void SkipList::insert(const Key searchKey, const Value value)
{
int i;
long newLevel;
SkipListElement* element;
SkipListElement* nextElement;
SkipListElement update(SKIPLIST_MAXLEVEL);
// scan all levels while key < searchKey
// starting with header in his level
element = myHeader;
for(i=myHeader->getLevel(); i>=0; i--) {
nextElement = element->getElement(i);
while( (nextElement != NIL) && (nextElement->getKey() < searchKey) ) {
element=nextElement;
nextElement = element->getElement(i);
}
update.setElement(i, element); // save level pointer
}
element=element->getElement(0); // key is < searchKey
// key exists. set new value
//
if( (element != NIL) && (element->getKey() == searchKey) ) {
// cerr << "(dup " << searchKey << ")"; // print # to cout. remove later!
element->setValue(value);
} else { // new key. add to list
// get new level and fix list level
newLevel = getNewLevel(SKIPLIST_MAXLEVEL, myProbability); // get new level
if (newLevel > myHeader->getLevel() ) { // adjust header level
for (i=myHeader->getLevel() + 1; i<=newLevel; i++) {
update.setElement(i, myHeader); // adjust new pointer of new element
}
myHeader->setLevel(newLevel); // set new header level
}
// make new element [NEW *******]
myLength++;
element = new SkipListElement(newLevel, searchKey, value);
for (i=0; i<= newLevel; i++ ) { // scan all levels
// set next pointer of new element
element->setElement(i, update.getElement(i)->getElement(i));
update.getElement(i)->setElement(i, element);
}
/*
// fix level of element -- why not?
if(newLevel < update.getLevel()) {
update.setLevel(newLevel);
}
*/
}
}
/***************************************************************************
* Function : SkipListFindOrInsert()
* Description : Searches for the specified data item
* If found returns it, otherwise allocates one using
* user specified function, sets key and data and then
* returns it.
* If no user specified function exists, the given key
* and data are inserted.
*
*
* Input : The list in which the element is to be inserted, key,
* element to be inserted, a allocation function if new key and
* data are to be allocated, a return value for a flag to indicate
* if allocation was called.
* Output : sets found if it found an element.
* Returns : Node ptr on success, NULL on failiure
* ***************************************************************************/
SkipListNode_t *
SkipListFindOrInsert( SkipList_t *list, void *key, void *value , SkipListUserAlloc_t allocFn, int *found )
{
int i = 0;
int newLevel = 0;
SkipListNode_t *x= NULL;
SkipListNode_t *update[SKIPLIST_MAXLEVEL];
void *newKey;
void *newValue;
*found = 0;
/*
* Scan all levels while (list-key<serach-key) starting
* with header in its level.
*/
for ( x=list->header, i=list->level; i >= 0; i-- ) {
while ( x->forward[i] != 0 &&
list->cmpFn(x->forward[i]->key, key) < 0 ) {
x = x->forward[i];
}
/*
* Save level pointer.
*/
update[i] = x;
}
x = x->forward[0];
/*
* Element already exists.
*/
if ( x && list->cmpFn(x->key, key) == 0 ) {
*found = 1;
return x;
}
/*
* Put a new element in the list for this key.
* Get the new level and fix the list level.
*/
newLevel = getNewLevel( list->maxLevels );
/*
* Adjust the header level.
*/
if ( newLevel > list->level ) {
for ( i=list->level+1; i<=newLevel; i++ ) {
update[i] = list->header;
}
list->level = newLevel;
}
if ( allocFn ) {
/*
* User has a callback function to allocate newKey and newValue
*/
if ( !allocFn(key,value,&newKey,&newValue) )
return NULL;
} else {
/*
* User intends to insert the supplied key and value
*/
newKey = key;
newValue = value;
}
/*
* Make the new element and insert it in the list.
*/
x = newSkipListNode( list, newKey, newValue, newLevel );
if (!x)
return NULL;
/*
* Scan all levels.
*/
for ( i=0; i<=newLevel; i++ ) {
/*
* Set the next pointer of the new element.
*/
x->forward[i] = update[i]->forward[i];
update[i]->forward[i] = x;
}
list->numNodes++;
return x;
}
/***************************************************************************
* Function : SkipListInstert()
* Description : Inserts the given element in the skip list at
* the right place based on the specified key.
* Input : The list in which the element is to be inserted, key,
* element to be inserted and a flag which indicates
* whether to replace the existing element, if any.
* Output : None.
* Returns : 0 -- success, -1 -- failure
* ***************************************************************************/
int
SkipListInsert( SkipList_t *list, void *key, void *value, int replace )
{
int i = 0;
int newLevel = 0;
SkipListNode_t *x= NULL;
SkipListNode_t *update[SKIPLIST_MAXLEVEL];
/*
* Scan all levels while (list-key<serach-key) starting
* with header in its level.
*/
for ( x=list->header, i=list->level; i >= 0; i-- ) {
while ( x->forward[i] != 0 &&
list->cmpFn(x->forward[i]->key, key) < 0 ) {
x = x->forward[i];
}
/*
* Save level pointer.
*/
update[i] = x;
}
x = x->forward[0];
/*
* Element already exists.
*/
if ( x && list->cmpFn(x->key, key) == 0 ) {
if ( replace ) {
list->freeFn( x->value );
x->key = key;
x->value = value;
return( 0 );
}
else
return( -1 );
}
/*
* Put a new element in the list for this key.
* Get the new level and fix the list level.
*/
newLevel = getNewLevel( list->maxLevels );
/*
* Adjust the header level.
*/
if ( newLevel > list->level ) {
for ( i=list->level+1; i<=newLevel; i++ ) {
update[i] = list->header;
}
list->level = newLevel;
}
/*
* Make the new element and insert it in the list.
*/
x = newSkipListNode( list, key, value, newLevel );
/*
* Scan all levels.
*/
for ( i=0; i<=newLevel; i++ ) {
/*
* Set the next pointer of the new element.
*/
x->forward[i] = update[i]->forward[i];
update[i]->forward[i] = x;
}
list->numNodes++;
return(0);
}
