now segmented list can be used as instance variable tables by -DMRB_USE_IV_SEGLIST; we still need to measure the performance and memory consumption

include/mrbconf.h

@@ -19,7 +19,10 @@
 /* number of object per heap page */
 //#define MRB_HEAP_PAGE_SIZE 1024
 
-/* initial size for IV khash */
+/* use segmented list for IV table */
+//#define MRB_USE_IV_SEGLIST
+
+/* initial size for IV khash; ignored when MRB_USE_IV_SEGLIST is set */
 //#define MRB_IV_INITIAL_SIZE 8
 
 /* default size of khash table bucket */

include/mruby.h

@@ -233,7 +233,7 @@ typedef struct mrb_state {
   int esize;
 
   struct RObject *exc;
-  struct kh_iv *globals;
+  struct iv_tbl *globals;
 
   struct mrb_irep **irep;
   size_t irep_len, irep_capa;

include/mruby/class.h

@@ -13,7 +13,7 @@ extern "C" {
 
 struct RClass {
   MRUBY_OBJECT_HEADER;
-  struct kh_iv *iv;
+  struct iv_tbl *iv;
   struct kh_mt *mt;
   struct RClass *super;
 };

include/mruby/data.h

@@ -18,7 +18,7 @@ struct mrb_data_type {
 
 struct RData {
   MRUBY_OBJECT_HEADER;
-  struct kh_iv *iv;
+  struct iv_tbl *iv;
   struct mrb_data_type *type;
   void *data;
 };

include/mruby/hash.h

@@ -13,7 +13,7 @@ extern "C" {
 
 struct RHash {
   MRUBY_OBJECT_HEADER;
-  struct kh_iv *iv;
+  struct iv_tbl *iv;
   struct kh_ht *ht;
 };
 

include/mruby/object.h

@@ -44,7 +44,7 @@ struct RBasic {
 
 struct RObject {
   MRUBY_OBJECT_HEADER;
-  struct kh_iv *iv;
+  struct iv_tbl *iv;
 };
 
 #define mrb_obj_ptr(v)    ((struct RObject*)((v).value.p))

include/mruby/variable.h

@@ -38,17 +38,21 @@ mrb_value mrb_const_get(mrb_state*, mrb_value, mrb_sym);
 void mrb_const_set(mrb_state*, mrb_value, mrb_sym, mrb_value);
 int mrb_const_defined(mrb_state*, mrb_value, mrb_sym);
 
-mrb_value mrb_obj_iv_get(mrb_state*, struct RObject*, mrb_sym);
-void mrb_obj_iv_set(mrb_state*, struct RObject*, mrb_sym, mrb_value);
-const char * mrb_class2name(mrb_state *mrb, struct RClass* klass);
+mrb_value mrb_obj_iv_get(mrb_state *mrb, struct RObject *obj, mrb_sym sym);
+void mrb_obj_iv_set(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v);
+int mrb_obj_iv_defined(mrb_state *mrb, struct RObject *obj, mrb_sym sym);
 mrb_value mrb_iv_get(mrb_state *mrb, mrb_value obj, mrb_sym sym);
 void mrb_iv_set(mrb_state *mrb, mrb_value obj, mrb_sym sym, mrb_value v);
+int mrb_iv_defined(mrb_state*, mrb_value, mrb_sym);
 mrb_value mrb_iv_remove(mrb_state *mrb, mrb_value obj, mrb_sym sym);
+void mrb_iv_copy(mrb_state *mrb, mrb_value dst, mrb_value src);
 int mrb_const_defined_at(mrb_state *mrb, struct RClass *klass, mrb_sym id);
 mrb_value mrb_f_global_variables(mrb_state *mrb, mrb_value self);
 mrb_value mrb_gv_get(mrb_state *mrb, mrb_sym sym);
 void mrb_gv_set(mrb_state *mrb, mrb_sym sym, mrb_value val);
 mrb_value mrb_obj_instance_variables(mrb_state*, mrb_value);
+mrb_value mrb_obj_iv_inspect(mrb_state*, struct RObject*);
+mrb_sym mrb_class_sym(mrb_state *mrb, struct RClass *c, struct RClass *outer);
 
 /* GC functions */
 void mrb_gc_mark_gv(mrb_state*);
@@ -57,9 +61,6 @@ void mrb_gc_mark_iv(mrb_state*, struct RObject*);
 size_t mrb_gc_mark_iv_size(mrb_state*, struct RObject*);
 void mrb_gc_free_iv(mrb_state*, struct RObject*);
 
-#include "mruby/khash.h"
-KHASH_DECLARE(iv, mrb_sym, mrb_value, 1)
-
 #if defined(__cplusplus)
 }  /* extern "C" { */
 #endif

src/class.c

@@ -15,7 +15,6 @@
 #include "mruby/array.h"
 #include "error.h"
 
