/*
 * %CopyrightBegin%
 * 
 * Copyright Ericsson AB 1996-2017. All Rights Reserved.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * %CopyrightEnd%
 */

/*
** General hash and index functions
** The idea behind this file was to capture the
** way Atom,Export and Module table was implemented
*/
#ifndef __INDEX_H__
#define __INDEX_H__

#include "hash.h"
#include "erl_alloc.h"

typedef struct index_slot 
{
    HashBucket bucket;
    int index;
} IndexSlot;


typedef struct index_table
{
    Hash htable;		/* Mapping obj -> index */
    ErtsAlcType_t type;
    int size;			/* Allocated size */
    int limit;			/* Max size */
    int entries;		/* Number of entries */
    IndexSlot*** seg_table;	/* Mapping index -> obj */
} IndexTable;

#define INDEX_PAGE_SHIFT 10
#define INDEX_PAGE_SIZE (1 << INDEX_PAGE_SHIFT)
#define INDEX_PAGE_MASK ((1 << INDEX_PAGE_SHIFT)-1)

IndexTable *erts_index_init(ErtsAlcType_t,IndexTable*,char*,int,int,HashFunctions);
void index_info(fmtfn_t, void *, IndexTable*);
int index_table_sz(IndexTable *);

int index_get(IndexTable*, void*);

IndexSlot* index_put_entry(IndexTable*, void*);
void erts_index_merge(Hash*, IndexTable*);

/* Erase all entries with index 'ix' and higher
*/
void index_erase_latest_from(IndexTable*, Uint ix);

ERTS_GLB_INLINE int index_put(IndexTable*, void*);
ERTS_GLB_INLINE IndexSlot* erts_index_lookup(IndexTable*, Uint);
ERTS_GLB_INLINE int erts_index_num_entries(IndexTable* t);

#if ERTS_GLB_INLINE_INCL_FUNC_DEF

ERTS_GLB_INLINE int index_put(IndexTable* t, void* tmpl)
{
    return index_put_entry(t, tmpl)->index;
}

ERTS_GLB_INLINE IndexSlot*
erts_index_lookup(IndexTable* t, Uint ix)
{
    return t->seg_table[ix>>INDEX_PAGE_SHIFT][ix&INDEX_PAGE_MASK];
}

ERTS_GLB_INLINE int erts_index_num_entries(IndexTable* t)
{
    int ret = t->entries;
    /*
     * Do a read barrier here to allow lock free iteration
     * on tables where entries are never erased.
     * index_put_entry() does matching write barrier.
     */
    ERTS_SMP_READ_MEMORY_BARRIER;
    return ret;
}

#endif

#endif
