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diff --git a/jni/ruby/class.c b/jni/ruby/class.c
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+++ b/jni/ruby/class.c
@@ -0,0 +1,1982 @@
+/**********************************************************************
+
+  class.c -
+
+  $Author: nagachika $
+  created at: Tue Aug 10 15:05:44 JST 1993
+
+  Copyright (C) 1993-2007 Yukihiro Matsumoto
+
+**********************************************************************/
+
+/*!
+ * \defgroup class Classes and their hierarchy.
+ * \par Terminology
+ * - class: same as in Ruby.
+ * - singleton class: class for a particular object
+ * - eigenclass: = singleton class
+ * - metaclass: class of a class. metaclass is a kind of singleton class.
+ * - metametaclass: class of a metaclass.
+ * - meta^(n)-class: class of a meta^(n-1)-class.
+ * - attached object: A singleton class knows its unique instance.
+ *   The instance is called the attached object for the singleton class.
+ * \{
+ */
+
+#include "internal.h"
+#include "ruby/st.h"
+#include "method.h"
+#include "constant.h"
+#include "vm_core.h"
+#include <ctype.h>
+
+#define id_attached id__attached__
+
+void
+rb_class_subclass_add(VALUE super, VALUE klass)
+{
+    rb_subclass_entry_t *entry, *head;
+
+    if (super && super != Qundef) {
+	entry = ALLOC(rb_subclass_entry_t);
+	entry->klass = klass;
+	entry->next = NULL;
+
+	head = RCLASS_EXT(super)->subclasses;
+	if (head) {
+	    entry->next = head;
+	    RCLASS_EXT(head->klass)->parent_subclasses = &entry->next;
+	}
+
+	RCLASS_EXT(super)->subclasses = entry;
+	RCLASS_EXT(klass)->parent_subclasses = &RCLASS_EXT(super)->subclasses;
+    }
+}
+
+static void
+rb_module_add_to_subclasses_list(VALUE module, VALUE iclass)
+{
+    rb_subclass_entry_t *entry, *head;
+
+    entry = ALLOC(rb_subclass_entry_t);
+    entry->klass = iclass;
+    entry->next = NULL;
+
+    head = RCLASS_EXT(module)->subclasses;
+    if (head) {
+	entry->next = head;
+	RCLASS_EXT(head->klass)->module_subclasses = &entry->next;
+    }
+
+    RCLASS_EXT(module)->subclasses = entry;
+    RCLASS_EXT(iclass)->module_subclasses = &RCLASS_EXT(module)->subclasses;
+}
+
+void
+rb_class_remove_from_super_subclasses(VALUE klass)
+{
+    rb_subclass_entry_t *entry;
+
+    if (RCLASS_EXT(klass)->parent_subclasses) {
+	entry = *RCLASS_EXT(klass)->parent_subclasses;
+
+	*RCLASS_EXT(klass)->parent_subclasses = entry->next;
+	if (entry->next) {
+	    RCLASS_EXT(entry->next->klass)->parent_subclasses = RCLASS_EXT(klass)->parent_subclasses;
+	}
+	xfree(entry);
+    }
+
+    RCLASS_EXT(klass)->parent_subclasses = NULL;
+}
+
+void
+rb_class_remove_from_module_subclasses(VALUE klass)
+{
+    rb_subclass_entry_t *entry;
+
+    if (RCLASS_EXT(klass)->module_subclasses) {
+	entry = *RCLASS_EXT(klass)->module_subclasses;
+	*RCLASS_EXT(klass)->module_subclasses = entry->next;
+
+	if (entry->next) {
+	    RCLASS_EXT(entry->next->klass)->module_subclasses = RCLASS_EXT(klass)->module_subclasses;
+	}
+
+	xfree(entry);
+    }
+
+    RCLASS_EXT(klass)->module_subclasses = NULL;
+}
+
+void
+rb_class_foreach_subclass(VALUE klass, void(*f)(VALUE))
+{
+    rb_subclass_entry_t *cur = RCLASS_EXT(klass)->subclasses;
+
+    /* do not be tempted to simplify this loop into a for loop, the order of
+       operations is important here if `f` modifies the linked list */
+    while (cur) {
+	VALUE curklass = cur->klass;
+	cur = cur->next;
+	f(curklass);
+    }
+}
+
+void
+rb_class_detach_subclasses(VALUE klass)
+{
+    rb_class_foreach_subclass(klass, rb_class_remove_from_super_subclasses);
+}
+
+void
+rb_class_detach_module_subclasses(VALUE klass)
+{
+    rb_class_foreach_subclass(klass, rb_class_remove_from_module_subclasses);
+}
+
+/**
+ * Allocates a struct RClass for a new class.
+ *
+ * \param flags     initial value for basic.flags of the returned class.
+ * \param klass     the class of the returned class.
+ * \return          an uninitialized Class object.
+ * \pre  \p klass must refer \c Class class or an ancestor of Class.
+ * \pre  \code (flags | T_CLASS) != 0  \endcode
+ * \post the returned class can safely be \c #initialize 'd.
+ *
+ * \note this function is not Class#allocate.
+ */
+static VALUE
+class_alloc(VALUE flags, VALUE klass)
+{
+    NEWOBJ_OF(obj, struct RClass, klass, (flags & T_MASK) | FL_PROMOTED1 /* start from age == 2 */ | (RGENGC_WB_PROTECTED_CLASS ? FL_WB_PROTECTED : 0));
+    obj->ptr = ALLOC(rb_classext_t);
+    RCLASS_IV_TBL(obj) = 0;
+    RCLASS_CONST_TBL(obj) = 0;
+    RCLASS_M_TBL_WRAPPER(obj) = 0;
+    RCLASS_SET_SUPER((VALUE)obj, 0);
+    RCLASS_ORIGIN(obj) = (VALUE)obj;
+    RCLASS_IV_INDEX_TBL(obj) = 0;
+
+    RCLASS_EXT(obj)->subclasses = NULL;
+    RCLASS_EXT(obj)->parent_subclasses = NULL;
+    RCLASS_EXT(obj)->module_subclasses = NULL;
+    RCLASS_SERIAL(obj) = rb_next_class_serial();
+
+    RCLASS_REFINED_CLASS(obj) = Qnil;
+    RCLASS_EXT(obj)->allocator = 0;
+    return (VALUE)obj;
+}
+
+
+/*!
+ * A utility function that wraps class_alloc.
+ *
+ * allocates a class and initializes safely.
+ * \param super     a class from which the new class derives.
+ * \return          a class object.
+ * \pre  \a super must be a class.
+ * \post the metaclass of the new class is Class.
+ */
+VALUE
+rb_class_boot(VALUE super)
+{
+    VALUE klass = class_alloc(T_CLASS, rb_cClass);
+
+    RCLASS_SET_SUPER(klass, super);
+    RCLASS_M_TBL_INIT(klass);
+
+    OBJ_INFECT(klass, super);
+    return (VALUE)klass;
+}
+
+
+/*!
+ * Ensures a class can be derived from super.
+ *
+ * \param super a reference to an object.
+ * \exception TypeError if \a super is not a Class or \a super is a singleton class.
+ */
+void
+rb_check_inheritable(VALUE super)
+{
+    if (!RB_TYPE_P(super, T_CLASS)) {
+	rb_raise(rb_eTypeError, "superclass must be a Class (%s given)",
+		 rb_obj_classname(super));
+    }
+    if (RBASIC(super)->flags & FL_SINGLETON) {
+	rb_raise(rb_eTypeError, "can't make subclass of singleton class");
+    }
+    if (super == rb_cClass) {
+	rb_raise(rb_eTypeError, "can't make subclass of Class");
+    }
+}
+
+
+/*!
+ * Creates a new class.
+ * \param super     a class from which the new class derives.
+ * \exception TypeError \a super is not inheritable.
+ * \exception TypeError \a super is the Class class.
