* id_table.h: introduce ID key table.

  [Feature #11420]
  This table only manage ID->VALUE table to reduce overhead of st.
  Some functions prefixed rb_id_table_* are provided.
* id_table.c: implement rb_id_table_*.
  There are several algorithms to implement it.
  Now, there are roughly 4 types:
    * st
    * array
    * hash (implemented by  Yura Sokolov)
    * mix of array and hash
  The macro ID_TABLE_IMPL can choose implementation.
  You can see detailes about them at the head of id_table.c.
  At the default, I choose 34 (mix of list and hash).
  This is not final decision.
  Please report your suitable parameters or
  your data structure.
  * symbol.c: introduce rb_id_serial_t and rb_id_to_serial()
    to represent ID by serial number.
  * internal.h: use id_table for method tables.
  * class.c, gc.c, marshal.c, vm.c, vm_method.c: ditto.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51541 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1527 insertions, 0 deletions

diff --git a/id_table.c b/id_table.c
new file mode 100644
index 0000000000..ad1df059bc
--- /dev/null
+++ b/id_table.c
@@ -0,0 +1,1527 @@
+/* This file is included by symbol.c */
+
+#include "id_table.h"
+
+#ifndef ID_TABLE_DEBUG
+#define ID_TABLE_DEBUG 0
+#endif
+
+#if ID_TABLE_DEBUG == 0
+#define NDEBUG
+#endif
+#include <assert.h>
+
+/*
+ * st
+ *    0: using st with debug information.
+ *    1: using st.
+ * array
+ *   11: simple array. ids = [ID1, ID2, ...], values = [val1, val2, ...]
+ *   12: simple array, and use rb_id_serial_t instead of ID.
+ *   13: simple array, and use rb_id_serial_t instead of ID. Swap recent access.
+ *   14: sorted array, and use rb_id_serial_t instead of ID.
+ *   15: sorted array, and use rb_id_serial_t instead of ID, linear small part.
+ * hash
+ *   21: funny falcon's Coalesced Hashing implementation [Feature #6962]
+ *   22: simple open addressing with quadratic probing.
+ * mix (array + hash)
+ *   31: array(12) (capa <= 32) + hash(22)
+ *   32: array(14) (capa <= 32) + hash(22)
+ *   33: array(12) (capa <= 64) + hash(22)
+ *   34: array(14) (capa <= 64) + hash(22)
+ *   34: array(15) (capa <= 64) + hash(22)
+ */
+
+#ifndef ID_TABLE_IMPL
+#define ID_TABLE_IMPL 34
+#endif
+
+#if ID_TABLE_IMPL == 0
+#define ID_TABLE_NAME st
+#define ID_TABLE_IMPL_TYPE struct st_id_table
+
+#define ID_TABLE_USE_ST 1
+#define ID_TABLE_USE_ST_DEBUG 1
+
+#elif ID_TABLE_IMPL == 1
+#define ID_TABLE_NAME st
+#define ID_TABLE_IMPL_TYPE struct st_id_table
+
+#define ID_TABLE_USE_ST 1
+#define ID_TABLE_USE_ST_DEBUG 0
+
+#elif ID_TABLE_IMPL == 11
+#define ID_TABLE_NAME list
+#define ID_TABLE_IMPL_TYPE struct list_id_table
+
+#define ID_TABLE_USE_LIST 1
+#define ID_TABLE_USE_CALC_VALUES 1
+
+#elif ID_TABLE_IMPL == 12
+#define ID_TABLE_NAME list
+#define ID_TABLE_IMPL_TYPE struct list_id_table
+
+#define ID_TABLE_USE_LIST 1
+#define ID_TABLE_USE_CALC_VALUES 1
+#define ID_TABLE_USE_ID_SERIAL 1
+
+#elif ID_TABLE_IMPL == 13
+#define ID_TABLE_NAME list
+#define ID_TABLE_IMPL_TYPE struct list_id_table
+
+#define ID_TABLE_USE_LIST 1
+#define ID_TABLE_USE_CALC_VALUES 1
+#define ID_TABLE_USE_ID_SERIAL 1
+#define ID_TABLE_SWAP_RECENT_ACCESS 1
+
+#elif ID_TABLE_IMPL == 14
+#define ID_TABLE_NAME list
+#define ID_TABLE_IMPL_TYPE struct list_id_table
+
+#define ID_TABLE_USE_LIST 1
+#define ID_TABLE_USE_CALC_VALUES 1
+#define ID_TABLE_USE_ID_SERIAL 1
+#define ID_TABLE_USE_LIST_SORTED 1
+
+#elif ID_TABLE_IMPL == 15
+#define ID_TABLE_NAME list
+#define ID_TABLE_IMPL_TYPE struct list_id_table
+
+#define ID_TABLE_USE_LIST 1
+#define ID_TABLE_USE_CALC_VALUES 1
+#define ID_TABLE_USE_ID_SERIAL 1
+#define ID_TABLE_USE_LIST_SORTED 1
+#define ID_TABLE_USE_LIST_SORTED_LINEAR_SMALL_RANGE 1
+
+#elif ID_TABLE_IMPL == 21
+#define ID_TABLE_NAME hash
+#define ID_TABLE_IMPL_TYPE sa_table
+
+#define ID_TABLE_USE_COALESCED_HASHING 1
+#define ID_TABLE_USE_ID_SERIAL 1
+
+#elif ID_TABLE_IMPL == 22
+#define ID_TABLE_NAME hash
+#define ID_TABLE_IMPL_TYPE struct hash_id_table
+
+#define ID_TABLE_USE_SMALL_HASH 1
+#define ID_TABLE_USE_ID_SERIAL 1
+
+#elif ID_TABLE_IMPL == 31
+#define ID_TABLE_NAME mix
+#define ID_TABLE_IMPL_TYPE struct mix_id_table
+
+#define ID_TABLE_USE_MIX 1
+#define ID_TABLE_USE_MIX_LIST_MAX_CAPA 32
+
+#define ID_TABLE_USE_ID_SERIAL 1
+
+#define ID_TABLE_USE_LIST 1
+#define ID_TABLE_USE_CALC_VALUES 1
+#define ID_TABLE_USE_SMALL_HASH 1
+
+#elif ID_TABLE_IMPL == 32
+#define ID_TABLE_NAME mix
+#define ID_TABLE_IMPL_TYPE struct mix_id_table
+
+#define ID_TABLE_USE_MIX 1
+#define ID_TABLE_USE_MIX_LIST_MAX_CAPA 32
+
+#define ID_TABLE_USE_ID_SERIAL 1
+
+#define ID_TABLE_USE_LIST 1
+#define ID_TABLE_USE_CALC_VALUES 1
+#define ID_TABLE_USE_LIST_SORTED 1
+
+#define ID_TABLE_USE_SMALL_HASH 1
+
+#elif ID_TABLE_IMPL == 33
+#define ID_TABLE_NAME mix
+#define ID_TABLE_IMPL_TYPE struct mix_id_table
+
+#define ID_TABLE_USE_MIX 1
+#define ID_TABLE_USE_MIX_LIST_MAX_CAPA 64
