Aegisub/aegisub/libaegisub/include/libaegisub/exception.h

305 lines
12 KiB
C++

// Copyright (c) 2009, Niels Martin Hansen
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
// * Neither the name of the Aegisub Group nor the names of its contributors
// may be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//
// Aegisub Project http://www.aegisub.org/
//
// $Id$
/// @file exception.h
/// @brief Base exception classes for structured error handling
/// @ingroup main_headers
///
#pragma once
#include <string>
#ifdef _WIN32
#include <memory>
#else
#include <tr1/memory>
#endif
/// @see aegisub.h
namespace agi {
/// @class Exception
/// @brief Base class for all exceptions in Aegisub.
///
/// All exceptions thrown by Aegisub should derive from this class.
/// It is incorrect to throw anything that is not a subclass of this.
///
/// However, there are no public constructors for this class, it should
/// not be instantiated and thrown directly. Throw instances of a
/// relevant sub class, declare a new one if necessary. It is allowed to
/// declare sub classes of Exception and derivates in private headers
/// and even inside source files, as long as a caller has a chance to
/// catch the exception thrown.
///
/// When throwing exceptions, throw temporaries, not heap allocated
/// objects. (C++ FAQ Lite 17.6.) I.e. this is correct:
/// @code
/// throw agi::SomeException("Message for exception");
/// @endcode
/// This is wrong:
/// @code
/// throw new agi::SomeException("Remember this is the wrong way!");
/// @endcode
/// Exceptions must not be allocated on heap, because of the risks of
/// leaking memory that way. (C++ FAQ Lite 17.8.)
///
/// When catching exceptions, make sure you catch them by reference,
/// otherwise polymorphism will not work. (The C++ Programming
/// Language Special Edition 14.2.1, C++ FAQ Lite 17.7.)
///
/// Catch like this:
/// @code
/// try {
/// /* ... */
/// }
/// catch (agi::UserCancelException &e) {
/// /* handle the fact that the user cancelled */
/// }
/// catch (agi::VideoInputException &e) {
/// /* handle the video provider failing */
/// }
/// @endcode
/// Don't always handle all exceptions the code you're protected might
/// throw, sometimes it's better to let an exception slip through and
/// let code further out handle it. Sometimes you might want to catch and
/// package an exception into something else, for example to represent
/// cases such as "subtitle file could not be read @e because the file
/// could not be opened for reading". This is the purpose of the "inner"
/// exceptions.
class Exception {
/// The error message
std::string message;
/// An inner exception, the cause of this exception
std::tr1::shared_ptr<Exception> inner;
protected:
/// @brief Protected constructor initialising members
/// @param msg The error message
/// @param inr The inner exception, optional
///
/// Deriving classes should always use this constructor for initialising
/// the base class.
Exception(const std::string &msg, const Exception *inr = 0)
: message(msg)
{
if (inr)
inner.reset(inr->Copy());
}
/// @brief Default constructor, not implemented
///
/// The default constructor is not implemented because it must not be used,
/// as it leaves the members un-initialised.
Exception();
public:
/// @brief Destructor
virtual ~Exception()
{
}
/// @brief Get the outer exception error message
/// @return Error message
virtual std::string GetMessage() const { return message; }
/// @brief Get error messages for chained exceptions
/// @return Chained error message
///
/// If there is an inner exception, prepend its chained error message to
/// our error message, with a CRLF between. Returns our own error message
/// alone if there is no inner exception.
std::string GetChainedMessage() const { if (inner.get()) return inner->GetChainedMessage() + "\r\n" + GetMessage(); else return GetMessage(); }
/// @brief Exception class printable name
///
/// Sub classes should implement this to return a constant character string
/// naming their exception in a hierarchic manner.
///
/// Exception classes inheriting directly from Exception define a top-level
/// name for their sub-tree, further sub-classes add further levels, each
/// level is separated by a slash. Characters allowed in the name for a
/// level are [a-z0-9_].
virtual const char * GetName() const = 0;
/// @brief Convert to char array as the error message
/// @return The error message
operator const char * () { return GetMessage().c_str(); }
/// @brief Convert to std::string as the error message
/// @return The error message
operator std::string () { return GetMessage(); }
/// @brief Create a copy of the exception allocated on the heap
/// @return A heap-allocated exception object
///
/// All deriving classes must implement this explicitly to avoid losing
/// information in the duplication.
virtual Exception *Copy() const = 0;
};
/// @brief Convenience macro to include the current location in code
///
/// Intended for use in error messages where it can sometimes be convenient to
/// indicate the exact position the error occurred at.
