92 lines
2.9 KiB
C++
92 lines
2.9 KiB
C++
#ifndef GCACHE_TOKEN_H
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#define GCACHE_TOKEN_H
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#include <QAtomicInt>
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/* QAtomic int count keep trak of token status:
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>0: locked (possibly multiple times)
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0: data ready in last cache
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-1: not in last cache
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-2: to removed from all caches
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-3: out of caches
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*/
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/** Holds the resources to be cached.
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The Priority template argument can simply be a floating point number
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or something more complex, (frame and error in pixel); the only
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requirement is the existence of a < comparison operator */
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template <typename Priority>
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class Token {
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public:
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///Resource loading status
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/*** - LOCKED: resource in the higher cache and locked
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- READY: resource in the higher cache
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- CACHE: resource in some cache (not the highest)
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- REMOVE: resource in some cache and scheduled for removal
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- OUTSIDE: resource not in the cache system */
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enum Status { LOCKED = 1, READY = 0, CACHE = -1, REMOVE = -2, OUTSIDE = -3 };
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///Do not access these members directly. Will be moved to private shortly.
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///used by various cache threads to sort objects [do not use, should be private]
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Priority priority;
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///set in the main thread [do not use, should be private]
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Priority new_priority;
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///swap space used in updatePriorities [do not use, should be private]
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Priority tmp_priority;
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///reference count of locked items [do not use, should be private]
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QAtomicInt count;
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public:
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Token(): count(OUTSIDE) {}
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///the new priority will be effective only after a call to Controller::updatePriorities()
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void setPriority(const Priority &p) {
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new_priority = p;
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}
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Priority getPriority() {
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return new_priority;
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}
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///return false if resource not in highest query. remember to unlock when done
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bool lock() {
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if(count.fetchAndAddAcquire(1) >= 0) return true;
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count.deref();
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return false;
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}
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///assumes it was locked first and 1 unlock for each lock.
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bool unlock() {
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return count.deref();
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}
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///can't be removed if locked and will return false
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bool remove() {
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count.testAndSetOrdered(READY, REMOVE);
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count.testAndSetOrdered(CACHE, REMOVE);
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return count <= REMOVE; //might have become OUSIDE in the meanwhile
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}
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bool isLocked() { return count > 0; }
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bool isInCache() { return count != OUTSIDE; } //careful, can be used only when provider thread is locked.
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///copy priority to swap space [do not use, should be private]
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void pushPriority() {
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tmp_priority = new_priority;
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}
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///copy priority from swap space [do not use, should be private]
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void pullPriority() {
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priority = tmp_priority;
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}
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bool operator<(const Token &a) const {
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if(count == a.count)
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return priority < a.priority;
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return count < a.count;
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}
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bool operator>(const Token &a) const {
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if(count == a.count)
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return priority > a.priority;
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return count > a.count;
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}
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};
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#endif // GCACHE_H
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