Add timeout to Queue read operations

This lets us poll a quit flag up a layer in the event loop.

Change-Id: Id25c5098ded06c5af1d74591e4d606c0b7220c38
diff --git a/aos/condition.cc b/aos/condition.cc
index d1ad3a9..1e137b7 100644
--- a/aos/condition.cc
+++ b/aos/condition.cc
@@ -1,28 +1,56 @@
 #include "aos/condition.h"
 
-#include <inttypes.h>
 #include <assert.h>
+#include <inttypes.h>
+#include <time.h>
 
-#include "aos/type_traits/type_traits.h"
+#include "aos/logging/logging.h"
 #include "aos/mutex/mutex.h"
+#include "aos/type_traits/type_traits.h"
 
 namespace aos {
 
+namespace chrono = ::std::chrono;
+
 static_assert(shm_ok<Condition>::value,
               "Condition should work in shared memory");
 
 Condition::Condition(Mutex *m) : impl_(), m_(m) {}
 
 bool Condition::Wait() {
-  const int ret = condition_wait(&impl_, &m_->impl_);
+  const int ret = condition_wait(&impl_, &m_->impl_, nullptr);
   assert(__builtin_expect(ret == 0 || ret == 1, 1));
   return ret == 1;
 }
 
-void Condition::Signal() {
-  condition_signal(&impl_, &m_->impl_);
+Condition::WaitResult Condition::WaitTimed(chrono::nanoseconds timeout) {
+  struct timespec end_time;
+  const bool do_timeout = timeout != chrono::nanoseconds(0);
+
+  if (do_timeout) {
+    PCHECK(clock_gettime(CLOCK_MONOTONIC, &end_time) == 0);
+    timeout += chrono::nanoseconds(end_time.tv_nsec);
+    chrono::seconds timeout_seconds =
+        chrono::duration_cast<chrono::seconds>(timeout);
+    end_time.tv_sec += timeout_seconds.count();
+    end_time.tv_nsec = (timeout - timeout_seconds).count();
+  }
+
+  const int ret =
+      condition_wait(&impl_, &m_->impl_, do_timeout ? &end_time : nullptr);
+  assert(__builtin_expect(ret == 0 || ret == 1 || ret == -1, 1));
+  switch (ret) {
+    case 0:
+      return WaitResult::kOk;
+    case 1:
+      return WaitResult::kOwnerDied;
+    default:
+      return WaitResult::kTimeout;
+  }
 }
 
+void Condition::Signal() { condition_signal(&impl_, &m_->impl_); }
+
 void Condition::Broadcast() {
   condition_broadcast(&impl_, &m_->impl_);
 }