/*

 * 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 SkCachedData_DEFINED

#define SkCachedData_DEFINED

#include "include/core/SkTypes.h"

#include "include/private/base/SkMutex.h"

#include "include/private/base/SkNoncopyable.h"

#include <cstddef>

class SkDiscardableMemory;

class SkCachedData : ::SkNoncopyable {

public:

    SkCachedData(void* mallocData, size_t size);

    SkCachedData(size_t size, SkDiscardableMemory*);

    virtual ~SkCachedData();

    size_t size() const { return fSize; }

    const void* data() const { return fData; }

    void* writable_data() { return fData; }

    void ref() const { this->internalRef(false); }

    void unref() const { this->internalUnref(false); }

    int testing_only_getRefCnt() const { return fRefCnt; }

    bool testing_only_isLocked() const { return fIsLocked; }

    bool testing_only_isInCache() const { return fInCache; }

    SkDiscardableMemory* diagnostic_only_getDiscardable() const {

        return kDiscardableMemory_StorageType == fStorageType ? fStorage.fDM : nullptr;

    }

protected:

    // called when fData changes. could be nullptr.

    virtual void onDataChange(void* oldData, void* newData) {}

private:

    SkMutex fMutex;     // could use a pool of these...

    enum StorageType {

        kDiscardableMemory_StorageType,

        kMalloc_StorageType

    };

    union {

        SkDiscardableMemory*    fDM;

        void*                   fMalloc;

    } fStorage;

    void*       fData;

    size_t      fSize;

    int         fRefCnt;    // low-bit means we're owned by the cache

    StorageType fStorageType;

    bool        fInCache;

    bool        fIsLocked;

    void internalRef(bool fromCache) const;

    void internalUnref(bool fromCache) const;

    void inMutexRef(bool fromCache);

    bool inMutexUnref(bool fromCache);  // returns true if we should delete "this"

    void inMutexLock();

    void inMutexUnlock();

    // called whenever our fData might change (lock or unlock)

    void setData(void* newData) {

        if (newData != fData) {

            // notify our subclasses of the change

            this->onDataChange(fData, newData);

            fData = newData;

        }

    }

    class AutoMutexWritable;

public:

#ifdef SK_DEBUG

    void validate() const;

#else

    void validate() const {}

#endif

   /*

     *  Attaching a data to to a SkResourceCache (only one at a time) enables the data to be

     *  unlocked when the cache is the only owner, thus freeing it to be purged (assuming the

     *  data is backed by a SkDiscardableMemory).

     *

     *  When attached, it also automatically attempts to "lock" the data when the first client

     *  ref's the data (typically from a find(key, visitor) call).

     *

     *  Thus the data will always be "locked" when a non-cache has a ref on it (whether or not

     *  the lock succeeded to recover the memory -- check data() to see if it is nullptr).

     */

    /*

     *  Call when adding this instance to a SkResourceCache::Rec subclass

     *  (typically in the Rec's constructor).

     */

    void attachToCacheAndRef() const { this->internalRef(true); }

    /*

     *  Call when removing this instance from a SkResourceCache::Rec subclass

     *  (typically in the Rec's destructor).

     */

    void detachFromCacheAndUnref() const { this->internalUnref(true); }

};

#endif