+ */
+VALUE
+rb_class_new(VALUE super)
+{
+    Check_Type(super, T_CLASS);
+    rb_check_inheritable(super);
+    return rb_class_boot(super);
+}
+
+static void
+clone_method(VALUE klass, ID mid, const rb_method_entry_t *me)
+{
+    VALUE newiseqval;
+    if (me->def && me->def->type == VM_METHOD_TYPE_ISEQ) {
+	rb_iseq_t *iseq;
+	NODE *new_cref;
+	newiseqval = rb_iseq_clone(me->def->body.iseq->self, klass);
+	GetISeqPtr(newiseqval, iseq);
+	rb_vm_rewrite_cref_stack(me->def->body.iseq->cref_stack, me->klass, klass, &new_cref);
+	RB_OBJ_WRITE(iseq->self, &iseq->cref_stack, new_cref);
+	rb_add_method(klass, mid, VM_METHOD_TYPE_ISEQ, iseq, me->flag);
+	RB_GC_GUARD(newiseqval);
+    }
+    else {
+	rb_method_entry_set(klass, mid, me, me->flag);
+    }
+}
+
+static int
+clone_method_i(st_data_t key, st_data_t value, st_data_t data)
+{
+    clone_method((VALUE)data, (ID)key, (const rb_method_entry_t *)value);
+    return ST_CONTINUE;
+}
+
+struct clone_const_arg {
+    VALUE klass;
+    st_table *tbl;
+};
+
+static int
+clone_const(ID key, const rb_const_entry_t *ce, struct clone_const_arg *arg)
+{
+    rb_const_entry_t *nce = ALLOC(rb_const_entry_t);
+    MEMCPY(nce, ce, rb_const_entry_t, 1);
+    RB_OBJ_WRITTEN(arg->klass, Qundef, ce->value);
+    RB_OBJ_WRITTEN(arg->klass, Qundef, ce->file);
+
+    st_insert(arg->tbl, key, (st_data_t)nce);
+    return ST_CONTINUE;
+}
+
+static int
+clone_const_i(st_data_t key, st_data_t value, st_data_t data)
+{
+    return clone_const((ID)key, (const rb_const_entry_t *)value, (struct clone_const_arg *)data);
+}
+
+static void
+class_init_copy_check(VALUE clone, VALUE orig)
+{
+    if (orig == rb_cBasicObject) {
+	rb_raise(rb_eTypeError, "can't copy the root class");
+    }
+    if (RCLASS_SUPER(clone) != 0 || clone == rb_cBasicObject) {
+	rb_raise(rb_eTypeError, "already initialized class");
+    }
+    if (FL_TEST(orig, FL_SINGLETON)) {
+	rb_raise(rb_eTypeError, "can't copy singleton class");
+    }
+}
+
+/* :nodoc: */
+VALUE
+rb_mod_init_copy(VALUE clone, VALUE orig)
+{
+    if (RB_TYPE_P(clone, T_CLASS)) {
+	class_init_copy_check(clone, orig);
+    }
+    if (!OBJ_INIT_COPY(clone, orig)) return clone;
+    if (!FL_TEST(CLASS_OF(clone), FL_SINGLETON)) {
+	RBASIC_SET_CLASS(clone, rb_singleton_class_clone(orig));
+	rb_singleton_class_attached(RBASIC(clone)->klass, (VALUE)clone);
+    }
+    RCLASS_SET_SUPER(clone, RCLASS_SUPER(orig));
+    RCLASS_EXT(clone)->allocator = RCLASS_EXT(orig)->allocator;
+    if (RCLASS_IV_TBL(clone)) {
+	st_free_table(RCLASS_IV_TBL(clone));
+	RCLASS_IV_TBL(clone) = 0;
+    }
+    if (RCLASS_CONST_TBL(clone)) {
+	rb_free_const_table(RCLASS_CONST_TBL(clone));
+	RCLASS_CONST_TBL(clone) = 0;
+    }
+    if (RCLASS_M_TBL_WRAPPER(clone)) {
+	rb_free_m_tbl_wrapper(RCLASS_M_TBL_WRAPPER(clone));
+	RCLASS_M_TBL_WRAPPER(clone) = 0;
+    }
+    if (RCLASS_IV_TBL(orig)) {
+	st_data_t id;
+
+	RCLASS_IV_TBL(clone) = rb_st_copy(clone, RCLASS_IV_TBL(orig));
+	CONST_ID(id, "__tmp_classpath__");
+	st_delete(RCLASS_IV_TBL(clone), &id, 0);
+	CONST_ID(id, "__classpath__");
+	st_delete(RCLASS_IV_TBL(clone), &id, 0);
+	CONST_ID(id, "__classid__");
+	st_delete(RCLASS_IV_TBL(clone), &id, 0);
+    }
+    if (RCLASS_CONST_TBL(orig)) {
+	struct clone_const_arg arg;
+
+	RCLASS_CONST_TBL(clone) = st_init_numtable();
+	arg.klass = clone;
+	arg.tbl = RCLASS_CONST_TBL(clone);
+	st_foreach(RCLASS_CONST_TBL(orig), clone_const_i, (st_data_t)&arg);
+    }
+    if (RCLASS_M_TBL(orig)) {
+	RCLASS_M_TBL_INIT(clone);
+	st_foreach(RCLASS_M_TBL(orig), clone_method_i, (st_data_t)clone);
+    }
+
+    return clone;
+}
+
+VALUE
+rb_singleton_class_clone(VALUE obj)
+{
+    return rb_singleton_class_clone_and_attach(obj, Qundef);
+}
+
+VALUE
+rb_singleton_class_clone_and_attach(VALUE obj, VALUE attach)
+{
+    VALUE klass = RBASIC(obj)->klass;
+
+    if (!FL_TEST(klass, FL_SINGLETON))
+	return klass;
+    else {
+	/* copy singleton(unnamed) class */
+	VALUE clone = class_alloc(RBASIC(klass)->flags, 0);
+
+	if (BUILTIN_TYPE(obj) == T_CLASS) {
+	    RBASIC_SET_CLASS(clone, clone);
+	}
+	else {
+	    RBASIC_SET_CLASS(clone, rb_singleton_class_clone(klass));
+	}
+
+	RCLASS_SET_SUPER(clone, RCLASS_SUPER(klass));
+	RCLASS_EXT(clone)->allocator = RCLASS_EXT(klass)->allocator;
+	if (RCLASS_IV_TBL(klass)) {
+	    RCLASS_IV_TBL(clone) = rb_st_copy(clone, RCLASS_IV_TBL(klass));
+	}
+	if (RCLASS_CONST_TBL(klass)) {
+	    struct clone_const_arg arg;
+	    RCLASS_CONST_TBL(clone) = st_init_numtable();
+	    arg.klass = clone;
+	    arg.tbl = RCLASS_CONST_TBL(clone);
+	    st_foreach(RCLASS_CONST_TBL(klass), clone_const_i, (st_data_t)&arg);
+	}
+	if (attach != Qundef) {
+	    rb_singleton_class_attached(clone, attach);
+	}
+	RCLASS_M_TBL_INIT(clone);
+	st_foreach(RCLASS_M_TBL(klass), clone_method_i, (st_data_t)clone);
+	rb_singleton_class_attached(RBASIC(clone)->klass, clone);
+	FL_SET(clone, FL_SINGLETON);
+
+	return clone;
+    }
+}
+
+/*!
+ * Attach a object to a singleton class.
+ * @pre \a klass is the singleton class of \a obj.
+ */
+void
+rb_singleton_class_attached(VALUE klass, VALUE obj)
+{
+    if (FL_TEST(klass, FL_SINGLETON)) {
+	if (!RCLASS_IV_TBL(klass)) {
+	    RCLASS_IV_TBL(klass) = st_init_numtable();
+	}
+	rb_st_insert_id_and_value(klass, RCLASS_IV_TBL(klass), id_attached, obj);
+    }
+}
+
+
+
+#define METACLASS_OF(k) RBASIC(k)->klass
+#define SET_METACLASS_OF(k, cls) RBASIC_SET_CLASS(k, cls)
+
+/*!
+ * whether k is a meta^(n)-class of Class class
+ * @retval 1 if \a k is a meta^(n)-class of Class class (n >= 0)
+ * @retval 0 otherwise
+ */
+#define META_CLASS_OF_CLASS_CLASS_P(k)  (METACLASS_OF(k) == (k))
+
+/*!
+ * whether k has a metaclass
+ * @retval 1 if \a k has a metaclass
+ * @retval 0 otherwise
+ */
+#define HAVE_METACLASS_P(k) \
+    (FL_TEST(METACLASS_OF(k), FL_SINGLETON) && \
+     rb_ivar_get(METACLASS_OF(k), id_attached) == (k))
+
+/*!
+ * ensures \a klass belongs to its own eigenclass.
+ * @return the eigenclass of \a klass
+ * @post \a klass belongs to the returned eigenclass.
+ *       i.e. the attached object of the eigenclass is \a klass.
+ * @note this macro creates a new eigenclass if necessary.
+ */
+#define ENSURE_EIGENCLASS(klass) \
+    (HAVE_METACLASS_P(klass) ? METACLASS_OF(klass) : make_metaclass(klass))
+
+
+/*!
+ * Creates a metaclass of \a klass
+ * \param klass     a class
+ * \return          created metaclass for the class
+ * \pre \a klass is a Class object
+ * \pre \a klass has no singleton class.