+
+#define ID_TABLE_USE_ID_SERIAL 1
+
+#define ID_TABLE_USE_LIST 1
+#define ID_TABLE_USE_CALC_VALUES 1
+#define ID_TABLE_USE_SMALL_HASH 1
+
+#elif ID_TABLE_IMPL == 34
+#define ID_TABLE_NAME mix
+#define ID_TABLE_IMPL_TYPE struct mix_id_table
+
+#define ID_TABLE_USE_MIX 1
+#define ID_TABLE_USE_MIX_LIST_MAX_CAPA 64
+
+#define ID_TABLE_USE_ID_SERIAL 1
+
+#define ID_TABLE_USE_LIST 1
+#define ID_TABLE_USE_CALC_VALUES 1
+#define ID_TABLE_USE_LIST_SORTED 1
+
+#define ID_TABLE_USE_SMALL_HASH 1
+
+#elif ID_TABLE_IMPL == 35
+#define ID_TABLE_NAME mix
+#define ID_TABLE_IMPL_TYPE struct mix_id_table
+
+#define ID_TABLE_USE_MIX 1
+#define ID_TABLE_USE_MIX_LIST_MAX_CAPA 64
+
+#define ID_TABLE_USE_ID_SERIAL 1
+
+#define ID_TABLE_USE_LIST 1
+#define ID_TABLE_USE_CALC_VALUES 1
+#define ID_TABLE_USE_LIST_SORTED 1
+#define ID_TABLE_USE_LIST_SORTED_LINEAR_SMALL_RANGE 1
+
+#define ID_TABLE_USE_SMALL_HASH 1
+
+#else
+#error
+#endif
+
+#if ID_TABLE_SWAP_RECENT_ACCESS && ID_TABLE_USE_LIST_SORTED
+#error
+#endif
+
+#if ID_TABLE_USE_ID_SERIAL
+typedef rb_id_serial_t id_key_t;
+static inline ID
+key2id(id_key_t key)
+{
+    return rb_id_serial_to_id(key);
+}
+
+static inline id_key_t
+id2key(ID id)
+{
+    return rb_id_to_serial(id);
+}
+#else /* ID_TABLE_USE_ID_SERIAL */
+
+typedef ID id_key_t;
+#define key2id(key) key
+#define id2key(id)  id
+
+#endif /* ID_TABLE_USE_ID_SERIAL */
+
+/***************************************************************
+ * 0: using st with debug information.
+ * 1: using st.
+ ***************************************************************/
+#if ID_TABLE_USE_ST
+#if ID_TABLE_USE_ST_DEBUG
+#define ID_TABLE_MARK 0x12345678
+
+struct st_id_table {
+    struct st_table *st;
+    unsigned int check;
+};
+
+static struct st_table *
+tbl2st(struct st_id_table *tbl) {
+    if (tbl->check != ID_TABLE_MARK) rb_bug("tbl2st: check error %x", tbl->check);
+    return tbl->st;
+}
+
+static struct st_id_table *
+st_id_table_create(size_t size)
+{
+    struct st_id_table *tbl = ALLOC(struct st_id_table);
+    tbl->st = st_init_numtable_with_size(size);
+    tbl->check = ID_TABLE_MARK;
+    return tbl;
+}
+
+static void
+st_id_table_free(struct st_id_table *tbl)
+{
+    st_free_table(tbl->st);
+    xfree(tbl);
+}
+
+#else /* ID_TABLE_USE_ST_DEBUG */
+
+struct st_id_table {
+    struct st_table st;
+};
+
+static struct st_table *
+tbl2st(struct st_id_table *tbl) {
+    return (struct st_table *)tbl;
+}
+
+static struct st_id_table *
+st_id_table_create(size_t size)
+{
+    return (struct st_id_table *)st_init_numtable_with_size(size);
+}
+
+static void
+st_id_table_free(struct st_id_table *tbl)
+{
+    st_free_table((struct st_table*)tbl);
+}
+
+#endif /* ID_TABLE_USE_ST_DEBUG */
+
+static void
+st_id_table_clear(struct st_id_table *tbl)
+{
+    st_clear(tbl2st(tbl));
+}
+
+static size_t
+st_id_table_size(struct st_id_table *tbl)
+{
+    return tbl2st(tbl)->num_entries;
+}
+
+static size_t
+st_id_table_memsize(struct st_id_table *tbl)
+{
+    size_t header_size = ID_TABLE_USE_ST_DEBUG ? sizeof(struct st_id_table) : 0;
+    return header_size + st_memsize(tbl2st(tbl));
+}
+
+static int
+st_id_table_lookup(struct st_id_table *tbl, ID id, VALUE *val)
+{
+    return st_lookup(tbl2st(tbl), (st_data_t)id, (st_data_t *)val);
+}
+
+static int
+st_id_table_insert(struct st_id_table *tbl, ID id, VALUE val)
+{
+    return st_insert(tbl2st(tbl), id, val);
+}
+
+static int
+st_id_table_delete(struct st_id_table *tbl, ID id)
+{
+    return st_delete(tbl2st(tbl), (st_data_t *)&id, NULL);
+}
+
+static void
+st_id_table_foreach(struct st_id_table *tbl, enum rb_id_table_iterator_result (*func)(ID id, VALUE val, void *data), void *data)
+{
+    st_foreach(tbl2st(tbl), (int (*)(ANYARGS))func, (st_data_t)data);
+}
+
+struct values_iter_data {
+    enum rb_id_table_iterator_result (*values_i)(VALUE val, void *data);
+    void *data;
+};
+
+static int
+each_values(st_data_t key, st_data_t val, st_data_t ptr)
+{
+    struct values_iter_data *values_iter_data = (struct values_iter_data *)ptr;
+    return values_iter_data->values_i(val, values_iter_data->data);
+}
+
+static void
+st_id_table_foreach_values(struct st_id_table *tbl, enum rb_id_table_iterator_result (*func)(VALUE val, void *data), void *data)
+{
+    struct values_iter_data values_iter_data;
+    values_iter_data.values_i = func;
+    values_iter_data.data = data;
+    st_foreach(tbl2st(tbl), each_values, (st_data_t)&values_iter_data);
+}
+#endif /* ID_TABLE_USE_ST */
+
+#if ID_TABLE_USE_LIST
+
+#define LIST_MIN_CAPA 4
+
+struct list_id_table {
+    int capa;
+    int num;
+    id_key_t *keys;
+#if ID_TABLE_USE_CALC_VALUES == 0
+    VALUE *values_;
+#endif
+};
+
+#if ID_TABLE_USE_CALC_VALUES
+#define TABLE_VALUES(tbl) ((VALUE *)((tbl)->keys + (tbl)->capa))
+#else
+#define TABLE_VALUES(tbl) (tbl)->values_
+#endif
+
+static struct list_id_table *
