SERVER-19977 Offer a stack based JSStringWrapper

Small string optimization for encoding utf8 strings from JS strings on
the stack. Additions to the api to use on stack buffers.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/mongo/scripting/mozjs/bson.cpp b/src/mongo/scripting/mozjs/bson.cpp
index f2c30407845..9f0a6125d22 100644
--- a/src/mongo/scripting/mozjs/bson.cpp
+++ b/src/mongo/scripting/mozjs/bson.cpp
@@ -194,15 +194,16 @@ void BSONInfo::resolve(JSContext* cx, JS::HandleObject obj, JS::HandleId id, boo
     }
 
     IdWrapper idw(cx, id);
+    JSStringWrapper jsstr;
 
-    if (!holder->_readOnly && holder->_removed.count(idw.toString())) {
+    auto sname = idw.toStringData(&jsstr);
+
+    if (!holder->_readOnly && holder->_removed.find(sname.toString()) != holder->_removed.end()) {
         return;
     }
 
     ObjectWrapper o(cx, obj);
 
-    std::string sname = IdWrapper(cx, id).toString();
-
     if (holder->_obj.hasField(sname)) {
         auto elem = holder->_obj[sname];