Add StringRef::compare for three way comparison

src/catch2/internal/catch_stringref.cpp

@@ -29,6 +29,27 @@ namespace Catch {
         return strncmp(m_start, rhs.m_start, rhs.m_size) < 0;
     }
 
+    int StringRef::compare( StringRef rhs ) const {
+        auto cmpResult =
+            strncmp( m_start, rhs.m_start, std::min( m_size, rhs.m_size ) );
+
+        // This means that strncmp found a difference before the strings
+        // ended, and we can return it directly
+        if ( cmpResult != 0 ) {
+            return cmpResult;
+        }
+
+        // If strings are equal up to length, then their comparison results on
+        // their size
+        if ( m_size < rhs.m_size ) {
+            return -1;
+        } else if ( m_size > rhs.m_size ) {
+            return 1;
+        } else {
+            return 0;
+        }
+    }
+
     auto operator << ( std::ostream& os, StringRef const& str ) -> std::ostream& {
         return os.write(str.data(), str.size());
     }

src/catch2/internal/catch_stringref.hpp

@@ -69,7 +69,6 @@ namespace Catch {
             return m_size;
         }
 
-    public: // substrings and searches
         // Returns a substring of [start, start + length).
         // If start + length > size(), then the substring is [start, start + size()).
         // If start > size(), then the substring is empty.
@@ -87,7 +86,6 @@ namespace Catch {
             return m_start;
         }
 
-    public: // iterators
         constexpr const_iterator begin() const { return m_start; }
         constexpr const_iterator end() const { return m_start + m_size; }
 
@@ -95,6 +93,14 @@ namespace Catch {
         friend std::string& operator += (std::string& lhs, StringRef const& sr);
         friend std::ostream& operator << (std::ostream& os, StringRef const& sr);
         friend std::string operator+(StringRef lhs, StringRef rhs);
+
+        /**
+         * Provides a three-way comparison with rhs
+         *
+         * Returns negative number if lhs < rhs, 0 if lhs == rhs, and a positive
+         * number if lhs > rhs
+         */
+        int compare( StringRef rhs ) const;
     };