add GapBuffer::compact()

src/core/GapBuffer.cc

@@ -1,5 +1,6 @@
 #include "GapBuffer.h"
 #include "System.h"
+#include <string.h>
 
 GapBuffer::GapBuffer(Encoding::Type encoding)
 {
@@ -33,6 +34,15 @@ std::shared_ptr<GapBuffer::Cursor> GapBuffer::add_cursor()
     return cursor;
 }
 
+void GapBuffer::compact()
+{
+    if (m_gap_position < m_size)
+    {
+        memmove(&m_buffer[m_gap_position], &m_buffer[m_gap_position + gap_size()], m_size - m_gap_position);
+        m_gap_position = m_size;
+    }
+}
+
 
 void GapBuffer::Iterator::go_forward()
 {

src/core/GapBuffer.h

@@ -102,9 +102,11 @@ public:
         }
         else
         {
-            return &m_buffer[offset + (m_buffer_size - m_size)];
+            return &m_buffer[offset + gap_size()];
         }
     }
+    size_t gap_size() const { return m_buffer_size - m_size; }
+    void compact();
 
 protected:
     uint8_t * m_buffer;