+list_id_table_init(struct list_id_table *tbl, size_t capa)
+{
+    if (capa > 0) {
+	tbl->capa = (int)capa;
+#if ID_TABLE_USE_CALC_VALUES
+	tbl->keys = (id_key_t *)xmalloc(sizeof(id_key_t) * capa + sizeof(VALUE) * capa);
+#else
+	tbl->keys = ALLOC_N(id_key_t, capa);
+	tbl->values_ = ALLOC_N(VALUE, capa);
+#endif
+    }
+    return tbl;
+}
+
+#ifndef ID_TABLE_USE_MIX
+static struct list_id_table *
+list_id_table_create(size_t capa)
+{
+    struct list_id_table *tbl = ZALLOC(struct list_id_table);
+    return list_id_table_init(tbl, capa);
+}
+#endif
+
+static void
+list_id_table_free(struct list_id_table *tbl)
+{
+    xfree(tbl->keys);
+#if ID_TABLE_USE_CALC_VALUES == 0
+    xfree(tbl->values_);
+#endif
+    xfree(tbl);
+}
+
+static void
+list_id_table_clear(struct list_id_table *tbl)
+{
+    tbl->num = 0;
+}
+
+static size_t
+list_id_table_size(struct list_id_table *tbl)
+{
+    return (size_t)tbl->num;
+}
+
+static size_t
+list_id_table_memsize(struct list_id_table *tbl)
+{
+    return (sizeof(id_key_t) + sizeof(VALUE)) * tbl->capa + sizeof(struct list_id_table);
+}
+
+static void
+list_table_extend(struct list_id_table *tbl)
+{
+    if (tbl->capa == tbl->num) {
+	const int capa = tbl->capa == 0 ? LIST_MIN_CAPA : (tbl->capa * 2);
+
+#if ID_TABLE_USE_CALC_VALUES
+	{
+	    VALUE *old_values, *new_values;
+	    VALUE *debug_values = NULL;
+	    const int num = tbl->num;
+	    const int size = sizeof(id_key_t) * capa + sizeof(VALUE) * capa;
+	    int i;
+
+	    if (num > 0) {
+		VALUE *orig_values = (VALUE *)(tbl->keys + num);
+		debug_values = ALLOC_N(VALUE, num);
+
+		for (i=0; i<num; i++) {
+		    debug_values[i] = orig_values[i];
+		}
+
+		if (0)
+		  for (i=0; i< 2 * num; i++) {
+		    unsigned char *cs = (unsigned char *)&tbl->keys[i];
+		    size_t j;
+		    fprintf(stderr, ">> %3d | %p - ", i, cs);
+		    for (j=0; j<sizeof(VALUE); j++) {
+			fprintf(stderr, "%x ", cs[j]);
+		    }
+		    fprintf(stderr, "\n");
+		  }
+	    }
+
+	    tbl->keys = (id_key_t *)xrealloc(tbl->keys, size);
+	    old_values = (VALUE *)(tbl->keys + num);
+	    new_values = (VALUE *)(tbl->keys + capa);
+
+	    /*  [ keys (num) ] [ values (num) ]
+	     *                 ^ old_values
+	     * realloc =>
+	     *  [ keys (capa = num * 2)  ] [ values (capa = num * 2) ]
+	     *                             ^ new_values
+	     */
+
+	    /* memmove */
+	    // fprintf(stderr, "memmove: %p -> %p (%d, capa: %d)\n", old_values, new_values, num, capa);
+	    assert(num < capa);
+	    assert(num == 0 || old_values < new_values);
+
+	    for (i=num-1; i>=0; i--) {
+		new_values[i] = old_values[i];
+	    }
+
+	    if (num > 0) {
+		for (i=0; i<num; i++) {
+		    assert(debug_values[i] == new_values[i]);
+		}
+		xfree(debug_values);
+	    }
+	}
+
+	tbl->capa = capa;
+#else
+	tbl->capa = capa;
+	tbl->keys = (id_key_t *)xrealloc(tbl->keys, sizeof(id_key_t) * capa);
+	tbl->values_ = (VALUE *)xrealloc(tbl->values_, sizeof(VALUE) * capa);
+#endif
+    }
+}
+
+#if ID_TABLE_DEBUG
+static void
+list_table_show(struct list_id_table *tbl)
+{
+    const id_key_t *keys = tbl->keys;
+    const int num = tbl->num;
+    int i;
+
+    fprintf(stderr, "tbl: %p (num: %d)\n", tbl, num);
+    for (i=0; i<num; i++) {
+	fprintf(stderr, " -> [%d] %s %d\n", i, rb_id2name(key2id(keys[i])), (int)keys[i]);
+    }
+}
+#endif
+
+static void
+tbl_assert(struct list_id_table *tbl)
+{
+#if ID_TABLE_DEBUG
+#if ID_TABLE_USE_LIST_SORTED
+    const id_key_t *keys = tbl->keys;
+    const int num = tbl->num;
+    int i;
+
+    for (i=0; i<num-1; i++) {
+	if (keys[i] >= keys[i+1]) {
+	    list_table_show(tbl);
+	    rb_bug(": not sorted.");
+	}
+    }
+#endif
+#endif
+}
+
+#if ID_TABLE_USE_LIST_SORTED
+static int
+list_ids_bsearch(const id_key_t *keys, id_key_t key, int num)
+{
+    int p, min = 0, max = num;
+
+#if ID_TABLE_USE_LIST_SORTED_LINEAR_SMALL_RANGE
+    if (num <= 64) {
+	if (num  > 32) {
+	    if (keys[num/2] <= key) {
+		min = num/2;
+	    } else {
+		max = num/2;
+	    }
+	}
+	for (p = min; p<num && keys[p] < key; p++) {
+	    assert(keys[p] != 0);
+	}
+	return (p<num && keys[p] == key) ? p : -p-1;
+    }
+#endif /* ID_TABLE_USE_LIST_SORTED_LINEAR_SMALL_RANGE */
+
+    while (1) {
+	p = min + (max - min) / 2;
+
+	if (min >= max) {
+	    break;
+	}
+	else {
+	    id_key_t kp = keys[p];
+	    assert(p < max);
+	    assert(p >= min);
+
+	    if      (kp > key) max = p;
+	    else if (kp < key) min = p+1;
+	    else {
+		assert(kp == key);
+		assert(p >= 0);
+		assert(p < num);
+		return p;
+	    }
+	}
+    }
+
+    assert(min == max);
+    assert(min == p);
+    return -p-1;
+}
+#endif /* ID_TABLE_USE_LIST_SORTED */
+
+static int
+list_table_index(struct list_id_table *tbl, id_key_t key)
+{
+    const int num = tbl->num;
+    const id_key_t *keys = tbl->keys;
+
+#if ID_TABLE_USE_LIST_SORTED
+    return list_ids_bsearch(keys, key, num);
+#else /* ID_TABLE_USE_LIST_SORTED */
