phoenix-firestorm/indra/llcommon/llstringtable.h

/**
 * @file llstringtable.h
 * @brief The LLStringTable class provides a _fast_ method for finding
 * unique copies of strings.
 *
 * $LicenseInfo:firstyear=2001&license=viewerlgpl$
 * 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_STRING_TABLE_H
#define LL_STRING_TABLE_H

#include "lldefs.h"
#include "llformat.h"
#include "llstl.h"
#include <list>
#include <set>

#if LL_WINDOWS
# if (_MSC_VER >= 1300 && _MSC_VER < 1400)
#  define STRING_TABLE_HASH_MAP 1
# endif
#else
//# define STRING_TABLE_HASH_MAP 1
#endif

const U32 MAX_STRINGS_LENGTH = 256;

class LL_COMMON_API LLStringTableEntry
{
public:
    LLStringTableEntry(const char *str);
    ~LLStringTableEntry();

    void incCount()     { mCount++; }
    BOOL decCount()     { return --mCount; }

    char *mString;
    S32  mCount;
};

class LL_COMMON_API LLStringTable
{
public:
    LLStringTable(int tablesize);
    ~LLStringTable();

    char *checkString(const char *str);
    char *checkString(const std::string& str);
    LLStringTableEntry *checkStringEntry(const char *str);
    LLStringTableEntry *checkStringEntry(const std::string& str);

    char *addString(const char *str);
    char *addString(const std::string& str);
    LLStringTableEntry *addStringEntry(const char *str);
    LLStringTableEntry *addStringEntry(const std::string& str);
    void  removeString(const char *str);

    S32 mMaxEntries;
    S32 mUniqueEntries;

#if STRING_TABLE_HASH_MAP
#if LL_WINDOWS
    typedef std::hash_multimap<U32, LLStringTableEntry *> string_hash_t;
#else
    typedef __gnu_cxx::hash_multimap<U32, LLStringTableEntry *> string_hash_t;
#endif
    string_hash_t mStringHash;
#else
    typedef std::list<LLStringTableEntry *> string_list_t;
    typedef string_list_t * string_list_ptr_t;
    string_list_ptr_t   *mStringList;
#endif
};

extern LL_COMMON_API LLStringTable gStringTable;

//============================================================================

// This class is designed to be used locally,
// e.g. as a member of an LLXmlTree
// Strings can be inserted only, then quickly looked up

typedef const std::string* LLStdStringHandle;

class LL_COMMON_API LLStdStringTable
{
public:
    LLStdStringTable(S32 tablesize = 0)
    {
        if (tablesize == 0)
        {
            tablesize = 256; // default
        }
        // Make sure tablesize is power of 2
        for (S32 i = 31; i>0; i--)
        {
            if (tablesize & (1<<i))
            {
                if (tablesize >= (3<<(i-1)))
                    tablesize = (1<<(i+1));
                else
                    tablesize = (1<<i);
                break;
            }
        }
        mTableSize = tablesize;
        mStringList = new string_set_t[tablesize];
    }
    ~LLStdStringTable()
    {
        cleanup();
        delete[] mStringList;
    }
    void cleanup()
    {
        // remove strings
        for (S32 i = 0; i<mTableSize; i++)
        {
            string_set_t& stringset = mStringList[i];
            for (LLStdStringHandle str : stringset)
            {
                delete str;
            }
            stringset.clear();
        }
    }

    LLStdStringHandle lookup(const std::string& s)
    {
        U32 hashval = makehash(s);
        return lookup(hashval, s);
    }

    LLStdStringHandle checkString(const std::string& s)
    {
        U32 hashval = makehash(s);
        return lookup(hashval, s);
    }

    LLStdStringHandle insert(const std::string& s)
    {
        U32 hashval = makehash(s);
        LLStdStringHandle result = lookup(hashval, s);
        if (result == NULL)
        {
            result = new std::string(s);
            mStringList[hashval].insert(result);
        }
        return result;
    }
    LLStdStringHandle addString(const std::string& s)
    {
        return insert(s);
    }

private:
    U32 makehash(const std::string& s)
    {
        S32 len = (S32)s.size();
        const char* c = s.c_str();
        U32 hashval = 0;
        for (S32 i=0; i<len; i++)
        {
            hashval = ((hashval<<5) + hashval) + *c++;
        }
        return hashval & (mTableSize-1);
    }
    LLStdStringHandle lookup(U32 hashval, const std::string& s)
    {
        string_set_t& stringset = mStringList[hashval];
        LLStdStringHandle handle = &s;
        string_set_t::iterator iter = stringset.find(handle); // compares actual strings
        if (iter != stringset.end())
        {
            return *iter;
        }
        else
        {
            return NULL;
        }
    }

private:
    S32 mTableSize;
    typedef std::set<LLStdStringHandle, compare_pointer_contents<std::string> > string_set_t;
    string_set_t* mStringList; // [mTableSize]
};


#endif