-KHASH_DEFINE(iv, mrb_sym, mrb_value,     1, kh_int_hash_func, kh_int_hash_equal);
 KHASH_DEFINE(mt, mrb_sym, struct RProc*, 1, kh_int_hash_func, kh_int_hash_equal);
 
 typedef struct fc_result {
@@ -65,30 +64,6 @@ mrb_name_class(mrb_state *mrb, struct RClass *c, mrb_sym name)
                  mrb_intern(mrb, "__classid__"), mrb_symbol_value(name));
 }
 
-static mrb_sym
-class_sym(mrb_state *mrb, struct RClass *c, struct RClass *outer)
-{
-  mrb_value name;
-
-  name = mrb_obj_iv_get(mrb, (struct RObject*)c, mrb_intern(mrb, "__classid__"));
-  if (mrb_nil_p(name)) {
-    khash_t(iv)* h;
-    khiter_t k;
-    mrb_value v;
-
-    if (!outer) outer = mrb->object_class;
-    h = outer->iv;
-    for (k = kh_begin(h); k != kh_end(h); k++) {
-      if (!kh_exist(h,k)) continue;
-      v = kh_value(h,k);
-      if (mrb_type(v) == c->tt && mrb_class_ptr(v) == c) {
-        return kh_key(h,k);
-      }
-    }
-  }
-  return SYM2ID(name);
-}
-
 static void
 make_metaclass(mrb_state *mrb, struct RClass *c)
 {
@@ -1114,16 +1089,16 @@ mrb_class_path(mrb_state *mrb, struct RClass *c)
   path = mrb_obj_iv_get(mrb, (struct RObject*)c, mrb_intern(mrb, "__classpath__"));
   if (mrb_nil_p(path)) {
     struct RClass *outer = mrb_class_outer_module(mrb, c);
-    mrb_sym sym = class_sym(mrb, c, outer);
-    if (outer && outer != mrb->object_class) {
+    mrb_sym sym = mrb_class_sym(mrb, c, outer);
+    if (sym == 0) {
+      return mrb_nil_value();
+    }
+    else if (outer && outer != mrb->object_class) {
       mrb_value base = mrb_class_path(mrb, outer);
       path = mrb_str_plus(mrb, base, mrb_str_new(mrb, "::", 2));
       name = mrb_sym2name_len(mrb, sym, &len);
       mrb_str_concat(mrb, path, mrb_str_new(mrb, name, len));
     }
-    else if (sym == 0) {
-      return mrb_nil_value();
-    }
     else {
       name = mrb_sym2name_len(mrb, sym, &len);
       path = mrb_str_new(mrb, name, len);

src/error.c

@@ -8,6 +8,7 @@
 #include <stdarg.h>
 #include <stdio.h>
 #include <setjmp.h>
+#include <string.h>
 #include "error.h"
 #include "mruby/variable.h"
 #include "mruby/string.h"

src/kernel.c

@@ -32,43 +32,6 @@ struct obj_ivar_tag {
   void * arg;
 };
 
-static mrb_value
-inspect_obj(mrb_state *mrb, mrb_value obj, mrb_value str, int recur)
-{
-  if (recur) {
-    mrb_str_cat2(mrb, str, " ...");
-  }
-  else {
-    khiter_t k;
-    kh_iv_t *h = RCLASS_IV_TBL(obj);
-
-    if (h) {
-      for (k = kh_begin(h); k != kh_end(h); k++) {
-        if (kh_exist(h, k)){
-          mrb_sym id = kh_key(h, k);
-          mrb_value value = kh_value(h, k);
-
-          /* need not to show internal data */
-          if (RSTRING_PTR(str)[0] == '-') { /* first element */
-            RSTRING_PTR(str)[0] = '#';
-            mrb_str_cat2(mrb, str, " ");
-          }
-          else {
-            mrb_str_cat2(mrb, str, ", ");
-          }
-          mrb_str_cat2(mrb, str, mrb_sym2name(mrb, id));
-          mrb_str_cat2(mrb, str, "=");
-          mrb_str_append(mrb, str, mrb_inspect(mrb, value));
-        }
-      }
-    }
-  }
-  mrb_str_cat2(mrb, str, ">");
-  RSTRING_PTR(str)[0] = '#';
-
-  return str;
-}
-
 int
 mrb_obj_basic_to_s_p(mrb_state *mrb, mrb_value obj)
 {
@@ -96,16 +59,7 @@ mrb_value
 mrb_obj_inspect(mrb_state *mrb, mrb_value obj)
 {
   if ((mrb_type(obj) == MRB_TT_OBJECT) && mrb_obj_basic_to_s_p(mrb, obj)) {
-    long len = ROBJECT_NUMIV(obj);
-
-    if (len > 0) {
-      mrb_value str;
-      const char *c = mrb_obj_classname(mrb, obj);
-
-      str = mrb_sprintf(mrb, "-<%s:%p", c, (void*)&obj);
-      return inspect_obj(mrb, obj, str, 0);
-    }
-    return mrb_any_to_s(mrb, obj);
+    return mrb_obj_iv_inspect(mrb, mrb_obj_ptr(obj));
   }
   else if (mrb_nil_p(obj)) {
     return mrb_str_new(mrb, "nil", 3);
@@ -347,13 +301,7 @@ init_copy(mrb_state *mrb, mrb_value dest, mrb_value obj)
       case MRB_TT_OBJECT:
       case MRB_TT_CLASS:
       case MRB_TT_MODULE:
-        if (ROBJECT(dest)->iv) {
-            kh_destroy(iv, ROBJECT(dest)->iv);
-            ROBJECT(dest)->iv = 0;
-        }
-        if (ROBJECT(obj)->iv) {
-            ROBJECT(dest)->iv = kh_copy(iv, mrb, ROBJECT(obj)->iv);
-        }
+	mrb_iv_copy(mrb, dest, obj);
         break;
 
