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    41 

    42 /*!

    43     \class Q3AsciiCache

    44     \brief The Q3AsciiCache class is a template class that provides a cache based on char* keys.

    45     \compat

    46 

    47     Q3AsciiCache is implemented as a template class. Define a template

    48     instance Q3AsciiCache\<X\> to create a cache that operates on

    49     pointers to X (X*).

    50 

    51     A cache is a least recently used (LRU) list of cache items. The

    52     cache items are accessed via \c char* keys. For Unicode keys use

    53     the Q3Cache template instead, which uses QString keys. A Q3Cache

    54     has the same performace as a Q3AsciiCache.

    55 

    56     Each cache item has a cost. The sum of item costs, totalCost(),

    57     will not exceed the maximum cache cost, maxCost(). If inserting a

    58     new item would cause the total cost to exceed the maximum cost,

    59     the least recently used items in the cache are removed.

    60 

    61     Apart from insert(), by far the most important function is find()

    62     (which also exists as operator[]()). This function looks up an

    63     item, returns it, and by default marks it as being the most

    64     recently used item.

    65 

    66     There are also methods to remove() or take() an object from the

    67     cache. Calling \link Q3PtrCollection::setAutoDelete()

    68     setAutoDelete(TRUE)\endlink tells the cache to delete items that

    69     are removed. The default is to not delete items when then are

    70     removed (i.e., remove() and take() are equivalent).

    71 

    72     When inserting an item into the cache, only the pointer is copied,

    73     not the item itself. This is called a shallow copy. It is possible

    74     to make the cache copy all of the item's data (known as a deep

    75     copy) when an item is inserted. insert() calls the virtual

    76     function Q3PtrCollection::newItem() for the item to be inserted.

    77     Inherit a cache and reimplement newItem() if you want deep copies.

    78 

    79     When removing a cache item the virtual function

    80     Q3PtrCollection::deleteItem() is called. Its default implementation

    81     in Q3AsciiCache is to delete the item if \link

    82     Q3PtrCollection::setAutoDelete() auto-deletion\endlink is enabled.

    83 

    84     There is a Q3AsciiCacheIterator which may be used to traverse the

    85     items in the cache in arbitrary order.

    86 

    87     \sa Q3AsciiCacheIterator, Q3Cache, Q3IntCache

    88 */

    89 

    90 /*!

    91   \fn Q3AsciiCache::Q3AsciiCache( const Q3AsciiCache<type> &c )

    92 

    93   \internal

    94 

    95   Do not use. A Q3AsciiCache cannot be copied. Calls qFatal() in debug version.

    96 */

    97 

    98 

    99 /*!

   100     \fn Q3AsciiCache::Q3AsciiCache( int maxCost, int size, bool caseSensitive, bool copyKeys )

   101 

   102     Constructs a cache whose contents will never have a total cost

   103     greater than \a maxCost and which is expected to contain less than

   104     \a size items.

   105 

   106     \a size is actually the size of an internal hash array; it's

   107     usually best to make it prime and at least 50% bigger than the

   108     largest expected number of items in the cache.

   109 

   110     Each inserted item has an associated cost. When inserting a new

   111     item, if the total cost of all items in the cache will exceed \a

   112     maxCost, the cache will start throwing out the older (least

   113     recently used) items until there is enough room for the new item

   114     to be inserted.

   115 

   116     If \a caseSensitive is TRUE (the default), the cache keys are case

   117     sensitive; if it is FALSE, they are case-insensitive.

   118     Case-insensitive comparison only affects the 26 letters in

   119     US-ASCII. If \a copyKeys is TRUE (the default), Q3AsciiCache makes

   120     a copy of the cache keys, otherwise it copies just the const char

   121     * pointer - slightly faster if you can guarantee that the keys

   122     will never change, but very risky.

   123 */

   124 

   125 /*!

   126     \fn Q3AsciiCache::~Q3AsciiCache()

   127 

   128     Removes all items from the cache and destroys it.

   129     All iterators that access this cache will be reset.

   130 */

   131 

   132 /*!

   133   \fn Q3AsciiCache<type>& Q3AsciiCache::operator=( const Q3AsciiCache<type> &c )

   134 

   135   \internal

   136 

   137   Do not use. A Q3AsciiCache cannot be copied. Calls qFatal() in debug version.

   138 */

   139 

   140 /*!

   141     \fn int Q3AsciiCache::maxCost() const

   142 

   143     Returns the maximum allowed total cost of the cache.

   144 

   145     \sa setMaxCost() totalCost()

   146 */

   147 

   148 /*!

   149     \fn int Q3AsciiCache::totalCost() const

   150 

   151     Returns the total cost of the items in the cache. This is an

   152     integer in the range 0 to maxCost().

   153 

   154     \sa setMaxCost()

   155 */

   156 

   157 /*!

   158     \fn void Q3AsciiCache::setMaxCost( int m )

   159 

   160     Sets the maximum allowed total cost of the cache to \a m. If the

   161     current total cost is greater than \a m, some items are removed

   162     immediately.

   163 

   164     \sa maxCost() totalCost()

   165 */

   166 

   167 /*!

