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import Cocoa
enum CoroutineState {
case Fresh, Running, Blocked, Canceled, Done
}
struct CoroutineCancellation: ErrorType {}
class CoroutineImpl<InputType, YieldType> {
let body: (yield: YieldType throws -> InputType) throws -> Void
var state = CoroutineState.Fresh
let lock = NSCondition()
var inputValue: InputType?
var yieldValue: YieldType?
init(body: (yield: YieldType throws -> InputType) throws -> Void) {
self.body = body
}
func getNext(value: InputType) -> YieldType? {
lock.lock()
inputValue = value
unblock()
while state == .Running {
lock.wait()
}
let result = yieldValue
yieldValue = nil
lock.unlock()
return result
}
func cancel() {
lock.lock()
state = .Canceled
lock.signal()
lock.unlock()
}
private func unblock() {
switch state {
case .Fresh:
state = .Running
dispatch_async(dispatch_get_global_queue(0, 0), {
do {
try self.body(yield: self.yield)
} catch {}
self.lock.lock()
self.state = .Done
self.lock.signal()
self.lock.unlock()
})
case .Running:
preconditionFailure("Must never call unblock() while running")
case .Blocked:
state = .Running
lock.signal()
case .Canceled:
break
case .Done:
break
}
}
private func yield(value: YieldType) throws -> InputType {
lock.lock()
self.yieldValue = value
state = .Blocked
lock.signal()
while state == .Blocked {
lock.wait()
}
let canceled = state == .Canceled
let input = inputValue
inputValue = nil
lock.unlock()
if canceled {
throw CoroutineCancellation()
}
return input!
}
}
class Coroutine<InputType, YieldType> {
let impl: CoroutineImpl<InputType, YieldType>
init(_ body: (yield: YieldType throws -> InputType) throws -> Void) {
impl = CoroutineImpl(body: body)
}
deinit {
impl.cancel()
}
func getNext(value: InputType) -> YieldType? {
return impl.getNext(value)
}
}
func coroutine<InputType, YieldType>(type: (InputType, YieldType).Type, _ body: (yield: YieldType throws -> InputType) throws -> Void) -> (InputType -> YieldType?){
let obj = Coroutine(body)
return obj.getNext
}
var c: Coroutine<Void, Int>? = Coroutine<Void, Int>({ yield in
for i in 0..<10 {
try yield(i)
}
})
c?.getNext()
c?.getNext()
c?.getNext()
c?.getNext()
c = nil
var d: (Void -> Int?)? = coroutine((Void, Int).self, { yield in
for i in 20..<30 {
try yield(i)
}
})
d?()
d?()
d?()
d = nil
let summer = coroutine((Int, Int).self, { yield in
var sum = 0
while true {
let value = try yield(sum)
print(value)
sum += value
}
})
summer(0)
summer(1)
summer(2)
summer(3)
summer(4)
summer(5)
sleep(1)
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