       default:
@@ -630,19 +578,12 @@ check_iv_name(mrb_state *mrb, mrb_sym id)
 mrb_value
 mrb_obj_ivar_defined(mrb_state *mrb, mrb_value self)
 {
-  khiter_t k;
-  kh_iv_t *h = RCLASS_IV_TBL(self);
   mrb_sym mid;
 
   mrb_get_args(mrb, "n", &mid);
   check_iv_name(mrb, mid);
-
-  if (h) {
-    k = kh_get(iv, h, mid);
-    if (k != kh_end(h)) {
-      return mrb_true_value();
-    }
-  }
+  if (mrb_obj_iv_defined(mrb, mrb_obj_ptr(self), mid))
+    return mrb_true_value();
   return mrb_false_value();
 }
 

src/variable.c

@@ -6,29 +6,374 @@
 
 #include "mruby.h"
 #include "mruby/class.h"
-#include "mruby/khash.h"
 #include "mruby/variable.h"
 #include "error.h"
 #include "mruby/array.h"
+#include "mruby/string.h"
 #include "mruby/proc.h"
+#ifndef MRB_USE_IV_SEGLIST
+#include "mruby/khash.h"
+#endif
 
 #ifdef ENABLE_REGEXP
 #include "re.h"
 #endif
 
+typedef int (iv_foreach_func)(mrb_state*,mrb_sym,mrb_value,void*);
+
+#ifdef MRB_USE_IV_SEGLIST
+
+#ifndef MRB_SEGMENT_SIZE
+#define MRB_SEGMENT_SIZE 4
+#endif
+
+typedef struct segment
+{
+  mrb_sym key[MRB_SEGMENT_SIZE];
+  mrb_value val[MRB_SEGMENT_SIZE];
+  struct segment *next;
+} segment;
+
+typedef struct iv_tbl {
+  segment *rootseg;
+  int size;
+  int last_len;
+} iv_tbl;
+
+static iv_tbl*
+iv_new(mrb_state *mrb)
+{
+  iv_tbl *t;
+
+  t = mrb_malloc(mrb, sizeof(iv_tbl));
+  if (t) {
+    t->size = 0;
+    t->rootseg =  NULL;
+    t->last_len = 0;
+  }
+  return t;
+}
+
+static void
+iv_put(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value val)
+{
+  segment *seg = t->rootseg;
+  segment *prev = NULL;
+  segment *matched_seg = NULL;
+  int matched_idx = 0;
+  int i;
+
+  while (seg) {
+    for (i=0; i<MRB_SEGMENT_SIZE; i++) {
+      mrb_sym key = seg->key[i];
+      /* found room in last segment after last_len */
+      if (!seg->next && i >= t->last_len) {
+	seg->key[i] = sym;
+	seg->val[i] = val;
+	t->last_len = i+1;
+	t->size++;
+	return;
+      }
+      if (key == 0 && !matched_seg) {
+	matched_seg = seg;
+	matched_idx = i;
+      }
+      else if (key == sym) {
+        seg->val[i] = val;
+        return;
+      }
+    }
+    prev = seg;
+    seg = seg->next;
+  }
+
+  /* not found */
+  t->size++;
+  if (matched_seg) {
+    matched_seg->key[matched_idx] = sym;
+    matched_seg->val[matched_idx] = val;
+    return;
+  }
+
+  seg = mrb_malloc(mrb, sizeof(segment));
+  if (!seg) return;
+  seg->next = NULL;
+  seg->key[0] = sym;
+  seg->val[0] = val;
+  t->last_len = 1;
+  if (prev) {
+    prev->next = seg;
+  }
+  else {
+    t->rootseg = seg;
+  }
+  return;
+}
+
+static int
+iv_get(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value *vp)
+{
+  segment *seg;
+  int i;
+
+  seg = t->rootseg;
+  while (seg) {
+    for (i=0; i<MRB_SEGMENT_SIZE; i++) {
+      mrb_sym key = seg->key[i];
+
+      if (!seg->next && i >= t->last_len) {
+	return 0;
+      }
+      if (key == sym) {
+	if (vp) *vp = seg->val[i];
+	return 1;
+      }
+    }
+    seg = seg->next;
+  }
+  return 0;
+}
+
+static int
+iv_del(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value *vp)
+{
+  segment *seg;
+  int i;
+
+  seg = t->rootseg;
+  while (seg) {
+    for (i=0; i<MRB_SEGMENT_SIZE; i++) {
+      mrb_sym key = seg->key[i];
+
+      if (!seg->next && i >= t->last_len) {
+	return 0;
+      }
+      if (key == sym) {
+	t->size--;
+	seg->key[i] = 0;
+	if (vp) *vp = seg->val[i];
+	return 1;
+      }
+    }
+    seg = seg->next;
+  }
+  return 0;
+}
+
+static int
