Add Buffer::n_lines()

src/core/Buffer.cc

@@ -502,3 +502,14 @@ void Buffer::set_filename(const std::string & filename)
 {
     m_filename = std::make_shared<std::string>(filename);
 }
+
+size_t Buffer::n_lines() const
+{
+    auto it = end();
+    it.go_back();
+    if (it.valid())
+    {
+        return it.line() + 1u;
+    }
+    return 0u;
+}

src/core/Buffer.h

@@ -192,6 +192,7 @@ public:
     void pop_operation();
     void undo();
     void redo();
+    size_t n_lines() const;
 
 #ifndef ENABLE_TESTING
 protected:

test/src/test_Buffer.cc

@@ -33,11 +33,13 @@ TEST(BufferTest, writes_an_empty_file_for_an_empty_buffer)
     Buffer b;
     ASSERT_TRUE(b.write_to_file("test/tmp/f"));
     TestSupport::compare_files("test/files/empty.txt", "test/tmp/f");
+    ASSERT_EQ(0u, b.n_lines());
 }
 
 TEST(BufferTest, allows_navigating_using_iterators)
 {
     Buffer b("test/files/line_endings/lf_format.txt");
+    ASSERT_EQ(2u, b.n_lines());
     auto iterator = b.add_cursor();
 
     EXPECT_EQ(0u, iterator->line());