/*

* Copyright (c) 2007-2009 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of the License "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description: 

* Hash class for imgcheck tool. All the executable names of ROM/ROFS 

* are stored into this hash table. After gathering the dependencies

* for those executables, dependencies existence is checked very 

* efficiently using this table.

*

*/

/**

 @file

 @internalComponent

 @released

*/

#include "common.h"

#include "hash.h"

/** 

Constructor, intializes the table size

@internalComponent

@released

@param aSize - Hash table size (Number of dissimilar data can stored)

*/

HashTable::HashTable(int aSize)

:iSize(aSize) {

}

/** 

Destructor

@internalComponent

@released

*/

HashTable::~HashTable() {

}

/** 

Function responsible to return the Hash value for the received string.

@internalComponent

@released

@param aString - const string& on which Hash value calcualtion 

*/

int HashTable::Hash(const string& aString) {

	unsigned int hashVal = 0;

	int length = aString.length() ;

	/* we start our hash out at 0 */

	/* for each character, we multiply the old hash by 31 and add the current

	 * character.  Remember that shifting a number left is equivalent to 

	 * multiplying it by 2 raised to the number of places shifted.  So we 

	 * are in effect multiplying hashval by 32 and then subtracting hashval.  

	 * Why do we do this?  Because shifting and subtraction are much more 

	 * efficient operations than multiplication.

	 */

	for(int strIter = 0; strIter < length ; strIter++) {

		hashVal = aString[strIter] + (hashVal << 5) - hashVal;

	}

	/* we then return the hash value mod the hashtable size so that it will

	 * fit into the necessary range

	 */

	return hashVal % iSize;

}

/** 

Function returns ture or false based on the string availability in Hash

@internalComponent

@released

@param aString - const char* which needs to be searched

*/

bool HashTable::IsAvailable(const string& aString) { 

	unsigned int hashVal = Hash(aString);

	if (iTable.count(hashVal) > 0) {

		pair<Table::iterator,Table::iterator> range = iTable.equal_range(hashVal);

		for(Table::iterator it = range.first; it != range.second ; it++) {				 

			if(aString == it->second ) {

				return true;

			}			 

		}

	}	

	return false;

}

/** 

Function responsible to insert a single string into Hash table

@internalComponent

@released

@param aString - const char* which needs to be inserted

*/

void HashTable::Insert(const string& aString) {

	unsigned int hashVal = Hash(aString);

	if(!IsAvailable(aString))  {

		iTable.insert(pair<unsigned int,string>(hashVal,aString));

	}

}

/** 

Function responsible to insert list of StringList into Hash table

@internalComponent

@released

@param aString - string which needs to be inserted

*/

void HashTable::InsertStringList(const StringList& aList) { 

	for(StringList::const_iterator it = aList.begin(); it != aList.end(); it++ ) {

		Insert(*it); 

	}

}

/** 

Function to delete an entry from Hash

@internalComponent

@released

@param aString - const char* which needs to be deleted

*/

void HashTable::Delete(const string& aString) {

	unsigned int hashVal = Hash(aString);

	if (iTable.count(hashVal) > 0) {

		pair<Table::iterator,Table::iterator> range = iTable.equal_range(hashVal);

		for(Table::iterator it = range.first; it != range.second ; it++) {			 

			if(aString == it->second ) {

				iTable.erase(it); 

				return ;

			}			 

		}

	}

}