cmdline/cmdline_result.h

/*
 * Copyright (C) 2015 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.
 */

#ifndef ART_CMDLINE_CMDLINE_RESULT_H_
#define ART_CMDLINE_CMDLINE_RESULT_H_

#include <assert.h>
#include <utils.h>

namespace art {
  // Result of an attempt to process the command line arguments. If fails, specifies
  // the specific error code and an error message.
  // Use the value-carrying CmdlineParseResult<T> to get an additional value out in a success case.
  struct CmdlineResult {
    enum Status {
      kSuccess,
      // Error codes:
      kUsage,
      kFailure,
      kOutOfRange,
      kUnknown,
    };

    // Short-hand for checking if the result was successful.
    operator bool() const {
      return IsSuccess();
    }

    // Check if the operation has succeeded.
    bool IsSuccess() const { return status_ == kSuccess; }
    // Check if the operation was not a success.
    bool IsError() const { return status_ != kSuccess; }
    // Get the specific status, regardless of whether it's failure or success.
    Status GetStatus() const { return status_; }

    // Get the error message, *must* only be called for error status results.
    const std::string& GetMessage() const { assert(IsError()); return message_; }

    // Constructor any status. No message.
    explicit CmdlineResult(Status status) : status_(status) {}

    // Constructor with an error status, copying the message.
    CmdlineResult(Status status, const std::string& message)
      : status_(status), message_(message) {
      assert(status != kSuccess);
    }

    // Constructor with an error status, taking over the message.
    CmdlineResult(Status status, std::string&& message)
      : status_(status), message_(message) {
      assert(status != kSuccess);
    }

    // Make sure copying exists
    CmdlineResult(const CmdlineResult&) = default;
    // Make sure moving is cheap
    CmdlineResult(CmdlineResult&&) = default;

  private:
    const Status status_;
    const std::string message_;
  };

  // TODO: code-generate this
  static inline std::ostream& operator<<(std::ostream& stream, CmdlineResult::Status status) {
    switch (status) {
      case CmdlineResult::kSuccess:
        stream << "kSuccess";
        break;
      case CmdlineResult::kUsage:
        stream << "kUsage";
        break;
      case CmdlineResult::kFailure:
        stream << "kFailure";
        break;
      case CmdlineResult::kOutOfRange:
        stream << "kOutOfRange";
        break;
      case CmdlineResult::kUnknown:
        stream << "kUnknown";
        break;
      default:
        UNREACHABLE();
    }
    return stream;
  }

}  // namespace art

#endif  // ART_CMDLINE_CMDLINE_RESULT_H_