+    int i;
+
+    for (i=0; i<num; i++) {
+	assert(keys[i] != 0);
+
+	if (keys[i] == key) {
+	    return (int)i;
+	}
+    }
+    return -1;
+#endif
+}
+
+static int
+list_id_table_lookup(struct list_id_table *tbl, ID id, VALUE *valp)
+{
+    id_key_t key = id2key(id);
+    int index = list_table_index(tbl, key);
+
+    if (index >= 0) {
+	*valp = TABLE_VALUES(tbl)[index];
+
+#if ID_TABLE_SWAP_RECENT_ACCESS
+	if (index > 0) {
+	    VALUE *values = TABLE_VALUES(tbl);
+	    id_key_t tk = tbl->keys[index-1];
+	    VALUE tv = values[index-1];
+	    tbl->keys[index-1] = tbl->keys[index];
+	    tbl->keys[index] = tk;
+	    values[index-1] = values[index];
+	    values[index] = tv;
+	}
+#endif /* ID_TABLE_SWAP_RECENT_ACCESS */
+	return TRUE;
+    }
+    else {
+	return FALSE;
+    }
+}
+
+static int
+list_id_table_insert(struct list_id_table *tbl, ID id, VALUE val)
+{
+    const id_key_t key = id2key(id);
+    const int index = list_table_index(tbl, key);
+
+    if (index >= 0) {
+	TABLE_VALUES(tbl)[index] = val;
+    }
+    else {
+	list_table_extend(tbl);
+	{
+	    const int num = tbl->num++;
+#if ID_TABLE_USE_LIST_SORTED
+	    const int insert_index = -(index + 1);
+	    id_key_t *keys = tbl->keys;
+	    VALUE *values = TABLE_VALUES(tbl);
+	    int i;
+
+	    if (0) fprintf(stderr, "insert: %d into %d on\n", (int)key, insert_index);
+
+	    for (i=num; i>insert_index; i--) {
+		keys[i] = keys[i-1];
+		values[i] = values[i-1];
+	    }
+	    keys[i] = key;
+	    values[i] = val;
+
+	    tbl_assert(tbl);
+#else
+	    tbl->keys[num] = key;
+	    TABLE_VALUES(tbl)[num] = val;
+#endif
+	}
+    }
+
+    return TRUE;
+}
+
+static int
+list_delete_index(struct list_id_table *tbl, id_key_t key, int index)
+{
+    if (index >= 0) {
+	VALUE *values = TABLE_VALUES(tbl);
+
+#if ID_TABLE_USE_LIST_SORTED
+	int i;
+	const int num = tbl->num;
+	id_key_t *keys = tbl->keys;
+
+	for (i=index+1; i<num; i++) { /* compaction */
+	    keys[i-1] = keys[i];
+	    values[i-1] = values[i];
+	}
+#else
+	tbl->keys[index] = tbl->keys[tbl->num-1];
+	values[index] = values[tbl->num-1];
+#endif
+	tbl->num--;
+	tbl_assert(tbl);
+
+	return TRUE;
+    }
+    else {
+	return FALSE;
+    }
+}
+
+static int
+list_id_table_delete(struct list_id_table *tbl, ID id)
+{
+    const id_key_t key = id2key(id);
+    int index = list_table_index(tbl, key);
+    return list_delete_index(tbl, key, index);
+}
+
+#define FOREACH_LAST() do {   \
+    switch (ret) {            \
+      case ID_TABLE_CONTINUE: \
+      case ID_TABLE_STOP:     \
+	break;                \
+      case ID_TABLE_DELETE:   \
+	list_delete_index(tbl, key, i); \
+	values = TABLE_VALUES(tbl);     \
+	num = tbl->num;                 \
+	i--; /* redo smae index */      \
+	break; \
+    } \
+} while (0)
+
+static void
+list_id_table_foreach(struct list_id_table *tbl, enum rb_id_table_iterator_result (*func)(ID id, VALUE val, void *data), void *data)
+{
+    int num = tbl->num;
+    int i;
+    const id_key_t *keys = tbl->keys;
+    const VALUE *values = TABLE_VALUES(tbl);
+
+    for (i=0; i<num; i++) {
+	const id_key_t key = keys[i];
+	enum rb_id_table_iterator_result ret = (*func)(key2id(key), values[i], data);
+	assert(key != 0);
+
+	FOREACH_LAST();
+	if (ret == ID_TABLE_STOP) return;
+    }
+}
+
+static void
+list_id_table_foreach_values(struct list_id_table *tbl, enum rb_id_table_iterator_result (*func)(VALUE val, void *data), void *data)
+{
+    int num = tbl->num;
+    int i;
+    const id_key_t *keys = tbl->keys;
+    VALUE *values = TABLE_VALUES(tbl);
+
+    for (i=0; i<num; i++) {
+	const id_key_t key = keys[i];
+	enum rb_id_table_iterator_result ret = (*func)(values[i], data);
+	assert(key != 0);
+
+	FOREACH_LAST();
+	if (ret == ID_TABLE_STOP) return;
+    }
+}
+#endif /* ID_TABLE_USE_LIST */
+
+
+#if ID_TABLE_USE_COALESCED_HASHING
+/* implementation is based on
+ * https://bugs.ruby-lang.org/issues/6962 by funny_falcon
+ */
+
+typedef unsigned int sa_index_t;
+
+#define SA_EMPTY    0
+#define SA_LAST     1
+#define SA_OFFSET   2
+#define SA_MIN_SIZE 4
+
+typedef struct sa_entry {
+    sa_index_t next;
+    id_key_t key;
+    VALUE value;
+} sa_entry;
+
+typedef struct {
+    sa_index_t num_bins;
+    sa_index_t num_entries;
+    sa_index_t free_pos;
+    sa_entry *entries;
+} sa_table;
+
+static void
+sa_init_table(register sa_table *table, sa_index_t num_bins)
+{
+    if (num_bins) {
+        table->num_entries = 0;
+        table->entries = ZALLOC_N(sa_entry, num_bins);
+        table->num_bins = num_bins;
+        table->free_pos = num_bins;
+    }
+}
+
+static sa_table*
+hash_id_table_create(size_t size)
+{
+    sa_table* table = ZALLOC(sa_table);
+    sa_init_table(table, (sa_index_t)size);
+    return table;
+}
+
+static void
+hash_id_table_clear(sa_table *table)
+{
+    xfree(table->entries);
+    memset(table, 0, sizeof(sa_table));
+}
+
+static void
+hash_id_table_free(sa_table *table)
