how to calculate market order lock volume.

market_order.rb

FUSE = '0.9'.to_d
  def estimate_required_funds(price_levels)
    required_funds = Account::ZERO
    expected_volume = volume

    start_from, _ = price_levels.first
    filled_at     = start_from

    until expected_volume.zero? || price_levels.empty?
      level_price, level_volume = price_levels.shift
      filled_at = level_price

      v = [expected_volume, level_volume].min
      required_funds += yield level_price, v
      expected_volume -= v
    end

    raise "Market is not deep enough" unless expected_volume.zero?
    raise "Volume too large" if (filled_at-start_from).abs/start_from > FUSE

    required_funds
  end

LOCKING_BUFFER_FACTOR = '1.1'.to_d
  def compute_locked
    case ord_type
    when 'limit'
      price*volume
    when 'market'
      funds = estimate_required_funds(Global[currency].asks) {|p, v| p*v }
      funds*LOCKING_BUFFER_FACTOR
    end
  end