+ * \post the class of \a klass is the returned class.
+ * \post the returned class is meta^(n+1)-class when \a klass is a meta^(n)-klass for n >= 0
+ */
+static inline VALUE
+make_metaclass(VALUE klass)
+{
+    VALUE super;
+    VALUE metaclass = rb_class_boot(Qundef);
+
+    FL_SET(metaclass, FL_SINGLETON);
+    rb_singleton_class_attached(metaclass, klass);
+
+    if (META_CLASS_OF_CLASS_CLASS_P(klass)) {
+	SET_METACLASS_OF(klass, metaclass);
+	SET_METACLASS_OF(metaclass, metaclass);
+    }
+    else {
+	VALUE tmp = METACLASS_OF(klass); /* for a meta^(n)-class klass, tmp is meta^(n)-class of Class class */
+	SET_METACLASS_OF(klass, metaclass);
+	SET_METACLASS_OF(metaclass, ENSURE_EIGENCLASS(tmp));
+    }
+
+    super = RCLASS_SUPER(klass);
+    while (RB_TYPE_P(super, T_ICLASS)) super = RCLASS_SUPER(super);
+    RCLASS_SET_SUPER(metaclass, super ? ENSURE_EIGENCLASS(super) : rb_cClass);
+
+    OBJ_INFECT(metaclass, RCLASS_SUPER(metaclass));
+
+    return metaclass;
+}
+
+/*!
+ * Creates a singleton class for \a obj.
+ * \pre \a obj must not a immediate nor a special const.
+ * \pre \a obj must not a Class object.
+ * \pre \a obj has no singleton class.
+ */
+static inline VALUE
+make_singleton_class(VALUE obj)
+{
+    VALUE orig_class = RBASIC(obj)->klass;
+    VALUE klass = rb_class_boot(orig_class);
+
+    FL_SET(klass, FL_SINGLETON);
+    RBASIC_SET_CLASS(obj, klass);
+    rb_singleton_class_attached(klass, obj);
+
+    SET_METACLASS_OF(klass, METACLASS_OF(rb_class_real(orig_class)));
+    return klass;
+}
+
+
+static VALUE
+boot_defclass(const char *name, VALUE super)
+{
+    VALUE obj = rb_class_boot(super);
+    ID id = rb_intern(name);
+
+    rb_name_class(obj, id);
+    rb_const_set((rb_cObject ? rb_cObject : obj), id, obj);
+    return obj;
+}
+
+void
+Init_class_hierarchy(void)
+{
+    rb_cBasicObject = boot_defclass("BasicObject", 0);
+    rb_cObject = boot_defclass("Object", rb_cBasicObject);
+    rb_cModule = boot_defclass("Module", rb_cObject);
+    rb_cClass =  boot_defclass("Class",  rb_cModule);
+
+    rb_const_set(rb_cObject, rb_intern_const("BasicObject"), rb_cBasicObject);
+    RBASIC_SET_CLASS(rb_cClass, rb_cClass);
+    RBASIC_SET_CLASS(rb_cModule, rb_cClass);
+    RBASIC_SET_CLASS(rb_cObject, rb_cClass);
+    RBASIC_SET_CLASS(rb_cBasicObject, rb_cClass);
+}
+
+
+/*!
+ * \internal
+ * Creates a new *singleton class* for an object.
+ *
+ * \pre \a obj has no singleton class.
+ * \note DO NOT USE the function in an extension libraries. Use \ref rb_singleton_class.
+ * \param obj     An object.
+ * \param unused  ignored.
+ * \return        The singleton class of the object.
+ */
+VALUE
+rb_make_metaclass(VALUE obj, VALUE unused)
+{
+    if (BUILTIN_TYPE(obj) == T_CLASS) {
+	return make_metaclass(obj);
+    }
+    else {
+	return make_singleton_class(obj);
+    }
+}
+
+
+/*!
+ * Defines a new class.
+ * \param id     ignored
+ * \param super  A class from which the new class will derive. NULL means \c Object class.
+ * \return       the created class
+ * \throw TypeError if super is not a \c Class object.
+ *
+ * \note the returned class will not be associated with \a id.
+ *       You must explicitly set a class name if necessary.
+ */
+VALUE
+rb_define_class_id(ID id, VALUE super)
+{
+    VALUE klass;
+
+    if (!super) super = rb_cObject;
+    klass = rb_class_new(super);
+    rb_make_metaclass(klass, RBASIC(super)->klass);
+
+    return klass;
+}
+
+
+/*!
+ * Calls Class#inherited.
+ * \param super  A class which will be called #inherited.
+ *               NULL means Object class.
+ * \param klass  A Class object which derived from \a super
+ * \return the value \c Class#inherited's returns
+ * \pre Each of \a super and \a klass must be a \c Class object.
+ */
+VALUE
+rb_class_inherited(VALUE super, VALUE klass)
+{
+    ID inherited;
+    if (!super) super = rb_cObject;
+    CONST_ID(inherited, "inherited");
+    return rb_funcall(super, inherited, 1, klass);
+}
+
+
+
+/*!
+ * Defines a top-level class.
+ * \param name   name of the class
+ * \param super  a class from which the new class will derive.
+ *               NULL means \c Object class.
+ * \return the created class
+ * \throw TypeError if the constant name \a name is already taken but
+ *                  the constant is not a \c Class.
+ * \throw NameError if the class is already defined but the class can not
+ *                  be reopened because its superclass is not \a super.
+ * \post top-level constant named \a name refers the returned class.
+ *
+ * \note if a class named \a name is already defined and its superclass is
+ *       \a super, the function just returns the defined class.
+ */
+VALUE
+rb_define_class(const char *name, VALUE super)
+{
+    VALUE klass;
+    ID id;
+
+    id = rb_intern(name);
+    if (rb_const_defined(rb_cObject, id)) {
+	klass = rb_const_get(rb_cObject, id);
+	if (!RB_TYPE_P(klass, T_CLASS)) {
+	    rb_raise(rb_eTypeError, "%s is not a class", name);
+	}
+	if (rb_class_real(RCLASS_SUPER(klass)) != super) {
+	    rb_raise(rb_eTypeError, "superclass mismatch for class %s", name);
+	}
+	return klass;
+    }
+    if (!super) {
+	rb_warn("no super class for `%s', Object assumed", name);
+    }
+    klass = rb_define_class_id(id, super);
+    rb_vm_add_root_module(id, klass);
+    rb_name_class(klass, id);
+    rb_const_set(rb_cObject, id, klass);
+    rb_class_inherited(super, klass);
+
+    return klass;
+}
+
+
+/*!
+ * Defines a class under the namespace of \a outer.
+ * \param outer  a class which contains the new class.
+ * \param name   name of the new class
+ * \param super  a class from which the new class will derive.
+ *               NULL means \c Object class.
+ * \return the created class
+ * \throw TypeError if the constant name \a name is already taken but
+ *                  the constant is not a \c Class.
+ * \throw NameError if the class is already defined but the class can not
+ *                  be reopened because its superclass is not \a super.
+ * \post top-level constant named \a name refers the returned class.
+ *
+ * \note if a class named \a name is already defined and its superclass is
+ *       \a super, the function just returns the defined class.
+ */
+VALUE
+rb_define_class_under(VALUE outer, const char *name, VALUE super)
+{
+    return rb_define_class_id_under(outer, rb_intern(name), super);
+}
+
+
+/*!
+ * Defines a class under the namespace of \a outer.
+ * \param outer  a class which contains the new class.
+ * \param id     name of the new class
+ * \param super  a class from which the new class will derive.
+ *               NULL means \c Object class.
+ * \return the created class
+ * \throw TypeError if the constant name \a name is already taken but
+ *                  the constant is not a \c Class.
+ * \throw NameError if the class is already defined but the class can not
+ *                  be reopened because its superclass is not \a super.
+ * \post top-level constant named \a name refers the returned class.
+ *
+ * \note if a class named \a name is already defined and its superclass is
+ *       \a super, the function just returns the defined class.