+iv_foreach(mrb_state *mrb, iv_tbl *t, iv_foreach_func *func, void *p)
+{
+  segment *seg;
+  int i, n;
+
+  seg = t->rootseg;
+  while (seg) {
+    for (i=0; i<MRB_SEGMENT_SIZE; i++) {
+      mrb_sym key = seg->key[i];
+
+      /* no value in last segment after last_len */
+      if (!seg->next && i >= t->last_len) {
+	return 0;
+      }
+      if (key != 0) {
+	n =(*func)(mrb, key, seg->val[i], p);
+	if (n > 0) return 0;
+	if (n < 0) {
+	  t->size--;
+	  seg->key[i] = 0;
+	}
+      }
+    }
+    seg = seg->next;
+  }
+  return 1;
+}
+
+static int
+iv_size(mrb_state *mrb, iv_tbl *t)
+{
+  segment *seg;
+  int size = 0;
+
+  if (!t) return 0;
+  if (t->size > 0) return t->size;
+  seg = t->rootseg;
+  while (seg) {
+    if (seg->next == NULL) {
+      size += t->last_len;
+      return size;
+    }
+    seg = seg->next;
+    size += MRB_SEGMENT_SIZE;
+  }
+  /* empty iv_tbl */
+  return 0;
+}
+
+static iv_tbl*
+iv_copy(mrb_state *mrb, iv_tbl *t)
+{
+  segment *seg;
+  iv_tbl *t2;
+
+  int i;
+
+  seg = t->rootseg;
+  t2 = iv_new(mrb);
+
+  while (seg != NULL) {
+    for (i=0; i<MRB_SEGMENT_SIZE; i++) {
+      mrb_sym key = seg->key[i];
+      mrb_value val = seg->val[i];
+
+      iv_put(mrb, t2, key, val);
+      if ((seg->next == NULL) && (i >= t->last_len)) {
+        return t2;
+      }
+    }
+    seg = seg->next;
+  }
+  return t2;
+}
+
+static void
+iv_free(mrb_state *mrb, iv_tbl *t)
+{
+  segment *seg;
+
+  seg = t->rootseg;
+  while (seg) {
+    segment *p = seg;
+    seg = seg->next;
+    mrb_free(mrb, p);
+  }
+  mrb_free(mrb, t);
+}
+
+#else
+
+#include "mruby/khash.h"
+
+#ifndef MRB_IV_INITIAL_SIZE
+#define MRB_IV_INITIAL_SIZE 8
+#endif
+
+KHASH_DECLARE(iv, mrb_sym, mrb_value, 1)
+KHASH_DEFINE(iv, mrb_sym, mrb_value, 1, kh_int_hash_func, kh_int_hash_equal);
+
+typedef struct iv_tbl {
+  khash_t(iv) h;
+} iv_tbl;
+
+static iv_tbl*
+iv_new(mrb_state *mrb)
+{
+  return (iv_tbl*)kh_init_size(iv, mrb, MRB_IV_INITIAL_SIZE);
+}
+
+static void
+iv_put(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value val)
+{
+  khash_t(iv) *h = &t->h;
+  khiter_t k;
+
+  k = kh_put(iv, h, sym);
+  kh_value(h, k) = val;
+}
+
+static int
+iv_get(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value *vp)
+{
+  khash_t(iv) *h = &t->h;
+  khiter_t k;
+
+  k = kh_get(iv, h, sym);
+  if (k != kh_end(h)) {
+    if (vp) *vp = kh_value(h, k);
+    return 1;
+  }
+  return 0;
+}
+
+static int
+iv_del(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value *vp)
+{
+  khash_t(iv) *h = &t->h;
+  khiter_t k;
+
+  if (h) {
+    k = kh_get(iv, h, sym);
+    if (k != kh_end(h)) {
+      mrb_value val = kh_value(h, k);
+      kh_del(iv, h, k);
+      if (vp) *vp = val;
+      return 1;
+    }
+  }
+  return 0;
+}
+
+static int
+iv_foreach(mrb_state *mrb, iv_tbl *t, iv_foreach_func *func, void *p)
+{
+  khash_t(iv) *h = &t->h;
+  khiter_t k;
+  int n;
+
+  if (h) {
+    for (k = kh_begin(h); k != kh_end(h); k++) {
+      if (kh_exist(h, k)){
+	n = (*func)(mrb, kh_key(h, k), kh_value(h, k), p);
+	if (n > 0) return 0;
+	if (n < 0) {
+	  kh_del(iv, h, k);
+	}
+      }
+    }
+  }
+  return 1;
+}
+
+static int
+iv_size(mrb_state *mrb, iv_tbl *t)
+{
+  khash_t(iv) *h = &t->h;
+
+  if (!h) return 0;
+  return kh_size(h);
+}
+
+static iv_tbl*
+iv_copy(mrb_state *mrb, iv_tbl *t)
+{
+  return (iv_tbl*)kh_copy(iv, mrb, &t->h);
+}
+
+static void
+iv_free(mrb_state *mrb, iv_tbl *t)
+{
+  kh_destroy(iv, &t->h);
+}
+
+#endif
+
 #ifndef MRB_IV_INITIAL_SIZE
 #define MRB_IV_INITIAL_SIZE 8
 #endif
 
