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