+{
+    xfree(table->entries);
+    xfree(table);
+}
+
+static size_t
+hash_id_table_memsize(sa_table *table)
+{
+    return sizeof(sa_table) + table->num_bins * sizeof (sa_entry);
+}
+
+static inline sa_index_t
+calc_pos(register sa_table* table, id_key_t key)
+{
+    return key & (table->num_bins - 1);
+}
+
+static void
+fix_empty(register sa_table* table)
+{
+    while(--table->free_pos &&
+            table->entries[table->free_pos-1].next != SA_EMPTY);
+}
+
+#define FLOOR_TO_4 ((~((sa_index_t)0)) << 2)
+static sa_index_t
+find_empty(register sa_table* table, register sa_index_t pos)
+{
+    sa_index_t new_pos = table->free_pos-1;
+    sa_entry *entry;
+    static unsigned offsets[][3] = {
+	    {1, 2, 3},
+	    {2, 3, 0},
+	    {3, 1, 0},
+	    {2, 1, 0}
+    };
+    unsigned *check = offsets[pos&3];
+    pos &= FLOOR_TO_4;
+    entry = table->entries+pos;
+
+    if (entry[check[0]].next == SA_EMPTY) { new_pos = pos + check[0]; goto check; }
+    if (entry[check[1]].next == SA_EMPTY) { new_pos = pos + check[1]; goto check; }
+    if (entry[check[2]].next == SA_EMPTY) { new_pos = pos + check[2]; goto check; }
+
+  check:
+    if (new_pos+1 == table->free_pos) fix_empty(table);
+    return new_pos;
+}
+
+static void resize(register sa_table* table);
+static int insert_into_chain(register sa_table*, register sa_index_t, st_data_t, sa_index_t pos);
+static int insert_into_main(register sa_table*, sa_index_t, st_data_t, sa_index_t pos, sa_index_t prev_pos);
+
+static int
+sa_insert(register sa_table* table, id_key_t key, VALUE value)
+{
+    register sa_entry *entry;
+    sa_index_t pos, main_pos;
+
+    if (table->num_bins == 0) {
+        sa_init_table(table, SA_MIN_SIZE);
+    }
+
+    pos = calc_pos(table, key);
+    entry = table->entries + pos;
+
+    if (entry->next == SA_EMPTY) {
+        entry->next = SA_LAST;
+        entry->key = key;
+        entry->value = value;
+        table->num_entries++;
+        if (pos+1 == table->free_pos) fix_empty(table);
+        return 0;
+    }
+
+    if (entry->key == key) {
+        entry->value = value;
+        return 1;
+    }
+
+    if (table->num_entries + (table->num_entries >> 2) > table->num_bins) {
+        resize(table);
+	return sa_insert(table, key, value);
+    }
+
+    main_pos = calc_pos(table, entry->key);
+    if (main_pos == pos) {
+        return insert_into_chain(table, key, value, pos);
+    }
+    else {
+        if (!table->free_pos) {
+            resize(table);
+            return sa_insert(table, key, value);
+        }
+        return insert_into_main(table, key, value, pos, main_pos);
+    }
+}
+
+static int
+hash_id_table_insert(register sa_table* table, ID id, VALUE value)
+{
+    return sa_insert(table, id2key(id), value);
+}
+
+static int
+insert_into_chain(register sa_table* table, id_key_t key, st_data_t value, sa_index_t pos)
+{
+    sa_entry *entry = table->entries + pos, *new_entry;
+    sa_index_t new_pos;
+
+    while (entry->next != SA_LAST) {
+        pos = entry->next - SA_OFFSET;
+        entry = table->entries + pos;
+        if (entry->key == key) {
+            entry->value = value;
+            return 1;
+        }
+    }
+
+    if (!table->free_pos) {
+        resize(table);
+        return sa_insert(table, key, value);
+    }
+
+    new_pos = find_empty(table, pos);
+    new_entry = table->entries + new_pos;
+    entry->next = new_pos + SA_OFFSET;
+
+    new_entry->next = SA_LAST;
+    new_entry->key = key;
+    new_entry->value = value;
+    table->num_entries++;
+    return 0;
+}
+
+static int
+insert_into_main(register sa_table* table, id_key_t key, st_data_t value, sa_index_t pos, sa_index_t prev_pos)
+{
+    sa_entry *entry = table->entries + pos;
+    sa_index_t new_pos = find_empty(table, pos);
+    sa_entry *new_entry = table->entries + new_pos;
+    sa_index_t npos;
+
+    *new_entry = *entry;
+
+    while((npos = table->entries[prev_pos].next - SA_OFFSET) != pos) {
+        prev_pos = npos;
+    }
+    table->entries[prev_pos].next = new_pos + SA_OFFSET;
+
+    entry->next = SA_LAST;
+    entry->key = key;
+    entry->value = value;
+    table->num_entries++;
+    return 0;
+}
+
+static sa_index_t
+new_size(sa_index_t num_entries)
+{
+    sa_index_t size = num_entries >> 3;
+    size |= size >> 1;
+    size |= size >> 2;
+    size |= size >> 4;
+    size |= size >> 8;
+    size |= size >> 16;
+    return (size + 1) << 3;
+}
+
+static void
+resize(register sa_table *table)
+{
+    sa_table tmp_table;
+    sa_entry *entry;
+    sa_index_t i;
+
+    if (table->num_entries == 0) {
+        xfree(table->entries);
+	memset(table, 0, sizeof(sa_table));
+        return;
+    }
+
+    sa_init_table(&tmp_table, new_size(table->num_entries + (table->num_entries >> 2)));
+    entry = table->entries;
+
+    for(i = 0; i < table->num_bins; i++, entry++) {
+        if (entry->next != SA_EMPTY) {
