Simple Hashtable implementation (hash collision resolution with open adressing)

hashtable.rb

class Hashtable
  INITIAL_TABLE_SIZE = 32
  Entry = Struct.new(:key, :value)

  def initialize
    @table = Array.new(INITIAL_TABLE_SIZE)
  end

  attr_accessor :table

  def []=(key, value)
    start_index = index = to_index(key)
    while @table[index] != nil && @table[index].key != key
      index = (index + 1) % @table.size
      expand_table_length if index == start_index
    end
    @table[index] = Entry.new(key, value)
  end

  def [](key)
    start_index = index = to_index(key)
    while @table[index] == nil || @table[index].key != key
      index = (index + 1) % @table.size
      return nil if index == start_index
    end
    @table[index].value
  end

  private

  def to_index(obj)
    obj.hash.abs % @table.size
  end

  def expand_table_length
    old_table = @table
    @table    = Array.new(old_table.size * 2)
    rehash(old_table)
  end

  def rehash(old_table)
    for e in old_table
      self[e.key] = e.value if e
    end
  end

end