Contents

# -*- encoding : utf-8 -*-
# Shake uses this reader to parse byte by byte without having to read byte by byte.
# Reading byte by byte is very inefficient, but we want to parse byte by byte since
# this makes parser construction much easier. So what we do is cache some chunk of the
# passed buffer and read from that. Once exhausted there will be some caching again,
# and ad infinitum until the passed buffer is exhausted
class Tracksperanto::BufferingReader
  
  DEFAULT_BUFFER_SIZE = 64 * 1024
  
  def initialize(with_io, buffer_size = DEFAULT_BUFFER_SIZE)
    @io = with_io
    @bufsize = buffer_size
    @buf = StringIO.new
  end
  
  # Will transparently read one byte off the contained IO, maintaining the internal cache.
  # If the cache has been depleted it will read a big chunk from the IO and cache it and then
  # return the byte
  def read_one_byte
    cache if @buf.pos == @buf.size
    
    return nil if @buf.size.zero?
    return @buf.read(1)
  end
  
  # Tells whether all the data has been both read from the passed buffer
  # and from the internal cache buffer (checks whether there is anything that
  # can be retreived using read_one_byte)
  def data_exhausted?
    @buf.eof? && @io.eof?
  end
  
  private
  
  def cache
    data = @io.read(@bufsize)
    @buf = StringIO.new(data.to_s) # Make nil become ""
  end
end

Version data entries

21 entries across 21 versions & 1 rubygems

Version	Path
tracksperanto-2.9.0	lib/tracksperanto/buffering_reader.rb