feat: add appendLine methods

Author: ronan-fesselier

CHANGELOG.md

@@ -4,11 +4,11 @@
 
 ### Added
 
-- NIL
+- Line-based operations: `appendLine(str)` and `appendLn(str)` - append string with automatic newline character
 
 ### Changed
 
-- NIL
+- chore(deps): bump google-benchmark from 1.9.4 to 1.9.5
 
 ### Deprecated
 

TODO.md

@@ -5,7 +5,6 @@ Project roadmap and task tracking for the nfx-stringbuilder library.
 ### Todo
 
 - [ ] Add convenience methods for common operations
-  - [ ] `appendLine(str)` / `appendLn(str)` - append with newline character
   - [ ] `join(container, delimiter)` - join collection elements with delimiter
   - [ ] `substr(pos, len)` for zero-copy access to portions
   - [ ] `replace(pos, len, str)` - in-place replacement
@@ -20,4 +19,4 @@ Project roadmap and task tracking for the nfx-stringbuilder library.
 
 ### Done ✓
 
-- NIL
+- [x] `appendLine(str)` / `appendLn(str)` - append with newline character (2026-02-08)

include/nfx/detail/string/StringBuilder.inl

@@ -320,6 +320,48 @@ namespace nfx::string
         return *this;
     }
 
+    //----------------------------------------------
+    // Line operations
+    //----------------------------------------------
+
+    inline StringBuilder& StringBuilder::appendLine( std::string_view str )
+    {
+        const size_t len = str.size();
+        const size_t newSize = m_size + len + 1; // +1 for newline
+
+        if( newSize > m_capacity ) [[unlikely]]
+        {
+            ensureCapacity( newSize );
+        }
+
+        // Append string content
+        if( len > 0 )
+        {
+            std::memcpy( m_buffer + m_size, str.data(), len );
+        }
+
+        // Append newline
+        m_buffer[m_size + len] = '\n';
+        m_size = newSize;
+
+        return *this;
+    }
+
+    inline StringBuilder& StringBuilder::appendLine( const std::string& str )
+    {
+        return appendLine( std::string_view{ str } );
+    }
+
+    inline StringBuilder& StringBuilder::appendLine( const char* str )
+    {
+        if( str ) [[likely]]
+        {
+            return appendLine( std::string_view{ str, strlen( str ) } );
+        }
+        // Just append newline if str is null
+        return append( '\n' );
+    }
+
     //----------------------------------------------
     // Prepend operations
     //----------------------------------------------

include/nfx/string/StringBuilder.h

@@ -359,6 +359,41 @@ namespace nfx::string
          */
         inline StringBuilder& append( double value );
 
+        //----------------------------------------------
+        // Line operations
+        //----------------------------------------------
+
+        /**
+         * @brief Appends string_view contents followed by a newline character
+         * @param str String view to append (default: empty)
+         * @return Reference to this StringBuilder for chaining
+         * @details Efficiently appends the string and newline in one operation.
+         *          Useful for building line-based formats like logs, CSV, or ISO 19848 messages.
+         *
+         * Example:
+         * @code
+         * builder.appendLine("Header")
+         *        .appendLine("Data1")
+         *        .appendLine("Data2");
+         * // Result: "Header\nData1\nData2\n"
+         * @endcode
+         */
+        inline StringBuilder& appendLine( std::string_view str = "" );
+
+        /**
+         * @brief Appends std::string contents followed by a newline character
+         * @param str String to append
+         * @return Reference to this StringBuilder for chaining
+         */
+        inline StringBuilder& appendLine( const std::string& str );
+
+        /**
+         * @brief Appends null-terminated C-string followed by a newline character
+         * @param str Null-terminated C-string to append (null pointer handled gracefully)
+         * @return Reference to this StringBuilder for chaining
+         */
+        inline StringBuilder& appendLine( const char* str );
+
         //----------------------------------------------
         // Prepend operations
         //----------------------------------------------

samples/Sample_StringBuilder.cpp

@@ -40,6 +40,27 @@
 #include <vector>
 #include <thread>
 
+//=====================================================================
+// Helper function: Calculate NMEA-0183 checksum
+//=====================================================================
+/**
+ * @brief Calculate NMEA-0183 checksum (XOR of all characters between $ and *)
+ * @param sentence NMEA sentence without $ prefix and * suffix
+ * @return Checksum as 2-digit uppercase hex string
+ */
+std::string calculateNmeaChecksum( std::string_view sentence )
+{
+    uint8_t checksum = 0;
+    for( char c : sentence )
+    {
+        checksum ^= static_cast<uint8_t>( c );
+    }
+
+    char result[3];
+    std::snprintf( result, sizeof( result ), "%02X", checksum );
+    return std::string{ result };
+}
+
 int main()
 {
     using namespace nfx::string;
@@ -619,10 +640,145 @@ int main()
     }
 
