G3D::WeakCache< Key, ValueRef > Class Template Reference

#include <WeakCache.h>

Public Member Functions
ValueRef	operator[] (const Key &k)
void	getValues (Array< ValueRef > &values)
void	clear ()
void	set (const Key &k, ValueRef v)
void	remove (const Key &k)

Private Types
typedef weak_ptr< typename ValueRef::element_type >	ValueWeakRef

Private Attributes
Table< Key, ValueWeakRef >	table

Detailed Description

template<class Key, class ValueRef>
class G3D::WeakCache< Key, ValueRef >

A cache that does not prevent its members from being garbage collected. Useful to avoid loading or computing an expression twice. Useful for memoization and dynamic programming.

Maintains a table of weak pointers. Weak pointers do not prevent an object from being garbage collected. If the object is garbage collected, the cache removes its reference.

There are no "contains" or "iterate" methods because elements can be flushed from the cache at any time if they are garbage collected.

Example:

   WeakCache<std::string, shared_ptr<Texture>> textureCache;

   shared_ptr<Texture> loadTexture(std::string s) {
       shared_ptr<Texture> t = textureCache[s];

       if (t.isNull()) {
           t = Texture::fromFile(s);
           textureCache.set(s, t);
       }

       return t;
   }

Member Typedef Documentation

template<class Key , class ValueRef >

typedef weak_ptr<typename ValueRef::element_type> G3D::WeakCache< Key, ValueRef >::ValueWeakRef

private

Member Function Documentation

template<class Key , class ValueRef >

void G3D::WeakCache< Key, ValueRef >::clear ( )

inline

 {
 table.clear();
 }

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template<class Key , class ValueRef >

void G3D::WeakCache< Key, ValueRef >::getValues ( Array< ValueRef > &  values )

inline

 {
 Array<Key> keys;
 table.getKeys(keys);
 for (int i = 0; i < keys.size(); ++i) {
 ValueRef value = (*this)[keys[i]];
 if(notNull(value)) {
 values.append(value);
 }
 }
 }

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template<class Key , class ValueRef >

ValueRef G3D::WeakCache< Key, ValueRef >::operator[] ( const Key &  k )

inline

Returns NULL if the object is not in the cache

 {
 if (table.containsKey(k)) {
 ValueWeakRef w = table[k];
 ValueRef s = w.lock();
 if (! s) {
 // This object has been collected; clean out its key
 table.remove(k);
 }
 return s;
 } else {
 return ValueRef();
 }
 }

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template<class Key , class ValueRef >

void G3D::WeakCache< Key, ValueRef >::remove ( const Key &  k )

inline

Removes k from the cache or does nothing if it is not currently in the cache.

 {
 if (table.containsKey(k)) {
 table.remove(k);
 }
 }

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template<class Key , class ValueRef >

void G3D::WeakCache< Key, ValueRef >::set ( const Key &  k, ValueRef  v  )

inline

 {
 table.set(k, v);
 }

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Member Data Documentation

template<class Key , class ValueRef >

Table<Key, ValueWeakRef> G3D::WeakCache< Key, ValueRef >::table

private

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The documentation for this class was generated from the following file:

• dep/g3dlite/include/G3D/WeakCache.h