108 lines
2.4 KiB
C
108 lines
2.4 KiB
C
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/**
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\file G3D/WeakCache.h
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\maintainer Morgan McGuire, graphics3d.com
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\created 2007-05-16
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\edited 2012-01-02
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Copyright 2000-2012, Morgan McGuire.
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All rights reserved.
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*/
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#ifndef G3D_WeakCache_h
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#define G3D_WeakCache_h
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#include "G3D/ReferenceCount.h"
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#include "G3D/Table.h"
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namespace G3D {
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/**
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A cache that does not prevent its members from being garbage collected.
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Useful to avoid loading or computing an expression twice. Useful
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for memoization and dynamic programming.
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Maintains a table of weak pointers. Weak pointers do not prevent
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an object from being garbage collected. If the object is garbage
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collected, the cache removes its reference.
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There are no "contains" or "iterate" methods because elements can be
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flushed from the cache at any time if they are garbage collected.
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Example:
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<pre>
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WeakCache<std::string, shared_ptr<Texture>> textureCache;
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shared_ptr<Texture> loadTexture(std::string s) {
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shared_ptr<Texture> t = textureCache[s];
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if (t.isNull()) {
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t = Texture::fromFile(s);
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textureCache.set(s, t);
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}
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return t;
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}
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</pre>
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*/
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template<class Key, class ValueRef>
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class WeakCache {
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typedef weak_ptr<typename ValueRef::element_type> ValueWeakRef;
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private:
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Table<Key, ValueWeakRef> table;
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public:
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/**
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Returns NULL if the object is not in the cache
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*/
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ValueRef operator[](const Key& k) {
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if (table.containsKey(k)) {
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ValueWeakRef w = table[k];
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ValueRef s = w.lock();
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if (! s) {
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// This object has been collected; clean out its key
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table.remove(k);
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}
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return s;
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} else {
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return ValueRef();
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}
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}
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void getValues(Array<ValueRef>& values) {
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Array<Key> keys;
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table.getKeys(keys);
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for (int i = 0; i < keys.size(); ++i) {
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ValueRef value = (*this)[keys[i]];
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if(notNull(value)) {
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values.append(value);
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}
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}
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}
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void clear() {
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table.clear();
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}
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void set(const Key& k, ValueRef v) {
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table.set(k, v);
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}
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/** Removes k from the cache or does nothing if it is not currently in the cache.*/
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void remove(const Key& k) {
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if (table.containsKey(k)) {
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table.remove(k);
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}
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}
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};
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}
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#endif
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