shaka-packager/media/base/status.h

// Copyright (c) 2013 Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_BASE_STATUS_H_
#define MEDIA_BASE_STATUS_H_

#include <string>

#include "base/logging.h"

namespace media {

namespace error {

// Error codes for the packager APIs.
enum Code {
  // Not an error; returned on success
  OK,

  // Unknown error.  An example of where this error may be returned is
  // errors raised by APIs that do not return enough error information
  // may be converted to this error.
  UNKNOWN,

  // The operation was cancelled (typically by the caller).
  CANCELLED,

  // Client specified an invalid argument. INVALID_ARGUMENT indicates
  // arguments that are problematic regardless of the state of the system
  // (e.g. a malformed file name).
  INVALID_ARGUMENT,

  // Operation is not implemented or not supported/enabled.
  UNIMPLEMENTED,

  // Cannot open file.
  FILE_FAILURE,

  // End of file.
  EOF,

  // Unable to parse the media file.
  PARSER_FAILURE,

  // TODO(kqyang): define packager specific error codes.
};

}  // namespace error

class Status {
 public:
  // Creates a "successful" status.
  Status() : error_code_(error::OK) {}

  // Create a status with the specified code, and error message. If "code == 0",
  // error_message is ignored and a Status object identical to Status::OK is
  // constructed.
  Status(error::Code error_code, const std::string& error_message) :
    error_code_(error_code) {
    if (!ok())
      error_message_ = error_message;
  }

  //Status(const Status&);
  //Status& operator=(const Status& x);
  ~Status() {}

  // Some pre-defined Status objects.
  static const Status& OK;             // Identical to 0-arg constructor.
  static const Status& UNKNOWN;

  // Store the specified error in this Status object.
  // If "error_code == error::OK", error_message is ignored and a Status object
  // identical to Status::OK is constructed.
  void SetError(error::Code error_code, const std::string& error_message) {
    if (error_code == error::OK) {
      Clear();
    } else {
      error_code_ = error_code;
      error_message_ = error_message;
    }
  }

  // If "ok()", stores "new_status" into *this.  If "!ok()", preserves
  // the current "error_code()/error_message()",
  //
  // Convenient way of keeping track of the first error encountered.
  // Instead of:
  //   if (overall_status.ok()) overall_status = new_status
  // Use:
  //   overall_status.Update(new_status);
  void Update(const Status& new_status) {
    if (ok())
      *this = new_status;
  }

  // Clear this status object to contain the OK code and no error message.
  void Clear() {
    error_code_ = error::OK;
    error_message_ = "";
  }

  // Accessor.
  bool ok() const {
    return error_code_ == error::OK;
  }
  error::Code error_code() const {
    return error_code_;
  }
  const std::string& error_message() const {
    return error_message_;
  }

  bool operator==(const Status& x) const {
    return error_code_ == x.error_code() && error_message_ == x.error_message();
  }
  bool operator!=(const Status& x) const {
    return !(*this == x);
  }

  // Returns true iff this has the same error_code as "x".  I.e., the two
  // Status objects are identical except possibly for the error message.
  bool Matches(const Status& x) const {
    return error_code_ == x.error_code();
  }

  // Return a combination of the error code name and message.
  std::string ToString() const;

  void Swap(Status* other) {
    error::Code error_code = error_code_;
    error_code_ = other->error_code_;
    other->error_code_ = error_code;
    error_message_.swap(other->error_message_);
  }

 private:
  error::Code error_code_;
  std::string error_message_;

  // Not using DISALLOW_COPY_AND_ASSIGN here intentionally to allow the compiler
  // generated copy constructor and assignment operator.
};

extern std::ostream& operator<<(std::ostream& os, const Status& x);

// Status success comparison.
// This is better than CHECK((val).ok()) because the embedded
// error string gets printed by the CHECK_EQ.
#define CHECK_OK(val) CHECK_EQ(Status::OK, (val))
#define DCHECK_OK(val) DCHECK_EQ(Status::OK, (val))

}  // namespace media

#endif  // MEDIA_BASE_STATUS_H_