2 files changed, 18 insertions, 7 deletions

diff --git a/src/mongo/bson/bsonobj.cpp b/src/mongo/bson/bsonobj.cpp
index 74d3edf1588..284058feecf 100644
--- a/src/mongo/bson/bsonobj.cpp
+++ b/src/mongo/bson/bsonobj.cpp
@@ -346,8 +346,7 @@ bool BSONObj::isFieldNamePrefixOf(const BSONObj& otherObj) const {
     return !a.more();
 }
 
-BSONObj BSONObj::extractFieldsUnDotted(const BSONObj& pattern) const {
-    BSONObjBuilder b;
+void BSONObj::extractFieldsUndotted(BSONObjBuilder* b, const BSONObj& pattern) const {
     BSONObjIterator i(pattern);
     while (i.moreWithEOO()) {
         BSONElement e = i.next();
@@ -355,13 +354,17 @@ BSONObj BSONObj::extractFieldsUnDotted(const BSONObj& pattern) const {
             break;
         BSONElement x = getField(e.fieldName());
         if (!x.eoo())
-            b.appendAs(x, "");
+            b->appendAs(x, "");
     }
-    return b.obj();
 }
 
-BSONObj BSONObj::filterFieldsUndotted(const BSONObj& filter, bool inFilter) const {
+BSONObj BSONObj::extractFieldsUndotted(const BSONObj& pattern) const {
     BSONObjBuilder b;
+    extractFieldsUndotted(&b, pattern);
+    return b.obj();
+}
+
+void BSONObj::filterFieldsUndotted(BSONObjBuilder* b, const BSONObj& filter, bool inFilter) const {
     BSONObjIterator i(*this);
     while (i.moreWithEOO()) {
         BSONElement e = i.next();
@@ -369,8 +372,13 @@ BSONObj BSONObj::filterFieldsUndotted(const BSONObj& filter, bool inFilter) cons
             break;
         BSONElement x = filter.getField(e.fieldName());
         if ((x.eoo() && !inFilter) || (!x.eoo() && inFilter))
-            b.append(e);
+            b->append(e);
     }
+}
+
+BSONObj BSONObj::filterFieldsUndotted(const BSONObj& filter, bool inFilter) const {
+    BSONObjBuilder b;
+    filterFieldsUndotted(&b, filter, inFilter);
     return b.obj();
 }
 
diff --git a/src/mongo/bson/bsonobj.h b/src/mongo/bson/bsonobj.h
index 215652bcd29..f22c9391bb6 100644
--- a/src/mongo/bson/bsonobj.h
+++ b/src/mongo/bson/bsonobj.h
@@ -52,6 +52,7 @@
 
 namespace mongo {
 
+class BSONObjBuilder;
 class BSONObjStlIterator;
 class ExtendedCanonicalV200Generator;
 class ExtendedRelaxedV200Generator;
@@ -393,9 +394,11 @@ public:
      *    this.extractFieldsUnDotted({b : "blah"}) -> {"" : 5}
      *
      */
-    BSONObj extractFieldsUnDotted(const BSONObj& pattern) const;
+    BSONObj extractFieldsUndotted(const BSONObj& pattern) const;
+    void extractFieldsUndotted(BSONObjBuilder* b, const BSONObj& pattern) const;
 
     BSONObj filterFieldsUndotted(const BSONObj& filter, bool inFilter) const;
+    void filterFieldsUndotted(BSONObjBuilder* b, const BSONObj& filter, bool inFilter) const;
 
     BSONElement getFieldUsingIndexNames(StringData fieldName, const BSONObj& indexKey) const;