+ */
+VALUE
+rb_define_class_id_under(VALUE outer, ID id, VALUE super)
+{
+    VALUE klass;
+
+    if (rb_const_defined_at(outer, id)) {
+	klass = rb_const_get_at(outer, id);
+	if (!RB_TYPE_P(klass, T_CLASS)) {
+	    rb_raise(rb_eTypeError, "%"PRIsVALUE" is not a class", rb_id2str(id));
+	}
+	if (rb_class_real(RCLASS_SUPER(klass)) != super) {
+	    rb_name_error(id, "%"PRIsVALUE" is already defined", rb_id2str(id));
+	}
+	return klass;
+    }
+    if (!super) {
+	rb_warn("no super class for `%"PRIsVALUE"::%"PRIsVALUE"', Object assumed",
+		rb_class_path(outer), rb_id2str(id));
+    }
+    klass = rb_define_class_id(id, super);
+    rb_set_class_path_string(klass, outer, rb_id2str(id));
+    rb_const_set(outer, id, klass);
+    rb_class_inherited(super, klass);
+    rb_gc_register_mark_object(klass);
+
+    return klass;
+}
+
+VALUE
+rb_module_new(void)
+{
+    VALUE mdl = class_alloc(T_MODULE, rb_cModule);
+    RCLASS_M_TBL_INIT(mdl);
+    return (VALUE)mdl;
+}
+
+VALUE
+rb_define_module_id(ID id)
+{
+    VALUE mdl;
+
+    mdl = rb_module_new();
+    rb_name_class(mdl, id);
+
+    return mdl;
+}
+
+VALUE
+rb_define_module(const char *name)
+{
+    VALUE module;
+    ID id;
+
+    id = rb_intern(name);
+    if (rb_const_defined(rb_cObject, id)) {
+	module = rb_const_get(rb_cObject, id);
+	if (RB_TYPE_P(module, T_MODULE))
+	    return module;
+	rb_raise(rb_eTypeError, "%s is not a module", rb_obj_classname(module));
+    }
+    module = rb_define_module_id(id);
+    rb_vm_add_root_module(id, module);
+    rb_const_set(rb_cObject, id, module);
+
+    return module;
+}
+
+VALUE
+rb_define_module_under(VALUE outer, const char *name)
+{
+    return rb_define_module_id_under(outer, rb_intern(name));
+}
+
+VALUE
+rb_define_module_id_under(VALUE outer, ID id)
+{
+    VALUE module;
+
+    if (rb_const_defined_at(outer, id)) {
+	module = rb_const_get_at(outer, id);
+	if (RB_TYPE_P(module, T_MODULE))
+	    return module;
+	rb_raise(rb_eTypeError, "%s::%s is not a module",
+		 rb_class2name(outer), rb_obj_classname(module));
+    }
+    module = rb_define_module_id(id);
+    rb_const_set(outer, id, module);
+    rb_set_class_path_string(module, outer, rb_id2str(id));
+    rb_gc_register_mark_object(module);
+
+    return module;
+}
+
+VALUE
+rb_include_class_new(VALUE module, VALUE super)
+{
+    VALUE klass = class_alloc(T_ICLASS, rb_cClass);
+
+    if (BUILTIN_TYPE(module) == T_ICLASS) {
+	module = RBASIC(module)->klass;
+    }
+    if (!RCLASS_IV_TBL(module)) {
+	RCLASS_IV_TBL(module) = st_init_numtable();
+    }
+    if (!RCLASS_CONST_TBL(module)) {
+	RCLASS_CONST_TBL(module) = st_init_numtable();
+    }
+    RCLASS_IV_TBL(klass) = RCLASS_IV_TBL(module);
+    RCLASS_CONST_TBL(klass) = RCLASS_CONST_TBL(module);
+
+    RCLASS_M_TBL_WRAPPER(OBJ_WB_UNPROTECT(klass)) =
+	RCLASS_M_TBL_WRAPPER(OBJ_WB_UNPROTECT(RCLASS_ORIGIN(module)));
+
+    RCLASS_SET_SUPER(klass, super);
+    if (RB_TYPE_P(module, T_ICLASS)) {
+	RBASIC_SET_CLASS(klass, RBASIC(module)->klass);
+    }
+    else {
+	RBASIC_SET_CLASS(klass, module);
+    }
+    OBJ_INFECT(klass, module);
+    OBJ_INFECT(klass, super);
+
+    return (VALUE)klass;
+}
+
+static int include_modules_at(const VALUE klass, VALUE c, VALUE module);
+
+void
+rb_include_module(VALUE klass, VALUE module)
+{
+    int changed = 0;
+
+    rb_frozen_class_p(klass);
+
+    if (!RB_TYPE_P(module, T_MODULE)) {
+	Check_Type(module, T_MODULE);
+    }
+
+    OBJ_INFECT(klass, module);
+
+    changed = include_modules_at(klass, RCLASS_ORIGIN(klass), module);
+    if (changed < 0)
+	rb_raise(rb_eArgError, "cyclic include detected");
+}
+
+static int
+add_refined_method_entry_i(st_data_t key, st_data_t value, st_data_t data)
+{
+    rb_add_refined_method_entry((VALUE) data, (ID) key);
+    return ST_CONTINUE;
+}
+
+static int
+include_modules_at(const VALUE klass, VALUE c, VALUE module)
+{
+    VALUE p, iclass;
+    int method_changed = 0, constant_changed = 0;
+    const st_table *const klass_m_tbl = RCLASS_M_TBL(RCLASS_ORIGIN(klass));
+
+    while (module) {
+	int superclass_seen = FALSE;
+
+	if (RCLASS_ORIGIN(module) != module)
+	    goto skip;
+	if (klass_m_tbl && klass_m_tbl == RCLASS_M_TBL(module))
+	    return -1;
+	/* ignore if the module included already in superclasses */
+	for (p = RCLASS_SUPER(klass); p; p = RCLASS_SUPER(p)) {
+	    switch (BUILTIN_TYPE(p)) {
+	      case T_ICLASS:
+		if (RCLASS_M_TBL_WRAPPER(p) == RCLASS_M_TBL_WRAPPER(module)) {
+		    if (!superclass_seen) {
+			c = p;  /* move insertion point */
+		    }
+		    goto skip;
+		}
+		break;
+	      case T_CLASS:
+		superclass_seen = TRUE;
+		break;
+	    }
+	}
+	iclass = rb_include_class_new(module, RCLASS_SUPER(c));
+	c = RCLASS_SET_SUPER(c, iclass);
+
+	if (BUILTIN_TYPE(module) == T_ICLASS) {
+	    rb_module_add_to_subclasses_list(RBASIC(module)->klass, iclass);
+	}
+	else {
+	    rb_module_add_to_subclasses_list(module, iclass);
+	}
+
+	if (FL_TEST(klass, RMODULE_IS_REFINEMENT)) {
+	    VALUE refined_class =
+		rb_refinement_module_get_refined_class(klass);
+
+	    st_foreach(RMODULE_M_TBL(module), add_refined_method_entry_i,
+		       (st_data_t) refined_class);
+	    FL_SET(c, RMODULE_INCLUDED_INTO_REFINEMENT);
+	}
+	if (RMODULE_M_TBL(module) && RMODULE_M_TBL(module)->num_entries)
+	    method_changed = 1;
+	if (RMODULE_CONST_TBL(module) && RMODULE_CONST_TBL(module)->num_entries)
+	    constant_changed = 1;
+      skip:
+	module = RCLASS_SUPER(module);
+    }
+
+    if (method_changed) rb_clear_method_cache_by_class(klass);
+    if (constant_changed) rb_clear_constant_cache();
+
+    return method_changed;
+}
+
+static int
+move_refined_method(st_data_t key, st_data_t value, st_data_t data)
+{
+    rb_method_entry_t *me = (rb_method_entry_t *) value;
+    st_table *tbl = (st_table *) data;
+
+    if (me->def->type == VM_METHOD_TYPE_REFINED) {
+	if (me->def->body.orig_me) {
+	    rb_method_entry_t *orig_me = me->def->body.orig_me, *new_me;
+	    me->def->body.orig_me = NULL;
+	    new_me = ALLOC(rb_method_entry_t);
+	    *new_me = *me;
+	    st_add_direct(tbl, key, (st_data_t) new_me);
+	    *me = *orig_me;
+	    xfree(orig_me);
+	    return ST_CONTINUE;
+	}
+	else {
+	    st_add_direct(tbl, key, (st_data_t) me);
+	    return ST_DELETE;
+	}
+    }
+    else {
+	return ST_CONTINUE;
+    }
+}
+
+void
+rb_prepend_module(VALUE klass, VALUE module)
+{
+    VALUE origin;
+    int changed = 0;
+
+    rb_frozen_class_p(klass);
+
+    Check_Type(module, T_MODULE);
+
+    OBJ_INFECT(klass, module);
+
+    origin = RCLASS_ORIGIN(klass);
+    if (origin == klass) {
+	origin = class_alloc(T_ICLASS, klass);
+	OBJ_WB_UNPROTECT(origin); /* TODO: conservative shading. Need more survey. */
+	RCLASS_SET_SUPER(origin, RCLASS_SUPER(klass));
+	RCLASS_SET_SUPER(klass, origin);
+	RB_OBJ_WRITE(klass, &RCLASS_ORIGIN(klass), origin);
+	RCLASS_M_TBL_WRAPPER(origin) = RCLASS_M_TBL_WRAPPER(klass);
+	RCLASS_M_TBL_INIT(klass);
+	st_foreach(RCLASS_M_TBL(origin), move_refined_method,
+		   (st_data_t) RCLASS_M_TBL(klass));
+    }
+    changed = include_modules_at(klass, klass, module);
+    if (changed < 0)
+	rb_raise(rb_eArgError, "cyclic prepend detected");
+    if (changed) {
+	rb_vm_check_redefinition_by_prepend(klass);
+    }
+}
+
+/*
+ *  call-seq:
+ *     mod.included_modules -> array
+ *
+ *  Returns the list of modules included in <i>mod</i>.
