Class: BlockCipherKit::IOLens

Inherits:
Object
  • Object
show all
Defined in:
lib/block_cipher_kit/io_lens.rb

Overview

Allows you to pass through the writes of a particular byte range only, discarding the rest

Instance Method Summary collapse

Constructor Details

#initialize(io, range) ⇒ IOLens

Returns a new instance of IOLens.



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# File 'lib/block_cipher_kit/io_lens.rb', line 5

def initialize(io, range)
  @io = io
  @range = range
  @pos = 0
end

Instance Method Details

#write(bytes) ⇒ Object 



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# File 'lib/block_cipher_kit/io_lens.rb', line 11

def write(bytes)
  previous_pos, @pos = @pos, @pos + bytes.bytesize
  return 0 if bytes.bytesize == 0

  location_in_output = Range.new(previous_pos, previous_pos + bytes.bytesize - 1)
  overlap = intersection_of(@range, location_in_output)
  if overlap
    at = overlap.begin - previous_pos
    n = overlap.end - overlap.begin + 1
    @io.write(bytes.byteslice(at, n))
  end

  bytes.bytesize
end