public:

typedef std::vector<Tensor> Tuple;

typedef AsyncOpKernel::DoneCallback DoneCallback;

typedef std::function<void(const Tuple&)> CallbackWithTuple;

virtual Status ValidateTuple(const Tuple& tuple) = 0;

virtual Status ValidateManyTuple(const Tuple& tuple) = 0;

// Stashes a function object for future execution, that will eventually

// enqueue the tuple of tensors into the queue, and returns immediately. The

// function object is guaranteed to call 'callback'.

virtual void TryEnqueue(const Tuple& tuple, OpKernelContext* ctx,

DoneCallback callback) = 0;

// Same as above, but the component tensors are sliced along the 0th dimension

// to make multiple queue-element components.

virtual void TryEnqueueMany(const Tuple& tuple, OpKernelContext* ctx,

DoneCallback callback) = 0;

// Stashes a function object for future execution, that will eventually

// dequeue an element from the queue and call 'callback' with that tuple

// element as argument.

virtual void TryDequeue(OpKernelContext* ctx, CallbackWithTuple callback) = 0;

// Same as above, but the stashed function object will attempt to dequeue

// num_elements items.

virtual void TryDequeueMany(int num_elements, OpKernelContext* ctx,

CallbackWithTuple callback) = 0;

// Signals that no more elements will be enqueued, and optionally

// cancels pending Enqueue(Many) operations.

//

// After calling this function, subsequent calls to Enqueue(Many)

// will fail. If `cancel_pending_enqueues` is true, all pending

// calls to Enqueue(Many) will fail as well.

//

// After calling this function, all current and subsequent calls to

// Dequeue(Many) will fail instead of blocking (though they may

// succeed if they can be satisfied by the elements in the queue at

// the time it was closed).

virtual void Close(OpKernelContext* ctx, bool cancel_pending_enqueues,

DoneCallback callback) = 0;

// Assuming *this represents a shared queue, verify that it matches

// another instantiation indicated by node_def.

virtual Status MatchesNodeDef(const NodeDef& node_def) = 0;

// Returns the number of elements in the queue.

virtual int32 size() = 0;

virtual const DataTypeVector& component_dtypes() const = 0;

string DebugString() override { return "A queue"; }

protected:

virtual ~QueueInterface() {}