+ *
+ *     module Mixin
+ *     end
+ *
+ *     module Outer
+ *       include Mixin
+ *     end
+ *
+ *     Mixin.included_modules   #=> []
+ *     Outer.included_modules   #=> [Mixin]
+ */
+
+VALUE
+rb_mod_included_modules(VALUE mod)
+{
+    VALUE ary = rb_ary_new();
+    VALUE p;
+    VALUE origin = RCLASS_ORIGIN(mod);
+
+    for (p = RCLASS_SUPER(mod); p; p = RCLASS_SUPER(p)) {
+	if (p != origin && BUILTIN_TYPE(p) == T_ICLASS) {
+	    VALUE m = RBASIC(p)->klass;
+	    if (RB_TYPE_P(m, T_MODULE))
+		rb_ary_push(ary, m);
+	}
+    }
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     mod.include?(module)    -> true or false
+ *
+ *  Returns <code>true</code> if <i>module</i> is included in
+ *  <i>mod</i> or one of <i>mod</i>'s ancestors.
+ *
+ *     module A
+ *     end
+ *     class B
+ *       include A
+ *     end
+ *     class C < B
+ *     end
+ *     B.include?(A)   #=> true
+ *     C.include?(A)   #=> true
+ *     A.include?(A)   #=> false
+ */
+
+VALUE
+rb_mod_include_p(VALUE mod, VALUE mod2)
+{
+    VALUE p;
+
+    Check_Type(mod2, T_MODULE);
+    for (p = RCLASS_SUPER(mod); p; p = RCLASS_SUPER(p)) {
+	if (BUILTIN_TYPE(p) == T_ICLASS) {
+	    if (RBASIC(p)->klass == mod2) return Qtrue;
+	}
+    }
+    return Qfalse;
+}
+
+/*
+ *  call-seq:
+ *     mod.ancestors -> array
+ *
+ *  Returns a list of modules included/prepended in <i>mod</i>
+ *  (including <i>mod</i> itself).
+ *
+ *     module Mod
+ *       include Math
+ *       include Comparable
+ *       prepend Enumerable
+ *     end
+ *
+ *     Mod.ancestors        #=> [Enumerable, Mod, Comparable, Math]
+ *     Math.ancestors       #=> [Math]
+ *     Enumerable.ancestors #=> [Enumerable]
+ */
+
+VALUE
+rb_mod_ancestors(VALUE mod)
+{
+    VALUE p, ary = rb_ary_new();
+
+    for (p = mod; p; p = RCLASS_SUPER(p)) {
+	if (BUILTIN_TYPE(p) == T_ICLASS) {
+	    rb_ary_push(ary, RBASIC(p)->klass);
+	}
+	else if (p == RCLASS_ORIGIN(p)) {
+	    rb_ary_push(ary, p);
+	}
+    }
+    return ary;
+}
+
+#define VISI(x) ((x)&NOEX_MASK)
+#define VISI_CHECK(x,f) (VISI(x) == (f))
+
+static int
+ins_methods_push(ID name, long type, VALUE ary, long visi)
+{
+    if (type == -1) return ST_CONTINUE;
+
+    switch (visi) {
+      case NOEX_PRIVATE:
+      case NOEX_PROTECTED:
+      case NOEX_PUBLIC:
+	visi = (type == visi);
+	break;
+      default:
+	visi = (type != NOEX_PRIVATE);
+	break;
+    }
+    if (visi) {
+	rb_ary_push(ary, ID2SYM(name));
+    }
+    return ST_CONTINUE;
+}
+
+static int
+ins_methods_i(st_data_t name, st_data_t type, st_data_t ary)
+{
+    return ins_methods_push((ID)name, (long)type, (VALUE)ary, -1); /* everything but private */
+}
+
+static int
+ins_methods_prot_i(st_data_t name, st_data_t type, st_data_t ary)
+{
+    return ins_methods_push((ID)name, (long)type, (VALUE)ary, NOEX_PROTECTED);
+}
+
+static int
+ins_methods_priv_i(st_data_t name, st_data_t type, st_data_t ary)
+{
+    return ins_methods_push((ID)name, (long)type, (VALUE)ary, NOEX_PRIVATE);
+}
+
+static int
+ins_methods_pub_i(st_data_t name, st_data_t type, st_data_t ary)
+{
+    return ins_methods_push((ID)name, (long)type, (VALUE)ary, NOEX_PUBLIC);
+}
+
+struct method_entry_arg {
+    st_table *list;
+    int recur;
+};
+
+static int
+method_entry_i(st_data_t key, st_data_t value, st_data_t data)
+{
+    const rb_method_entry_t *me = (const rb_method_entry_t *)value;
+    struct method_entry_arg *arg = (struct method_entry_arg *)data;
+    long type;
+
+    if (me && me->def->type == VM_METHOD_TYPE_REFINED) {
+	VALUE klass = me->klass;
+	me = rb_resolve_refined_method(Qnil, me, NULL);
+	if (!me) return ST_CONTINUE;
+	if (!arg->recur && me->klass != klass) return ST_CONTINUE;
+    }
+    if (!st_lookup(arg->list, key, 0)) {
+	if (UNDEFINED_METHOD_ENTRY_P(me)) {
+	    type = -1; /* none */
+	}
+	else {
+	    type = VISI(me->flag);
+	}
+	st_add_direct(arg->list, key, type);
+    }
+    return ST_CONTINUE;
+}
+
+static VALUE
+class_instance_method_list(int argc, const VALUE *argv, VALUE mod, int obj, int (*func) (st_data_t, st_data_t, st_data_t))
+{
+    VALUE ary;
+    int recur, prepended = 0;
+    struct method_entry_arg me_arg;
+
+    if (argc == 0) {
+	recur = TRUE;
+    }
+    else {
+	VALUE r;
+	rb_scan_args(argc, argv, "01", &r);
+	recur = RTEST(r);
+    }
+
+    if (!recur && RCLASS_ORIGIN(mod) != mod) {
+	mod = RCLASS_ORIGIN(mod);
+	prepended = 1;
+    }
+
+    me_arg.list = st_init_numtable();
+    me_arg.recur = recur;
+    for (; mod; mod = RCLASS_SUPER(mod)) {
+	if (RCLASS_M_TBL(mod)) st_foreach(RCLASS_M_TBL(mod), method_entry_i, (st_data_t)&me_arg);
+	if (BUILTIN_TYPE(mod) == T_ICLASS && !prepended) continue;
+	if (obj && FL_TEST(mod, FL_SINGLETON)) continue;
+	if (!recur) break;
+    }
+    ary = rb_ary_new();
+    st_foreach(me_arg.list, func, ary);
+    st_free_table(me_arg.list);
+
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     mod.instance_methods(include_super=true)   -> array
+ *
+ *  Returns an array containing the names of the public and protected instance
+ *  methods in the receiver. For a module, these are the public and protected methods;
+ *  for a class, they are the instance (not singleton) methods. If the optional
+ *  parameter is <code>false</code>, the methods of any ancestors are not included.
+ *
+ *     module A
+ *       def method1()  end
+ *     end
+ *     class B
+ *       include A
+ *       def method2()  end
+ *     end
+ *     class C < B
+ *       def method3()  end
+ *     end
+ *
+ *     A.instance_methods(false)                   #=> [:method1]
+ *     B.instance_methods(false)                   #=> [:method2]
+ *     B.instance_methods(true).include?(:method1) #=> true
+ *     C.instance_methods(false)                   #=> [:method3]
+ *     C.instance_methods.include?(:method2)       #=> true
+ */
+
+VALUE
+rb_class_instance_methods(int argc, const VALUE *argv, VALUE mod)
+{
+    return class_instance_method_list(argc, argv, mod, 0, ins_methods_i);
+}
+
+/*
+ *  call-seq:
+ *     mod.protected_instance_methods(include_super=true)   -> array
+ *
+ *  Returns a list of the protected instance methods defined in
+ *  <i>mod</i>. If the optional parameter is <code>false</code>, the
+ *  methods of any ancestors are not included.
