QAsciiDict - Template class that provides a dictionary
based on
#include <qasciidict.h>
Inherits QGDict.
Public Members
QAsciiDict ( int size=17, bool caseSensitive=TRUE, bool
copyKeys=TRUE )
QAsciiDict ( const QAsciiDict<type> & dict )
~QAsciiDict ()
QAsciiDict<type>& operator= ( const QAsciiDict<type> &
dict )
virtual uint count () const
uint size () const
bool isEmpty () const
void insert ( const char * key, const type * item )
void replace ( const char * key, const type * item )
bool remove ( const char * key )
type* take ( const char * key )
type* find ( const char * key ) const
type* operator[] ( const char * key ) const
virtual void clear ()
void resize ( uint newsize )
void statistics () const
DESCRIPTION
The QAsciiDict class is a template class that provides a
dictionary based on char* keys.
QAsciiDict is implemented as a template class. Define a
template instance QAsciiDict<X> to create a dictionary
that operates on pointers to X, or X*.
A dictionary is a collection that associates an item with
a key. The key is used for inserting and looking up an
item. QAsciiDict has char* keys. QAsciiDict cannot handle
Unicode keys, instead use the QDict template which uses
QString keys. A QDict has the same performace as a
QAsciiDict.
The dictionary has very fast insertion and lookup.
Example:
#include <qdict.h>
#include <stdio.h>
void main()
{
// Creates a dictionary that maps char* ==> char* (case insensitive)
QAsciiDict<char> dict( 17, FALSE );
dict.insert( "Russia", "Moscow" );
dict.insert( "Norway", "Oslo" );
printf( "%s\n", dict["Norway"] );
printf( "%s\n", dict["FRANCE"] );
printf( "%s\n", dict["russia"] );
if ( !dict["Italy"] )
printf( "Italy not defined\n" );
}
Program output:
Oslo
Paris
Moscow
Italy not defined
The dictionary in our example maps char* keys to char*
items. Note that the mapping is case insensitive
(specified in the constructor). QAsciiDict implements the
[] operator to lookup an item.
QAsciiDict is implemented by QGDict as a hash array with a
fixed number of entries. Each array entry points to a
singly linked list of buckets, in which the dictionary
items are stored.
When an item is inserted with a key, the key is converted
(hashed) to an integer index into the hash array. The item
is inserted before the first bucket in the list of
buckets.
Looking up an item is normally very fast. The key is again
hashed to an array index. Then QAsciiDict scans the list
of buckets and returns the item found or null if the item
was not found. You cannot insert null pointers into a
dictionary.
The size of the hash array is very important. In order to
get good performance, you should use a suitably large
prime number. Suitable means equal to or larger than the
maximum expected number of dictionary items.
Items with equal keys are allowed. When inserting two
items with the same key, only the last inserted item will
be visible (last in, first out) until it is removed.
Example:
#include <qdict.h>
#include <stdio.h>
void main()
{
// Creates a dictionary that maps char* ==> char* (case sensitive)
dict.insert( "Germany", "Berlin" );
dict.insert( "Germany", "Bonn" );
printf( "%s\n", dict["Germany"] );
dict.remove( "Germany" ); // Oct 3rd 1990
printf( "%s\n", dict["Germany"] );
}
Program output:
Bonn
Berlin
The QAsciiDictIterator class can traverse the dictionary
contents, but only in an arbitrary order. Multiple
iterators may independently traverse the same dictionary.
Calling setAutoDelete(TRUE) for a dictionary tells it to
delete items that are removed . The default is to not
delete items when they are removed.
When inserting an item into a dictionary, only the pointer
is copied, not the item itself. This is called a shallow
copy. It is possible to make the dictionary copy all of
the item's data (known as a deep copy) when an item is
inserted. insert() calls the virtual function
QCollection::newItem() for the item to be inserted.
Inherit a dictionary and reimplement it if you want deep
copies.
When removing a dictionary item, the virtual function
QCollection::deleteItem() is called. QAsciiDict's default
implementation is to delete the item if auto-deletion is
enabled.
See also QAsciiDictIterator, QDict, QIntDict, QPtrDict and
Collection Classes
MEMBER FUNCTION DOCUMENTATION
QAsciiDict::QAsciiDict ( const QAsciiDict & dict )
Constructs a copy of dict.
