BINDER

最新推荐文章于 2022-12-20 12:44:44 发布

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class IInterface : public virtual RefBase
{
public:
            IInterface();
            sp<IBinder>         asBinder();
            sp<const IBinder>   asBinder() const;
            
protected:
    virtual                     ~IInterface();
    virtual IBinder*            onAsBinder() = 0;
};

// ----------------------------------------------------------------------

template<typename INTERFACE>
inline sp<INTERFACE> interface_cast(const sp<IBinder>& obj)
{
    return INTERFACE::asInterface(obj);
}

// ----------------------------------------------------------------------

template<typename INTERFACE>
class BnInterface : public INTERFACE, public BBinder
{
public:
    virtual sp<IInterface>      queryLocalInterface(const String16& _descriptor);
    virtual const String16&     getInterfaceDescriptor() const;

protected:
    virtual IBinder*            onAsBinder();
};

// ----------------------------------------------------------------------

template<typename INTERFACE>
class BpInterface : public INTERFACE, public BpRefBase
{
public:
                                BpInterface(const sp<IBinder>& remote);

protected:
    virtual IBinder*            onAsBinder();
};

// ----------------------------------------------------------------------

#define DECLARE_META_INTERFACE(INTERFACE)                               \
    static const android::String16 descriptor;                          \
    static android::sp<I##INTERFACE> asInterface(                       \
            const android::sp<android::IBinder>& obj);                  \
    virtual const android::String16& getInterfaceDescriptor() const;    \
    I##INTERFACE();                                                     \
    virtual ~I##INTERFACE();                                            \


#define IMPLEMENT_META_INTERFACE(INTERFACE, NAME)                       \
    const android::String16 I##INTERFACE::descriptor(NAME);             \
    const android::String16&                                            \
            I##INTERFACE::getInterfaceDescriptor() const {              \
        return I##INTERFACE::descriptor;                                \
    }                                                                   \
    android::sp<I##INTERFACE> I##INTERFACE::asInterface(                \
            const android::sp<android::IBinder>& obj)                   \
    {                                                                   \
        android::sp<I##INTERFACE> intr;                                 \
        if (obj != NULL) {                                              \
            intr = static_cast<I##INTERFACE*>(                          \
                obj->queryLocalInterface(                               \
                        I##INTERFACE::descriptor).get());               \
            if (intr == NULL) {                                         \
                intr = new Bp##INTERFACE(obj);                          \
            }                                                           \
        }                                                               \
        return intr;                                                    \
    }                                                                   \
    I##INTERFACE::I##INTERFACE() { }                                    \
    I##INTERFACE::~I##INTERFACE() { }                                   \


#define CHECK_INTERFACE(interface, data, reply)                         \
    if (!data.checkInterface(this)) { return PERMISSION_DENIED; }       \


// ----------------------------------------------------------------------
// No user-serviceable parts after this...

template<typename INTERFACE>
inline sp<IInterface> BnInterface<INTERFACE>::queryLocalInterface(
        const String16& _descriptor)
{
    if (_descriptor == INTERFACE::descriptor) return this;
    return NULL;
}

template<typename INTERFACE>
inline const String16& BnInterface<INTERFACE>::getInterfaceDescriptor() const
{
    return INTERFACE::getInterfaceDescriptor();
}

template<typename INTERFACE>
IBinder* BnInterface<INTERFACE>::onAsBinder()
{
    return this;
}

template<typename INTERFACE>
inline BpInterface<INTERFACE>::BpInterface(const sp<IBinder>& remote)
    : BpRefBase(remote)
{
}

template<typename INTERFACE>
inline IBinder* BpInterface<INTERFACE>::onAsBinder()
{
    return remote();
}
    
// ----------------------------------------------------------------------

}; // namespace android

void BBinder::attachObject(
    const void* objectID, void* object, void* cleanupCookie,
    object_cleanup_func func)
{
    Extras* e = mExtras;

    if (!e) {
        e = new Extras;
        if (android_atomic_cmpxchg(0, reinterpret_cast<int32_t>(e),
                reinterpret_cast<volatile int32_t="">(&mExtras)) != 0) {
            delete e;
            e = mExtras;
        }
        if (e == 0) return; // out of memory
    }