-static void
-mark_tbl(mrb_state *mrb, struct kh_iv *h)
+static int
+iv_mark_i(mrb_state *mrb, mrb_sym sym, mrb_value v, void *p)
 {
-  khiter_t k;
+  mrb_gc_mark_value(mrb, v);
+  return 0;
+}
 
-  if (!h) return;
-  for (k = kh_begin(h); k != kh_end(h); k++)
-    if (kh_exist(h, k))
-      mrb_gc_mark_value(mrb, kh_value(h, k));
+static void
+mark_tbl(mrb_state *mrb, iv_tbl *t)
+{
+  if (t) {
+    iv_foreach(mrb, t, iv_mark_i, 0);
+  }
 }
 
 void
@@ -40,7 +385,8 @@ mrb_gc_mark_gv(mrb_state *mrb)
 void
 mrb_gc_free_gv(mrb_state *mrb)
 {
-  kh_destroy(iv, mrb->globals);
+  if (mrb->globals)
+    iv_free(mrb, mrb->globals);
 }
 
 void
@@ -52,16 +398,15 @@ mrb_gc_mark_iv(mrb_state *mrb, struct RObject *obj)
 size_t
 mrb_gc_mark_iv_size(mrb_state *mrb, struct RObject *obj)
 {
-  struct kh_iv *h = obj->iv;
-
-  if (!h) return 0;
-  return kh_size(h);
+  return iv_size(mrb, obj->iv);
 }
 
 void
 mrb_gc_free_iv(mrb_state *mrb, struct RObject *obj)
 {
-  kh_destroy(iv, obj->iv);
+  if (obj->iv) {
+    iv_free(mrb, obj->iv);
+  }
 }
 
 mrb_value
@@ -75,26 +420,6 @@ mrb_vm_special_set(mrb_state *mrb, mrb_sym i, mrb_value v)
 {
 }
 
-static mrb_value
-ivget(mrb_state *mrb, struct kh_iv *h, mrb_sym sym)
-{
-  khiter_t k;
-
-  k = kh_get(iv, h, sym);
-  if (k != kh_end(h))
-    return kh_value(h, k);
-  return mrb_nil_value();
-}
-
-mrb_value
-mrb_obj_iv_get(mrb_state *mrb, struct RObject *obj, mrb_sym sym)
-{
-  if (!obj->iv) {
-    return mrb_nil_value();
-  }
-  return ivget(mrb, obj->iv, sym);
-}
-
 static int
 obj_iv_p(mrb_value obj)
 {
@@ -110,6 +435,16 @@ obj_iv_p(mrb_value obj)
   }
 }
 
+mrb_value
+mrb_obj_iv_get(mrb_state *mrb, struct RObject *obj, mrb_sym sym)
+{
+  mrb_value v;
+
+  if (obj->iv && iv_get(mrb, obj->iv, sym, &v))
+    return v;
+  return mrb_nil_value();
+}
+
 mrb_value
 mrb_iv_get(mrb_state *mrb, mrb_value obj, mrb_sym sym)
 {
@@ -119,54 +454,110 @@ mrb_iv_get(mrb_state *mrb, mrb_value obj, mrb_sym sym)
   return mrb_nil_value();
 }
 
-static void
-ivset(mrb_state *mrb, struct kh_iv *h, mrb_sym sym, mrb_value v)
-{
-  khiter_t k;
-
-  k = kh_put(iv, h, sym);
-  kh_value(h, k) = v;
-}
-
 void
 mrb_obj_iv_set(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v)
 {
-  khash_t(iv) *h;
+  iv_tbl *t = obj->iv;
 
