2 smobs.hh -- declare smob related stuff.
4 source file of the GNU LilyPond music typesetter
6 (c) 1999--2006 Han-Wen Nienhuys <hanwen@xs4all.nl>
12 #include "lily-guile.hh"
13 #include "virtual-methods.hh"
16 Smobs are GUILEs mechanism of exporting C(++) objects to the Scheme
17 world. They are documented in the GUILE manual.
20 In LilyPond, smobs are created from C++ objects through macros.
21 There are two types of smob objects.
23 1. Simple smobs are intended for simple objects like numbers:
24 immutable objects that can be copied without change of meaning.
26 To obtain an SCM version of a simple smob, use the member function
29 Simple smobs are created by adding the
30 DECLARE_SIMPLE_SMOBS(Classname, ) to the declaration
32 2. Complex smobs are objects that have an identity. These objects
33 carry this identity in the form of a self_scm () method, which is a
34 SCM pointer to the object itself.
36 The constructor for a complex smob should have 3 steps:
38 * initialize all SCM members to a non-immediate value (like SCM_EOL)
40 * call smobify_self ()
42 * initialize SCM members
46 Complex_smob::Complex_smob () {
47 scm_member_ = SCM_EOL;
49 scm_member_ = <..what you want to store..>
52 after construction, the self_scm () field of a complex smob is
53 protected from Garbage Collection. This protection should be
54 removed once the object is put into another (reachable) Scheme data
57 Complex_smob *p = new Complex_smob;
58 list = scm_cons (p->self_scm (), list);
59 scm_gc_unprotect_object (p->self_scm ());
61 Complex smobs are made with DECLARE_SMOBS (Classname, ) in the class
66 Common public methods to C++ smob objects:
68 unsmob (SCM x) - unpacks X and returns pointer to the C++ object, or 0
69 if it has the wrong type.
71 SCM equal_p (SCM a, SCM b) - compare A and B. Returns a Scheme boolean
76 For implementating a class, the following should be provided
78 - an equal_p () function (a default is in the
79 IMPLEMENT_DEFAULT_EQUAL_P macro in ly-smobs.icc)
81 - mark_smob () function, that calls scm_gc_mark () on all Scheme
84 - a print_smob () function, that displays a representation for
87 - A call to one of the IMPLEMENT_SMOBS or IMPLEMENT_SIMPLE_SMOBS macros
88 from file "ly-smobs.icc"
91 #define DECLARE_SIMPLE_SMOBS(CL, dummy) \
93 SCM smobbed_copy () const; \
94 DECLARE_BASE_SMOBS (CL)
96 #define DECLARE_BASE_SMOBS(CL) \
97 friend class Non_existent_class; \
99 static scm_t_bits smob_tag_; \
100 static SCM mark_smob (SCM); \
101 static size_t free_smob (SCM s); \
102 static int print_smob (SCM s, SCM p, scm_print_state*); \
104 static SCM equal_p (SCM a, SCM b); \
105 static CL *unsmob (SCM s) \
107 if (SCM_NIMP (s) && SCM_CELL_TYPE (s) == smob_tag_) \
108 return (CL *) SCM_CELL_WORD_1 (s); \
112 static SCM smob_p (SCM); \
113 static void init_smobs (); \
116 #define DECLARE_SMOBS(CL, dummy) \
117 DECLARE_BASE_SMOBS (CL) \
120 SCM unprotected_smobify_self (); \
122 void smobify_self (); \
124 SCM protection_cons_; \
128 SCM self_scm () const { return self_scm_; } \
131 #define DECLARE_UNSMOB(CL, name) \
133 unsmob_ ## name (SCM s) \
135 return CL::unsmob (s); \
138 #define DECLARE_TYPE_P(CL) extern SCM CL ## _type_p_proc
140 void protect_smob (SCM smob, SCM *prot_cons);
141 void unprotect_smob (SCM *prot_cons);
143 #endif /* SMOBS_HH */