Class: AMQ::IntAllocator

Inherits:
Object
  • Object
show all
Defined in:
lib/amq/int_allocator.rb

Overview

Simple bitset-based integer allocator, heavily inspired by com.rabbitmq.utility.IntAllocator class in the RabbitMQ Java client.

Unlike monotonically incrementing identifier, this allocator is suitable for very long running programs that aggressively allocate and release channels.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(lo, hi) ⇒ IntAllocator

Returns a new instance of IntAllocator.

Parameters:

  • lo (Integer) —

    Lower boundary of the integer range available for allocation

  • hi (Integer) —

    Upper boundary of the integer range available for allocation

Raises:

  • (ArgumentError) —

    if upper boundary is not greater than the lower one



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# File 'lib/amq/int_allocator.rb', line 27

def initialize(lo, hi)
  raise ArgumentError.new "upper boundary must be greater than the lower one (given: hi = #{hi}, lo = #{lo})" unless hi > lo

  @hi = hi
  @lo = lo

  @number_of_bits = hi - lo
  @range          = Range.new(1, @number_of_bits)
  @free_set       = BitSet.new(@number_of_bits)
end

Instance Attribute Details

#hi ⇒ Integer (readonly)

Returns Upper boundary of the integer range available for allocation.

Returns:

  • (Integer) —

    Upper boundary of the integer range available for allocation



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# File 'lib/amq/int_allocator.rb', line 20

def hi
  @hi
end

#lo ⇒ Integer (readonly)

Returns Lower boundary of the integer range available for allocation.

Returns:

  • (Integer) —

    Lower boundary of the integer range available for allocation



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# File 'lib/amq/int_allocator.rb', line 22

def lo
  @lo
end

#number_of_bits ⇒ Integer (readonly)

Returns Number of integers in the allocation range.

Returns:

  • (Integer) —

    Number of integers in the allocation range



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# File 'lib/amq/int_allocator.rb', line 18

def number_of_bits
  @number_of_bits
end

Instance Method Details

#allocate ⇒ Integer

Attempts to allocate next available integer. If allocation succeeds, allocated value is returned. Otherwise, -1 is returned.

Current implementation of this method is O(n), where n is number of bits in the range available for allocation.

Returns:

  • (Integer) —

    Allocated integer if allocation succeeded. -1 otherwise.



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# File 'lib/amq/int_allocator.rb', line 45

def allocate

  if n = @free_set.next_clear_bit

    if n < @hi - 1 then
      @free_set.set(n)
      n + 1
    else
      -1
    end

  else
    -1
  end
end

#allocated?(reservation) ⇒ Boolean

Returns true if provided argument was previously allocated, false otherwise.

Returns:

  • (Boolean) —

    true if provided argument was previously allocated, false otherwise



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# File 'lib/amq/int_allocator.rb', line 71

def allocated?(reservation)
  @free_set.get(reservation-1)
end

#free(reservation) ⇒ NilClass Also known as: release

Releases previously allocated integer. If integer provided as argument was not previously allocated, this method has no effect.

Returns:

  • (NilClass) —

    nil



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# File 'lib/amq/int_allocator.rb', line 65

def free(reservation)
  @free_set.unset(reservation-1)
end

#reset ⇒ Object

Releases the whole allocation range



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# File 'lib/amq/int_allocator.rb', line 76

def reset
  @free_set.clear
end