reader.lua

local strsub = string.sub

local function new_string_reader(src)
 local pos = 1
 local function reader()
 local chunk = strsub(src, pos, pos + 4096 - 32)
 pos = pos + #chunk
 return #chunk > 0 and chunk or nil
 end
 return reader
end

local function new_file_reader(filename)
 local f
 if filename then
 f = assert(io.open(filename, 'r'), "cannot open file " .. filename)
 else
 f = io.stdin
 end
 local function reader()
 return f:read(4096 - 32)
 end
 return reader
end

return { 
 string = new_string_reader,
 file = new_file_reader,
}