/**
 * @file llsimplehash.h
 *
 * $LicenseInfo:firstyear=2003&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#ifndef LL_LLSIMPLEHASH_H
#define LL_LLSIMPLEHASH_H

#include "llstl.h"

template <typename HASH_KEY_TYPE>
class LLSimpleHashEntry
{
protected:
    HASH_KEY_TYPE mHashKey;
    LLSimpleHashEntry<HASH_KEY_TYPE>* mNextEntry;
public:
    LLSimpleHashEntry(HASH_KEY_TYPE key) :
        mHashKey(key),
        mNextEntry(0)
    {
    }
    virtual ~LLSimpleHashEntry()
    {
    }
    HASH_KEY_TYPE getHashKey() const
    {
        return mHashKey;
    }
    LLSimpleHashEntry<HASH_KEY_TYPE>* getNextEntry() const
    {
        return mNextEntry;
    }
    void setNextEntry(LLSimpleHashEntry<HASH_KEY_TYPE>* next)
    {
        mNextEntry = next;
    }
};

template <typename HASH_KEY_TYPE, int TABLE_SIZE>
class LL_COMMON_API LLSimpleHash
{
public:
    LLSimpleHash()
    {
        llassert(TABLE_SIZE);
        llassert((TABLE_SIZE ^ (TABLE_SIZE-1)) == (TABLE_SIZE | (TABLE_SIZE-1))); // power of 2
        memset(mEntryTable, 0, sizeof(mEntryTable));
    }
    virtual ~LLSimpleHash()
    {
    }

    virtual int getIndex(HASH_KEY_TYPE key)
    {
        return key & (TABLE_SIZE-1);
    }

    bool insert(LLSimpleHashEntry<HASH_KEY_TYPE>* entry)
    {
        llassert(entry->getNextEntry() == 0);
        int index = getIndex(entry->getHashKey());
        entry->setNextEntry(mEntryTable[index]);
        mEntryTable[index] = entry;
        return true;
    }
    LLSimpleHashEntry<HASH_KEY_TYPE>* find(HASH_KEY_TYPE key)
    {
        int index = getIndex(key);
        LLSimpleHashEntry<HASH_KEY_TYPE>* res = mEntryTable[index];
        while(res && (res->getHashKey() != key))
        {
            res = res->getNextEntry();
        }
        return res;
    }
    bool erase(LLSimpleHashEntry<HASH_KEY_TYPE>* entry)
    {
        return erase(entry->getHashKey());
    }
    bool erase(HASH_KEY_TYPE key)
    {
        int index = getIndex(key);
        LLSimpleHashEntry<HASH_KEY_TYPE>* prev = 0;
        LLSimpleHashEntry<HASH_KEY_TYPE>* res = mEntryTable[index];
        while(res && (res->getHashKey() != key))
        {
            prev = res;
            res = res->getNextEntry();
        }
        if (res)
        {
            LLSimpleHashEntry<HASH_KEY_TYPE>* next = res->getNextEntry();
            if (prev)
            {
                prev->setNextEntry(next);
            }
            else
            {
                mEntryTable[index] = next;
            }
            return true;
        }
        else
        {
            return false;
        }
    }
    // Removes and returns an arbitrary ("first") element from the table
    // Used for deleting the entire table.
    LLSimpleHashEntry<HASH_KEY_TYPE>* pop_element()
    {
        for (int i=0; i<TABLE_SIZE; i++)
        {
            LLSimpleHashEntry<HASH_KEY_TYPE>* entry = mEntryTable[i];
            if (entry)
            {
                mEntryTable[i] = entry->getNextEntry();
                return entry;
            }
        }
        return 0;
    }
    // debugging
    LLSimpleHashEntry<HASH_KEY_TYPE>* get_element_at_index(S32 index) const
    {
        return mEntryTable[index];
    }


private:
    LLSimpleHashEntry<HASH_KEY_TYPE>* mEntryTable[TABLE_SIZE];
};

#endif // LL_LLSIMPLEHASH_H