+ */
+
+VALUE
+rb_class_protected_instance_methods(int argc, const VALUE *argv, VALUE mod)
+{
+    return class_instance_method_list(argc, argv, mod, 0, ins_methods_prot_i);
+}
+
+/*
+ *  call-seq:
+ *     mod.private_instance_methods(include_super=true)    -> array
+ *
+ *  Returns a list of the private instance methods defined in
+ *  <i>mod</i>. If the optional parameter is <code>false</code>, the
+ *  methods of any ancestors are not included.
+ *
+ *     module Mod
+ *       def method1()  end
+ *       private :method1
+ *       def method2()  end
+ *     end
+ *     Mod.instance_methods           #=> [:method2]
+ *     Mod.private_instance_methods   #=> [:method1]
+ */
+
+VALUE
+rb_class_private_instance_methods(int argc, const VALUE *argv, VALUE mod)
+{
+    return class_instance_method_list(argc, argv, mod, 0, ins_methods_priv_i);
+}
+
+/*
+ *  call-seq:
+ *     mod.public_instance_methods(include_super=true)   -> array
+ *
+ *  Returns a list of the public instance methods defined in <i>mod</i>.
+ *  If the optional parameter is <code>false</code>, the methods of
+ *  any ancestors are not included.
+ */
+
+VALUE
+rb_class_public_instance_methods(int argc, const VALUE *argv, VALUE mod)
+{
+    return class_instance_method_list(argc, argv, mod, 0, ins_methods_pub_i);
+}
+
+/*
+ *  call-seq:
+ *     obj.methods(regular=true)    -> array
+ *
+ *  Returns a list of the names of public and protected methods of
+ *  <i>obj</i>. This will include all the methods accessible in
+ *  <i>obj</i>'s ancestors.
+ *  If the optional parameter is <code>false</code>, it
+ *  returns an array of <i>obj<i>'s public and protected singleton methods,
+ *  the array will not include methods in modules included in <i>obj</i>.
+ *
+ *     class Klass
+ *       def klass_method()
+ *       end
+ *     end
+ *     k = Klass.new
+ *     k.methods[0..9]    #=> [:klass_method, :nil?, :===,
+ *                        #    :==~, :!, :eql?
+ *                        #    :hash, :<=>, :class, :singleton_class]
+ *     k.methods.length   #=> 56
+ *
+ *     k.methods(false)   #=> []
+ *     def k.singleton_method; end
+ *     k.methods(false)   #=> [:singleton_method]
+ *
+ *     module M123; def m123; end end
+ *     k.extend M123
+ *     k.methods(false)   #=> [:singleton_method]
+ */
+
+VALUE
+rb_obj_methods(int argc, const VALUE *argv, VALUE obj)
+{
+    rb_check_arity(argc, 0, 1);
+    if (argc > 0 && !RTEST(argv[0])) {
+	return rb_obj_singleton_methods(argc, argv, obj);
+    }
+    return class_instance_method_list(argc, argv, CLASS_OF(obj), 1, ins_methods_i);
+}
+
+/*
+ *  call-seq:
+ *     obj.protected_methods(all=true)   -> array
+ *
+ *  Returns the list of protected methods accessible to <i>obj</i>. If
+ *  the <i>all</i> parameter is set to <code>false</code>, only those methods
+ *  in the receiver will be listed.
+ */
+
+VALUE
+rb_obj_protected_methods(int argc, const VALUE *argv, VALUE obj)
+{
+    return class_instance_method_list(argc, argv, CLASS_OF(obj), 1, ins_methods_prot_i);
+}
+
+/*
+ *  call-seq:
+ *     obj.private_methods(all=true)   -> array
+ *
+ *  Returns the list of private methods accessible to <i>obj</i>. If
+ *  the <i>all</i> parameter is set to <code>false</code>, only those methods
+ *  in the receiver will be listed.
+ */
+
+VALUE
+rb_obj_private_methods(int argc, const VALUE *argv, VALUE obj)
+{
+    return class_instance_method_list(argc, argv, CLASS_OF(obj), 1, ins_methods_priv_i);
+}
+
+/*
+ *  call-seq:
+ *     obj.public_methods(all=true)   -> array
+ *
+ *  Returns the list of public methods accessible to <i>obj</i>. If
+ *  the <i>all</i> parameter is set to <code>false</code>, only those methods
+ *  in the receiver will be listed.
+ */
+
+VALUE
+rb_obj_public_methods(int argc, const VALUE *argv, VALUE obj)
+{
+    return class_instance_method_list(argc, argv, CLASS_OF(obj), 1, ins_methods_pub_i);
+}
+
+/*
+ *  call-seq:
+ *     obj.singleton_methods(all=true)    -> array
+ *
+ *  Returns an array of the names of singleton methods for <i>obj</i>.
+ *  If the optional <i>all</i> parameter is true, the list will include
+ *  methods in modules included in <i>obj</i>.
+ *  Only public and protected singleton methods are returned.
+ *
+ *     module Other
+ *       def three() end
+ *     end
+ *
+ *     class Single
+ *       def Single.four() end
+ *     end
+ *
+ *     a = Single.new
+ *
+ *     def a.one()
+ *     end
+ *
+ *     class << a
+ *       include Other
+ *       def two()
+ *       end
+ *     end
+ *
+ *     Single.singleton_methods    #=> [:four]
+ *     a.singleton_methods(false)  #=> [:two, :one]
+ *     a.singleton_methods         #=> [:two, :one, :three]
+ */
+
+VALUE
+rb_obj_singleton_methods(int argc, const VALUE *argv, VALUE obj)
+{
+    VALUE recur, ary, klass, origin;
+    struct method_entry_arg me_arg;
+    st_table *mtbl;
+
+    if (argc == 0) {
+	recur = Qtrue;
+    }
+    else {
+	rb_scan_args(argc, argv, "01", &recur);
+    }
+    klass = CLASS_OF(obj);
+    origin = RCLASS_ORIGIN(klass);
+    me_arg.list = st_init_numtable();
+    me_arg.recur = RTEST(recur);
+    if (klass && FL_TEST(klass, FL_SINGLETON)) {
+	if ((mtbl = RCLASS_M_TBL(origin)) != 0)
+	    st_foreach(mtbl, method_entry_i, (st_data_t)&me_arg);
+	klass = RCLASS_SUPER(klass);
+    }
+    if (RTEST(recur)) {
+	while (klass && (FL_TEST(klass, FL_SINGLETON) || RB_TYPE_P(klass, T_ICLASS))) {
+	    if (klass != origin && (mtbl = RCLASS_M_TBL(klass)) != 0)
+		st_foreach(mtbl, method_entry_i, (st_data_t)&me_arg);
+	    klass = RCLASS_SUPER(klass);
+	}
+    }
+    ary = rb_ary_new();
+    st_foreach(me_arg.list, ins_methods_i, ary);
+    st_free_table(me_arg.list);
+
+    return ary;
+}
+
+/*!
+ * \}
+ */
+/*!
+ * \defgroup defmethod Defining methods
+ * There are some APIs to define a method from C.
+ * These API takes a C function as a method body.
+ *
+ * \par Method body functions
+ * Method body functions must return a VALUE and
+ * can be one of the following form:
+ * <dl>
+ * <dt>Fixed number of parameters</dt>
+ * <dd>
+ *     This form is a normal C function, excepting it takes
+ *     a receiver object as the first argument.
+ *
+ *     \code
+ *     static VALUE my_method(VALUE self, VALUE x, VALUE y);
+ *     \endcode
+ * </dd>
+ * <dt>argc and argv style</dt>
+ * <dd>
+ *     This form takes three parameters: \a argc, \a argv and \a self.
+ *     \a self is the receiver. \a argc is the number of arguments.
+ *     \a argv is a pointer to an array of the arguments.
+ *
+ *     \code
+ *     static VALUE my_method(int argc, VALUE *argv, VALUE self);
+ *     \endcode
+ * </dd>
+ * <dt>Ruby array style</dt>
+ * <dd>
+ *     This form takes two parameters: self and args.
+ *     \a self is the receiver. \a args is an Array object which
+ *     contains the arguments.
+ *
+ *     \code
+ *     static VALUE my_method(VALUE self, VALUE args);
+ *     \endcode
+ * </dd>
+ *
+ * \par Number of parameters
+ * Method defining APIs takes the number of parameters which the
+ * method will takes. This number is called \a argc.
