There are two types of numerical parameter in redis protocol:
- *[0-9]+ defined array size
- $[0-9]+ defined string size
Currently, array size is stored to args_count, and string size is
stored to _arg_size / _size_left.
It's bit hard to understand since both uses same word "arg(s)", let's
rename string size variables to _bytes_count / _bytes_left.