class Concurrent::Collection::NonConcurrentMapBackend

@!visibility private

def [](key) 

def [](key)
  @backend[key]
end

def []=(key, value) 

def []=(key, value)
  @backend[key] = value
end

def clear 

def clear
  @backend.clear
  self
end

def compute(key) 

def compute(key)
  store_computed_value(key, yield(get_or_default(key, nil)))
end

def compute_if_absent(key) 

def compute_if_absent(key)
  if NULL != (stored_value = @backend.fetch(key, NULL))
    stored_value
  else
    @backend[key] = yield
  end
end

def compute_if_present(key) 

def compute_if_present(key)
  if NULL != (stored_value = @backend.fetch(key, NULL))
    store_computed_value(key, yield(stored_value))
  end
end

def delete(key) 

def delete(key)
  @backend.delete(key)
end

def delete_pair(key, value) 

def delete_pair(key, value)
  if pair?(key, value)
    @backend.delete(key)
    true
  else
    false
  end
end

def dupped_backend 

def dupped_backend
  @backend.dup
end

def each_pair 

def each_pair
  dupped_backend.each_pair do |k, v|
    yield k, v
  end
  self
end

def get_and_set(key, value) 

def get_and_set(key, value)
  stored_value = get_or_default(key, nil)
  @backend[key] = value
  stored_value
end

def get_or_default(key, default_value) 

def get_or_default(key, default_value)
  @backend.fetch(key, default_value)
end

def initialize(options = nil, &default_proc)

reasons.
SynchronizedMapBackend which uses a non-reentrant mutex for performance
directly without calling each other. This is important because of the
WARNING: all public methods of the class must operate on the @backend 
def initialize(options = nil, &default_proc)
  validate_options_hash!(options) if options.kind_of?(::Hash)
  set_backend(default_proc)
  @default_proc = default_proc
end

def initialize_copy(other) 

def initialize_copy(other)
  super
  set_backend(@default_proc)
  self
end

def key?(key) 

def key?(key)
  @backend.key?(key)
end

def merge_pair(key, value) 

def merge_pair(key, value)
  if NULL == (stored_value = @backend.fetch(key, NULL))
    @backend[key] = value
  else
    store_computed_value(key, yield(stored_value))
  end
end

def pair?(key, expected_value) 

def pair?(key, expected_value)
  NULL != (stored_value = @backend.fetch(key, NULL)) && expected_value.equal?(stored_value)
end

def replace_if_exists(key, new_value) 

def replace_if_exists(key, new_value)
  if NULL != (stored_value = @backend.fetch(key, NULL))
    @backend[key] = new_value
    stored_value
  end
end

def replace_pair(key, old_value, new_value) 

def replace_pair(key, old_value, new_value)
  if pair?(key, old_value)
    @backend[key] = new_value
    true
  else
    false
  end
end

def set_backend(default_proc) 

def set_backend(default_proc)
  if default_proc
    @backend = ::Hash.new { |_h, key| default_proc.call(self, key) }
  else
    @backend = {}
  end
end

def size 

def size
  @backend.size
end

def store_computed_value(key, new_value) 

def store_computed_value(key, new_value)
  if new_value.nil?
    @backend.delete(key)
    nil
  else
    @backend[key] = new_value
  end
end