Class: Cosmos::BufferedFile

Inherits:
File show all
Defined in:
lib/cosmos/io/buffered_file.rb

Constant Summary collapse

BUFFER_SIZE = 
16 * 1024

Constants inherited from File

File::NON_ASCII_PRINTABLE

Instance Method Summary collapse

Methods inherited from File

build_timestamped_filename, find_in_search_path, is_ascii?

Constructor Details

#initialize(*args) ⇒ BufferedFile

Initialize the BufferedFile. Takes the same args as File



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# File 'lib/cosmos/io/buffered_file.rb', line 19

def initialize(*args)
  super(*args)
  @buffer = ''
  @buffer_index = 0
end

Instance Method Details

#pos ⇒ Object

Get the current file position



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# File 'lib/cosmos/io/buffered_file.rb', line 65

def pos
  parent_pos = super()
  return parent_pos - (@buffer.length - @buffer_index)
end

#read(read_length) ⇒ Object

Read using an internal buffer to avoid system calls



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# File 'lib/cosmos/io/buffered_file.rb', line 26

def read(read_length)
  if read_length <= (@buffer.length - @buffer_index)
    # Return part of the buffer without having to go to the OS
    result = @buffer[@buffer_index, read_length]
    @buffer_index += read_length
    return result
  elsif read_length > BUFFER_SIZE
    # Reading more than our buffer
    if @buffer.length > 0
      if @buffer_index > 0
        @buffer.slice!(0..(@buffer_index - 1))
        @buffer_index = 0
      end
      @buffer << super(read_length - @buffer.length).to_s
      return @buffer.slice!(0..-1)
    else
      return super(read_length)
    end
  else
    # Read into the buffer
    if @buffer_index > 0
      @buffer.slice!(0..(@buffer_index - 1))
      @buffer_index = 0
    end
    @buffer << super(BUFFER_SIZE - @buffer.length).to_s
    if @buffer.length <= 0
      return nil
    end
    if read_length <= @buffer.length
      result = @buffer[@buffer_index, read_length]
      @buffer_index += read_length
      return result
    else
      return @buffer.slice!(0..-1)
    end
  end
end

#seek(*args) ⇒ Object

Seek to a given file position



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# File 'lib/cosmos/io/buffered_file.rb', line 71

def seek(*args)
  case args.length
  when 1
    amount = args[0]
    whence = IO::SEEK_SET
  when 2
    amount = args[0]
    whence = args[1]
  else
    # Invalid number of arguments given - let super handle
    return super(*args)
  end

  if whence == IO::SEEK_CUR
    buffer_index = @buffer_index + amount
    if (buffer_index >= 0) && (buffer_index < @buffer.length)
      @buffer_index = buffer_index
      return 0
    end
    super(self.pos, IO::SEEK_SET)
  end

  @buffer.clear
  @buffer_index = 0
  return super(*args)
end