+            sa_insert(&tmp_table, entry->key, entry->value);
+        }
+    }
+    xfree(table->entries);
+    *table = tmp_table;
+}
+
+static int
+hash_id_table_lookup(register sa_table *table, ID id, VALUE *valuep)
+{
+    register sa_entry *entry;
+    id_key_t key = id2key(id);
+
+    if (table->num_entries == 0) return 0;
+
+    entry = table->entries + calc_pos(table, key);
+    if (entry->next == SA_EMPTY) return 0;
+
+    if (entry->key == key) goto found;
+    if (entry->next == SA_LAST) return 0;
+
+    entry = table->entries + (entry->next - SA_OFFSET);
+    if (entry->key == key) goto found;
+
+    while(entry->next != SA_LAST) {
+        entry = table->entries + (entry->next - SA_OFFSET);
+        if (entry->key == key) goto found;
+    }
+    return 0;
+found:
+    if (valuep) *valuep = entry->value;
+    return 1;
+}
+
+static size_t
+hash_id_table_size(sa_table *table)
+{
+    return table->num_entries;
+}
+
+static int
+hash_id_table_delete(sa_table *table, ID id)
+{
+    sa_index_t pos, prev_pos = ~0;
+    sa_entry *entry;
+    id_key_t key = id2key(id);
+
+    if (table->num_entries == 0) goto not_found;
+
+    pos = calc_pos(table, key);
+    entry = table->entries + pos;
+
+    if (entry->next == SA_EMPTY) goto not_found;
+
+    do {
+        if (entry->key == key) {
+            if (entry->next != SA_LAST) {
+                sa_index_t npos = entry->next - SA_OFFSET;
+                *entry = table->entries[npos];
+                memset(table->entries + npos, 0, sizeof(sa_entry));
+            }
+            else {
+                memset(table->entries + pos, 0, sizeof(sa_entry));
+                if (~prev_pos) {
+                    table->entries[prev_pos].next = SA_LAST;
+                }
+            }
+            table->num_entries--;
+            if (table->num_entries < table->num_bins / 4) {
+                resize(table);
+            }
+            return 1;
+        }
+        if (entry->next == SA_LAST) break;
+        prev_pos = pos;
+        pos = entry->next - SA_OFFSET;
+        entry = table->entries + pos;
+    } while(1);
+
+not_found:
+    return 0;
+}
+
+enum foreach_type {
+    foreach_key_values,
+    foreach_values
+};
+
+static void
+hash_foreach(sa_table *table, enum rb_id_table_iterator_result (*func)(ANYARGS), void *arg, enum foreach_type type)
+{
+    sa_index_t i;
+
+    if (table->num_bins > 0) {
+	for(i = 0; i < table->num_bins ; i++) {
+	    if (table->entries[i].next != SA_EMPTY) {
+		id_key_t key = table->entries[i].key;
+		st_data_t val = table->entries[i].value;
+		enum rb_id_table_iterator_result ret;
+
+		switch (type) {
+		  case foreach_key_values:
+		    ret = (*func)(key2id(key), val, arg);
+		    break;
+		  case foreach_values:
+		    ret = (*func)(val, arg);
+		    break;
+		}
+
+		switch (ret) {
+		  case ID_TABLE_DELETE:
+		    rb_warn("unsupported yet");
+		    break;
+		  default:
+		    break;
+		}
+		if (ret == ID_TABLE_STOP) break;
+	    }
+	}
+    }
+}
+
+static void
+hash_id_table_foreach(sa_table *table, enum rb_id_table_iterator_result (*func)(ID, VALUE, void *), void *arg)
+{
+    hash_foreach(table, func, arg, foreach_key_values);
+}
+
+static void
+hash_id_table_foreach_values(sa_table *table, enum rb_id_table_iterator_result (*func)(VALUE, void *), void *arg)
+{
+    hash_foreach(table, func, arg, foreach_values);
+}
+#endif /* ID_TABLE_USE_COALESCED_HASHING */
+
+#ifdef ID_TABLE_USE_SMALL_HASH
+/* simple open addressing with quadratic probing.
+   uses mark-bit on collisions - need extra 1 bit,
+   ID is strictly 3 bits larger than rb_id_serial_t */
+
+typedef struct rb_id_item {
+    id_key_t key;
+#if SIZEOF_VALUE == 8
+    int      collision;
+#endif
+    VALUE    val;
+} item_t;
+
+struct hash_id_table {
+    int capa;
+    int num;
+    int used;
+    item_t *items;
+};
+
+#if SIZEOF_VALUE == 8
+#define ITEM_GET_KEY(tbl, i) ((tbl)->items[i].key)
+#define ITEM_KEY_ISSET(tbl, i) ((tbl)->items[i].key)
+#define ITEM_COLLIDED(tbl, i) ((tbl)->items[i].collision)
+#define ITEM_SET_COLLIDED(tbl, i) ((tbl)->items[i].collision = 1)
+static inline void
+ITEM_SET_KEY(struct hash_id_table *tbl, int i, id_key_t key)
+{
+    tbl->items[i].key = key;
+}
+#else
+#define ITEM_GET_KEY(tbl, i) ((tbl)->items[i].key >> 1)
+#define ITEM_KEY_ISSET(tbl, i) ((tbl)->items[i].key > 1)
+#define ITEM_COLLIDED(tbl, i) ((tbl)->items[i].key & 1)
+#define ITEM_SET_COLLIDED(tbl, i) ((tbl)->items[i].key |= 1)
+static inline void
+ITEM_SET_KEY(struct hash_id_table *tbl, int i, id_key_t key)
+{
+    tbl->items[i].key = (key << 1) | ITEM_COLLIDED(tbl, i);
+}
+#endif
+
+static inline int
+round_capa(int capa) {
+    /* minsize is 4 */
+    capa >>= 2;
+    capa |= capa >> 1;
+    capa |= capa >> 2;
+    capa |= capa >> 4;
+    capa |= capa >> 8;
+    capa |= capa >> 16;
+    return (capa + 1) << 2;
+}
+
+static struct hash_id_table *