   168     \fn uint Q3AsciiCache::count() const

   169 

   170     Returns the number of items in the cache.

   171 

   172     \sa totalCost() size()

   173 */

   174 

   175 /*!

   176     \fn uint Q3AsciiCache::size() const

   177 

   178     Returns the size of the hash array used to implement the cache.

   179     This should be a bit bigger than count() is likely to be.

   180 */

   181 

   182 /*!

   183     \fn bool Q3AsciiCache::isEmpty() const

   184 

   185     Returns TRUE if the cache is empty; otherwise returns FALSE.

   186 */

   187 

   188 /*!

   189     \fn bool Q3AsciiCache::insert( const char *k, const type *d, int c, int p )

   190 

   191     Inserts the item \a d into the cache using key \a k, and with an

   192     associated cost of \a c. Returns TRUE if the item is successfully

   193     inserted. Returns FALSE if the item is not inserted, for example,

   194     if the cost of the item exceeds maxCost().

   195 

   196     The cache's size is limited, and if the total cost is too high,

   197     Q3AsciiCache will remove old, least recently used items until there

   198     is room for this new item.

   199 

   200     Items with duplicate keys can be inserted.

   201 

   202     The parameter \a p is internal and should be left at the default

   203     value (0).

   204 

   205     \warning If this function returns FALSE, you must delete \a d

   206     yourself. Additionally, be very careful about using \a d after

   207     calling this function, because any other insertions into the

   208     cache, from anywhere in the application or within Qt itself, could

   209     cause the object to be discarded from the cache and the pointer to

   210     become invalid.

   211 */

   212 

   213 /*!

   214     \fn bool Q3AsciiCache::remove( const char *k )

   215 

   216     Removes the item with key \a k and returns TRUE if the item was

   217     present in the cache; otherwise returns FALSE.

   218 

   219     The item is deleted if auto-deletion has been enabled, i.e., if

   220     you have called \link Q3PtrCollection::setAutoDelete()

   221     setAutoDelete(TRUE)\endlink.

   222 

   223     If there are two or more items with equal keys, the one that was

   224     inserted last is removed.

   225 

   226     All iterators that refer to the removed item are set to point to

   227     the next item in the cache's traversal order.

   228 

   229     \sa take(), clear()

   230 */

   231 

   232 /*!

   233     \fn type *Q3AsciiCache::take( const char *k )

   234 

   235     Takes the item associated with \a k out of the cache without

   236     deleting it and returns a pointer to the item taken out, or 0

   237     if the key does not exist in the cache.

   238 

   239     If there are two or more items with equal keys, the one that was

   240     inserted last is taken.

   241 

   242     All iterators that refer to the taken item are set to point to the

   243     next item in the cache's traversal order.

   244 

   245     \sa remove(), clear()

   246 */

   247 

   248 /*!

   249     \fn void Q3AsciiCache::clear()

   250 

   251     Removes all items from the cache, and deletes them if \link

   252     Q3PtrCollection::setAutoDelete() auto-deletion\endlink has been

   253     enabled.

   254 

   255     All cache iterators that operate on this cache are reset.

   256 

   257     \sa remove() take()

   258 */

   259 

   260 /*!

   261     \fn type *Q3AsciiCache::find( const char *k, bool ref ) const

   262 

   263     Returns the item with key \a k, or 0 if the key does not exist

   264     in the cache. If \a ref is TRUE (the default), the item is moved

   265     to the front of the least recently used list.

   266 

   267     If there are two or more items with equal keys, the one that was

   268     inserted last is returned.

   269 */

   270 

   271 /*!

   272     \fn type *Q3AsciiCache::operator[]( const char *k ) const

   273 

   274     Returns the item with key \a k, or 0 if \a k does not exist in

   275     the cache, and moves the item to the front of the least recently

   276     used list.

   277 

   278     If there are two or more items with equal keys, the one that was

   279     inserted last is returned.

   280 

   281     This is the same as find( k, TRUE ).

   282 

   283     \sa find()

   284 */

   285 

   286 /*!

   287     \fn void Q3AsciiCache::statistics() const

   288 

   289     A debug-only utility function. Prints out cache usage, hit/miss,

   290     and distribution information using qDebug(). This function does

   291     nothing in the release library.

   292 */

   293 

   294 /*!

   295     \class Q3AsciiCacheIterator

   296     \brief The Q3AsciiCacheIterator class provides an iterator for Q3AsciiCache collections.

   297     \compat

   298 

   299     Note that the traversal order is arbitrary; you are not guaranteed

   300     any particular order. If new objects are inserted into the cache

   301     while the iterator is active, the iterator may or may not see

   302     them.

   303 

   304     Multiple iterators are completely independent, even when they

   305     operate on the same Q3AsciiCache. Q3AsciiCache updates all iterators

   306     that refer an item when that item is removed.

   307 

   308     Q3AsciiCacheIterator provides an operator++() and an operator+=()

   309     to traverse the cache; current() and currentKey() to access the

   310     current cache item and its key. It also provides atFirst() and

   311     atLast(), which return TRUE if the iterator points to the first or

   312     last item in the cache respectively. The isEmpty() function

   313     returns TRUE if the cache is empty; and count() returns the number

   314     of items in the cache.

