llstringtable.cpp

/** 
 * @file llstringtable.cpp
 * @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
 * $/LicenseInfo$
 */

#include "linden_common.h"

#include "llstringtable.h"
#include "llstl.h"

LLStringTable gStringTable(32768);

LLStringTableEntry::LLStringTableEntry(const char *str)
: mString(NULL), mCount(1)
{
	// Copy string
	U32 length = (U32)strlen(str) + 1;	 /*Flawfinder: ignore*/
	length = llmin(length, MAX_STRINGS_LENGTH);
	mString = new char[length];
	strncpy(mString, str, length);	 /*Flawfinder: ignore*/
	mString[length - 1] = 0;
}

LLStringTableEntry::~LLStringTableEntry()
{
	delete [] mString;
	mCount = 0;
}

LLStringTable::LLStringTable(int tablesize)
: mUniqueEntries(0)
{
	S32 i;
	if (!tablesize)
		tablesize = 4096; // some arbitrary default
	// Make sure tablesize is power of 2
	for (i = 31; i>0; i--)
	{
		if (tablesize & (1<<i))
		{
			if (tablesize >= (3<<(i-1)))
				tablesize = (1<<(i+1));
			else
				tablesize = (1<<i);
			break;
		}
	}
	mMaxEntries = tablesize;

#if !STRING_TABLE_HASH_MAP
	// ALlocate strings
	mStringList = new string_list_ptr_t[mMaxEntries];
	// Clear strings
	for (i = 0; i < mMaxEntries; i++)
	{
		mStringList[i] = NULL;
	}
#endif
}

LLStringTable::~LLStringTable()
{
#if !STRING_TABLE_HASH_MAP
	if (mStringList)
	{
		for (S32 i = 0; i < mMaxEntries; i++)
		{
			if (mStringList[i])
			{
				string_list_t::iterator iter;
				for (iter = mStringList[i]->begin(); iter != mStringList[i]->end(); iter++)
					delete *iter; // *iter = (LLStringTableEntry*)
			}
			delete mStringList[i];
		}
		delete [] mStringList;
		mStringList = NULL;
	}
#else
	// Need to clean up the string hash
	for_each(mStringHash.begin(), mStringHash.end(), DeletePairedPointer());
	mStringHash.clear();
#endif
}


static U32 hash_my_string(const char *str, int max_entries)
{
	U32 retval = 0;
#if 0
	while (*str)
	{
		retval <<= 1;
		retval += *str++;
	}
#else
	while (*str)
	{
		retval = (retval<<4) + *str;
		U32 x = (retval & 0xf0000000);
		if (x) retval = retval ^ (x>>24);
		retval = retval & (~x);
		str++;
	}
#endif
	return (retval & (max_entries-1)); // max_entries is gauranteed to be power of 2
}

char* LLStringTable::checkString(const std::string& str)
{
	return checkString(str.c_str());
}

char* LLStringTable::checkString(const char *str)
{
    LLStringTableEntry* entry = checkStringEntry(str);
    if (entry)
    {
	return entry->mString;
    }
    else
    {
	return NULL;
    }
}

LLStringTableEntry* LLStringTable::checkStringEntry(const std::string& str)
{
    return checkStringEntry(str.c_str());
}

LLStringTableEntry* LLStringTable::checkStringEntry(const char *str)
{
	if (str)
	{
		char *ret_val;
		LLStringTableEntry	*entry;
		U32					hash_value = hash_my_string(str, mMaxEntries);
#if STRING_TABLE_HASH_MAP
#if 1 // Microsoft
		string_hash_t::iterator lower = mStringHash.lower_bound(hash_value);
		string_hash_t::iterator upper = mStringHash.upper_bound(hash_value);
#else // stlport
		std::pair<string_hash_t::iterator, string_hash_t::iterator> P = mStringHash.equal_range(hash_value);
		string_hash_t::iterator lower = P.first;
		string_hash_t::iterator upper = P.second;
#endif
		for (string_hash_t::iterator iter = lower; iter != upper; iter++)
		{
			entry = iter->second;
			ret_val = entry->mString;
			if (!strncmp(ret_val, str, MAX_STRINGS_LENGTH))
			{
				return entry;
			}
		}
#else
		string_list_t		*strlist = mStringList[hash_value];
		if (strlist)
		{
			string_list_t::iterator iter;
			for (iter = strlist->begin(); iter != strlist->end(); iter++)
			{
				entry = *iter;
				ret_val = entry->mString;
				if (!strncmp(ret_val, str, MAX_STRINGS_LENGTH))
				{
					return entry;
				}
			}
		}
#endif
	}
	return NULL;
}

char* LLStringTable::addString(const std::string& str)
{
	//RN: safe to use temporary c_str since string is copied
	return addString(str.c_str());
}

char* LLStringTable::addString(const char *str)
{

    LLStringTableEntry* entry = addStringEntry(str);
    if (entry)
    {
	return entry->mString;
    }
    else
    {
	return NULL;
    }
}