+ * \a argc can be:
+ * <dl>
+ * <dt>zero or positive number</dt>
+ * <dd>This means the method body function takes a fixed number of parameters</dd>
+ * <dt>-1</dt>
+ * <dd>This means the method body function is "argc and argv" style.</dd>
+ * <dt>-2</dt>
+ * <dd>This means the method body function is "self and args" style.</dd>
+ * </dl>
+ * \{
+ */
+
+void
+rb_define_method_id(VALUE klass, ID mid, VALUE (*func)(ANYARGS), int argc)
+{
+    rb_add_method_cfunc(klass, mid, func, argc, NOEX_PUBLIC);
+}
+
+void
+rb_define_method(VALUE klass, const char *name, VALUE (*func)(ANYARGS), int argc)
+{
+    rb_add_method_cfunc(klass, rb_intern(name), func, argc, NOEX_PUBLIC);
+}
+
+void
+rb_define_protected_method(VALUE klass, const char *name, VALUE (*func)(ANYARGS), int argc)
+{
+    rb_add_method_cfunc(klass, rb_intern(name), func, argc, NOEX_PROTECTED);
+}
+
+void
+rb_define_private_method(VALUE klass, const char *name, VALUE (*func)(ANYARGS), int argc)
+{
+    rb_add_method_cfunc(klass, rb_intern(name), func, argc, NOEX_PRIVATE);
+}
+
+void
+rb_undef_method(VALUE klass, const char *name)
+{
+    rb_add_method(klass, rb_intern(name), VM_METHOD_TYPE_UNDEF, 0, NOEX_UNDEF);
+}
+
+/*!
+ * \}
+ */
+/*!
+ * \addtogroup class
+ * \{
+ */
+
+#define SPECIAL_SINGLETON(x,c) do {\
+    if (obj == (x)) {\
+	return (c);\
+    }\
+} while (0)
+
+static inline VALUE
+special_singleton_class_of(VALUE obj)
+{
+    SPECIAL_SINGLETON(Qnil, rb_cNilClass);
+    SPECIAL_SINGLETON(Qfalse, rb_cFalseClass);
+    SPECIAL_SINGLETON(Qtrue, rb_cTrueClass);
+    return Qnil;
+}
+
+VALUE
+rb_special_singleton_class(VALUE obj)
+{
+    return special_singleton_class_of(obj);
+}
+
+/*!
+ * \internal
+ * Returns the singleton class of \a obj. Creates it if necessary.
+ *
+ * \note DO NOT expose the returned singleton class to
+ *       outside of class.c.
+ *       Use \ref rb_singleton_class instead for
+ *       consistency of the metaclass hierarchy.
+ */
+static VALUE
+singleton_class_of(VALUE obj)
+{
+    VALUE klass;
+
+    if (FIXNUM_P(obj) || FLONUM_P(obj) || STATIC_SYM_P(obj)) {
+      no_singleton:
+	rb_raise(rb_eTypeError, "can't define singleton");
+    }
+    if (SPECIAL_CONST_P(obj)) {
+	klass = special_singleton_class_of(obj);
+	if (NIL_P(klass))
+	    rb_bug("unknown immediate %p", (void *)obj);
+	return klass;
+    }
+    else {
+	switch (BUILTIN_TYPE(obj)) {
+	  case T_FLOAT: case T_BIGNUM: case T_SYMBOL:
+	    goto no_singleton;
+	}
+    }
+
+    klass = RBASIC(obj)->klass;
+    if (!(FL_TEST(klass, FL_SINGLETON) &&
+	  rb_ivar_get(klass, id_attached) == obj)) {
+	klass = rb_make_metaclass(obj, klass);
+    }
+
+    if (OBJ_TAINTED(obj)) {
+	OBJ_TAINT(klass);
+    }
+    else {
+	FL_UNSET(klass, FL_TAINT);
+    }
+    if (OBJ_FROZEN(obj)) OBJ_FREEZE_RAW(klass);
+
+    return klass;
+}
+
+void
+rb_freeze_singleton_class(VALUE x)
+{
+    /* should not propagate to meta-meta-class, and so on */
+    if (!(RBASIC(x)->flags & FL_SINGLETON)) {
+	VALUE klass = RBASIC_CLASS(x);
+	if (klass && (klass = RCLASS_ORIGIN(klass)) != 0 &&
+	    FL_TEST(klass, (FL_SINGLETON|FL_FREEZE)) == FL_SINGLETON) {
+	    OBJ_FREEZE_RAW(klass);
+	}
+    }
+}
+
+/*!
+ * Returns the singleton class of \a obj, or nil if obj is not a
+ * singleton object.
+ *
+ * \param obj an arbitrary object.
+ * \return the singleton class or nil.
+ */
+VALUE
+rb_singleton_class_get(VALUE obj)
+{
+    VALUE klass;
+
+    if (SPECIAL_CONST_P(obj)) {
+	return rb_special_singleton_class(obj);
+    }
+    klass = RBASIC(obj)->klass;
+    if (!FL_TEST(klass, FL_SINGLETON)) return Qnil;
+    if (rb_ivar_get(klass, id_attached) != obj) return Qnil;
+    return klass;
+}
+
+/*!
+ * Returns the singleton class of \a obj. Creates it if necessary.
+ *
+ * \param obj an arbitrary object.
+ * \throw TypeError if \a obj is a Fixnum or a Symbol.
+ * \return the singleton class.
+ *
+ * \post \a obj has its own singleton class.
+ * \post if \a obj is a class,
+ *       the returned singleton class also has its own
+ *       singleton class in order to keep consistency of the
+ *       inheritance structure of metaclasses.
+ * \note a new singleton class will be created
+ *       if \a obj does not have it.
+ * \note the singleton classes for nil, true and false are:
+ *       NilClass, TrueClass and FalseClass.
+ */
+VALUE
+rb_singleton_class(VALUE obj)
+{
+    VALUE klass = singleton_class_of(obj);
+
+    /* ensures an exposed class belongs to its own eigenclass */
+    if (RB_TYPE_P(obj, T_CLASS)) (void)ENSURE_EIGENCLASS(klass);
+
+    return klass;
+}
+
+/*!
+ * \}
+ */
+
+/*!
+ * \addtogroup defmethod
+ * \{
+ */
+
+/*!
+ * Defines a singleton method for \a obj.
+ * \param obj    an arbitrary object
+ * \param name   name of the singleton method
+ * \param func   the method body
+ * \param argc   the number of parameters, or -1 or -2. see \ref defmethod.
+ */
+void
+rb_define_singleton_method(VALUE obj, const char *name, VALUE (*func)(ANYARGS), int argc)
+{
+    rb_define_method(singleton_class_of(obj), name, func, argc);
+}
+
+
+
+/*!
+ * Defines a module function for \a module.
+ * \param module  an module or a class.
+ * \param name    name of the function
+ * \param func    the method body
+ * \param argc    the number of parameters, or -1 or -2. see \ref defmethod.
+ */
+void
+rb_define_module_function(VALUE module, const char *name, VALUE (*func)(ANYARGS), int argc)
+{
+    rb_define_private_method(module, name, func, argc);
+    rb_define_singleton_method(module, name, func, argc);
+}
+
+
+/*!
+ * Defines a global function
+ * \param name    name of the function
+ * \param func    the method body
+ * \param argc    the number of parameters, or -1 or -2. see \ref defmethod.
+ */
+void
+rb_define_global_function(const char *name, VALUE (*func)(ANYARGS), int argc)
+{
+    rb_define_module_function(rb_mKernel, name, func, argc);
+}
+
+
+/*!
+ * Defines an alias of a method.
+ * \param klass  the class which the original method belongs to
+ * \param name1  a new name for the method
+ * \param name2  the original name of the method
+ */
+void
+rb_define_alias(VALUE klass, const char *name1, const char *name2)
+{
+    rb_alias(klass, rb_intern(name1), rb_intern(name2));
+}
+
+/*!
+ * Defines (a) public accessor method(s) for an attribute.
+ * \param klass  the class which the attribute will belongs to
+ * \param name   name of the attribute
+ * \param read   a getter method for the attribute will be defined if \a read is non-zero.
+ * \param write  a setter method for the attribute will be defined if \a write is non-zero.
