Clean out some bugs in sender

keystroke.cpp

@@ -0,0 +1,44 @@
+#include <assert.h>
+
+#include "keystroke.hpp"
+
+void KeyStroke::subtract( KeyStroke * const prefix )
+{
+  for ( deque<char>::iterator i = prefix->user_bytes.begin();
+	i != prefix->user_bytes.end();
+	i++ ) {
+    assert( *i == user_bytes.front() );
+    user_bytes.pop_front();
+  }
+}
+
+string KeyStroke::diff_from( KeyStroke const & existing, int length_limit )
+{
+  string ret;
+
+  deque<char>::iterator my_it = user_bytes.begin();
+
+  for ( deque<char>::const_iterator i = existing.user_bytes.begin();
+	i != existing.user_bytes.end();
+	i++ ) {
+    assert( *i == *my_it );
+    my_it++;
+  }
+
+  while ( (my_it != user_bytes.end())
+	  && ( (length_limit < 0) ? true : (int(ret.size()) < length_limit) ) ) {
+    ret += string( &( *my_it ), 1 );
+    my_it++;
+  }
+
+  return ret;
+}
+
+void KeyStroke::apply_string( string diff )
+{
+  for ( string::iterator i = diff.begin();
+	i != diff.end();
+	i++ ) {
+    user_bytes.push_back( *i );
+  }
+}