File::read and File::write throw exception on error, so they don't need to return a negative value to indicate error.

Don't throw exceptions from error formatting functions. Gracefully fallback to a less descriptive message instead.

Factor out argument processing logic common between format and printf to FormatterBase::{next_arg,get_arg}.

Change "number is too big in format" to "number is too big" because the error can occur not only in the format function.