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selector.rb
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selector.rb
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# Copyright, 2021, by Samuel G. D. Williams. <http://www.codeotaku.com>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
# The code in this class has been taken from io-event gem. It has been cleaned
# up and appropriated for use in this gem.
class FiberScheduler
class Selector
EAGAIN = Errno::EAGAIN::Errno
class Waiter
def initialize(fiber, events, tail)
@fiber = fiber
@events = events
@tail = tail
end
def alive?
@fiber&.alive?
end
def transfer(events)
if (fiber = @fiber)
@fiber = nil
fiber.transfer(events & @events) if fiber.alive?
end
@tail&.transfer(events)
end
def invalidate
@fiber = nil
end
def each(&block)
if (fiber = @fiber)
yield fiber, @events
end
@tail&.each(&block)
end
end
def initialize(fiber)
@fiber = fiber
@waiting = {}.compare_by_identity
@ready = []
end
def close
@fiber = nil
@waiting = nil
@ready = nil
end
def transfer
@fiber.transfer
end
def push(fiber)
@ready.push(fiber)
end
def io_wait(fiber, io, events)
waiter = @waiting[io] = Waiter.new(fiber, events, @waiting[io])
@fiber.transfer
ensure
waiter&.invalidate
end
def io_read(fiber, io, buffer, length, offset = 0)
loop do
maximum_size = buffer.size - offset
result = Fiber.new(blocking: true) {
io.read_nonblock(maximum_size, exception: false)
}.resume
case result
when :wait_readable
if length > 0
io_wait(fiber, io, IO::READABLE)
else
return -EAGAIN
end
when :wait_writable
if length > 0
io_wait(fiber, io, IO::WRITABLE)
else
return -EAGAIN
end
when nil
break
else
buffer.set_string(result, offset)
size = result.bytesize
offset += size
break if size >= length
length -= size
end
end
offset
end
def io_write(fiber, io, buffer, length, offset = 0)
loop do
maximum_size = buffer.size - offset
chunk = buffer.get_string(offset, maximum_size)
result = Fiber.new(blocking: true) {
io.write_nonblock(chunk, exception: false)
}.resume
case result
when :wait_readable
if length > 0
io_wait(fiber, io, IO::READABLE)
else
return -EAGAIN
end
when :wait_writable
if length > 0
io_wait(fiber, io, IO::WRITABLE)
else
return -EAGAIN
end
else
offset += result
break if result >= length
length -= result
end
end
offset
end
def process_wait(fiber, pid, flags)
reader, writer = IO.pipe
thread = Thread.new do
Process::Status.wait(pid, flags)
ensure
writer.close
end
io_wait(fiber, reader, IO::READABLE)
thread.value
ensure
reader.close
writer.close
thread&.kill
end
def select(duration = nil)
if @ready.any?
# If we have popped items from the ready list, they may influence the
# duration calculation, so we don't delay the event loop:
duration = 0
count = @ready.size
count.times do
fiber = @ready.shift
fiber.transfer if fiber.alive?
end
end
readable = []
writable = []
@waiting.each do |io, waiter|
waiter.each do |fiber, events|
if (events & IO::READABLE) > 0
readable << io
end
if (events & IO::WRITABLE) > 0
writable << io
end
end
end
duration = 0 if @ready.any?
readable, writable, _ = IO.select(readable, writable, nil, duration)
ready = Hash.new(0)
readable&.each do |io|
ready[io] |= IO::READABLE
end
writable&.each do |io|
ready[io] |= IO::WRITABLE
end
ready.each do |io, events|
waiter = @waiting.delete(io)
waiter.transfer(events)
end
ready.size
end
end
end