Each item in dict are inserted into this dictionary. Only
the pointers are copied (shallow copy).
QAsciiDict::QAsciiDict ( int size=17, bool caseSensitive=TRUE,
bool copyKeys=TRUE )
Constructs a dictionary with the following properties:
Arguments:
size is the size of the internal hash array.
lookup or not.
copyKeys specifies whether to copy the key strings.
Setting size to a suitably large prime number
(equal to or greater than the expected number of
entries) makes the hash distribution better and
hence the loopup faster.
Setting caseSensitive to TRUE will treat "abc" and "Abc"
as different keys. Setting it to FALSE will make the
dictionary ignore case. Case insensitive comparison
includes only the 26 standard letters A..Z, not French or
German accents or Scandinavian letters.
Setting copyKeys to TRUE will make the dictionary copy the
key when an item is inserted. Setting it to FALSE will
make the dictionary only use the pointer to the key.
QAsciiDict::~QAsciiDict ()
Removes all items from the dictionary and destroys it.
All iterators that access this dictionary will be reset.
See also setAutoDelete().
void QAsciiDict::clear () [virtual]
Removes all items from the dictionary.
The removed items are deleted if auto-deletion is enabled.
All dictionary iterators that operate on dictionary are
reset.
See also remove(), take() and setAutoDelete().
Reimplemented from QCollection.
uint QAsciiDict::count () const [virtual]
Returns the number of items in the dictionary.
See also isEmpty().
Reimplemented from QCollection.
type * QAsciiDict::find ( const char * key ) const
Returns the item associated with key, or null if the key
does not exist in the dictionary.
This function uses an internal hashing algorithm to
optimize lookup.
If there are two or more items with equal keys, then the
last inserted of these will be found.
See also operator[]().
void QAsciiDict::insert ( const char * key, const type * item )
Inserts the key with the item into the dictionary.
The key does not have to be a unique dictionary key. If
multiple items are inserted with the same key, only the
last item will be visible.
Null items are not allowed.
See also replace().
bool QAsciiDict::isEmpty () const
Returns TRUE if the dictionary is empty, i.e. count() ==
0. Returns FALSE otherwise.
See also count().
QAsciiDict & QAsciiDict::operator= ( const QAsciiDict
& dict )
Assigns dict to this dictionary and returns a reference to
this dictionary.
This dictionary is first cleared, then each item in dict
is inserted into this dictionary. Only the pointers are
copied (shallow copy), unless newItem() has been
reimplemented().
type * QAsciiDict::operator[] ( const char * key ) const
Returns the item associated with key, or null if the key
does not exist in the dictionary.
This function uses an internal hashing algorithm to
optimize lookup.
If there are two or more items with equal keys, then the
last inserted of these will be found.
Equivalent to the find() function.
See also find().
bool QAsciiDict::remove ( const char * key )
Removes the item associated with key from the dictionary.
Returns TRUE if successful, or FALSE if the key does not
exist in the dictionary.
If there are two or more items with equal keys, then the
last inserted of these will be removed.
The removed item is deleted if auto-deletion is enabled.
will be set to point to the next item in the dictionary
traversing order.
See also take(), clear() and setAutoDelete().
void QAsciiDict::replace ( const char * key, const type * item )
Replaces an item which has a key equal to key with item.
If the item does not already exist, it will be inserted.
Null items are not allowed.
Equivalent to:
QAsciiDict<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
last inserted of these will be replaced.
See also insert().
void QAsciiDict::resize ( uint newsize )
Changes the size of the hashtable the newsize. The
contents of the dictionary are preserved, but all
iterators on the dictionary become invalid.
uint QAsciiDict::size () const
Returns the size of the internal hash array (as specified
in the constructor).
See also count().
void QAsciiDict::statistics () const
Debugging-only function that prints out the dictionary
distribution using qDebug().
type * QAsciiDict::take ( const char * 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
last inserted of these will be taken.
Returns a pointer to the item taken out, or null 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
traversal order.
SEE ALSO
http://doc.trolltech.com/qasciidict.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2001 Trolltech AS,
http://www.trolltech.com. See the license file included
in the distribution for a complete license statement.
AUTHOR
Generated automatically from the source code.
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