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channel.rb
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channel.rb
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require 'forwardable'
require 'concurrent/channel/buffer'
require 'concurrent/channel/selector'
require 'concurrent/maybe'
require 'concurrent/executor/cached_thread_pool'
module Concurrent
# {include:file:docs-source/channel.md}
# @!macro warn.edge
class Channel
extend Forwardable
include Enumerable
# NOTE: Move to global IO pool once stable
GOROUTINES = Concurrent::CachedThreadPool.new
private_constant :GOROUTINES
BUFFER_TYPES = {
unbuffered: Buffer::Unbuffered,
buffered: Buffer::Buffered,
dropping: Buffer::Dropping,
sliding: Buffer::Sliding
}.freeze
private_constant :BUFFER_TYPES
DEFAULT_VALIDATOR = ->(value){ true }
private_constant :DEFAULT_VALIDATOR
Error = Class.new(StandardError)
class ValidationError < Error
def initialize(message = nil)
message ||= 'invalid value'
end
end
def_delegators :buffer,
:size, :capacity, :close, :closed?,
:blocking?, :empty?, :full?
alias_method :length, :size
alias_method :stop, :close
def initialize(opts = {})
# undocumented -- for internal use only
if opts.is_a? Buffer::Base
self.buffer = opts
return
end
capacity = opts[:capacity] || opts[:size]
buffer = opts[:buffer]
if capacity && buffer == :unbuffered
raise ArgumentError.new('unbuffered channels cannot have a capacity')
elsif capacity.nil? && buffer.nil?
self.buffer = BUFFER_TYPES[:unbuffered].new
elsif capacity == 0 && buffer == :buffered
self.buffer = BUFFER_TYPES[:unbuffered].new
elsif buffer == :unbuffered
self.buffer = BUFFER_TYPES[:unbuffered].new
elsif capacity.nil? || capacity < 1
raise ArgumentError.new('capacity must be at least 1 for this buffer type')
else
buffer ||= :buffered
self.buffer = BUFFER_TYPES[buffer].new(capacity)
end
self.validator = opts.fetch(:validator, DEFAULT_VALIDATOR)
end
def put(item)
return false unless validate(item, false, false)
do_put(item)
end
alias_method :send, :put
alias_method :<<, :put
def put!(item)
validate(item, false, true)
ok = do_put(item)
raise Error if !ok
ok
end
def put?(item)
if !validate(item, true, false)
Concurrent::Maybe.nothing('invalid value')
elsif do_put(item)
Concurrent::Maybe.just(true)
else
Concurrent::Maybe.nothing
end
end
def offer(item)
return false unless validate(item, false, false)
do_offer(item)
end
def offer!(item)
validate(item, false, true)
ok = do_offer(item)
raise Error if !ok
ok
end
def offer?(item)
if !validate(item, true, false)
Concurrent::Maybe.nothing('invalid value')
elsif do_offer(item)
Concurrent::Maybe.just(true)
else
Concurrent::Maybe.nothing
end
end
def take
item = do_take
item == Concurrent::NULL ? nil : item
end
alias_method :receive, :take
alias_method :~, :take
def take!
item = do_take
raise Error if item == Concurrent::NULL
item
end
def take?
item = do_take
item = if item == Concurrent::NULL
Concurrent::Maybe.nothing
else
Concurrent::Maybe.just(item)
end
item
end
# @example
#
# jobs = Channel.new
#
# Channel.go do
# loop do
# j, more = jobs.next
# if more
# print "received job #{j}\n"
# else
# print "received all jobs\n"
# break
# end
# end
# end
def next
item, more = do_next
item = nil if item == Concurrent::NULL
return item, more
end
def next?
item, more = do_next
item = if item == Concurrent::NULL
Concurrent::Maybe.nothing
else
Concurrent::Maybe.just(item)
end
return item, more
end
def poll
(item = do_poll) == Concurrent::NULL ? nil : item
end
def poll!
item = do_poll
raise Error if item == Concurrent::NULL
item
end
def poll?
if (item = do_poll) == Concurrent::NULL
Concurrent::Maybe.nothing
else
Concurrent::Maybe.just(item)
end
end
def each
raise ArgumentError.new('no block given') unless block_given?
loop do
item, more = do_next
if item != Concurrent::NULL
yield(item)
elsif !more
break
end
end
end
class << self
def timer(seconds)
Channel.new(Buffer::Timer.new(seconds))
end
alias_method :after, :timer
def ticker(interval)
Channel.new(Buffer::Ticker.new(interval))
end
alias_method :tick, :ticker
def select(*args)
raise ArgumentError.new('no block given') unless block_given?
selector = Selector.new
yield(selector, *args)
selector.execute
end
alias_method :alt, :select
def go(*args, &block)
go_via(GOROUTINES, *args, &block)
end
def go_via(executor, *args, &block)
raise ArgumentError.new('no block given') unless block_given?
executor.post(*args, &block)
end
def go_loop(*args, &block)
go_loop_via(GOROUTINES, *args, &block)
end
def go_loop_via(executor, *args, &block)
raise ArgumentError.new('no block given') unless block_given?
executor.post(block, *args) do
loop do
break unless block.call(*args)
end
end
end
end
private
def validator
@validator
end
def validator=(value)
@validator = value
end
def buffer
@buffer
end
def buffer=(value)
@buffer = value
end
def validate(value, allow_nil, raise_error)
if !allow_nil && value.nil?
raise_error ? raise(ValidationError.new('nil is not a valid value')) : false
elsif !validator.call(value)
raise_error ? raise(ValidationError) : false
else
true
end
rescue => ex
# the validator raised an exception
return raise_error ? raise(ex) : false
end
def do_put(item)
buffer.put(item)
end
def do_offer(item)
buffer.offer(item)
end
def do_take
buffer.take
end
def do_next
buffer.next
end
def do_poll
buffer.poll
end
end
end