READ ONLY state for buffers

src/row_op.c

@@ -77,8 +77,10 @@ void bufferRowInsertBytes(struct buffer_t *buffer, row_t *row, int at,
  * \param at Index of the char to delete
  * \param row Row on operation is made */
 void bufferRowDelByte(struct buffer_t *buffer, row_t *row, int at, int n) {
-  if (at < 0 || at >= row->size)
-    return;
+    if (buffer->state == READ_ONLY)
+        return;
+    if (at < 0 || at >= row->size)
+        return;
   memmove(row->chars + at, row->chars + at + n, row->size - at - n);
   row->size -= n;
   row->chars[row->size] = '\0';