message_callback_data.h

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// Copyright 2010-2021 Google LLC
// 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.

#ifndef OR_TOOLS_MATH_OPT_SOLVERS_MESSAGE_CALLBACK_DATA_H_
#define OR_TOOLS_MATH_OPT_SOLVERS_MESSAGE_CALLBACK_DATA_H_

#include <string>

#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
#include "ortools/math_opt/callback.pb.h"

namespace operations_research {
namespace math_opt {

// Buffer for solvers messages that enforces the contract of
// CallbackDataProto.messages for CALLBACK_EVENT_MESSAGE events.
//
// This contract mandates that each message is a full finished line. As a
// consequence, if the solver calls the callback with a partial last line, this
// one must not be passed immediately in CallbackDataProto.messages but kept
// until the end of the line is reached (or the solve is done).
//
// To implement that this class has two methods:
//
// - Parse() that is to be called for each received message from the solver.
//
// - Flush() that must be called at the end of the solve to generate the data
//   corresponding the last message sent by the solver if it was an unfinished -
//   line.
class MessageCallbackData {
 public:
  MessageCallbackData() = default;

  MessageCallbackData(const MessageCallbackData&) = delete;
  MessageCallbackData& operator=(const MessageCallbackData&) = delete;

  // Parses the input message, returning a message callback data proto with all
  // finished lines. Returns nullopt if the input message did not contained any
  // '\n'.
  //
  // It updates this object with the last unfinished line to use it to complete
  // the next message.
  //
  // Note that CallbackDataProto.runtime field is not set. It must be set by the
  // caller appropriately.
  absl::optional<CallbackDataProto> Parse(absl::string_view message);

  // Returns a message callback data proto with the last unfinished line if it
  // exists.
  //
  // Note that CallbackDataProto.runtime field is not set. It must be set by the
  // caller appropriately.
  absl::optional<CallbackDataProto> Flush();

 private:
  // The last message line not ending with '\n'.
  std::string unfinished_line_;
};

}  // namespace math_opt
}  // namespace operations_research

#endif  // OR_TOOLS_MATH_OPT_SOLVERS_MESSAGE_CALLBACK_DATA_H_