add Buffer::get_string() and GapBuffer::get_string()

src/core/Buffer.h

@@ -13,6 +13,7 @@ public:
     Buffer(const char * filename = nullptr);
     bool write_to_file(const char * filename);
     auto add_cursor() { return m_gap_buffer->add_cursor(); }
+    auto get_string() { return m_gap_buffer->get_string(); }
 
 protected:
     bool m_eol_at_eof;

src/core/GapBuffer.cc

@@ -76,6 +76,18 @@ void GapBuffer::insert(Cursor & insert_cursor, uint32_t code_point)
     }
 }
 
+/**
+ * Get the contents of the gap buffer as a string.
+ *
+ * This makes a copy of the entire buffer in a std::string. This method is
+ * intended for use by unit tests.
+ */
+std::string GapBuffer::get_string()
+{
+    compact();
+    return std::string((char *)m_buffer, m_size);
+}
+
 /**
  * Verify that there is enough free space in the gap, and if not, grow the gap
  * and move data.

src/core/GapBuffer.h

@@ -6,6 +6,7 @@
 #include "Encoding.h"
 #include <memory>
 #include <list>
+#include <string>
 
 class GapBuffer
 {
@@ -115,6 +116,7 @@ public:
     size_t gap_size() const { return m_buffer_size - m_size; }
     void compact();
     void insert(Cursor & insert_cursor, uint32_t code_point);
+    std::string get_string();
 
 protected:
     uint8_t * m_buffer;