Scanf

Features

Scanf provides the macros @scanf([io, ] "%format", args...) and @sscanf(string, "%format", args...).

The format string must be a string literal, which is evaluated once at macro expansion time.

Alternatively f = Scanf.Format(format_string) creates a format object, which can be used like Scanf.format([io|string,] f, args...).

The arguments are of type Ref{T} where T is a concrete type. All output data are stored in new objects of that type.

The format strings follow the definition of GNU-scanf manual page scanf with some adaptations:

• All unicode characters are supported in format strings and input data.

• strings are not NUL-terminated, \0 is a valid character in format string and input data.

• in format strings, whitespace specifiers are only ASCII space characters " \n\r\t\f\v".

• in input data, all characters x with isspace(x) == true are skipped by all whitespace specifiers in the format string.

• The %n$... form of format specifications is not supported.

• The optional modifiers ' and m are not supported / not applicable.

• The optional type modifiers like l, h, etc. are not supported; the taget type is derived form the reference type of the corresponding argument, though.

• for type specifier %c, without width specified, the corresponding argument must have type Ref{Char}.

• for type specifier %Nc, with a width field N, the argument must have type Vector{Char}. This vector is re-used and resized to the number of characters actually read.

• the type specifier n, returns an integer value, which is the byte offset in the input data, consumed so far.

• the type specifier p requires a Ref{Ptr{Nothing}} output argument.

• all floating point type specifiers efgaEFGA are used interchangeably. They support all input data, as produced by the corresponding @printf type specifiers, especially the hexadecimal floating point format.

• The return value of both functions is the amount of output arguments populated by the functions. Also the arguments for %n are counted.

Usage

    using Scanf
   
    ra = Ref{Int}()
    rb = Ref{String}()

    @sscanf("  13 This is a prime number", "%d%[a-zA-Z]"), ra, rb)