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Q3IntDict Class Reference

The Q3IntDict class is a template class that provides a dictionary based on long keys. More...

 #include <Q3IntDict>

This class is part of the Qt 3 support library. It is provided to keep old source code working. We strongly advise against using it in new code. See Porting to Qt 4 for more information.

Inherits: Q3PtrCollection.

Public Functions

Q3IntDict ( int size = 17 )
Q3IntDict ( const Q3IntDict<type> & dict )
~Q3IntDict ()
type * find ( long key ) const
void insert ( long key, const type * item )
bool isEmpty () const
bool remove ( long key )
void replace ( long key, const type * item )
void resize ( uint newsize )
uint size () const
void statistics () const
type * take ( long key )
Q3IntDict<type> & operator= ( const Q3IntDict<type> & dict )
type * operator[] ( long key ) const

Reimplemented Public Functions

virtual void clear ()
virtual uint count () const

Protected Functions

virtual QDataStream & read ( QDataStream & s, Q3PtrCollection::Item & item )
virtual QDataStream & write ( QDataStream & s, Q3PtrCollection::Item item ) const

Detailed Description

The Q3IntDict class is a template class that provides a dictionary based on long keys.

Q3IntDict is implemented as a template class. Define a template instance Q3IntDict<X> to create a dictionary that operates on pointers to X (X*).

A dictionary is a collection of key-value pairs. The key is an long used for insertion, removal and lookup. The value is a pointer. Dictionaries provide very fast insertion and lookup.

Example:

 Q3IntDict<QLineEdit> fields; // long int keys, QLineEdit* values
 for ( int i = 0; i < 3; i++ )
     fields.insert( i, new QLineEdit( this ) );

 fields[0]->setText( "Homer" );
 fields[1]->setText( "Simpson" );
 fields[2]->setText( "45" );

 Q3IntDictIterator<QLineEdit> it( fields );
 for ( ; it.current(); ++it )
     cout << it.currentKey() << ": " << it.current()->text() << endl;

 for ( int i = 0; i < 3; i++ )
     cout << fields[i]->text() << " "; // Prints "Homer Simpson 45"
 cout << endl;

 fields.remove( 1 ); // Does not delete the line edit
 for ( int i = 0; i < 3; i++ )
     if ( fields[i] )
         cout << fields[i]->text() << " "; // Prints "Homer 45"

See Q3Dict for full details, including the choice of dictionary size, and how deletions are handled.

See also Q3IntDictIterator, Q3Dict, Q3AsciiDict, and Q3PtrDict.

Member Function Documentation

Q3IntDict::Q3IntDict ( int size = 17 )

Constructs a dictionary using an internal hash array of size size.

Setting size to a suitably large prime number (equal to or greater than the expected number of entries) makes the hash distribution better which leads to faster lookup.

Q3IntDict::Q3IntDict ( const Q3IntDict<type> & dict )

Constructs a copy of dict.

Each item in dict is inserted into this dictionary. Only the pointers are copied (shallow copy).

Q3IntDict::~Q3IntDict ()

Removes all items from the dictionary and destroys it.

All iterators that access this dictionary will be reset.

See also setAutoDelete().

void Q3IntDict::clear () [virtual]

Reimplemented from Q3PtrCollection::clear().

Removes all items from the dictionary.

The removed items are deleted if auto-deletion is enabled.

All dictionary iterators that access this dictionary will be reset.

See also remove(), take(), and setAutoDelete().

uint Q3IntDict::count () const [virtual]

Reimplemented from Q3PtrCollection::count().

Returns the number of items in the dictionary.

See also isEmpty().

type * Q3IntDict::find ( long key ) const

Returns the item associated with key, or 0 if the key does not exist in the dictionary.

If there are two or more items with equal keys, then the most recently inserted item will be found.

Equivalent to operator[].

See also operator[]().

void Q3IntDict::insert ( long key, const type * item )

Insert item item into the dictionary using key key.

Multiple items can have the same key, in which case only the last item will be accessible using operator[]().

item may not be 0.

See also replace().

bool Q3IntDict::isEmpty () const

Returns TRUE if the dictionary is empty; otherwise returns FALSE.

See also count().

QDataStream & Q3IntDict::read ( QDataStream & s, Q3PtrCollection::Item & item ) [virtual protected]

Reads a dictionary item from the stream s and returns a reference to the stream.

The default implementation sets item to 0.

See also write().

bool Q3IntDict::remove ( long key )

Removes the item associated with key from the dictionary. Returns TRUE if successful, i.e. if the key is in the dictionary; otherwise returns FALSE.

If there are two or more items with equal keys, then the most recently inserted item will be removed.

The removed item is deleted if auto-deletion is enabled.

All dictionary iterators that refer to the removed item will be set to point to the next item in the dictionary's traversal order.

See also take(), clear(), and setAutoDelete().

void Q3IntDict::replace ( long key, const type * item )

If the dictionary has key key, this key's item is replaced with item. If the dictionary doesn't contain key key, item is inserted into the dictionary using key key.

item may not be 0.

Equivalent to:

 Q3IntDict<char> dict;
 //      ...
 if ( dict.find(key) )
     dict.remove( key );
 dict.insert( key, item );

If there are two or more items with equal keys, then the most recently inserted item will be replaced.

See also insert().

void Q3IntDict::resize ( uint newsize )

Changes the size of the hashtable to newsize. The contents of the dictionary are preserved, but all iterators on the dictionary become invalid.

uint Q3IntDict::size () const

Returns the size of the internal hash array (as specified in the constructor).

See also count().

void Q3IntDict::statistics () const

Debugging-only function that prints out the dictionary distribution using qDebug().

type * Q3IntDict::take ( long key )

Takes the item associated with key out of the dictionary without deleting it (even if auto-deletion is enabled).

If there are two or more items with equal keys, then the most recently inserted item will be taken.

Returns a pointer to the item taken out, or 0 if the key does not exist in the dictionary.

All dictionary iterators that refer to the taken item will be set to point to the next item in the dictionary's traversing order.

See also remove(), clear(), and setAutoDelete().

QDataStream & Q3IntDict::write ( QDataStream & s, Q3PtrCollection::Item item ) const [virtual protected]

Writes a dictionary item to the stream s and returns a reference to the stream.

See also read().

Q3IntDict<type> & Q3IntDict::operator= ( const Q3IntDict<type> & dict )

Assigns dict to this dictionary and returns a reference to this dictionary.

This dictionary is first cleared and then each item in dict is inserted into this dictionary. Only the pointers are copied (shallow copy), unless newItem() has been reimplemented.

type * Q3IntDict::operator[] ( long key ) const

Returns the item associated with key, or 0 if the key does not exist in the dictionary.

If there are two or more items with equal keys, then the most recently inserted item will be found.

Equivalent to the find() function.

See also find().

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