Class: SlidingWindow

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/sliding_window.rb

Overview

Implementation of the sliding window algorithm.

Instance Method Summary collapse

Constructor Details

#initialize(buffer, max_size = 5, &block) ⇒ SlidingWindow

Initialize the sliding window. Given a buffer to slide over, the maximum size of the window, and a block to test whether the window matches anything, enumerate the sliding window instance to get at the matches.

buffer - The buffer to slide the window over. It can be any type, as long as

it responds to `#[]` and `#size`.

max_size - The maximum allowed length of the window. Defaults to 5. block - A block which will test whether the position of the current window

matches anything of interest. The block is passed the current window
into the buffer and is expected to return an object if the window
matches (it can be anything), otherwise `nil`. The objects returned
by this block will be yielded to the enumerable.



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# File 'lib/sliding_window.rb', line 19

def initialize(buffer, max_size = 5, &block)
  raise('The given buffer must respond to #[] and #size.') unless buffer.respond_to?(:[]) && buffer.respond_to?(:size)
  raise('The maximum buffer size must be greater than or equal to one.') if max_size.nil? || max_size < 1
  raise('A block is required to indicate whether a window matches anything of interest.') unless block_given?

  @buffer = buffer
  @max_size = max_size
  @mapper = block
end

Instance Method Details

#each ⇒ Object

Enumerable yields each time the window matches on something. The internal window is slid forward as expected.



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# File 'lib/sliding_window.rb', line 31

def each
  position = (0..@max_size - 1)

  loop do
    match = @mapper.call(@buffer[position])

    if match.nil?
      position = (position.begin..position.end - 1)
      position = slide_unmatched_window(position) if position.end < position.begin
    else
      yield match
      position = slide_matched_window(position)
    end

    break if position.first >= @buffer.size
  end
end