From: fred <fred>
Date: Tue, 26 Mar 2002 22:48:02 +0000 (+0000)
Subject: lilypond-1.3.74
X-Git-Tag: release/1.5.59~1767
X-Git-Url: https://git.donarmstrong.com/?a=commitdiff_plain;h=92b53ea361db4534bec7c5731276fe11ac239686;p=lilypond.git

lilypond-1.3.74
---

diff --git a/lily/include/smobs.hh b/lily/include/smobs.hh
index dff21977b1..edd1f2e60c 100644
--- a/lily/include/smobs.hh
+++ b/lily/include/smobs.hh
@@ -12,48 +12,120 @@
 
 #include "lily-guile.hh"
 
-/**
-   A smob is a C++ class with static member functions to glue it with
-   Scheme. Every instance carries SELF_SCM_, a pointer to the Scheme
-   smob of itself.  Upon destruction, SELF_SCM_ is set to SCM_EOL.
 
-   smob_free() checks if SELF_SCM_ equals its argument, so we can also
-   use a smobbified object on the stack: the destruction will happen
-   before GC hits the object.
+/*
 
-   This is discouraged, though, because it causes memory leaks, and has
-   weird semantics.
+   Each smobbed C-object may only be interfaced by a single, unique
+   smob cell. Therefore NEVER provide a public function that will
+   create a smobcell for an existing object pointer.
+
+   There are two ways to reach this goal:
+
+   simple smobs:
+
+   - Data structures that are encapsulated by GUILE. If constructed
+   through GUILE, you may only store them as protected SCMs, and may
+   not copy the pointer the object itself. Typical interface
+
+   struct Ssmob {
+   public:
+     SCM make_copy_scm () const {
+       Ssmob *sp = new Ssmob (*this);
+       return sp->smobbed_self ();
+     }
+   };
+
+   or
+
+   struct Ssmob {
+   public:
+     DECLARE_SIMPLE_SMOBS;
+     static SCM make_scm (void initdata) {
+       Ssmob * sp = new Ssmob (initdata);
+       return sp->smobbed_self();
+     }
+   private:
+     Ssmob (initdata);
+   }
+
+   Objets of type Ssmob may live on the stack, or on the heap, or as
+   part of other objects.  However, as soon as the object is smobbed,
+   by definition (by definition of the constructors, in this example),
+   lives on the heap as a separate object
    
+   - complex smobs: data structures whose identity is referenced and
+   stored both in C++ and in GUILE form. From going from C++ to GUILE,
+   you use smob_ptr->self_scm_
+
+   class Csmob {
+     DECLARE_SMOBS;
+     Csmob () { smobify_self(); }
+     Csmob (Csmob const & s) {
+       // don't copy self_scm_
+       smobify_self ();
+     }
+   };
+   
+   A complex smob is a C++ class with static member functions to glue
+   it with Scheme. Every instance carries SELF_SCM_, a pointer to the
+   unique Scheme smob cell of itself.
+
+   Upon creation, SELF_SCM_ is protected, so if you choose to store it
+   in C++ structures, you need to do
+
+   class Bla {
+   Csmob *ptr;
+   ~Bla () {  scm_unprotect_object (ptr->self_scm_); }
+   
+   };
+
+   If protection is done via GUILE, don't forget to unprotect AFTER putting
+   stuff into the GUILE datastructs
 
+
+   guile_data = gh_cons (ptr->self_scm_, guile_data);
+   ptr->self_scm_
+
+   Since GUILE takes care of the freeing the object, the destructor
+   is private.
+
+   DUMMY a thing to make sure compiles only work if this header
+   if this file is there.
+
+
+   WARNING:
+
+   smobify_self() might trigger a GC, so make sure that objects are  
+   sane when you do smobify_self().
 */
 
-#define DECLARE_SMOBS					\
-	SCM smobify_self ();					\
+#define DECLARE_SIMPLE_SMOBS(CL,dummy) \
+protected: \
+	friend class Non_existant_class ; \
+	SCM smobbed_self () const; \
+private:\
+	static long smob_tag_;					\
 	static SCM mark_smob (SCM);				\
 	static scm_sizet free_smob (SCM s);			\
 	static int print_smob (SCM s, SCM p, scm_print_state*);	\
-	static long smob_tag_;					\
+public: \
 	static SCM equal_p (SCM a, SCM b);\
+	static CL * unsmob (SCM);\
 	static void init_smobs();				\
-	void unsmobify_self ();\
-        void do_smobify_self();\
-	SCM self_scm_;
+private:
 
 
-#ifndef SCM_CELL_TYPE
-#define SCM_CELL_TYPE(X) SCM_CAR(X)
-#endif
-
-#ifndef SCM_CELL_WORD_1
-#define SCM_CELL_WORD_1(X) SCM_CDR(X)
-#endif	
+#define DECLARE_SMOBS(CL,dummy)					\
+	DECLARE_SIMPLE_SMOBS(CL,dammy) \
+protected:\
+	virtual ~CL();\
+private: \
+	SCM smobify_self ();					\
+	SCM self_scm_; \
+public: \
+	SCM self_scm () const { return self_scm_; } \
+private:
 
-/**
-   Check if S is of the specified C++ class.
- */
-#define SMOB_IS_TYPE_B(TYPE, S)  (SCM_NIMP(S) && SCM_CELL_TYPE(S) == TYPE::smob_tag_)
 
-/// Cast S.  No checks are done.
-#define SMOB_TO_TYPE(TYPE, S)  ((TYPE*) SCM_CELL_WORD_1(S))
 #endif /* SMOBS_HH */