deskflow/src/lib/base/XBase.h

/*
 * Deskflow -- mouse and keyboard sharing utility
 * SPDX-FileCopyrightText: (C) 2012 - 2016 Symless Ltd.
 * SPDX-FileCopyrightText: (C) 2002 Chris Schoeneman
 * SPDX-License-Identifier: GPL-2.0-only WITH LicenseRef-OpenSSL-Exception
 */

#pragma once

#include <stdexcept>
#include <string>

//! Exception base class
/*!
This is the base class of most exception types.
*/
class XBase : public std::runtime_error
{
public:
  //! Use getWhat() as the result of what()
  XBase();
  //! Use \c msg as the result of what()
  XBase(const std::string &msg);
  ~XBase() throw() override = default;

  //! Reason for exception
  const char *what() const throw() override;

protected:
  //! Get a human readable string describing the exception
  virtual std::string getWhat() const throw()
  {
    return "";
  }

  //! Format a string
  /*!
  Looks up a message format using \c id, using \c defaultFormat if
  no format can be found, then replaces positional parameters in
  the format string and returns the result.
  */
  virtual std::string format(const char *id, const char *defaultFormat, ...) const throw();

private:
  mutable std::string m_what;
};

/*!
\def XBASE_SUBCLASS
Convenience macro to subclass from XBase (or a subclass of it),
providing the c'tor taking a const std::string&.  getWhat() is not
declared.
*/
#define XBASE_SUBCLASS(name_, super_)                                                                                  \
  class name_ : public super_                                                                                          \
  {                                                                                                                    \
  public:                                                                                                              \
    name_() : super_()                                                                                                 \
    {                                                                                                                  \
    }                                                                                                                  \
    name_(const std::string &msg) : super_(msg)                                                                        \
    {                                                                                                                  \
    }                                                                                                                  \
    virtual ~name_() throw()                                                                                           \
    {                                                                                                                  \
    }                                                                                                                  \
  }

/*!
\def XBASE_SUBCLASS
Convenience macro to subclass from XBase (or a subclass of it),
providing the c'tor taking a const std::string&.  getWhat() must be
implemented.
*/
#define XBASE_SUBCLASS_WHAT(name_, super_)                                                                             \
  class name_ : public super_                                                                                          \
  {                                                                                                                    \
  public:                                                                                                              \
    name_() : super_()                                                                                                 \
    {                                                                                                                  \
    }                                                                                                                  \
    name_(const std::string &msg) : super_(msg)                                                                        \
    {                                                                                                                  \
    }                                                                                                                  \
    virtual ~name_() throw()                                                                                           \
    {                                                                                                                  \
    }                                                                                                                  \
                                                                                                                       \
  protected:                                                                                                           \
    virtual std::string getWhat() const throw();                                                                       \
  }

/*!
\def XBASE_SUBCLASS_FORMAT
Convenience macro to subclass from XBase (or a subclass of it),
providing the c'tor taking a const std::string&.  what() is overridden
to call getWhat() when first called;  getWhat() can format the
error message and can call what() to get the message passed to the
c'tor.
*/
#define XBASE_SUBCLASS_FORMAT(name_, super_)                                                                           \
  class name_ : public super_                                                                                          \
  {                                                                                                                    \
  private:                                                                                                             \
    enum EState                                                                                                        \
    {                                                                                                                  \
      kFirst,                                                                                                          \
      kFormat,                                                                                                         \
      kDone                                                                                                            \
    };                                                                                                                 \
                                                                                                                       \
  public:                                                                                                              \
    name_() : super_(), m_state(kDone)                                                                                 \
    {                                                                                                                  \
    }                                                                                                                  \
    name_(const std::string &msg) : super_(msg), m_state(kFirst)                                                       \
    {                                                                                                                  \
    }                                                                                                                  \
    virtual ~name_() throw()                                                                                           \
    {                                                                                                                  \
    }                                                                                                                  \
                                                                                                                       \
    virtual const char *what() const throw()                                                                           \
    {                                                                                                                  \
      if (m_state == kFirst) {                                                                                         \
        m_state = kFormat;                                                                                             \
        m_formatted = getWhat();                                                                                       \
        m_state = kDone;                                                                                               \
      }                                                                                                                \
      if (m_state == kDone) {                                                                                          \
        return m_formatted.c_str();                                                                                    \
      } else {                                                                                                         \
        return super_::what();                                                                                         \
      }                                                                                                                \
    }                                                                                                                  \
                                                                                                                       \
  protected:                                                                                                           \
    virtual std::string getWhat() const throw();                                                                       \
                                                                                                                       \
  private:                                                                                                             \
    mutable EState m_state;                                                                                            \
    mutable std::string m_formatted;                                                                                   \
  }