pw_transfer/public/pw_transfer/client.h

// Copyright 2022 The Pigweed Authors
//
// 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
//
//     https://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 <array>

#include "pw_function/function.h"
#include "pw_status/status.h"
#include "pw_stream/stream.h"
#include "pw_transfer/internal/client_context.h"
#include "pw_transfer/internal/config.h"
#include "pw_transfer/transfer.raw_rpc.pb.h"
#include "pw_transfer/transfer_thread.h"

namespace pw::transfer {

class Client {
 public:
  using CompletionFunc = Function<void(Status)>;

  // Initializes a transfer client on a specified RPC client and channel.
  // Transfers are processed on a work queue so as not to block any RPC threads.
  // The work queue does not have to be unique to the transfer client; it can be
  // shared with other modules (including additional transfer clients).
  //
  // As data is processed within the work queue's context, the original RPC
  // messages received by the transfer service are not available. Therefore,
  // the transfer client requires an additional buffer where transfer data can
  // stored during the context switch.
  //
  // The size of this buffer is the largest amount of bytes that can be sent
  // within a single transfer chunk (read or write), excluding any transport
  // layer overhead. Not all of this size is used to send data -- there is
  // additional overhead in the pw_rpc and pw_transfer protocols (typically
  // ~22B/chunk).
  //
  // An optional max_bytes_to_receive argument can be provided to set the
  // default number of data bytes the client will request from the server at a
  // time. If not provided, this defaults to the size of the data buffer. A
  // larger value can make transfers more efficient as it minimizes the
  // back-and-forth between client and server; however, it also increases the
  // impact of packet loss, potentially requiring larger retransmissions to
  // recover.
  Client(rpc::Client& rpc_client,
         uint32_t channel_id,
         TransferThread& transfer_thread,
         size_t max_bytes_to_receive = 0,
         uint32_t extend_window_divisor = cfg::kDefaultExtendWindowDivisor)
      : client_(rpc_client, channel_id),
        transfer_thread_(transfer_thread),
        max_parameters_(max_bytes_to_receive > 0
                            ? max_bytes_to_receive
                            : transfer_thread.max_chunk_size(),
                        transfer_thread.max_chunk_size(),
                        extend_window_divisor),
        has_read_stream_(false),
        has_write_stream_(false) {}

  // Begins a new read transfer for the given resource ID. The data read from
  // the server is written to the provided writer. Returns OK if the transfer is
  // successfully started. When the transfer finishes (successfully or not), the
  // completion callback is invoked with the overall status.
  Status Read(uint32_t resource_id,
              stream::Writer& output,
              CompletionFunc&& on_completion,
              chrono::SystemClock::duration timeout = cfg::kDefaultChunkTimeout,
              ProtocolVersion version = kDefaultProtocolVersion);

  // Begins a new write transfer for the given resource ID. Data from the
  // provided reader is sent to the server. When the transfer finishes
  // (successfully or not), the completion callback is invoked with the overall
  // status.
  Status Write(
      uint32_t resource_id,
      stream::Reader& input,
      CompletionFunc&& on_completion,
      chrono::SystemClock::duration timeout = cfg::kDefaultChunkTimeout,
      ProtocolVersion version = kDefaultProtocolVersion);

  // Terminates an ongoing transfer for the specified resource ID.
  //
  // TODO(frolv): This should not take a resource_id, but a handle to an active
  // transfer session.
  void CancelTransfer(uint32_t resource_id);

  Status set_extend_window_divisor(uint32_t extend_window_divisor) {
    if (extend_window_divisor <= 1) {
      return Status::InvalidArgument();
    }

    max_parameters_.set_extend_window_divisor(extend_window_divisor);
    return OkStatus();
  }

 private:
  // TODO(frolv): This should be switched to default to kLatest once
  // implementation of protocol v2 is complete.
  static constexpr ProtocolVersion kDefaultProtocolVersion =
      ProtocolVersion::kLegacy;

  using Transfer = pw_rpc::raw::Transfer;

  void OnRpcError(Status status, internal::TransferType type);

  Transfer::Client client_;
  TransferThread& transfer_thread_;
  internal::TransferParameters max_parameters_;

  bool has_read_stream_;
  bool has_write_stream_;
};

}  // namespace pw::transfer