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require 'concurrent/synchronization'
module Concurrent
# @!macro semaphore
# @!visibility private
# @!macro internal_implementation_note
class MutexSemaphore < Synchronization::LockableObject
# @!macro semaphore_method_initialize
def initialize(count)
unless count.is_a?(Fixnum) && count >= 0
fail ArgumentError, 'count must be an non-negative integer'
end
super()
synchronize { ns_initialize count }
end
# @!macro semaphore_method_acquire
def acquire(permits = 1)
unless permits.is_a?(Fixnum) && permits > 0
fail ArgumentError, 'permits must be an integer greater than zero'
end
synchronize do
try_acquire_timed(permits, nil)
nil
end
end
# @!macro semaphore_method_available_permits
def available_permits
synchronize { @free }
end
# @!macro semaphore_method_drain_permits
#
# Acquires and returns all permits that are immediately available.
#
# @return [Integer]
def drain_permits
synchronize do
@free.tap { |_| @free = 0 }
end
end
# @!macro semaphore_method_try_acquire
def try_acquire(permits = 1, timeout = nil)
unless permits.is_a?(Fixnum) && permits > 0
fail ArgumentError, 'permits must be an integer greater than zero'
end
synchronize do
if timeout.nil?
try_acquire_now(permits)
else
try_acquire_timed(permits, timeout)
end
end
end
# @!macro semaphore_method_release
def release(permits = 1)
unless permits.is_a?(Fixnum) && permits > 0
fail ArgumentError, 'permits must be an integer greater than zero'
end
synchronize do
@free += permits
permits.times { ns_signal }
end
nil
end
# Shrinks the number of available permits by the indicated reduction.
#
# @param [Fixnum] reduction Number of permits to remove.
#
# @raise [ArgumentError] if `reduction` is not an integer or is negative
#
# @raise [ArgumentError] if `@free` - `@reduction` is less than zero
#
# @return [nil]
#
# @!visibility private
def reduce_permits(reduction)
unless reduction.is_a?(Fixnum) && reduction >= 0
fail ArgumentError, 'reduction must be an non-negative integer'
end
synchronize { @free -= reduction }
nil
end
protected
# @!visibility private
def ns_initialize(count)
@free = count
end
private
# @!visibility private
def try_acquire_now(permits)
if @free >= permits
@free -= permits
true
else
false
end
end
# @!visibility private
def try_acquire_timed(permits, timeout)
ns_wait_until(timeout) { try_acquire_now(permits) }
end
end
end
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