collectOne

[folly.git] / folly / futures / helpers.h

diff --git a/folly/futures/helpers.h b/folly/futures/helpers.h
index 75f925374bd22521b2a5c8fc22e6113d823f1d48..7f074a06664a5a363db0cb64508d3e7b3ae2d4c3 100644 (file)
--- a/folly/futures/helpers.h
+++ b/folly/futures/helpers.h
@@ -226,6 +226,23 @@ auto collectAny(Collection&& c) -> decltype(collectAny(c.begin(), c.end())) {
   return collectAny(c.begin(), c.end());
 }
 
+/** Similar to collectAny, collectAnyWithoutException return the first Future to
+ * complete without exceptions. If none of the future complete without
+ * excpetions, the last exception will be returned as a result.
+  */
+template <class InputIterator>
+Future<std::pair<
+    size_t,
+    typename std::iterator_traits<InputIterator>::value_type::value_type>>
+collectAnyWithoutException(InputIterator first, InputIterator last);
+
+/// Sugar for the most common case
+template <class Collection>
+auto collectAnyWithoutException(Collection&& c)
+    -> decltype(collectAnyWithoutException(c.begin(), c.end())) {
+  return collectAnyWithoutException(c.begin(), c.end());
+}
+
 /** when n Futures have completed, the Future completes with a vector of
   the index and Try of those n Futures (the indices refer to the original
   order, but the result vector will be in an arbitrary order)