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 SkNoncopyable {
public:
    SK_DECLARE_INST_COUNT_ROOT(GrCacheable)

    // These method signatures are written to mirror SkRefCnt. However, we don't require
    // thread safety as GrCacheable objects are not intended to cross thread boundaries.
    // internal_dispose() exists because of GrTexture's reliance on it. It will be removed
    // soon.
    void ref() const { ++fRefCnt; }
    void unref() const { --fRefCnt; if (0 == fRefCnt) { this->internal_dispose(); } }
    virtual void internal_dispose() const { SkDELETE(this); }
    bool unique() const { return 1 == fRefCnt; }
#ifdef SK_DEBUG
    void validate() const {
        SkASSERT(fRefCnt > 0);
    }
#endif

    virtual ~GrCacheable() { SkASSERT(0 == fRefCnt); }

    /**
     * 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 getUniqueID() const { return fUniqueID; }

protected:
    GrCacheable()
        : fRefCnt(1)
        , fCacheEntry(NULL)
        , fUniqueID(CreateUniqueID()) {}

    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:
    static uint32_t CreateUniqueID();

    mutable int32_t         fRefCnt;
    GrResourceCacheEntry*   fCacheEntry;  // NULL if not in cache
    const uint32_t          fUniqueID;

    typedef SkNoncopyable INHERITED;
};

#endif