Update cancellation docs

docs/cancellation/README.md

@@ -1,28 +1,38 @@
 ---
-layout: docs
+layout: docs title: Cancellation permalink: /cancellation/
-title: Cancellation
-permalink: /cancellation/
 ---
-Amp provides primitives to allow the cancellation of operations, namely `CancellationTokenSource` and `CancellationToken`.
+Amp provides a `Cancellation` primitive to allow the cancellation of operations.
 
 ```php
-$tokenSource = new CancellationTokenSource;
+request("...", new Amp\TimeoutCancellation(30));
-$promise = asyncRequest("...", $tokenSource->getToken());
-
-Loop::delay(1000, function () use ($tokenSource) {
-    $tokenSource->cancel();
-});
-
-$result = yield $promise;
 ```
 
-Every operation that supports cancellation accepts an instance of `CancellationToken` as (optional) argument. Within a coroutine, `$token->throwIfRequested()` can be used to fail the operation with a `CancelledException`. As `$token` is often an optional parameter and might be `null`, these calls need to be guared with a `if ($token)` or similar check. Instead of doing so, it's often easier to simply set the token to `$token = $token ?? new NullCancellationToken` at the beginning of the method.
+```php
+$deferredCancellation = new Amp\DeferredCancellation();
+Loop::onSignal(SIG_INT, function () use ($deferredCancellation) {
+    $deferredCancellation->cancel();
+});
 
-While `throwIfRequested()` works well within coroutines, some operations might want to subscribe with a callback instead. They can do so using `CancellationToken::subscribe()` to subscribe any cancellation requests that might happen.
+request("...", $deferredCancellation->getCancellation());
+```
 
-If the operation consists of any sub-operations that support cancellation, it passes that same `CancellationToken` instance down to these sub-operations.
+Every operation that supports cancellation accepts an instance of `Cancellation` as (optional)
-  
+argument. `$cancellation->throwIfRequested()` can be used to fail the operation with a `CancelledException`.
-The original caller creates a `CancellationToken` by creating an instance of `CancellationTokenSource` and passing `$cancellationTokenSource->getToken()` to the operation as shown in the above example. Only the original caller has access to the `CancellationTokenSource` and can cancel the operation using `CancellationTokenSource::cancel()`, similar to the way it works with `Deferred` and `Promise`.
+As `$cancellation` is often an optional parameter and might be `null`, these calls need to be guarded with
+a `if ($cancellation)` or similar check. Instead of doing so, it's often easier to simply set the token
+to `$cancellation ??= new NullCancellationToken` at the beginning of the method.
+
+While `throwIfRequested()` works well, some operations might want to subscribe with a callback instead. They can do so
+using `Cancellation::subscribe()` to subscribe any cancellation requests that might happen.
+
+If the operation consists of any sub-operations that support cancellation, it passes that same `Cancellation`
+instance down to these sub-operations.
+
+The original caller creates a `Cancellation` by creating an instance of `DeferredCancellation` and
+passing `$deferred->getCancellation()` to the operation as shown in the above example, or using one of the other
+implementations of `Cancellation`, such as `TimeoutCancellation`. Only the original caller has access to
+the `DeferredCancellation` and can cancel the operation using `DeferredCancellation::cancel()`, similar to the way it
+works with `DeferredFuture` and `Future`.
 
 {:.note}
 > Cancellations are advisory only. A DNS resolver might ignore cancellation requests after the query has been sent as the response has to be processed anyway and can still be cached. An HTTP client might continue a nearly finished HTTP request to reuse the connection, but might abort a chunked encoding response as it cannot know whether continuing is actually cheaper than aborting.