SkPixelRef.h

/*
 * Copyright 2008 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkPixelRef_DEFINED
#define SkPixelRef_DEFINED

#include "../private/SkAtomics.h"
#include "../private/SkMutex.h"
#include "../private/SkTDArray.h"
#include "SkBitmap.h"
#include "SkFilterQuality.h"
#include "SkImageInfo.h"
#include "SkPixmap.h"
#include "SkRefCnt.h"
#include "SkSize.h"
#include "SkString.h"
#include "SkYUVSizeInfo.h"

class SkColorTable;
class SkData;
struct SkIRect;

class GrTexture;
class SkDiscardableMemory;

class SK_API SkPixelRef : public SkRefCnt {
public:
    explicit SkPixelRef(const SkImageInfo&);
    virtual ~SkPixelRef();

    const SkImageInfo& info() const {
        return fInfo;
    }

    void* pixels() const { return fRec.fPixels; }

    SkColorTable* colorTable() const { return fRec.fColorTable; }

    size_t rowBytes() const { return fRec.fRowBytes; }

    struct LockRec {
        LockRec() : fPixels(NULL), fColorTable(NULL) {}

        void*           fPixels;
        SkColorTable*   fColorTable;
        size_t          fRowBytes;

        void zero() { sk_bzero(this, sizeof(*this)); }

        bool isZero() const {
            return NULL == fPixels && NULL == fColorTable && 0 == fRowBytes;
        }
    };

    SkDEBUGCODE(bool isLocked() const { return fLockCount > 0; })
    SkDEBUGCODE(int getLockCount() const { return fLockCount; })

    bool lockPixels();

    bool lockPixels(LockRec* rec);

    void unlockPixels();

    bool lockPixelsAreWritable() const;

    uint32_t getGenerationID() const;

#ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK

    uint32_t getStableID() const { return fStableID; }
#endif

    void notifyPixelsChanged();

    void changeAlphaType(SkAlphaType at);

    bool isImmutable() const { return fMutability != kMutable; }

    void setImmutable();

    const char* getURI() const { return fURI.size() ? fURI.c_str() : NULL; }

    void setURI(const char uri[]) {
        fURI.set(uri);
    }

    void setURI(const char uri[], size_t len) {
        fURI.set(uri, len);
    }

    void setURI(const SkString& uri) { fURI = uri; }

    SkData* refEncodedData() {
        return this->onRefEncodedData();
    }

    struct LockRequest {
        SkISize         fSize;
        SkFilterQuality fQuality;
    };

    struct LockResult {
        LockResult() : fPixels(NULL), fCTable(NULL) {}

        void        (*fUnlockProc)(void* ctx);
        void*       fUnlockContext;

        const void* fPixels;
        SkColorTable* fCTable;  // should be NULL unless colortype is kIndex8
        size_t      fRowBytes;
        SkISize     fSize;

        void unlock() {
            if (fUnlockProc) {
                fUnlockProc(fUnlockContext);
                fUnlockProc = NULL; // can't unlock twice!
            }
        }
    };

    bool requestLock(const LockRequest&, LockResult*);

    bool queryYUV8(SkYUVSizeInfo* sizeInfo, SkYUVColorSpace* colorSpace) const {
        return this->onQueryYUV8(sizeInfo, colorSpace);
    }

    bool getYUV8Planes(const SkYUVSizeInfo& sizeInfo, void* planes[3]) {
        return this->onGetYUV8Planes(sizeInfo, planes);
    }

    bool readPixels(SkBitmap* dst, SkColorType colorType, const SkIRect* subset = NULL);

    // Register a listener that may be called the next time our generation ID changes.
    //
    // We'll only call the listener if we're confident that we are the only SkPixelRef with this
    // generation ID.  If our generation ID changes and we decide not to call the listener, we'll
    // never call it: you must add a new listener for each generation ID change.  We also won't call
    // the listener when we're certain no one knows what our generation ID is.
    //
    // This can be used to invalidate caches keyed by SkPixelRef generation ID.
    struct GenIDChangeListener {
        virtual ~GenIDChangeListener() {}
        virtual void onChange() = 0;
    };