-  if (!obj->iv) {
-    h = obj->iv = kh_init_size(iv, mrb, MRB_IV_INITIAL_SIZE);
-  }
-  else {
-    h = obj->iv;
+  if (!t) {
+    t = obj->iv = iv_new(mrb);
   }
   mrb_write_barrier(mrb, (struct RBasic*)obj);
-  ivset(mrb, h, sym, v);
+  iv_put(mrb, t, sym, v);
 }
 
 void
-mrb_iv_set(mrb_state *mrb, mrb_value obj, mrb_sym sym, mrb_value v) /* mrb_ivar_set */
+mrb_iv_set(mrb_state *mrb, mrb_value obj, mrb_sym sym, mrb_value v)
 {
   if (obj_iv_p(obj)) {
     mrb_obj_iv_set(mrb, mrb_obj_ptr(obj), sym, v);
   }
+  else {
+    mrb_raise(mrb, E_ARGUMENT_ERROR, "cannot set instance variable");
+  }
+}
+
+int
+mrb_obj_iv_defined(mrb_state *mrb, struct RObject *obj, mrb_sym sym)
+{
+  iv_tbl *t;
+
+  t = obj->iv;
+  if (t) {
+    return iv_get(mrb, t, sym, NULL);
+  }
+  return 0;
+}
+
+int
+mrb_iv_defined(mrb_state *mrb, mrb_value obj, mrb_sym sym)
+{
+  if (!obj_iv_p(obj)) return 0;
+  return mrb_obj_iv_defined(mrb, mrb_obj_ptr(obj), sym);
+}
+
+void
+mrb_iv_copy(mrb_state *mrb, mrb_value dest, mrb_value src)
+{
+  struct RObject *d = mrb_obj_ptr(dest);
+  struct RObject *s = mrb_obj_ptr(src);
+
+  if (d->iv) {
+    iv_free(mrb, d->iv);
+    d->iv = 0;
+  }
+  if (s->iv) {
+    d->iv = iv_copy(mrb, s->iv);
+  }
+}
+
+static int
+inspect_i(mrb_state *mrb, mrb_sym sym, mrb_value v, void *p)
+{
+  mrb_value str = *(mrb_value*)p;
+  const char *s;
+  int len;
+
+  /* need not to show internal data */
+  if (RSTRING_PTR(str)[0] == '-') { /* first element */
+    RSTRING_PTR(str)[0] = '#';
+    mrb_str_cat2(mrb, str, " ");
+  }
+  else {
+    mrb_str_cat2(mrb, str, ", ");
+  }
+  s = mrb_sym2name_len(mrb, sym, &len);
+  mrb_str_cat(mrb, str, s, len);
+  mrb_str_cat(mrb, str, "=", 1);
+  mrb_str_append(mrb, str, mrb_inspect(mrb, v));
+  return 0;
+}
+
+mrb_value
+mrb_obj_iv_inspect(mrb_state *mrb, struct RObject *obj)
+{
+  iv_tbl *t = obj->iv;
+  int len = iv_size(mrb, t);
+
+  if (len > 0) {
+    const char *cn = mrb_obj_classname(mrb, mrb_obj_value(obj));
+    mrb_value str = mrb_sprintf(mrb, "-<%s:%p", cn, (void*)obj);
+
+    iv_foreach(mrb, t, inspect_i, &str);
+    return str;
+  }
+  return mrb_any_to_s(mrb, mrb_obj_value(obj));
 }
 
 mrb_value
 mrb_iv_remove(mrb_state *mrb, mrb_value obj, mrb_sym sym)
 {
-  mrb_value val;
-
   if (obj_iv_p(obj)) {
-    khash_t(iv) *h = mrb_obj_ptr(obj)->iv;
-    khiter_t k;
+    iv_tbl *t = mrb_obj_ptr(obj)->iv;
+    mrb_value val;
 
-    if (h) {
-      k = kh_get(iv, h, sym);
-      if (k != kh_end(h)) {
-	val = kh_value(h, k);
-	kh_del(iv, h, k);
-	return val;
-      }
+    if (iv_del(mrb, t, sym, &val)) {
+      return val;
     }
   }
   return mrb_undef_value();
@@ -186,6 +577,21 @@ mrb_vm_iv_set(mrb_state *mrb, mrb_sym sym, mrb_value v)
   mrb_iv_set(mrb, mrb->stack[0], sym, v);
 }
 
+static int
+iv_i(mrb_state *mrb, mrb_sym sym, mrb_value v, void *p)
+{
+  mrb_value ary;
+  const char* s;
+  int len;
+
+  ary = *(mrb_value*)p;
+  s = mrb_sym2name_len(mrb, sym, &len);
+  if (len > 1 && s[0] == '@') {
+    mrb_ary_push(mrb, ary, mrb_symbol_value(sym));
+  }
+  return 0;
+}
+
 /* 15.3.1.3.23 */
 /*
  *  call-seq:
@@ -207,25 +613,10 @@ mrb_value
 mrb_obj_instance_variables(mrb_state *mrb, mrb_value self)
 {
   mrb_value ary;
-  kh_iv_t *h;
-  khint_t i;
-  int len;
-  const char* p;
 
