get_or_throw and get_optional

[folly.git] / folly / MapUtil.h

diff --git a/folly/MapUtil.h b/folly/MapUtil.h
index 25863370da41ca5557bbe57086a92e116f94df3c..b00bccff4d99b0122340397fcd7554fca89d2290 100644 (file)
--- a/folly/MapUtil.h
+++ b/folly/MapUtil.h
@@ -17,6 +17,9 @@
 #ifndef FOLLY_MAPUTIL_H_
 #define FOLLY_MAPUTIL_H_
 
+#include <folly/Conv.h>
+#include <folly/Optional.h>
+
 namespace folly {
 
 /**
@@ -32,6 +35,36 @@ typename Map::mapped_type get_default(
   return (pos != map.end() ? pos->second : dflt);
 }
 
+/**
+ * Given a map and a key, return the value corresponding to the key in the map,
+ * or throw an exception of the specified type.
+ */
+template <class E = std::out_of_range, class Map>
+typename Map::mapped_type get_or_throw(
+    const Map& map, const typename Map::key_type& key,
+    const std::string& exceptionStrPrefix = std::string()) {
+  auto pos = map.find(key);
+  if (pos != map.end()) {
+    return pos->second;
+  }
+  throw E(folly::to<std::string>(exceptionStrPrefix, key));
+}
+
+/**
+ * Given a map and a key, return a Optional<V> if the key exists and None if the
+ * key does not exist in the map.
+ */
+template <class Map>
+folly::Optional<typename Map::mapped_type> get_optional(
+    const Map& map, const typename Map::key_type& key) {
+  auto pos = map.find(key);
+  if (pos != map.end()) {
+    return folly::Optional<typename Map::mapped_type>(pos->second);
+  } else {
+    return folly::none;
+  }
+}
+
 /**
  * Given a map and a key, return a reference to the value corresponding to the
  * key in the map, or the given default reference if the key doesn't exist in