     //=====================================================================
-    // 15. Prepend operations - Building strings in reverse
+    // 15. Line-based operations - appendLine() / appendLn()
+    //=====================================================================
+    {
+        std::cout << "15. Line-based operations - appendLine() / appendLn()\n";
+        std::cout << "------------------------------------------------------\n";
+
+        // Basic line appending
+        std::cout << "Basic line appending:\n";
+        {
+            StringBuilder builder;
+            builder.appendLine( "First line" ).appendLine( "Second line" ).appendLine( "Third line" );
+
+            std::cout << "  Result:\n" << builder.toString();
+            std::cout << "  Note: Each appendLine() adds '\\n' automatically\n";
+            std::cout << "\n";
+        }
+
+        // Building CSV-like data
+        std::cout << "Building CSV-like data:\n";
+        {
+            StringBuilder builder;
+            builder.appendLine( "Name,Age,City" )
+                .appendLine( "Alice,30,Paris" )
+                .appendLine( "Bob,25,London" )
+                .appendLine( "Charlie,35,Berlin" );
+
+            std::cout << "  Result:\n" << builder.toString();
+            std::cout << "\n";
+        }
+
+        std::cout << "Building NMEA-0183 messages with checksums:\n";
+        {
+            StringBuilder builder;
+
+            // Helper lambda to build NMEA sentence with checksum
+            auto buildNmeaSentence = [&builder]( std::string_view sentence ) {
+                builder.append( "$" ).append( sentence );
+                std::string checksum = calculateNmeaChecksum( sentence );
+                builder.append( "*" ).append( checksum );
+                builder.appendLine();
+            };
+
+            // GPS Fix Data (GPGGA)
+            buildNmeaSentence( "GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,," );
+
+            // GPS DOP and active satellites (GPGSA)
+            buildNmeaSentence( "GPGSA,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1" );
+
+            // Satellites in view (GPGSV)
+            buildNmeaSentence( "GPGSV,2,1,08,01,40,083,46,02,17,308,41,12,07,344,39,14,22,228,45" );
+
+            // Meteorological Composite (WIMDA) - Full message
+            buildNmeaSentence( "WIMDA,29.92,I,1.013,B,15.5,C,10.2,C,45.0,,12.5,C,270.0,T,270.0,M,5.2,N,2.7,M" );
+
+            // Wind Speed and Angle (WIMWV)
+            buildNmeaSentence( "WIMWV,270.0,T,5.2,N,A" );
+
+            // Water Temperature (WIMTW)
+            buildNmeaSentence( "WIMTW,10.2,C" );
+
+            std::cout << "  Result:\n" << builder.toString();
+            std::cout << "  Note: All messages include valid NMEA-0183 checksums\n";
+            std::cout << "        Format: $SENTENCE*XX where XX is XOR checksum\n";
+            std::cout << "\n";
+        }
+
+        // Building a realistic NMEA-0183 data stream
+        std::cout << "Building realistic NMEA-0183 data stream:\n";
+        {
+            StringBuilder builder;
+
+            // Simulate a GPS/Weather station output
+            auto addNmea = [&builder]( std::string_view sentence ) {
+                builder.append( "$" ).append( sentence );
+                builder.append( "*" ).append( calculateNmeaChecksum( sentence ) );
+                builder.appendLine();
+            };
+
+            // Position update
+            addNmea( "GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W" );
+            addNmea( "GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,," );
+
+            // Weather data
+            addNmea( "WIMDA,30.12,I,1.020,B,18.3,C,12.5,C,52.0,,10.8,C,285.0,T,285.0,M,12.5,N,6.4,M" );
+            addNmea( "WIMWV,285.0,T,12.5,N,A" );
+
+            // Depth sounder
+            addNmea( "SDDBT,45.2,f,13.8,M,7.5,F" );
+
+            std::cout << "  Result:\n" << builder.toString();
+            std::cout << "\n";
+        }
+
+        // Building log entries
+        std::cout << "Building multi-line log entries:\n";
+        {
+            StringBuilder builder;
+
+            auto now = std::chrono::system_clock::now();
+            auto timestamp = std::chrono::duration_cast<std::chrono::milliseconds>( now.time_since_epoch() ).count();
+
+            builder.appendLine( "[INFO] Application started" )
+                .append( "[DEBUG] Timestamp: " )
+                .append( timestamp )
+                .appendLine()
+                .appendLine( "[INFO] Configuration loaded" )
+                .appendLine( "[WARN] Cache not found, creating new" );
+
+            std::cout << "  Result:\n" << builder.toString();
+            std::cout << "\n";
+        }
+
+        // Building JSON-like structure (simplified)
+        std::cout << "Building structured text:\n";
+        {
+            StringBuilder builder;
+            builder.appendLine( "{" )
+                .appendLine( "  \"name\": \"StringBuilder\"," )
+                .appendLine( "  \"version\": \"0.5.0\"," )
+                .appendLine( "  \"features\": [" )
+                .appendLine( "    \"SBO\"," )
+                .appendLine( "    \"Zero-copy\"," )
+                .appendLine( "    \"High-performance\"" )
+                .appendLine( "  ]" )
+                .appendLine( "}" );
+
+            std::cout << "  Result:\n" << builder.toString();
+            std::cout << "  Note: Indentation handled manually\n";
+            std::cout << "\n";
+        }
+
+        std::cout << "\n";
+    }
+
+    //=====================================================================
+    // 16. Prepend operations - Building strings in reverse
     //=====================================================================
     {
-        std::cout << "15. Prepend operations - Building strings in reverse\n";
+        std::cout << "16. Prepend operations - Building strings in reverse\n";
         std::cout << "----------------------------------------------------\n";
 
         // Basic prepend