   ary = mrb_ary_new(mrb);
   if (obj_iv_p(self)) {
-    h = ROBJECT_IVPTR(self);
-    if (h) {
-      for (i=0;i<kh_end(h);i++) {
-        if (kh_exist(h, i)) {
-          p = mrb_sym2name_len(mrb, kh_key(h,i), &len);
-          if (len > 1 && *p == '@') {
-            if (mrb_type(kh_value(h, i)) != MRB_TT_UNDEF)
-              mrb_ary_push(mrb, ary, mrb_str_new(mrb, p, len));
-          }
-        }
-      }
-    }
+    iv_foreach(mrb, mrb_obj_ptr(self)->iv, iv_i, &ary);
   }
   return ary;
 }
@@ -238,11 +629,11 @@ mrb_vm_cv_get(mrb_state *mrb, mrb_sym sym)
   if (!c) c = mrb->ci->target_class;
   while (c) {
     if (c->iv) {
-      khash_t(iv) *h = c->iv;
-      khiter_t k = kh_get(iv, h, sym);
+      iv_tbl *t = c->iv;
+      mrb_value v;
 
-      if (k != kh_end(h))
-        return kh_value(h, k);
+      if (iv_get(mrb, t, sym, &v))
+	return v;
     }
     c = c->super;
   }
@@ -253,43 +644,34 @@ void
 mrb_vm_cv_set(mrb_state *mrb, mrb_sym sym, mrb_value v)
 {
   struct RClass *c = mrb->ci->proc->target_class;
-  khash_t(iv) *h;
-  khiter_t k;
 
   if (!c) c = mrb->ci->target_class;
   while (c) {
     if (c->iv) {
-      h = c->iv;
-      k = kh_get(iv, h, sym);
-      if (k != kh_end(h)) {
-        k = kh_put(iv, h, sym);
-        kh_value(h, k) = v;
+      iv_tbl *t = c->iv;
+
+      if (iv_get(mrb, t, sym, NULL)) {
+	iv_put(mrb, t, sym, v);
         return;
       }
     }
     c = c->super;
   }
   c = mrb->ci->target_class;
-  h = c->iv;
-  if (!h) {
-    c->iv = h = kh_init_size(iv, mrb, MRB_IV_INITIAL_SIZE);
+  if (!c->iv) {
+    c->iv = iv_new(mrb);
   }
-  k = kh_put(iv, h, sym);
-  kh_value(h, k) = v;
+  iv_put(mrb, c->iv, sym, v);
 }
 
 int
 mrb_const_defined(mrb_state *mrb, mrb_value mod, mrb_sym sym)
 {
-  khiter_t k;
   struct RClass *m = mrb_class_ptr(mod);
-  struct kh_iv *h = m->iv;
+  iv_tbl *t = m->iv;
 
-  if (!h) return 0;
-  k = kh_get(iv, h, sym);
-  if (k != kh_end(h))
-    return 1;
-  return 0;
+  if (!t) return 0;
+  return iv_get(mrb, t, sym, NULL);
 }
 
 static void
@@ -309,19 +691,17 @@ static mrb_value
 const_get(mrb_state *mrb, struct RClass *base, mrb_sym sym)
 {
   struct RClass *c = base;
-  khash_t(iv) *h;
-  khiter_t k;
+  mrb_value v;
+  iv_tbl *t;
   int retry = 0;
   mrb_sym cm;
 
  L_RETRY:
   while (c) {
     if (c->iv) {
-      h = c->iv;
-      k = kh_get(iv, h, sym);
-      if (k != kh_end(h)) {
-        return kh_value(h, k);
-      }
+      t = c->iv;
+      if (iv_get(mrb, t, sym, &v))
+	return v;
     }
     c = c->super;
   }
@@ -374,13 +754,13 @@ mrb_vm_const_set(mrb_state *mrb, mrb_sym sym, mrb_value v)
   struct RClass *c = mrb->ci->proc->target_class;
 
   if (!c) c = mrb->ci->target_class;
-  mrb_obj_iv_set(mrb, (struct RObject*)c, sym, v);
+  mrb_iv_set(mrb, mrb_obj_value(c), sym, v);
 }
 
 void
 mrb_define_const(mrb_state *mrb, struct RClass *mod, const char *name, mrb_value v)
 {
-  mrb_obj_iv_set(mrb, (struct RObject*)mod, mrb_intern(mrb, name), v);
+  mrb_iv_set(mrb, mrb_obj_value(mod), mrb_intern(mrb, name), v);
 }
 
 void
@@ -392,24 +772,38 @@ mrb_define_global_const(mrb_state *mrb, const char *name, mrb_value val)
 mrb_value
 mrb_gv_get(mrb_state *mrb, mrb_sym sym)
 {
+  mrb_value v;
+
   if (!mrb->globals) {
     return mrb_nil_value();
   }
-  return ivget(mrb, mrb->globals, sym);
+  if (iv_get(mrb, mrb->globals, sym, &v))
+    return v;
+  return mrb_nil_value();
 }
 