    AutoMutex _l(e->mLock);
    e->mObjects.attach(objectID, object, cleanupCookie, func);
}
</volatile></int32_t>

//IBinder 虚基类实现了以下两个函数
class IBinder : public virtual RefBase
{
public:
    enum {
        FIRST_CALL_TRANSACTION  = 0x00000001,
        LAST_CALL_TRANSACTION   = 0x00ffffff,

        PING_TRANSACTION        = B_PACK_CHARS('_','P','N','G'),
        DUMP_TRANSACTION        = B_PACK_CHARS('_','D','M','P'),
        INTERFACE_TRANSACTION   = B_PACK_CHARS('_', 'N', 'T', 'F'),

        // Corresponds to TF_ONE_WAY -- an asynchronous call.
        FLAG_ONEWAY             = 0x00000001
    };

                          IBinder();

    /**
     * Check if this IBinder implements the interface named by
     * @a descriptor.  If it does, the base pointer to it is returned,
     * which you can safely static_cast<> to the concrete C++ interface.
     */
    virtual sp<iinterface>  queryLocalInterface(const String16& descriptor);

    /**
     * Return the canonical name of the interface provided by this IBinder
     * object.
     */
    virtual const String16& getInterfaceDescriptor() const = 0;

    virtual bool            isBinderAlive() const = 0;
    virtual status_t        pingBinder() = 0;
    virtual status_t        dump(int fd, const Vector<string16>& args) = 0;

    virtual status_t        transact(   uint32_t code,
                                        const Parcel& data,
                                        Parcel* reply,
                                        uint32_t flags = 0) = 0;

    /**
     * This method allows you to add data that is transported through
     * IPC along with your IBinder pointer.  When implementing a Binder
     * object, override it to write your desired data in to @a outData.
     * You can then call getConstantData() on your IBinder to retrieve
     * that data, from any process.  You MUST return the number of bytes
     * written in to the parcel (including padding).
     */
    class DeathRecipient : public virtual RefBase
    {
    public:
        virtual void binderDied(const wp<ibinder>& who) = 0;
    };

    /**
     * Register the @a recipient for a notification if this binder
     * goes away.  If this binder object unexpectedly goes away
     * (typically because its hosting process has been killed),
     * then DeathRecipient::binderDied() will be called with a referene
     * to this.
     *
     * The @a cookie is optional -- if non-NULL, it should be a
     * memory address that you own (that is, you know it is unique).
     *
     * @note You will only receive death notifications for remote binders,
     * as local binders by definition can't die without you dying as well.
     * Trying to use this function on a local binder will result in an
     * INVALID_OPERATION code being returned and nothing happening.
     *
     * @note This link always holds a weak reference to its recipient.
     *
     * @note You will only receive a weak reference to the dead
     * binder.  You should not try to promote this to a strong reference.
     * (Nor should you need to, as there is nothing useful you can
     * directly do with it now that it has passed on.)
     */
    virtual status_t        linkToDeath(const sp<deathrecipient>& recipient,
                                        void* cookie = NULL,
                                        uint32_t flags = 0) = 0;

    /**
     * Remove a previously registered death notification.
     * The @a recipient will no longer be called if this object
     * dies.  The @a cookie is optional.  If non-NULL, you can
     * supply a NULL @a recipient, and the recipient previously
     * added with that cookie will be unlinked.
     */
    virtual status_t        unlinkToDeath(  const wp<deathrecipient>& recipient,
                                            void* cookie = NULL,
                                            uint32_t flags = 0,
                                            wp<deathrecipient>* outRecipient = NULL) = 0;

    virtual bool            checkSubclass(const void* subclassID) const;

    typedef void (*object_cleanup_func)(const void* id, void* obj, void* cleanupCookie);

    virtual void            attachObject(   const void* objectID,
                                            void* object,
                                            void* cleanupCookie,
                                            object_cleanup_func func) = 0;
    virtual void*           findObject(const void* objectID) const = 0;
    virtual void            detachObject(const void* objectID) = 0;

    virtual BBinder*        localBinder();
    virtual BpBinder*       remoteBinder();

protected:
    virtual          ~IBinder();

private:
};

