skia2/include/gpu/GrCacheable.h

/*
 * Copyright 2014 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef GrCacheable_DEFINED
#define GrCacheable_DEFINED

#include "SkRefCnt.h"

class GrResourceCacheEntry;

/**
 * Base class for objects that can be kept in the GrResourceCache.
 */
class GrCacheable : public SkRefCnt {
public:
    SK_DECLARE_INST_COUNT(GrCacheable)

    /**
     * Retrieves the amount of GPU memory used by this resource in bytes. It is
     * approximate since we aren't aware of additional padding or copies made
     * by the driver.
     *
     * @return the amount of GPU memory used in bytes
     */
    virtual size_t gpuMemorySize() const = 0;

    /**
     * Checks whether the GPU memory allocated to this resource is still in effect.
     * It can become invalid if its context is destroyed or lost, in which case it
     * should no longer count against the GrResourceCache budget.
     *
     * @return true if this resource is still holding GPU memory
     *         false otherwise.
     */
    virtual bool isValidOnGpu() const = 0;

    void setCacheEntry(GrResourceCacheEntry* cacheEntry) { fCacheEntry = cacheEntry; }
    GrResourceCacheEntry* getCacheEntry() { return fCacheEntry; }

    /**
     * Gets an id that is unique for this GrCacheable object. It is static in that it does
     * not change when the content of the GrCacheable object changes. This will never return
     * 0.
     */
    uint32_t getGenerationID() const;

protected:
    GrCacheable()
        : fCacheEntry(NULL)
        , fGenID(0) {}

    bool isInCache() const { return NULL != fCacheEntry; }

    /**
     * This entry point should be called whenever gpuMemorySize() begins
     * reporting a different size. If the object is in the cache, it will call
     * gpuMemorySize() immediately and pass the new size on to the resource
     * cache.
     */
    void didChangeGpuMemorySize() const;

private:
    GrResourceCacheEntry*   fCacheEntry;  // NULL if not in cache
    mutable uint32_t        fGenID;

    typedef SkRefCnt INHERITED;
};

#endif