   315 

   316     Note that atFirst() and atLast() refer to the iterator's arbitrary

   317     ordering, not to the cache's internal least recently used list.

   318 

   319     \sa Q3AsciiCache

   320 */

   321 

   322 /*!

   323     \fn Q3AsciiCacheIterator::Q3AsciiCacheIterator( const Q3AsciiCache<type> &cache )

   324 

   325     Constructs an iterator for \a cache. The current iterator item is

   326     set to point to the first item in the \a cache.

   327 */

   328 

   329 /*!

   330     \fn Q3AsciiCacheIterator::Q3AsciiCacheIterator (const Q3AsciiCacheIterator<type> & ci)

   331 

   332     Constructs an iterator for the same cache as \a ci. The new

   333     iterator starts at the same item as ci.current() but moves

   334     independently from there on.

   335 */

   336 

   337 /*!

   338     \fn Q3AsciiCacheIterator<type>& Q3AsciiCacheIterator::operator=( const Q3AsciiCacheIterator<type> &ci )

   339 

   340     Makes this an iterator for the same cache as \a ci. The new

   341     iterator starts at the same item as ci.current(), but moves

   342     independently thereafter.

   343 */

   344 

   345 /*!

   346     \fn uint Q3AsciiCacheIterator::count() const

   347 

   348     Returns the number of items in the cache over which this iterator

   349     operates.

   350 

   351     \sa isEmpty()

   352 */

   353 

   354 /*!

   355     \fn bool Q3AsciiCacheIterator::isEmpty() const

   356 

   357     Returns TRUE if the cache is empty, i.e. count() == 0; otherwise

   358     returns FALSE.

   359     

   360     \sa count()

   361 */

   362 

   363 /*!

   364     \fn bool Q3AsciiCacheIterator::atFirst() const

   365 

   366     Returns TRUE if the iterator points to the first item in the

   367     cache; otherwise returns FALSE. Note that this refers to the

   368     iterator's arbitrary ordering, not to the cache's internal least

   369     recently used list.

   370 

   371     \sa toFirst(), atLast()

   372 */

   373 

   374 /*!

   375     \fn bool Q3AsciiCacheIterator::atLast() const

   376 

   377     Returns TRUE if the iterator points to the last item in the cache;

   378     otherwise returns FALSE. Note that this refers to the iterator's

   379     arbitrary ordering, not to the cache's internal least recently

   380     used list.

   381 

   382     \sa toLast(), atFirst()

   383 */

   384 

   385 /*!

   386     \fn type *Q3AsciiCacheIterator::toFirst()

   387 

   388     Sets the iterator to point to the first item in the cache and

   389     returns a pointer to the item.

   390 

   391     Sets the iterator to 0 and returns 0 if the cache is empty.

   392 

   393     \sa toLast() isEmpty()

   394 */

   395 

   396 /*!

   397     \fn type *Q3AsciiCacheIterator::toLast()

   398 

   399     Sets the iterator to point to the last item in the cache and

   400     returns a pointer to the item.

   401 

   402     Sets the iterator to 0 and returns 0 if the cache is empty.

   403 

   404     \sa toFirst() isEmpty()

   405 */

   406 

   407 /*!

   408     \fn Q3AsciiCacheIterator::operator type *() const

   409 

   410     Cast operator. Returns a pointer to the current iterator item.

   411     Same as current().

   412 */

   413 

   414 /*!

   415     \fn type *Q3AsciiCacheIterator::current() const

   416 

   417     Returns a pointer to the current iterator item.

   418 */

   419 

   420 /*!

   421     \fn const char *Q3AsciiCacheIterator::currentKey() const

   422 

   423     Returns the key for the current iterator item.

   424 */

   425 

   426 /*!

   427     \fn type *Q3AsciiCacheIterator::operator()()

   428 

   429     Makes the succeeding item current and returns the original current

   430     item.

   431 

   432     If the current iterator item was the last item in the cache or if

   433     it was 0, 0 is returned.

   434 */

   435 

   436 /*!

   437     \fn type *Q3AsciiCacheIterator::operator+=( uint jump )

   438 

   439     Returns the item \a jump positions after the current item, or 0

   440     if it is beyond the last item. Makes this the current item.

   441 */

   442 

   443 /*!

   444     \fn type *Q3AsciiCacheIterator::operator-=( uint jump )

   445 

   446     Returns the item \a jump positions before the current item, or 0

   447     if it is before the first item. Makes this the current item.

   448 */

   449 

   450 /*!

   451     \fn type *Q3AsciiCacheIterator::operator++()

   452 

   453     Prefix ++ makes the iterator point to the item just after

   454     current(), and makes that the new current item for the iterator. If

   455     current() was the last item, operator++() returns 0.

   456 */

   457 

   458 /*!

   459     \fn type *Q3AsciiCacheIterator::operator--()

   460 

   461     Prefix -- makes the iterator point to the item just before

   462     current(), and makes that the new current item for the iterator. If

   463     current() was the first item, operator--() returns 0.

   464 */

   465