#define AG_WHERE " (at " __FILE__ ":" #__LINE__ ")"
/// @brief Convenience macro for declaring exceptions with no support for inner exception
/// @param classname Name of the exception class to declare
/// @param baseclass Class to derive from
/// @param displayname The printable name of the exception (return of GetName())
///
/// This macro covers most cases of exception classes where support for inner
/// exceptions is not relevant/wanted.
#define DEFINE_SIMPLE_EXCEPTION_NOINNER(classname,baseclass,displayname) \
class classname : public baseclass { \
public: \
classname(const std::string &msg) : baseclass(msg) { } \
const char * GetName() const { return displayname; } \
Exception * Copy() const { return new classname(*this); } \
};
/// @brief Convenience macro for declaring exceptions supporting inner exceptions
/// @param classname Name of the exception class to declare
/// @param baseclass Class to derive from
/// @param displayname The printable name of the exception (return of GetName())
///
/// This macro covers most cases of exception classes that should support
/// inner exceptions.
#define DEFINE_SIMPLE_EXCEPTION(classname,baseclass,displayname) \
class classname : public baseclass { \
public: \
classname(const std::string &msg, Exception *inner) : baseclass(msg, inner) { } \
const char * GetName() const { return displayname; } \
Exception * Copy() const { return new classname(*this); } \
};
/// @brief Macro for declaring non-instantiable exception base classes
/// @param classname Name of the exception class to declare
/// @param baseclass Class to derive from
///
/// Declares an exception class that does not implement the GetName() function
/// and as such (unless a base class implements it) is not constructable.
/// Classes declared by this macro do not support inner exceptions.
#define DEFINE_BASE_EXCEPTION_NOINNER(classname,baseclass) \
class classname : public baseclass { \
public: \
classname(const std::string &msg) : baseclass(msg) { } \
};
/// @brief Macro for declaring non-instantiable exception base classes with inner
/// exception support
/// @param classname Name of the exception class to declare
/// @param baseclass Class to derive from
///
/// Declares an exception class that does not implement the GetName() function
/// and as such (unless a base class implements it) is not constructable.
/// Classes declared by this macro do support inner exceptions.
#define DEFINE_BASE_EXCEPTION(classname,baseclass) \
class classname : public baseclass { \
public: \
classname(const std::string &msg, Exception *inner) : baseclass(msg, inner) { } \
};
/// @class agi::UserCancelException
/// @extends agi::Exception
/// @brief Exception for "user cancel" events
///
/// I.e. when we want to abort an operation because the user requested that we do so.
/// Not actually an error and should not be handled as such.
///
/// This is intended to signal that an operation should be completely aborted at the
/// request of the user, and should usually be handled as close to the main UI as
/// possible, user cancel exceptions should unwind anything that was going on at the
/// moment. For this to work, RAII methodology has to be used consequently in the
/// code in question.
DEFINE_SIMPLE_EXCEPTION_NOINNER(UserCancelException,Exception,"nonerror/user_cancel")
/// @class agi::InternalError
/// @extends agi:Exception
/// @brief Errors that should never happen and point to some invalid assumption in the code
///
/// Throw an internal error when a sanity check fails, and the insanity should have
/// been caught and handled at an earlier stage, i.e. when something seems to
/// have become inconsistent. All internal errors are of the type "this should never
/// happen", most often you'll want this kind of error unwind all the way past the main UI
/// and eventually cause an abort().
DEFINE_SIMPLE_EXCEPTION(InternalError, Exception, "internal_error")
/// @class agi::FileSystemError
/// @extends agi::Exception
/// @brief Base class for errors related to the file system
///
/// This base class can not be instantiated.
/// File system errors do not support inner exceptions, as they are always originating
/// causes for errors.
DEFINE_BASE_EXCEPTION_NOINNER(FileSystemError,Exception)
/// @class agi::FileNotAccessibleError
/// @extends agi::FileSystemError
/// @brief A file can't be accessed for some reason
DEFINE_SIMPLE_EXCEPTION_NOINNER(FileNotAccessibleError,FileSystemError,"filesystem/not_accessible")
/// @class FileNotFoundError
/// @brief A file can't be accessed because there's no file by the given name
class FileNotFoundError : public FileNotAccessibleError {
public:
/// @brief Constructor, automatically builds the error message
/// @param filename Name of the file that could not be found
FileNotFoundError(const std::string &filename) : FileNotAccessibleError(std::string("File not found: ") + filename) { }
// Not documented, see agi::Exception class
const char * GetName() const { return "filesystem/not_accessible/not_found"; }
// Not documented, see agi::Exception class
Exception * Copy() const { return new FileNotFoundError(*this); }
};
/// @class agi::InvalidInputException
/// @extends agi::Exception
/// @brief Some input data were invalid and could not be processed
DEFINE_BASE_EXCEPTION(InvalidInputException,Exception)
}