ret = 0;
err_out:
	return ret;
}

/**
 * ntfs_attr_pwrite - positioned write to an ntfs attribute
 * @na:		ntfs attribute to write to
 * @pos:	position in the attribute to write to
 * @count:	number of bytes to write
 * @b:		data buffer to write to disk
 *
 * This function will write @count bytes from data buffer @b to ntfs attribute
 * @na at position @pos.
 *
 * On success, return the number of successfully written bytes. If this number
 * is lower than @count this means that an error was encountered during the
 * write so that the write is partial. 0 means nothing was written (also return
 * 0 when @count is 0).
 *
 * On error and nothing has been written, return -1 with errno set
 * appropriately to the return code of ntfs_pwrite(), or to EINVAL in case of
 * invalid arguments.
 */
s64 ntfs_attr_pwrite(ntfs_attr *na, const s64 pos, s64 count, const void *b)
{
	s64 written, to_write, ofs, old_initialized_size, old_data_size;
	s64 total = 0;
	VCN update_from = -1;
	ntfs_volume *vol;
	ntfs_attr_search_ctx *ctx = NULL;
	runlist_element *rl;
	s64 eo, hole;
	struct {
		unsigned int undo_initialized_size	: 1;
		unsigned int undo_data_size		: 1;
	} need_to = { 0, 0 };

	ntfs_log_enter("Entering for inode 0x%llx, attr 0x%x, pos 0x%llx, count "
			"0x%llx.\n", 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;
		ntfs_log_perror("%s", __FUNCTION__);
		goto errno_set;
	}
	vol = na->ni->vol;
	/*
	 * 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;
		goto errno_set;
	}
	/* If this is a compressed attribute it needs special treatment. */
	if (NAttrCompressed(na)) {
		// TODO: Implement writing compressed attributes! (AIA)
		// return ntfs_attr_pwrite_compressed(ntfs_attr *na,
		//		const s64 pos, s64 count, void *b);
		errno = EOPNOTSUPP;
		goto errno_set;
	}
	
	if (!count)
		goto out;
	/* If the write reaches beyond the end, extend the attribute. */
	old_data_size = na->data_size;
	if (pos + count > na->data_size) {
		if (ntfs_attr_truncate(na, pos + count)) {
			ntfs_log_perror("Failed to enlarge attribute");
			goto errno_set;
		}
		need_to.undo_data_size = 1;
	}
	old_initialized_size = na->initialized_size;
	/* If it is a resident attribute, write the data to the mft record. */
	if (!NAttrNonResident(na)) {
		char *val;

		ctx = ntfs_attr_get_search_ctx(na->ni, NULL);
		if (!ctx)
			goto err_out;
		if (ntfs_attr_lookup(na->type, na->name, na->name_len, 0,
				0, NULL, 0, ctx)) {
			ntfs_log_perror("%s: lookup failed", __FUNCTION__);
			goto err_out;
		}
		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;
			ntfs_log_perror("%s: Sanity check failed", __FUNCTION__);
			goto err_out;
		}
		memcpy(val + pos, b, count);
		if (ntfs_mft_record_write(vol, ctx->ntfs_ino->mft_no,
				ctx->mrec)) {
			/*
			 * NOTE: We are in a bad state at this moment. We have
			 * dirtied the mft record but we failed to commit it to
			 * disk. Since we have read the mft record ok before,
			 * it is unlikely to fail writing it, so is ok to just
			 * return error here... (AIA)
			 */
			ntfs_log_perror("%s: failed to write mft record", __FUNCTION__);
			goto err_out;
		}
		ntfs_attr_put_search_ctx(ctx);
		total = count;
		goto out;
	}
	
	/* Handle writes beyond initialized_size. */
	if (pos + count > na->initialized_size) {
		if (ntfs_attr_map_whole_runlist(na))
			goto err_out;
		/* Set initialized_size to @pos + @count. */
		ctx = ntfs_attr_get_search_ctx(na->ni, NULL);
		if (!ctx)
			goto err_out;
		if (ntfs_attr_lookup(na->type, na->name, na->name_len, 0,
				0, NULL, 0, ctx))
			goto err_out;
		
		/* If write starts beyond initialized_size, zero the gap. */
		if (pos > na->initialized_size)
			if (ntfs_attr_fill_zero(na, na->initialized_size, 
						pos - na->initialized_size))
				goto err_out;
			
		ctx->attr->initialized_size = cpu_to_sle64(pos + count);
		if (ntfs_mft_record_write(vol, ctx->ntfs_ino->mft_no,
				ctx->mrec)) {
			/*
			 * Undo the change in the in-memory copy and send it
			 * back for writing.
			 */
			ctx->attr->initialized_size =
					cpu_to_sle64(old_initialized_size);
			ntfs_mft_record_write(vol, ctx->ntfs_ino->mft_no,
					ctx->mrec);
			goto err_out;
		}
		na->initialized_size = pos + count;
		ntfs_attr_put_search_ctx(ctx);
		ctx = NULL;
		/*
		 * NOTE: At this point the initialized_size in the mft record
		 * has been updated BUT there is random data on disk thus if
		 * we decide to abort, we MUST change the initialized_size
		 * again.
		 */
		need_to.undo_initialized_size = 1;
	}
	/* 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 write.
		 * However, we already extended the size of the attribute,
		 * so getting this here must be an error of some kind.
		 */
		if (errno == ENOENT) {
			errno = EIO;
			ntfs_log_perror("%s: Failed to find VCN #1", __FUNCTION__);
		}
		goto err_out;