Web-ja: update introduction

[lilypond.git] / lily / protected-scm.cc

diff --git a/lily/protected-scm.cc b/lily/protected-scm.cc
index 356bbf2121510dcd5fe7ea9dec6a6ad1305f3a27..3a16254187a05b0b7880a53ec9250c47071e8aee 100644 (file)
--- a/lily/protected-scm.cc
+++ b/lily/protected-scm.cc
@@ -1,61 +1,96 @@
-/*   
-  protected-scm.cc --  implement Protected_scm
-  
-  source file of the GNU LilyPond music typesetter
-  
-  (c) 1998--1999 Han-Wen Nienhuys <hanwen@cs.uu.nl>
-  
- */
+/*
+  This file is part of LilyPond, the GNU music typesetter.
+
+  Copyright (C) 1998--2015 Han-Wen Nienhuys <hanwen@xs4all.nl>
+
+  LilyPond 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.
+
+  LilyPond 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 LilyPond.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
 #include "protected-scm.hh"
-extern "C"
-{
-#include <libguile/gc.h>
-};
 
+// We store the data in the car of a cons cell: it is faster to keep
+// only one object protected during the life time of Protected_scm
+// than several.
 
 Protected_scm::Protected_scm ()
+  : object_ (SCM_UNDEFINED)
 {
-  object_ = 0;
 }
 
 Protected_scm::Protected_scm (SCM s)
+  : object_ (s)
 {
-  object_ = s  ? scm_protect_object (s): 0;
+  // Only allow immediate objects at construction time.  Protected_scm
+  // is intended for variables of static duration, and creating
+  // non-immediate objects when GUILE is not yet up is a bad idea.
+  assert (SCM_IMP (s));
 }
 
-Protected_scm::Protected_scm (Protected_scm const &s)
+SCM Protected_scm::list_ = SCM_EOL;
+SCM Protected_scm::last_ = SCM_EOL;
+
+void
+Protected_scm::protectify (SCM s)
 {
-  object_ = s.object_ ? scm_protect_object (s.object_) : 0;
+  s = scm_list_1 (s);
+  if (SCM_CONSP (last_))
+    SCM_SETCDR (last_, s);
+  else
+    list_ = scm_permanent_object (s);
+  last_ = object_ = s;
 }
 
-Protected_scm & 
-Protected_scm::operator =(Protected_scm const &s)
+Protected_scm &
+Protected_scm::operator = (SCM s)
 {
-  if (this == &s)
-    return *this;
-  if (object_)
-    scm_unprotect_object(object_);
+  if (SCM_CONSP (object_))
+    SCM_SETCAR (object_, s);
+  else if (SCM_IMP (s))
+    object_ = s;
+  else
+    protectify (s);
 
-  object_ = (s.object_) ? scm_protect_object (s.object_): 0;
   return *this;
 }
 
-Protected_scm::~Protected_scm ()
+Protected_scm &
+Protected_scm::operator = (Protected_scm const &s)
 {
-  if  (object_)
-    {
-      scm_unprotect_object (object_);
-      object_ =0L;             // be nice to conservative GC
-    }
+  return *this = (SCM) s;
 }
 
-Protected_scm::operator SCM () const
+Protected_scm::operator SCM const & () const
 {
+  if (SCM_CONSP (object_))
+    return *SCM_CARLOC (object_);
   return object_;
 }
 
-SCM 
-Protected_scm::to_SCM () const
+Protected_scm::operator SCM & ()
 {
-  return object_;
+  // The reference may be used to overwrite an immediate value with a
+  // non-immediate one, so we _have_ to create full protection.
+  if (!SCM_CONSP (object_))
+    protectify (object_);
+
+  return *SCM_CARLOC (object_);
+}
+
+bool
+Protected_scm::is_bound () const
+{
+  if (SCM_CONSP (object_))
+    return !SCM_UNBNDP (SCM_CAR (object_));
+  return !SCM_UNBNDP (object_);
 }