SERVER-36475 Reduce use of stringstream in BSONObj.jsonString

4 files changed, 35 insertions, 8 deletions

diff --git a/src/mongo/bson/bsonelement.cpp b/src/mongo/bson/bsonelement.cpp
index f0ea59acddc..ba44d546370 100644
--- a/src/mongo/bson/bsonelement.cpp
+++ b/src/mongo/bson/bsonelement.cpp
@@ -57,6 +57,14 @@ using std::string;
 
 string BSONElement::jsonString(JsonStringFormat format, bool includeFieldNames, int pretty) const {
     std::stringstream s;
+    BSONElement::jsonStringStream(format, includeFieldNames, pretty, s);
+    return s.str();
+}
+
+void BSONElement::jsonStringStream(JsonStringFormat format,
+                                   bool includeFieldNames,
+                                   int pretty,
+                                   std::stringstream& s) const {
     if (includeFieldNames)
         s << '"' << escape(fieldName()) << "\" : ";
     switch (type()) {
@@ -129,7 +137,7 @@ string BSONElement::jsonString(JsonStringFormat format, bool includeFieldNames,
             }
             break;
         case Object:
-            s << embeddedObject().jsonString(format, pretty);
+            embeddedObject().jsonStringStream(format, pretty, false, s);
             break;
         case mongo::Array: {
             if (embeddedObject().isEmpty()) {
@@ -151,7 +159,7 @@ string BSONElement::jsonString(JsonStringFormat format, bool includeFieldNames,
                     if (strtol(e.fieldName(), 0, 10) > count) {
                         s << "undefined";
                     } else {
-                        s << e.jsonString(format, false, pretty ? pretty + 1 : 0);
+                        e.jsonStringStream(format, false, pretty ? pretty + 1 : 0, s);
                         e = i.next();
                     }
                     count++;
@@ -303,7 +311,6 @@ string BSONElement::jsonString(JsonStringFormat format, bool includeFieldNames,
             string message = ss.str();
             massert(10312, message.c_str(), false);
     }
-    return s.str();
 }
 
 namespace {
diff --git a/src/mongo/bson/bsonelement.h b/src/mongo/bson/bsonelement.h
index 43cb8aa206b..09d15a6140d 100644
--- a/src/mongo/bson/bsonelement.h
+++ b/src/mongo/bson/bsonelement.h
@@ -207,9 +207,16 @@ public:
                   bool full = false,
                   bool redactValues = false,
                   int depth = 0) const;
+
     std::string jsonString(JsonStringFormat format,
                            bool includeFieldNames = true,
                            int pretty = 0) const;
+
+    void jsonStringStream(JsonStringFormat format,
+                          bool includeFieldNames,
+                          int pretty,
+                          std::stringstream& s) const;
+
     operator std::string() const {
         return toString();
     }
diff --git a/src/mongo/bson/bsonobj.cpp b/src/mongo/bson/bsonobj.cpp
index ff03f9aac79..2fd01c2d8e2 100644
--- a/src/mongo/bson/bsonobj.cpp
+++ b/src/mongo/bson/bsonobj.cpp
@@ -114,16 +114,25 @@ BSONObj BSONObj::getOwned() const {
 }
 
 string BSONObj::jsonString(JsonStringFormat format, int pretty, bool isArray) const {
-    if (isEmpty())
-        return isArray ? "[]" : "{}";
+    std::stringstream s;
+    BSONObj::jsonStringStream(format, pretty, isArray, s);
+    return s.str();
+}
 
-    StringBuilder s;
+void BSONObj::jsonStringStream(JsonStringFormat format,
+                               int pretty,
+                               bool isArray,
+                               std::stringstream& s) const {
+    if (isEmpty()) {
+        s << (isArray ? "[]" : "{}");
+        return;
+    }
     s << (isArray ? "[ " : "{ ");
     BSONObjIterator i(*this);
     BSONElement e = i.next();
     if (!e.eoo())
         while (1) {
-            s << e.jsonString(format, !isArray, pretty ? pretty + 1 : 0);
+            e.jsonStringStream(format, !isArray, pretty ? pretty + 1 : 0, s);
             e = i.next();
             if (e.eoo())
                 break;
@@ -137,7 +146,6 @@ string BSONObj::jsonString(JsonStringFormat format, int pretty, bool isArray) co
             }
         }
     s << (isArray ? " ]" : " }");
-    return s.str();
 }
 
 bool BSONObj::valid(BSONVersion version) const {
diff --git a/src/mongo/bson/bsonobj.h b/src/mongo/bson/bsonobj.h
index ee441046c25..2c9f41ceb60 100644
--- a/src/mongo/bson/bsonobj.h
+++ b/src/mongo/bson/bsonobj.h
@@ -254,6 +254,11 @@ public:
                            int pretty = 0,
                            bool isArray = false) const;
 
+    void jsonStringStream(JsonStringFormat format,
+                          int pretty,
+                          bool isArray,
+                          std::stringstream& s) const;
+
     /** note: addFields always adds _id even if not specified */
     int addFields(BSONObj& from, std::set<std::string>& fields); /* returns n added */