object_diagnostics.rb

module ObjectDiagnostics
  extend self

  #This is handy when you want to determine what types of objects are contributing to memory bloat  
  #returns the change in object counts since the last time this method was called
  def change_in_object_counts
    
    #this will start all counts at 0 for the initial run
    @previous_counts ||= Hash.new(0)

    #garbage collect before getting the current count so that we are only looking at objects that are causing bloat
    ObjectSpace.garbage_collect

    current_counts = ObjectSpace.count_objects

    count_differences = {}
    current_counts.each do |key, value|
      count_differences[key] = ( value - @previous_counts[key] )
    end

    @previous_counts = current_counts

    count_differences
  end

  def display(method, options = {})
    res = format(method, options)
    
    res.each { |l| puts l }
  end
  
  def format(method, options = {})
    res = calculate(method, options)
    
    case method
    when :array_by_content
      res.map! { |k, count| "#{count}: #{k.inspect[0..50]}"}
    when :string_by_content
      res.map! { |k, count| "#{count}: #{k[0..50].inspect}"}
    else
      res.map! { |k, count| "#{count}: #{k}" }
    end
    
    res
  end

  def calculate(method, options = {})
    h = Hash.new { |h,k| h[k] = 0 }
    mod = Object
    
    p = case method
    when :class_by_count
      proc { |obj| h[obj.class.to_s] += 1 rescue nil }
    when :array_by_length
      mod = Array
      proc { |obj| h[obj.length] += 1 }
    when :array_by_content
      mod = Array
      proc { |obj| h[obj] += 1 rescue nil }
    when :string_by_length
      mod = String
      proc { |obj| h[obj.length] += 1 }
    when :string_by_content
      mod = String
      proc { |obj| h[obj] += 1 }
    else
      raise "Unknown method: #{method}"
    end
    
    ObjectSpace.each_object(mod, &p)
    
    res = h.sort_by { |(k, v)| v }
    
    if top = options[:top]
      res = res[-top ... -1]
    end
    
    res
  end
end