+hash_id_table_init(struct hash_id_table *tbl, int capa)
+{
+    MEMZERO(tbl, struct hash_id_table, 1);
+    if (capa > 0) {
+	capa = round_capa(capa);
+	tbl->capa = (int)capa;
+	tbl->items = ZALLOC_N(item_t, capa);
+    }
+    return tbl;
+}
+
+#ifndef ID_TABLE_USE_MIX
+static struct hash_id_table *
+hash_id_table_create(size_t capa)
+{
+    struct hash_id_table *tbl = ALLOC(struct hash_id_table);
+    return hash_id_table_init(tbl, (int)capa);
+}
+#endif
+
+static void
+hash_id_table_free(struct hash_id_table *tbl)
+{
+    xfree(tbl->items);
+    xfree(tbl);
+}
+
+static void
+hash_id_table_clear(struct hash_id_table *tbl)
+{
+    tbl->num = 0;
+    tbl->used = 0;
+    MEMZERO(tbl->items, item_t, tbl->capa);
+}
+
+static size_t
+hash_id_table_size(struct hash_id_table *tbl)
+{
+    return (size_t)tbl->num;
+}
+
+static size_t
+hash_id_table_memsize(struct hash_id_table *tbl)
+{
+    return sizeof(item_t) * tbl->capa + sizeof(struct hash_id_table);
+}
+
+static int
+hash_table_index(struct hash_id_table* tbl, id_key_t key)
+{
+    if (tbl->capa > 0) {
+	int mask = tbl->capa - 1;
+	int ix = key & mask;
+	int d = 1;
+	while (key != ITEM_GET_KEY(tbl, ix)) {
+	    if (!ITEM_COLLIDED(tbl, ix))
+		return -1;
+	    ix = (ix + d) & mask;
+	    d++;
+	}
+	return ix;
+    }
+    return -1;
+}
+
+static void
+hash_table_raw_insert(struct hash_id_table *tbl, id_key_t key, VALUE val)
+{
+    int mask = tbl->capa - 1;
+    int ix = key & mask;
+    int d = 1;
+    assert(key != 0);
+    while (ITEM_KEY_ISSET(tbl, ix)) {
+	ITEM_SET_COLLIDED(tbl, ix);
+	ix = (ix + d) & mask;
+	d++;
+    }
+    tbl->num++;
+    if (!ITEM_COLLIDED(tbl, ix)) {
+	tbl->used++;
+    }
+    ITEM_SET_KEY(tbl, ix, key);
+    tbl->items[ix].val = val;
+}
+
+static int
+hash_delete_index(struct hash_id_table *tbl, int ix)
+{
+    if (ix >= 0) {
+	if (!ITEM_COLLIDED(tbl, ix)) {
+	    tbl->used--;
+	}
+	tbl->num--;
+	ITEM_SET_KEY(tbl, ix, 0);
+	tbl->items[ix].val = 0;
+	return TRUE;
+    } else {
+	return FALSE;
+    }
+}
+
+static void
+hash_table_extend(struct hash_id_table* tbl)
+{
+    if (tbl->used + (tbl->used >> 1) >= tbl->capa) {
+	int new_cap = round_capa(tbl->num + (tbl->num >> 1));
+	int i;
+	item_t* old;
+	struct hash_id_table tmp_tbl = {new_cap, 0, 0};
+	tmp_tbl.items = ZALLOC_N(item_t, new_cap);
+	for (i = 0; i < tbl->capa; i++) {
+	    id_key_t key = ITEM_GET_KEY(tbl, i);
+	    if (key != 0) {
+		hash_table_raw_insert(&tmp_tbl, key, tbl->items[i].val);
+	    }
+	}
+	old = tbl->items;
+	*tbl = tmp_tbl;
+	xfree(old);
+    }
+}
+
+#if ID_TABLE_DEBUG && 0
+static void
+hash_table_show(struct hash_id_table *tbl)
+{
+    const id_key_t *keys = tbl->keys;
+    const int capa = tbl->capa;
+    int i;
+
+    fprintf(stderr, "tbl: %p (capa: %d, num: %d, used: %d)\n", tbl, tbl->capa, tbl->num, tbl->used);
+    for (i=0; i<capa; i++) {
+	if (ITEM_KEY_ISSET(tbl, i)) {
+	    fprintf(stderr, " -> [%d] %s %d\n", i, rb_id2name(key2id(keys[i])), (int)keys[i]);
+	}
+    }
+}
+#endif
+
+static int
+hash_id_table_lookup(struct hash_id_table *tbl, ID id, VALUE *valp)
+{
+    id_key_t key = id2key(id);
+    int index = hash_table_index(tbl, key);
+
+    if (index >= 0) {
+	*valp = tbl->items[index].val;
+	return TRUE;
+    }
+    else {
+	return FALSE;
+    }
+}
+
+static int
+hash_id_table_insert_key(struct hash_id_table *tbl, const id_key_t key, const VALUE val)
+{
+    const int index = hash_table_index(tbl, key);
+
+    if (index >= 0) {
+	tbl->items[index].val = val;
+    }
+    else {
+	hash_table_extend(tbl);
+	hash_table_raw_insert(tbl, key, val);
+    }
+    return TRUE;
+}
+
+static int
+hash_id_table_insert(struct hash_id_table *tbl, ID id, VALUE val)
+{
+    return hash_id_table_insert_key(tbl, id2key(id), val);
+}
+
+static int
+hash_id_table_delete(struct hash_id_table *tbl, ID id)
+{
+    const id_key_t key = id2key(id);
+    int index = hash_table_index(tbl, key);
+    return hash_delete_index(tbl, index);
+}
+
+static void
+hash_id_table_foreach(struct hash_id_table *tbl, enum rb_id_table_iterator_result (*func)(ID id, VALUE val, void *data), void *data)
+{
+    int i, capa = tbl->capa;
+
+    for (i=0; i<capa; i++) {
+	if (ITEM_KEY_ISSET(tbl, i)) {
+	    const id_key_t key = ITEM_GET_KEY(tbl, i);
+	    enum rb_id_table_iterator_result ret = (*func)(key2id(key), tbl->items[i].val, data);
+	    assert(key != 0);
+
+	    if (ret == ID_TABLE_DELETE)
+		hash_delete_index(tbl, i);
+	    else if (ret == ID_TABLE_STOP)
+		return;
+	}
+    }
+}
+
+static void
+hash_id_table_foreach_values(struct hash_id_table *tbl, enum rb_id_table_iterator_result (*func)(VALUE val, void *data), void *data)
+{
+    int i, capa = tbl->capa;
+
+    for (i=0; i<capa; i++) {
+	if (ITEM_KEY_ISSET(tbl, i)) {
+	    enum rb_id_table_iterator_result ret = (*func)(tbl->items[i].val, data);
+
+	    if (ret == ID_TABLE_DELETE)
+	      hash_delete_index(tbl, i);
+	    else if (ret == ID_TABLE_STOP)