//但是这两个函数都在子类BBinder BpBinder中重写
BBinder* IBinder::localBinder()
{
    return NULL;
}

BpBinder* IBinder::remoteBinder()
{
    return NULL;
}


//BBinder重写了localBinder()
BBinder* BBinder::localBinder()
{
    return this;
}

//BpBinder重写了remoteBinder()
BpBinder* BpBinder::remoteBinder()
{
    return this;
}

</deathrecipient></deathrecipient></deathrecipient></ibinder></string16></iinterface>

//DECLARE_META_INTERFACE(AudioTrack)展开为 
    static const android::String16 descriptor; 
    static android::sp<iAudioTrack> asInterface(const android::sp<android::iBinder>& obj);
    virtual const android::String16& getInterfaceDescriptor() const;
    IAudioTrack();
    virtual ~IAudioTrack();


//IMPLEMENT_META_INTERFACE(AudioTrack, "android.media.IAudioTrack")展开为
    const android::String16  IAudioTrack::descriptor("android.media.IAudioTrack");
    const android::String16& IAudioTrack::getInterfaceDescriptor() const {
        return IAudioTrack::descriptor;
    }
    android::sp<IAudioTrack> IAudioTrack::asInterface(const android::sp<IAudioTrack>& obj)
    {
        android::sp<IAudioTrack> intr;
        if (obj != NULL) {
            intr = static_cast<IAudiotrack>(obj->queryLocalInterface(IAudioTrack::descriptor).get());
            if (intr == NULL) {
                intr = new BpAudioTrack(obj);
            }
        }
        return intr;
    }
    IAudioTrack::IAudioTrack() { }
    IAudioTrack::~IAudioTrack() { }

//interface_case<AudioTrack>的展开
template<typename INTERFACE>
inline sp<INTERFACE> interface_cast(const sp<IBinder>& obj)
{
    return INTERFACE::asInterface(obj);
}
//展开后变成:
template<typename IAudioTrack>
inline sp<IAudioTrack> interface_cast(const sp<IBinder>& obj)
{
    return IAudioTrack::asInterface(obj);
}

BpAudioFlinger{
    //...
    virtual sp<IAudioTrack> createTrack(
                                pid_t pid,
                                int streamType,
                                uint32_t sampleRate,
                                int format,
                                int channelCount,
                                int frameCount,
                                uint32_t flags,
                                const sp<imemory>& sharedBuffer,
                                int output,
                                int *sessionId,
                                status_t *status)
    {
        Parcel data, reply;
        sp<IAudioTrack> track;
        data.writeInterfaceToken(IAudioFlinger::getInterfaceDescriptor());
        data.writeInt32(pid);
        data.writeInt32(streamType);
        data.writeInt32(sampleRate);
        data.writeInt32(format);
        data.writeInt32(channelCount);
        data.writeInt32(frameCount);
        data.writeInt32(flags);
        data.writeStrongBinder(sharedBuffer->asBinder());
        data.writeInt32(output);
        int lSessionId = 0;
        if (sessionId != NULL) {
            lSessionId = *sessionId;
        }
        data.writeInt32(lSessionId);
        //这里的remote是BpAudioFlinger的成员函数.
        status_t lStatus = remote()->transact(CREATE_TRACK, data, &reply);
        if (lStatus != NO_ERROR) {
            LOGE("createTrack error: %s", strerror(-lStatus));
        } else {
            lSessionId = reply.readInt32();
            if (sessionId != NULL) {
                *sessionId = lSessionId;
            }
            lStatus = reply.readInt32();
            track = interface_cast<IAudioTrack>(reply.readStrongBinder());//这里创建BpAudioTrack(reply.readStrongBinder())
        }
        if (status) {
            *status = lStatus;
        }
        return track;
    }
    //...
}
</imemory>