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// Copyright (C) 2016 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#pragma once
#include "base/EnumFlags.h"
#include "base/BufferQueue.h"
#include "base/SmallVector.h"
#include "base/Stream.h"
#include <functional>
#include <memory>
namespace emugl {
// Turn the RenderChannel::State enum into flags.
using namespace ::android::base::EnumFlags;
// RenderChannel - For each guest-to-host renderer connection, this provides
// an interface for the guest side to interact with the corresponding renderer
// thread on the host. Its main purpose is to send and receive wire protocol
// bytes in an asynchronous way (compatible with Android pipes).
//
// Usage is the following:
// 1) Get an instance pointer through a dedicated Renderer function
// (e.g. RendererImpl::createRenderChannel()).
//
// 2) Call setEventCallback() to indicate which callback should be called
// when the channel's state has changed due to a host thread event.
//
class RenderChannel {
public:
// A type used to pass byte packets between the guest and the
// RenderChannel instance. Experience has shown that using a
// SmallFixedVector<char, N> instance instead of a std::vector<char>
// avoids a lot of un-necessary heap allocations. The current size
// of 512 was selected after profiling existing traffic, including
// the one used in protocol-heavy benchmark like Antutu3D.
using Buffer = android::base::SmallFixedVector<char, 512>;
// Bit-flags for the channel state.
// |CanRead| means there is data from the host to read.
// |CanWrite| means there is room to send data to the host.
// |Stopped| means the channel was stopped.
enum class State {
// Can't use None here, some system header declares it as a macro.
Empty = 0,
CanRead = 1 << 0,
CanWrite = 1 << 1,
Stopped = 1 << 2,
};
using IoResult = android::base::BufferQueueResult;
using Duration = uint64_t;
// Type of a callback used to tell the guest when the RenderChannel
// state changes. Used by setEventCallback(). The parameter contains
// the State bits matching the event, i.e. it is the logical AND of
// the last value passed to setWantedEvents() and the current
// RenderChannel state.
using EventCallback = std::function<void(State)>;
// Sets a single (!) callback that is called when the channel state's
// changes due to an event *from* *the* *host* only. |callback| is a
// guest-provided callback that will be called from the host renderer
// thread, not the guest one.
virtual void setEventCallback(EventCallback&& callback) = 0;
// Used to indicate which i/o events the guest wants to be notified
// through its StateChangeCallback. |state| must be a combination of
// State::CanRead or State::CanWrite only. This will *not* call the
// callback directly since this happens in the guest thread.
virtual void setWantedEvents(State state) = 0;
// Get the current state flags.
virtual State state() const = 0;
// Try to writes the data in |buffer| into the channel. On success,
// return IoResult::Ok and moves |buffer|. On failure, return
// IoResult::TryAgain if the channel was full, or IoResult::Error
// if it is stopped.
virtual IoResult tryWrite(Buffer&& buffer) = 0;
// Try to read data from the channel. On success, return IoResult::Ok and
// sets |*buffer| to contain the data. On failure, return
// IoResult::TryAgain if the channel was empty, or IoResult::Error if
// it was stopped.
virtual IoResult tryRead(Buffer* buffer) = 0;
// Try to read data from the channel. On success, return IoResult::Ok and
// sets |*buffer| to contain the data. On failure, return IoResult::Error
// if it was stopped. Returns IoResult::Timeout if we waited passed
// waitUntilUs.
virtual IoResult readBefore(Buffer* buffer, Duration waitUntilUs) = 0;
// Abort all pending operations. Any following operation is a noop.
// Once a channel is stopped, it cannot be re-started.
virtual void stop() = 0;
// Callback function when snapshotting the virtual machine.
virtual void onSave(android::base::Stream* stream) = 0;
protected:
~RenderChannel() = default;
};
// Shared pointer to RenderChannel instance.
using RenderChannelPtr = std::shared_ptr<RenderChannel>;
} // namespace emugl
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