Timeouts: Add convenience helpers to kj::Timer interface for adding a timeout to any Promise.

c++/Makefile.am

@@ -221,7 +221,8 @@ libkj_async_la_LDFLAGS = -release $(VERSION) -no-undefined
 libkj_async_la_SOURCES=                                        \
   src/kj/async.c++                                             \
   src/kj/async-unix.c++                                        \
-  src/kj/async-io.c++
+  src/kj/async-io.c++                                          \
+  src/kj/time.c++
 endif !LITE_MODE
 
 if !LITE_MODE

c++/src/kj/CMakeLists.txt

@@ -38,7 +38,6 @@ set(kj_headers
   mutex.h
   thread.h
   threadlocal.h
-  time.h
   main.h
   windows-sanity.h
 )
@@ -59,6 +58,7 @@ set(kj-async_sources
   async.c++
   async-unix.c++
   async-io.c++
+  time.c++
 )
 set(kj-async_headers
   async-prelude.h
@@ -66,6 +66,7 @@ set(kj-async_headers
   async-inl.h
   async-unix.h
   async-io.h
+  time.h
 )
 if(NOT CAPNP_LITE)
   add_library(kj-async ${kj-async_sources})

c++/src/kj/async-io-test.c++

@@ -204,5 +204,17 @@ TEST(AsyncIo, PipeThreadDisconnects) {
   EXPECT_EQ(0, pipeThread.pipe->tryRead(buf, 1, 1).wait(ioContext.waitScope));
 }
 
+TEST(AsyncIo, Timeouts) {
+  auto ioContext = setupAsyncIo();
+
+  Timer& timer = ioContext.provider->getTimer();
+
+  auto promise1 = timer.timeoutAfter(1 * MILLISECONDS, kj::Promise<int>(kj::NEVER_DONE));
+  auto promise2 = timer.timeoutAfter(1 * MILLISECONDS, kj::Promise<int>(123));
+
+  EXPECT_TRUE(kj::runCatchingExceptions([&]() { promise1.wait(ioContext.waitScope); }) != nullptr);
+  EXPECT_EQ(123, promise2.wait(ioContext.waitScope));
+}
+
 }  // namespace
 }  // namespace kj

c++/src/kj/time.c++

+// Copyright (c) 2014 Google Inc. (contributed by Remy Blank <rblank@google.com>)
+// Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
+// Licensed under the MIT License:
+//
+// 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.
+
+#include "time.h"
+#include "debug.h"
+
+namespace kj {
+
+kj::Exception Timer::makeTimeoutException() {
+  return kj::Exception(
+      kj::Exception::Nature::LOCAL_BUG, kj::Exception::Durability::OVERLOADED,
+      __FILE__, __LINE__, kj::heapString("operation timed out"));
+}
+
+}  // namespace kj

c++/src/kj/time.h

@@ -80,8 +80,38 @@ public:
 
   virtual Promise<void> afterDelay(Duration delay) = 0;
   // Equivalent to atTime(now() + delay).
+
+  template <typename T>
+  Promise<T> timeoutAt(TimePoint time, Promise<T>&& promise);
+  // Return a promise equivalent to `promise` but which throws an exception (and cancels the
+  // original promise) if it hasn't completed by `time`.
+
+  template <typename T>
+  Promise<T> timeoutAfter(Duration delay, Promise<T>&& promise);
+  // Return a promise equivalent to `promise` but which throws an exception (and cancels the
+  // original promise) if it hasn't completed after `delay` from now.
+
+private:
+  static kj::Exception makeTimeoutException();
 };
 
+// =======================================================================================
+// inline implementation details
+
+template <typename T>
+Promise<T> Timer::timeoutAt(TimePoint time, Promise<T>&& promise) {
+  return promise.exclusiveJoin(atTime(time).then([]() -> kj::Promise<T> {
+    return makeTimeoutException();
+  }));
+}
+
+template <typename T>
+Promise<T> Timer::timeoutAfter(Duration delay, Promise<T>&& promise) {
+  return promise.exclusiveJoin(afterDelay(delay).then([]() -> kj::Promise<T> {
+    return makeTimeoutException();
+  }));
+}
+
 }  // namespace kj
 
 #endif  // KJ_TIME_H_