ObjFW  Diff

		[data addItem: "\x54"];

		tmp32 = OF_BSWAP32_IF_BE(
		    (uint32_t)[_modificationDate timeIntervalSince1970]);
		[data addItems: &tmp32
			 count: sizeof(tmp32)];
	}

	for (OFData *extension in _extensions) {
		size_t extensionLength = [extension count];

		if ([extension itemSize] != 1)
			@throw [OFInvalidArgumentException exception];

		if (extensionLength > UINT16_MAX - 2)
			@throw [OFOutOfRangeException exception];

		tmp16 = OF_BSWAP16_IF_BE((uint16_t)extensionLength + 2);
		[data addItems: &tmp16
			 count: sizeof(tmp16)];
		[data addItems: [extension items]
			 count: [extension count]];
	}

	/* Zero-length extension to terminate */
	[data increaseCountBy: 2];

	headerSize = [data count];

	if (headerSize > UINT16_MAX)