+ */
+void
+rb_define_attr(VALUE klass, const char *name, int read, int write)
+{
+    rb_attr(klass, rb_intern(name), read, write, FALSE);
+}
+
+int
+rb_obj_basic_to_s_p(VALUE obj)
+{
+    const rb_method_entry_t *me = rb_method_entry(CLASS_OF(obj), rb_intern("to_s"), 0);
+    if (me && me->def && me->def->type == VM_METHOD_TYPE_CFUNC &&
+	me->def->body.cfunc.func == rb_any_to_s)
+	return 1;
+    return 0;
+}
+
+#include <stdarg.h>
+
+int
+rb_scan_args(int argc, const VALUE *argv, const char *fmt, ...)
+{
+    int i;
+    const char *p = fmt;
+    VALUE *var;
+    va_list vargs;
+    int f_var = 0, f_hash = 0, f_block = 0;
+    int n_lead = 0, n_opt = 0, n_trail = 0, n_mand;
+    int argi = 0;
+    VALUE hash = Qnil;
+
+    if (ISDIGIT(*p)) {
+	n_lead = *p - '0';
+	p++;
+	if (ISDIGIT(*p)) {
+	    n_opt = *p - '0';
+	    p++;
+	    if (ISDIGIT(*p)) {
+		n_trail = *p - '0';
+		p++;
+		goto block_arg;
+	    }
+	}
+    }
+    if (*p == '*') {
+	f_var = 1;
+	p++;
+	if (ISDIGIT(*p)) {
+	    n_trail = *p - '0';
+	    p++;
+	}
+    }
+  block_arg:
+    if (*p == ':') {
+	f_hash = 1;
+	p++;
+    }
+    if (*p == '&') {
+	f_block = 1;
+	p++;
+    }
+    if (*p != '\0') {
+	rb_fatal("bad scan arg format: %s", fmt);
+    }
+    n_mand = n_lead + n_trail;
+
+    if (argc < n_mand)
+	goto argc_error;
+
+    va_start(vargs, fmt);
+
+    /* capture an option hash - phase 1: pop */
+    if (f_hash && n_mand < argc) {
+	VALUE last = argv[argc - 1];
+
+	if (NIL_P(last)) {
+	    /* nil is taken as an empty option hash only if it is not
+	       ambiguous; i.e. '*' is not specified and arguments are
+	       given more than sufficient */
+	    if (!f_var && n_mand + n_opt < argc)
+		argc--;
+	}
+	else {
+	    hash = rb_check_hash_type(last);
+	    if (!NIL_P(hash)) {
+		VALUE opts = rb_extract_keywords(&hash);
+		if (!hash) argc--;
+		hash = opts ? opts : Qnil;
+	    }
+	}
+    }
+    /* capture leading mandatory arguments */
+    for (i = n_lead; i-- > 0; ) {
+	var = va_arg(vargs, VALUE *);
+	if (var) *var = argv[argi];
+	argi++;
+    }
+    /* capture optional arguments */
+    for (i = n_opt; i-- > 0; ) {
+	var = va_arg(vargs, VALUE *);
+	if (argi < argc - n_trail) {
+	    if (var) *var = argv[argi];
+	    argi++;
+	}
+	else {
+	    if (var) *var = Qnil;
+	}
+    }
+    /* capture variable length arguments */
+    if (f_var) {
+	int n_var = argc - argi - n_trail;
+
+	var = va_arg(vargs, VALUE *);
+	if (0 < n_var) {
+	    if (var) *var = rb_ary_new4(n_var, &argv[argi]);
+	    argi += n_var;
+	}
+	else {
+	    if (var) *var = rb_ary_new();
+	}
+    }
+    /* capture trailing mandatory arguments */
+    for (i = n_trail; i-- > 0; ) {
+	var = va_arg(vargs, VALUE *);
+	if (var) *var = argv[argi];
+	argi++;
+    }
+    /* capture an option hash - phase 2: assignment */
+    if (f_hash) {
+	var = va_arg(vargs, VALUE *);
+	if (var) *var = hash;
+    }
+    /* capture iterator block */
+    if (f_block) {
+	var = va_arg(vargs, VALUE *);
+	if (rb_block_given_p()) {
+	    *var = rb_block_proc();
+	}
+	else {
+	    *var = Qnil;
+	}
+    }
+    va_end(vargs);
+
+    if (argi < argc) {
+      argc_error:
+	rb_error_arity(argc, n_mand, f_var ? UNLIMITED_ARGUMENTS : n_mand + n_opt);
+    }
+
+    return argc;
+}
+
+VALUE
+rb_keyword_error_new(const char *error, VALUE keys)
+{
+    const char *msg = "";
+    VALUE error_message;
+
+    if (RARRAY_LEN(keys) == 1) {
+	keys = RARRAY_AREF(keys, 0);
+    }
+    else {
+	keys = rb_ary_join(keys, rb_usascii_str_new2(", "));
+	msg = "s";
+    }
+
+    error_message = rb_sprintf("%s keyword%s: %"PRIsVALUE, error, msg, keys);
+
+    return rb_exc_new_str(rb_eArgError, error_message);
+}
+
+NORETURN(static void rb_keyword_error(const char *error, VALUE keys));
+static void
+rb_keyword_error(const char *error, VALUE keys)
+{
+    rb_exc_raise(rb_keyword_error_new(error, keys));
+}
+
+NORETURN(static void unknown_keyword_error(VALUE hash, const ID *table, int keywords));
+static void
+unknown_keyword_error(VALUE hash, const ID *table, int keywords)
+{
+    st_table *tbl = rb_hash_tbl_raw(hash);
+    VALUE keys;
+    int i;
+    for (i = 0; i < keywords; i++) {
+	st_data_t key = ID2SYM(table[i]);
+	st_delete(tbl, &key, NULL);
+    }
+    keys = rb_funcall(hash, rb_intern("keys"), 0, 0);
+    if (!RB_TYPE_P(keys, T_ARRAY)) rb_raise(rb_eArgError, "unknown keyword");
+    rb_keyword_error("unknown", keys);
+}
+
+static int
+separate_symbol(st_data_t key, st_data_t value, st_data_t arg)
+{
+    VALUE *kwdhash = (VALUE *)arg;
+
+    if (!SYMBOL_P(key)) kwdhash++;
+    if (!*kwdhash) *kwdhash = rb_hash_new();
+    rb_hash_aset(*kwdhash, (VALUE)key, (VALUE)value);
+    return ST_CONTINUE;
+}
+
+VALUE
+rb_extract_keywords(VALUE *orighash)
+{
+    VALUE parthash[2] = {0, 0};
+    VALUE hash = *orighash;
+
+    if (RHASH_EMPTY_P(hash)) {
+	*orighash = 0;
+	return hash;
+    }
+    st_foreach(rb_hash_tbl_raw(hash), separate_symbol, (st_data_t)&parthash);
+    *orighash = parthash[1];
+    return parthash[0];
+}
+
+int
+rb_get_kwargs(VALUE keyword_hash, const ID *table, int required, int optional, VALUE *values)
+{
+    int i = 0, j;
+    int rest = 0;
+    VALUE missing = Qnil;
+    st_data_t key;
+
+#define extract_kwarg(keyword, val) \
+    (key = (st_data_t)(keyword), values ? \
+     st_delete(rb_hash_tbl_raw(keyword_hash), &key, (val)) : \
+     st_lookup(rb_hash_tbl_raw(keyword_hash), key, (val)))
+
+    if (NIL_P(keyword_hash)) keyword_hash = 0;
+
+    if (optional < 0) {
+	rest = 1;
+	optional = -1-optional;
+    }
+    if (values) {
+	for (j = 0; j < required + optional; j++) {
+	    values[j] = Qundef;
+	}
+    }
+    if (required) {
+	for (; i < required; i++) {
+	    VALUE keyword = ID2SYM(table[i]);
+	    if (keyword_hash) {
+		st_data_t val;
+		if (extract_kwarg(keyword, &val)) {
+		    if (values) values[i] = (VALUE)val;
+		    continue;
+		}
+	    }
+	    if (NIL_P(missing)) missing = rb_ary_tmp_new(1);
+	    rb_ary_push(missing, keyword);
+	}
+	if (!NIL_P(missing)) {
+	    rb_keyword_error("missing", missing);
+	}
+    }
+    j = i;
+    if (optional && keyword_hash) {
+	for (i = 0; i < optional; i++) {
+	    st_data_t val;
+	    if (extract_kwarg(ID2SYM(table[required+i]), &val)) {
+		if (values) values[required+i] = (VALUE)val;
+		j++;
+	    }
+	}
+    }
+    if (!rest && keyword_hash) {
+	if (RHASH_SIZE(keyword_hash) > (unsigned int)j) {
+	    unknown_keyword_error(keyword_hash, table, required+optional);
+	}
+    }
+    return j;
+#undef extract_kwarg
+}
+
+/*!
+ * \}
+ */