+		return;
+	}
+    }
+}
+#endif /* ID_TABLE_USE_SMALL_HASH */
+
+#if ID_TABLE_USE_MIX
+
+struct mix_id_table {
+    union {
+	struct {
+	    int capa;
+	    int num;
+	} size;
+	struct list_id_table list;
+	struct hash_id_table hash;
+    } aux;
+};
+
+#define LIST_P(mix) ((mix)->aux.size.capa <= ID_TABLE_USE_MIX_LIST_MAX_CAPA)
+
+static struct mix_id_table *
+mix_id_table_create(size_t size)
+{
+    struct mix_id_table *mix = ZALLOC(struct mix_id_table);
+    list_id_table_init((struct list_id_table *)mix, size);
+    return mix;
+}
+
+static void
+mix_id_table_free(struct mix_id_table *tbl)
+{
+    if (LIST_P(tbl)) list_id_table_free(&tbl->aux.list);
+    else             hash_id_table_free(&tbl->aux.hash);
+}
+
+static void
+mix_id_table_clear(struct mix_id_table *tbl)
+{
+    if (LIST_P(tbl)) list_id_table_clear(&tbl->aux.list);
+    else             hash_id_table_clear(&tbl->aux.hash);
+}
+
+static size_t
+mix_id_table_size(struct mix_id_table *tbl)
+{
+    if (LIST_P(tbl)) return list_id_table_size(&tbl->aux.list);
+    else             return hash_id_table_size(&tbl->aux.hash);
+}
+
+static size_t
+mix_id_table_memsize(struct mix_id_table *tbl)
+{
+    if (LIST_P(tbl)) return list_id_table_memsize(&tbl->aux.list) - sizeof(struct list_id_table) + sizeof(struct mix_id_table);
+    else             return hash_id_table_memsize(&tbl->aux.hash);
+}
+
+static int
+mix_id_table_insert(struct mix_id_table *tbl, ID id, VALUE val)
+{
+    if (LIST_P(tbl)) {
+	int r = list_id_table_insert(&tbl->aux.list, id, val);
+
+	if (!LIST_P(tbl)) {
+	    /* overflow. TODO: this promotion should be done in list_extend_table */
+	    struct list_id_table *list = &tbl->aux.list;
+	    struct hash_id_table *hash = &tbl->aux.hash;
+	    id_key_t *keys = list->keys;
+	    VALUE *values = TABLE_VALUES(list);
+	    const int num = list->num;
+	    int i;
+
+	    hash_id_table_init(hash, 0);
+
+	    for (i=0; i<num; i++) {
+		hash_id_table_insert_key(hash, keys[i], values[i]);
+	    }
+
+	    assert(LIST_P(tbl) == 0);
+	}
+	return r;
+    }
+    else {
+	return hash_id_table_insert(&tbl->aux.hash, id, val);
+    }
+}
+
+static int
+mix_id_table_lookup(struct mix_id_table *tbl, ID id, VALUE *valp)
+{
+    if (LIST_P(tbl)) return list_id_table_lookup(&tbl->aux.list, id, valp);
+    else             return hash_id_table_lookup(&tbl->aux.hash, id, valp);
+}
+
+static int
+mix_id_table_delete(struct mix_id_table *tbl, ID id)
+{
+    if (LIST_P(tbl)) return list_id_table_delete(&tbl->aux.list, id);
+    else             return hash_id_table_delete(&tbl->aux.hash, id);
+}
+
+static void
+mix_id_table_foreach(struct mix_id_table *tbl, enum rb_id_table_iterator_result (*func)(ID id, VALUE val, void *data), void *data)
+{
+    if (LIST_P(tbl)) list_id_table_foreach(&tbl->aux.list, func, data);
+    else             hash_id_table_foreach(&tbl->aux.hash, func, data);
+}
+
+static void
+mix_id_table_foreach_values(struct mix_id_table *tbl, enum rb_id_table_iterator_result (*func)(VALUE val, void *data), void *data)
+{
+    if (LIST_P(tbl)) list_id_table_foreach_values(&tbl->aux.list, func, data);
+    else             hash_id_table_foreach_values(&tbl->aux.hash, func, data);
+}
+
+#endif /* ID_TABLE_USE_MIX */
+
+/* IMPL(create) will be "hash_id_table_create" and so on */
+#define IMPL2(name, op) name##_id_table_##op
+#define IMPL1(name, op) IMPL2(name, op)
+#define IMPL(op)        IMPL1(ID_TABLE_NAME, op)
+
+struct rb_id_table *rb_id_table_create(size_t size) {return (struct rb_id_table *)IMPL(create)(size);}
+void rb_id_table_free(struct rb_id_table *tbl)      {       IMPL(free)((ID_TABLE_IMPL_TYPE *)tbl);}
+void rb_id_table_clear(struct rb_id_table *tbl)     {       IMPL(clear)((ID_TABLE_IMPL_TYPE *)tbl);}
+size_t rb_id_table_size(struct rb_id_table *tbl)    {return IMPL(size)((ID_TABLE_IMPL_TYPE *)tbl);}
+size_t rb_id_table_memsize(struct rb_id_table *tbl) {return IMPL(memsize)((ID_TABLE_IMPL_TYPE *)tbl);}
+
+int rb_id_table_insert(struct rb_id_table *tbl, ID id, VALUE val)   {return IMPL(insert)((ID_TABLE_IMPL_TYPE *)tbl, id, val);}
+int rb_id_table_lookup(struct rb_id_table *tbl, ID id, VALUE *valp) {return IMPL(lookup)((ID_TABLE_IMPL_TYPE *)tbl, id, valp);}
+int rb_id_table_delete(struct rb_id_table *tbl, ID id)              {return IMPL(delete)((ID_TABLE_IMPL_TYPE *)tbl, id);}
+
+void rb_id_table_foreach(struct rb_id_table *tbl, enum rb_id_table_iterator_result (*func)(ID id, VALUE val, void *data), void *data) {
+     IMPL(foreach)((ID_TABLE_IMPL_TYPE *)tbl, func, data);}
+void rb_id_table_foreach_values(struct rb_id_table *tbl, enum rb_id_table_iterator_result (*func)(VALUE val, void *data), void *data) {
+     IMPL(foreach_values)((ID_TABLE_IMPL_TYPE *)tbl, func, data);}
+
+#if ID_TABLE_STARTUP_SIG
+__attribute__((constructor))
+static void
+show_impl(void)
+{
+    fprintf(stderr, "impl: %d\n", ID_TABLE_IMPL);
+}
+#endif