LLStringTableEntry* LLStringTable::addStringEntry(const std::string& str)
{
    return addStringEntry(str.c_str());
}

LLStringTableEntry* LLStringTable::addStringEntry(const char *str)
{
	if (str)
	{
		char *ret_val = NULL;
		U32					hash_value = hash_my_string(str, mMaxEntries);
#if STRING_TABLE_HASH_MAP
#if 1 // Microsoft
		string_hash_t::iterator lower = mStringHash.lower_bound(hash_value);
		string_hash_t::iterator upper = mStringHash.upper_bound(hash_value);
#else // stlport
		std::pair<string_hash_t::iterator, string_hash_t::iterator> P = mStringHash.equal_range(hash_value);
		string_hash_t::iterator lower = P.first;
		string_hash_t::iterator upper = P.second;
#endif
		for (string_hash_t::iterator iter = lower; iter != upper; iter++)
		{
			entry = iter->second;
			ret_val = entry->mString;
			if (!strncmp(ret_val, str, MAX_STRINGS_LENGTH))
			{
				entry->incCount();
				return entry;
			}
		}

		// not found, so add!
		LLStringTableEntry* newentry = new LLStringTableEntry(str);
		ret_val = newentry->mString;
		mStringHash.insert(string_hash_t::value_type(hash_value, newentry));
#else
		string_list_t		*strlist = mStringList[hash_value];

		if (strlist)
		{
            for (LLStringTableEntry *entry : *strlist)
			{
				ret_val = entry->mString;
				if (!strncmp(ret_val, str, MAX_STRINGS_LENGTH))
				{
					entry->incCount();
					return entry;
				}
			}
		}
		else
		{
			mStringList[hash_value] = new string_list_t;
			strlist = mStringList[hash_value];
		}

		// not found, so add!
		LLStringTableEntry *newentry = new LLStringTableEntry(str);
		//ret_val = newentry->mString;
		strlist->push_front(newentry);
#endif
		mUniqueEntries++;
		return newentry;
	}
	else
	{
		return NULL;
	}
}

void LLStringTable::removeString(const char *str)
{
	if (str)
	{
		char *ret_val;
		U32					hash_value = hash_my_string(str, mMaxEntries);
#if STRING_TABLE_HASH_MAP
		{
#if 1 // Microsoft
			string_hash_t::iterator lower = mStringHash.lower_bound(hash_value);
			string_hash_t::iterator upper = mStringHash.upper_bound(hash_value);
#else // stlport
			std::pair<string_hash_t::iterator, string_hash_t::iterator> P = mStringHash.equal_range(hash_value);
			string_hash_t::iterator lower = P.first;
			string_hash_t::iterator upper = P.second;
#endif
			for (string_hash_t::iterator iter = lower; iter != upper; iter++)
			{
				entry = iter->second;
				ret_val = entry->mString;
				if (!strncmp(ret_val, str, MAX_STRINGS_LENGTH))
				{
					if (!entry->decCount())
					{
						mUniqueEntries--;
						if (mUniqueEntries < 0)
						{
							LL_ERRS() << "LLStringTable:removeString trying to remove too many strings!" << LL_ENDL;
						}
						delete iter->second;
						mStringHash.erase(iter);
					}
					return;
				}
			}
		}
#else
		string_list_t		*strlist = mStringList[hash_value];
				if (strlist)
		{
            for (LLStringTableEntry *entry : *strlist)
			{
				ret_val = entry->mString;
				if (!strncmp(ret_val, str, MAX_STRINGS_LENGTH))
				{
					if (!entry->decCount())
					{
						mUniqueEntries--;
						if (mUniqueEntries < 0)
						{
							LL_ERRS() << "LLStringTable:removeString trying to remove too many strings!" << LL_ENDL;
						}
						strlist->remove(entry);
						delete entry;
					}
					return;
				}
			}
		}
#endif
	}
}