SERVER-19450 UnorderedFastKeyTable/StringMap construct with std::initializer_list

4 files changed, 33 insertions, 8 deletions

diff --git a/src/mongo/util/string_map.h b/src/mongo/util/string_map.h
index 724b03b9124..13e93977fcc 100644
--- a/src/mongo/util/string_map.h
+++ b/src/mongo/util/string_map.h
@@ -55,11 +55,11 @@ struct StringMapDefaultConvertorOther {
 };
 
 template <typename V>
-class StringMap : public UnorderedFastKeyTable<StringData,   // K_L
-                                               std::string,  // K_S
-                                               V,            // V
-                                               StringMapDefaultHash,
-                                               StringMapDefaultEqual,
-                                               StringMapDefaultConvertor,
-                                               StringMapDefaultConvertorOther> {};
-}
+using StringMap = UnorderedFastKeyTable<StringData,   // K_L
+                                        std::string,  // K_S
+                                        V,
+                                        StringMapDefaultHash,
+                                        StringMapDefaultEqual,
+                                        StringMapDefaultConvertor,
+                                        StringMapDefaultConvertorOther>;
+}  // namespace mongo
diff --git a/src/mongo/util/string_map_test.cpp b/src/mongo/util/string_map_test.cpp
index 6e49d34bdc5..0fbcfe2d28f 100644
--- a/src/mongo/util/string_map_test.cpp
+++ b/src/mongo/util/string_map_test.cpp
@@ -205,4 +205,14 @@ TEST(StringMapTest, Assign) {
     y = m;
     ASSERT_EQUALS(5, y["eliot"]);
 }
+
+TEST(StringMapTest, InitWithInitializerList) {
+    StringMap<int> smap{
+        {"q", 1}, {"coollog", 2}, {"mango", 3}, {"mango", 4},
+    };
+
+    ASSERT_EQ(1, smap["q"]);
+    ASSERT_EQ(2, smap["coollog"]);
+    ASSERT_EQ(3, smap["mango"]);
+}
 }
diff --git a/src/mongo/util/unordered_fast_key_table.h b/src/mongo/util/unordered_fast_key_table.h
index 781cc1e3fe1..aa42b786ce3 100644
--- a/src/mongo/util/unordered_fast_key_table.h
+++ b/src/mongo/util/unordered_fast_key_table.h
@@ -103,6 +103,8 @@ public:
 
     UnorderedFastKeyTable(const UnorderedFastKeyTable& other);
 
+    UnorderedFastKeyTable(std::initializer_list<std::pair<key_type, mapped_type>> entries);
+
     UnorderedFastKeyTable& operator=(const UnorderedFastKeyTable& other) {
         other.copyTo(this);
         return *this;
diff --git a/src/mongo/util/unordered_fast_key_table_internal.h b/src/mongo/util/unordered_fast_key_table_internal.h
index bddca264a9f..22ea22561a0 100644
--- a/src/mongo/util/unordered_fast_key_table_internal.h
+++ b/src/mongo/util/unordered_fast_key_table_internal.h
@@ -122,6 +122,19 @@ inline UnorderedFastKeyTable<K_L, K_S, V, H, E, C, C_LS>::UnorderedFastKeyTable(
       _convertorOther(other._convertorOther) {}
 
 template <typename K_L, typename K_S, typename V, typename H, typename E, typename C, typename C_LS>
+inline UnorderedFastKeyTable<K_L, K_S, V, H, E, C, C_LS>::UnorderedFastKeyTable(
+    std::initializer_list<std::pair<key_type, mapped_type>> entries)
+    : UnorderedFastKeyTable<K_L, K_S, V, H, E, C, C_LS>() {
+    for (auto&& entry : entries) {
+        // Only insert the entry if the key is not equivalent to the key of any other element
+        // already in the table.
+        if (find(entry.first) == end()) {
+            get(entry.first) = entry.second;
+        }
+    }
+}
+
+template <typename K_L, typename K_S, typename V, typename H, typename E, typename C, typename C_LS>
 inline void UnorderedFastKeyTable<K_L, K_S, V, H, E, C, C_LS>::copyTo(
     UnorderedFastKeyTable* out) const {
     out->_size = _size;