 void
 mrb_gv_set(mrb_state *mrb, mrb_sym sym, mrb_value v)
 {
-  khash_t(iv) *h;
+  iv_tbl *t;
 
   if (!mrb->globals) {
-    h = mrb->globals = kh_init(iv, mrb);
+    t = mrb->globals = iv_new(mrb);
   }
   else {
-    h = mrb->globals;
+    t = mrb->globals;
   }
-  ivset(mrb, h, sym, v);
+  iv_put(mrb, t, sym, v);
+}
+
+static int
+gv_i(mrb_state *mrb, mrb_sym sym, mrb_value v, void *p)
+{
+  mrb_value ary;
+
+  ary = *(mrb_value*)p;
+  mrb_ary_push(mrb, ary, mrb_symbol_value(sym));
+  return 0;
 }
 
 /* 15.3.1.2.4  */
@@ -425,73 +819,34 @@ mrb_gv_set(mrb_state *mrb, mrb_sym sym, mrb_value v)
 mrb_value
 mrb_f_global_variables(mrb_state *mrb, mrb_value self)
 {
-  char buf[3];
-  khint_t i;
-  struct kh_iv *h = mrb->globals;
+  iv_tbl *t = mrb->globals;
   mrb_value ary = mrb_ary_new(mrb);
+  int i;
+  char buf[3];
 
-  if (h) {
-    for (i=0;i < kh_end(h);i++) {
-      if (kh_exist(h, i)) {
-        mrb_ary_push(mrb, ary, mrb_symbol_value(kh_key(h,i)));
-      }
-    }
+  if (t) {
+    iv_foreach(mrb, t, gv_i, &ary);
   }
   buf[0] = '$';
   buf[2] = 0;
   for (i = 1; i <= 9; ++i) {
-      buf[1] = (char)(i + '0');
-      mrb_ary_push(mrb, ary, mrb_symbol_value(mrb_intern(mrb, buf)));
+    buf[1] = (char)(i + '0');
+    mrb_ary_push(mrb, ary, mrb_symbol_value(mrb_intern2(mrb, buf, 2)));
   }
   return ary;
 }
 
-int
-mrb_st_lookup(struct kh_iv *table, mrb_sym id, khiter_t *value)
-{
-  khash_t(iv) *h;
-  khiter_t k;
-
-  if (table) {
-    h = (khash_t(iv)*)table;
-    k = kh_get(iv, h, id);
-    if (k != kh_end(h)) {
-      if (value != 0)  *value = k;//kh_value(h, k);
-      return 1;/* TRUE */
-    }
-    return 0;/* FALSE */
-  }
-  else {
-    return 0;/* FALSE */
-  }
-}
-
-static int
-kiv_lookup(khash_t(iv)* table, mrb_sym key, mrb_value *value)
-{
-  khash_t(iv) *h=table;
-  khiter_t k;
-
-  k = kh_get(iv, h, key);
-  if (k != kh_end(h)) {
-    *value = kh_value(h, k);
-    return 1;
-  }
-  return 0;
-}
-
 static int
 mrb_const_defined_0(mrb_state *mrb, struct RClass *klass, mrb_sym id, int exclude, int recurse)
 {
-  mrb_value value;
   struct RClass * tmp;
   int mod_retry = 0;
 
   tmp = klass;
 retry:
   while (tmp) {
-    if (tmp->iv && kiv_lookup(tmp->iv, id, &value)) {
-      return (int)1/*Qtrue*/;
+    if (tmp->iv && iv_get(mrb, tmp->iv, id, NULL)) {
+      return 1;
     }
     if (!recurse && (klass != mrb->object_class)) break;
     tmp = tmp->super;
@@ -525,3 +880,38 @@ mrb_class_obj_get(mrb_state *mrb, const char *name)
   return mrb_class_ptr(mrb_const_get(mrb, mod, sym));
 }
 
+struct csym_arg {
+  struct RClass *c;
+  mrb_sym sym;
+};
+
+static int
+csym_i(mrb_state *mrb, mrb_sym sym, mrb_value v, void *p)
+{
+  struct csym_arg *a = (struct csym_arg*)p;
+  struct RClass *c = a->c;
+
+  if (mrb_type(v) == c->tt && mrb_class_ptr(v) == c) {
+    a->sym = sym;
+    return 1;			/* stop iteration*/
+  }
+  return 0;
+}
+
+mrb_sym
+mrb_class_sym(mrb_state *mrb, struct RClass *c, struct RClass *outer)
+{
+  mrb_value name;
+
+  name = mrb_obj_iv_get(mrb, (struct RObject*)c, mrb_intern(mrb, "__classid__"));
+  if (mrb_nil_p(name)) {
+    struct csym_arg arg;
+
+    arg.c = c;
+    arg.sym = 0;
+
+    iv_foreach(mrb, outer->iv, csym_i, &arg);
+    return arg.sym;
+  }
+  return SYM2ID(name);
+}