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



27
28
29
30
31
32
33
34
35
36
# 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

#hiInteger (readonly)

Returns Upper boundary of the integer range available for allocation

Returns:

  • (Integer)

    Upper boundary of the integer range available for allocation



20
21
22
# File 'lib/amq/int_allocator.rb', line 20

def hi
  @hi
end

#loInteger (readonly)

Returns Lower boundary of the integer range available for allocation

Returns:

  • (Integer)

    Lower boundary of the integer range available for allocation



22
23
24
# File 'lib/amq/int_allocator.rb', line 22

def lo
  @lo
end

#number_of_bitsInteger (readonly)

Returns Number of integers in the allocation range

Returns:

  • (Integer)

    Number of integers in the allocation range



18
19
20
# File 'lib/amq/int_allocator.rb', line 18

def number_of_bits
  @number_of_bits
end

Instance Method Details

#allocateInteger

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



45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
# 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



71
72
73
# 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



65
66
67
# File 'lib/amq/int_allocator.rb', line 65

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

#resetObject

Releases the whole allocation range



76
77
78
# File 'lib/amq/int_allocator.rb', line 76

def reset
  @free_set.clear
end