    // Takes ownership of listener.
    void addGenIDChangeListener(GenIDChangeListener* listener);

    // Call when this pixelref is part of the key to a resourcecache entry. This allows the cache
    // to know automatically those entries can be purged when this pixelref is changed or deleted.
    void notifyAddedToCache() {
        fAddedToCache.store(true);
    }

    virtual SkDiscardableMemory* diagnostic_only_getDiscardable() const { return NULL; }

    bool isLazyGenerated() const { return this->onIsLazyGenerated(); }

protected:
    virtual bool onNewLockPixels(LockRec*) = 0;

    virtual void onUnlockPixels() = 0;

    virtual bool onLockPixelsAreWritable() const;

    virtual bool onReadPixels(SkBitmap* dst, SkColorType colorType, const SkIRect* subsetOrNull);

    // default impl returns NULL.
    virtual SkData* onRefEncodedData();

    // default impl does nothing.
    virtual void onNotifyPixelsChanged();

    virtual bool onQueryYUV8(SkYUVSizeInfo*, SkYUVColorSpace*) const {
        return false;
    }
    virtual bool onGetYUV8Planes(const SkYUVSizeInfo&, void*[3] /*planes*/) {
        return false;
    }

    virtual size_t getAllocatedSizeInBytes() const;

    virtual bool onRequestLock(const LockRequest&, LockResult*);

    virtual bool onIsLazyGenerated() const { return false; }

    SkBaseMutex* mutex() const { return &fMutex; }

    // only call from constructor. Flags this to always be locked, removing
    // the need to grab the mutex and call onLockPixels/onUnlockPixels.
    // Performance tweak to avoid those calls (esp. in multi-thread use case).
    void setPreLocked(void*, size_t rowBytes, SkColorTable*);

private:
    mutable SkMutex fMutex;

    // mostly const. fInfo.fAlpahType can be changed at runtime.
    const SkImageInfo fInfo;

    // LockRec is only valid if we're in a locked state (isLocked())
    LockRec         fRec;
    int             fLockCount;

    bool lockPixelsInsideMutex();

    // Bottom bit indicates the Gen ID is unique.
    bool genIDIsUnique() const { return SkToBool(fTaggedGenID.load() & 1); }
    mutable SkAtomic<uint32_t> fTaggedGenID;

#ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK
    const uint32_t fStableID;
#endif

    SkTDArray<GenIDChangeListener*> fGenIDChangeListeners;  // pointers are owned

    SkString    fURI;

    // Set true by caches when they cache content that's derived from the current pixels.
    SkAtomic<bool> fAddedToCache;

    enum {
        kMutable,               // PixelRefs begin mutable.
        kTemporarilyImmutable,  // Considered immutable, but can revert to mutable.
        kImmutable,             // Once set to this state, it never leaves.
    } fMutability : 8;          // easily fits inside a byte

    // only ever set in constructor, const after that
    bool fPreLocked;

    void needsNewGenID();
    void callGenIDChangeListeners();

    void setTemporarilyImmutable();
    void restoreMutability();
    friend class SkSurface_Raster;   // For the two methods above.

    bool isPreLocked() const { return fPreLocked; }
    friend class SkImage_Raster;
    friend class SkSpecialImage_Raster;

    // When copying a bitmap to another with the same shape and config, we can safely
    // clone the pixelref generation ID too, which makes them equivalent under caching.
    friend class SkBitmap;  // only for cloneGenID
    void cloneGenID(const SkPixelRef&);

    void setImmutableWithID(uint32_t genID);
    friend class SkImage_Gpu;
    friend class SkImageCacherator;
    friend class SkSpecialImage_Gpu;

    typedef SkRefCnt INHERITED;
};

class SkPixelRefFactory : public SkRefCnt {
public:
    virtual SkPixelRef* create(const SkImageInfo&, size_t rowBytes, SkColorTable*) = 0;
};

#endif