Fix StringData::substr with single argument

Original version had an overflow bug
mongodb · Jan 9, 2013 · 0c05bdf · 0c05bdf
1 parent b2ab973
commit 0c05bdf
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Showing 2 changed files with 39 additions and 11 deletions.
diff --git a/src/mongo/base/string_data-inl.h b/src/mongo/base/string_data-inl.h
@@ -91,7 +91,8 @@ namespace mongo {
         if ( pos > size() )
             throw std::out_of_range( "out of range" );
 
-        if ( pos + n > size() )
+        // truncate to end of string
+        if ( n > size() - pos )
             n = size() - pos;
 
         return StringData( _data + pos, n );

diff --git a/src/mongo/base/string_data_test.cpp b/src/mongo/base/string_data_test.cpp
@@ -124,18 +124,45 @@ namespace {
     }
 
     // this is to verify we match std::string
-#define SUBSTR_TEST_HELP(big,small,start,len)   \
-    ASSERT_EQUALS( (string)small, ((string)big).substr( start, len ) ); \
-    ASSERT_EQUALS( StringData(small), StringData(big).substr( start, len ) );
+    void SUBSTR_TEST_HELP(StringData big, StringData small, size_t start, size_t len) {
+        ASSERT_EQUALS(small.toString(), big.toString().substr(start, len));
+        ASSERT_EQUALS(small, StringData(big).substr(start, len));
+    }
+    void SUBSTR_TEST_HELP(StringData big, StringData small, size_t start) {
+        ASSERT_EQUALS(small.toString(), big.toString().substr(start));
+        ASSERT_EQUALS(small, StringData(big).substr(start));
+    }
+
+// [12] is number of args to substr
+#define SUBSTR_1_TEST_HELP(big,small,start)   \
+    ASSERT_EQUALS( StringData(small).toString(), StringData(big).toString().substr(start) ); \
+    ASSERT_EQUALS( StringData(small), StringData(big).substr(start) );
+
+#define SUBSTR_2_TEST_HELP(big,small,start,len)   \
+    ASSERT_EQUALS( StringData(small).toString(), StringData(big).toString().substr(start, len) ); \
+    ASSERT_EQUALS( StringData(small), StringData(big).substr(start, len) );
 
     TEST(Substr, Simple1 ) {
-        SUBSTR_TEST_HELP( "abcde", "abcde", 0, 10 );
-        SUBSTR_TEST_HELP( "abcde", "abcde", 0, 5 );
-        SUBSTR_TEST_HELP( "abcde", "abc", 0, 3 );
-        SUBSTR_TEST_HELP( "abcde", "cde", 2, 5 );
-        SUBSTR_TEST_HELP( "abcde", "cde", 2, 3 );
-        SUBSTR_TEST_HELP( "abcde", "cd", 2, 2 );
-        SUBSTR_TEST_HELP( "abcde", "cd", 2, 2 );
+        SUBSTR_1_TEST_HELP( "abcde", "abcde", 0 );
+        SUBSTR_2_TEST_HELP( "abcde", "abcde", 0, 10 );
+        SUBSTR_2_TEST_HELP( "abcde", "abcde", 0, 5 );
+        SUBSTR_2_TEST_HELP( "abcde", "abc", 0, 3 );
+        SUBSTR_1_TEST_HELP( "abcde", "cde", 2 );
+        SUBSTR_2_TEST_HELP( "abcde", "cde", 2, 5 );
+        SUBSTR_2_TEST_HELP( "abcde", "cde", 2, 3 );
+        SUBSTR_2_TEST_HELP( "abcde", "cd", 2, 2 );
+        SUBSTR_2_TEST_HELP( "abcde", "cd", 2, 2 );
+        SUBSTR_1_TEST_HELP( "abcde", "", 5 );
+        SUBSTR_2_TEST_HELP( "abcde", "", 5, 0 );
+        SUBSTR_2_TEST_HELP( "abcde", "", 5, 10 );
+
+        // make sure we don't blow past the end of the StringData
+        SUBSTR_1_TEST_HELP( StringData("abcdeXXX", 5), "abcde", 0);
+        SUBSTR_2_TEST_HELP( StringData("abcdeXXX", 5), "abcde", 0, 10);
+        SUBSTR_1_TEST_HELP( StringData("abcdeXXX", 5), "de", 3);
+        SUBSTR_2_TEST_HELP( StringData("abcdeXXX", 5), "de", 3, 7);
+        SUBSTR_1_TEST_HELP( StringData("abcdeXXX", 5), "", 5);
+        SUBSTR_2_TEST_HELP( StringData("abcdeXXX", 5), "", 5, 1);
     }
 
     TEST( equalCaseInsensitiveTest, Simple1 ) {