How to get Automa to work with stdin?

General Usage
1

I have some code which parses a string using Automa. I believe it simply travels through the string from left to right. I would like to make it work on a string coming from stdin but I am not sure how to do it. Here is my code (written by Jakob Nissen):

import Automa
import Automa.RegExp: @re_str
const re = Automa.RegExp

machine = (function ()
    # Primitives
    start = re"\["
    stop = re"\]"
    sep = re"," * re.opt(re.space())
    number = re"[0-9]+"
    numelem = number * (sep | stop)
    elems = re"[^\[]+" * re.rep(start | stop | sep | numelem)
    start.actions[:enter] = [:start]
    stop.actions[:enter] = [:stop]
    number.actions[:enter] = [:mark]
    number.actions[:exit] = [:number]
    return Automa.compile(elems)
end)()
actions = Dict(
    :start => quote
        # level > 1 && error("X")
        level == 1 && (inner = UInt32[])
        level += 1
    end,
    :stop => quote
        # level == 0 && error("")
        level == 2 && push!(outer, inner)
        level -= 1
        level == 0 && (done = true)
    end,
    :mark => :(mark = p),
    :number => quote
    n = UInt32(0)
    @inbounds for i in mark:p-1
        n = n * 10 + UInt32(data[i] - 0x30)
    end
    push!(inner, n)
end
)
context = Automa.CodeGenContext()
@eval function parsestring(data::Union{String,Vector{UInt8}})
    mark = 0
    level = 0
    done = false
    inner = UInt32[]
    outer = Vector{UInt32}[]
    $(Automa.generate_init_code(context, machine))
    p_end = p_eof = lastindex(data)
    $(Automa.generate_exec_code(context, machine, actions))
    if (cs != 0) & (!done)
        error("failed to parse on byte ", p)
    end
    return outer
end

How can you change this so that parsestring accepts a string coming from stdin?

2

Is your input a single line of text? If so, you can do readline(stdin) to take a single line of input from stdin as a String:

# File: read_from_stdin.jl

line = readline(stdin)
println("I got this line: \"", line, "\"")

Usage:

$ echo "hello world" | julia read_from_stdin.jl
I got this line: "hello world"

It could be more efficient to avoid reading the whole input into a string and instead building the automaton to read directly from an ::IO. But it’s hard for me to tell how easy that would be to do with Automa.jl.

3

It is a single line but I can’t read it all in as it is huge. That’s why I want to process it on the fly from standard in.