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.
@param [Integer] lo Lower boundary of the integer range available for allocation @param [Integer] hi Upper boundary of the integer range available for allocation @raise [ArgumentError] if upper boundary is not greater than the lower one
# File lib/amqp/int_allocator.rb, line 26 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
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.
@return [Integer] Allocated integer if allocation succeeded. nil otherwise.
# File lib/amqp/int_allocator.rb, line 44 def allocate if n = find_unallocated_position @free_set.set(n) n else -1 end end
@return [Boolean] true if provided argument was previously allocated, false otherwise
# File lib/amqp/int_allocator.rb, line 64 def allocated?(reservation) @free_set.get(reservation) end
Releases previously allocated integer. If integer provided as argument was not previously allocated, this method has no effect.
@return [NilClass] nil
# File lib/amqp/int_allocator.rb, line 58 def free(reservation) @free_set.unset(reservation) end
This implementation is significantly less efficient that what the RabbitMQ Java client has (based on java.lang.Long#nextSetBit and java.lang.Long.numberOfTrailingZeros, and thus binary search over bits). But for channel id generation, this is a good enough implementation.
@private
# File lib/amqp/int_allocator.rb, line 83 def find_unallocated_position r = nil @range.each do |i| if !@free_set.get(i) r = i break; end end r end
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