SERVER-6400 FieldRef has a equalsDottedField to compare it to a full string

3 files changed, 52 insertions, 0 deletions

diff --git a/src/mongo/db/field_ref.cpp b/src/mongo/db/field_ref.cpp
index c3dbc47ed5d..68ab798b320 100644
--- a/src/mongo/db/field_ref.cpp
+++ b/src/mongo/db/field_ref.cpp
@@ -16,6 +16,7 @@
 
 #include "mongo/db/field_ref.h"
 
+#include "mongo/util/log.h"
 #include "mongo/util/assert_util.h"
 
 namespace mongo {
@@ -115,6 +116,34 @@ namespace mongo {
         return res;
     }
 
+    bool FieldRef::equalsDottedField( const StringData& other ) const {
+        StringData rest = other;
+
+
+        for ( size_t i = 0; i < _size; i++ ) {
+
+            StringData part = getPart( i );
+
+            if ( !rest.startsWith( part ) )
+                return false;
+
+            if ( i == _size - 1 )
+                return rest.size() == part.size();
+
+            // make sure next thing is a dot
+            if ( rest.size() == part.size() )
+                return false;
+
+            if ( rest[part.size()] != '.' )
+                return false;
+
+            rest = rest.substr( part.size() + 1 );
+        }
+
+        return false;
+    }
+
+
     size_t FieldRef::numReplaced() const {
         size_t res = 0;
         for (size_t i = 0; i < _replacements.size(); i++) {
diff --git a/src/mongo/db/field_ref.h b/src/mongo/db/field_ref.h
index ea7b7dab34d..ecc94bce046 100644
--- a/src/mongo/db/field_ref.h
+++ b/src/mongo/db/field_ref.h
@@ -88,6 +88,11 @@ namespace mongo {
          */
         size_t numReplaced() const;
 
+        /**
+         * compares the full dotted path represented by this FieldRef to other
+         */
+        bool equalsDottedField( const StringData& other ) const;
+
     private:
         // Dotted fields are most often not longer than three parts. We use a mixed structure
         // here that will not require any extra memory allocation when that is the case. And
diff --git a/src/mongo/db/field_ref_test.cpp b/src/mongo/db/field_ref_test.cpp
index cdf4aa7ad92..5c2b6dda00e 100644
--- a/src/mongo/db/field_ref_test.cpp
+++ b/src/mongo/db/field_ref_test.cpp
@@ -139,4 +139,22 @@ namespace {
         ASSERT_EQUALS(fieldRef.numReplaced(), 1U);
     }
 
+    TEST(Equality, Simple1 ) {
+        FieldRef a;
+        a.parse( "a.b" );
+        ASSERT( a.equalsDottedField( "a.b" ) );
+        ASSERT( !a.equalsDottedField( "a" ) );
+        ASSERT( !a.equalsDottedField( "b" ) );
+        ASSERT( !a.equalsDottedField( "a.b.c" ) );
+    }
+
+    TEST(Equality, Simple2 ) {
+        FieldRef a;
+        a.parse( "a" );
+        ASSERT( !a.equalsDottedField( "a.b" ) );
+        ASSERT( a.equalsDottedField( "a" ) );
+        ASSERT( !a.equalsDottedField( "b" ) );
+        ASSERT( !a.equalsDottedField( "a.b.c" ) );
+    }
+
 } // namespace mongo