SERVER-6399 Allowed creation of empty string data's.

2 files changed, 20 insertions, 5 deletions

diff --git a/src/mongo/base/string_data.h b/src/mongo/base/string_data.h
index bcb144e966a..1990138704c 100644
--- a/src/mongo/base/string_data.h
+++ b/src/mongo/base/string_data.h
@@ -37,20 +37,22 @@ namespace mongo {
      *
      *  + The object StringData wraps around must be alive while the StringData is.
      *
-     *  + Because strings accept null characters, we allow them in StringData. But this use is
-     *    *strongly* discouraged. One problem this case may encounter is when asking for data()
-     *    out of a StringData that was feed with, say "a\0b". If interpreted as a c-string,
-     *    the null character would cut the original string short.
+     *  + Because string data can be used to pass a substring around, one should never assume a
+     *    rawData() terminates with a null.
      */
     class StringData {
     public:
 
+        /** Constructs an empty string data */
+        StringData()
+            : _data(NULL), _size(0) {}
+
         /**
          * Constructs a StringData, for the case where the length of string is not known. 'c'
          * must be a pointer to a null-terminated string.
          */
         StringData( const char* c )
-            : _data(c), _size(string::npos){}
+            : _data(c), _size((c == NULL) ? 0 : string::npos) {}
 
         /**
          * Constructs a StringData explicitly, for the case where the length of the string is
diff --git a/src/mongo/base/string_data_test.cpp b/src/mongo/base/string_data_test.cpp
index 2dffa88f1ad..14b5ac5e471 100644
--- a/src/mongo/base/string_data_test.cpp
+++ b/src/mongo/base/string_data_test.cpp
@@ -24,6 +24,12 @@ namespace {
     using mongo::StringData;
     using std::string;
 
+    TEST(Construction, Empty) {
+        StringData strData;
+        ASSERT_EQUALS(strData.size(), 0U);
+        ASSERT_TRUE(strData.rawData() == NULL);
+    }
+
     TEST(Construction, FromStdString) {
         std::string base("aaa");
         StringData strData(base);
@@ -38,6 +44,13 @@ namespace {
         ASSERT_EQUALS(strData.toString(), base);
     }
 
+    TEST(Construction, FromNullCString) {
+        char* c = NULL;
+        StringData strData(c);
+        ASSERT_EQUALS(strData.size(), 0U);
+        ASSERT_TRUE(strData.rawData() == NULL);
+    }
+
     TEST(Construction, FromLiteral) {
         StringData strData("ccc", StringData::LiteralTag());
         ASSERT_EQUALS(strData.size(), 3U);