Make Select a singleton

It's going to manipulate process-global signal state, so multiple
instances do not make sense.

src/util/Makefile.am

@@ -2,7 +2,7 @@ AM_CXXFLAGS = $(WARNING_CXXFLAGS) $(PICKY_CXXFLAGS) $(HARDEN_CFLAGS) $(MISC_CXXF
 
 noinst_LIBRARIES = libmoshutil.a
 
-libmoshutil_a_SOURCES = locale_utils.cc locale_utils.h swrite.cc swrite.h dos_assert.h fatal_assert.h sigfd.h select.h
+libmoshutil_a_SOURCES = locale_utils.cc locale_utils.h swrite.cc swrite.h dos_assert.h fatal_assert.h sigfd.h select.h select.cc
 
 if !USE_LIBSTDDJB
   libmoshutil_a_SOURCES += sigfd.cc

src/util/select.cc

@@ -0,0 +1,21 @@
+/*
+    Mosh: the mobile shell
+    Copyright 2012 Keith Winstein
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "select.h"
+
+Select *Select::instance = NULL;

src/util/select.h

@@ -33,6 +33,17 @@ static fd_set dummy_fd_set;
 /* Convenience wrapper for select(2). */
 class Select {
 public:
+  static Select &get_instance( void ) {
+    // NB: not thread-safe
+    if ( !instance ) {
+      instance = new Select;
+    }
+    return *instance;
+  }
+
+private:
+  static Select *instance;
+
   Select()
     : max_fd( -1 )
 
@@ -47,6 +58,11 @@ public:
     FD_ZERO( &error_fds );
   }
 
+  /* not implemented */
+  Select( const Select & );
+  Select &operator=( const Select & );
+
+public:
   void add_fd( int fd )
   {
     if ( fd > max_fd ) {