Method write_count2

src/common/MemoryStreams.hpp:170–170

	size_t read_count2() const { return write_pos < impl.size() ? 0 : write_pos - impl.size(); }
	const unsigned char *read_ptr2() { return impl.data(); }
	size_t write_count2() const { return write_pos < impl.size() ? read_pos : 0; }
	unsigned char *write_ptr2() { return impl.data(); }

	void copy_from(IInputStream &in);