83 lines
2.9 KiB
C++
83 lines
2.9 KiB
C++
#ifndef ILLEGAL_SEND_ERROR_H
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#define ILLEGAL_SEND_ERROR_H
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/**
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\file
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Class template definition file.
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\copyright
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Copyright (C) 2002, 2003 Oliver Schoenborn
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This software is provided 'as-is', without
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any express or implied warranty. In no event
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will the authors be held liable for any
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damages arising from the use of this
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software.
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You can redistribute it and/or modify it
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under the terms found in the LICENSE file that
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is included in the library distribution.
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\endcopyright
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*/
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#include <string>
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#include <sstream>
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#include <typeinfo>
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#include <stdexcept>
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/**
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\class EventSender<EvType>::IllegalSendError
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An exception that gets thrown when EventSender<EvType>::send() is called
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recursively at least once. This situation is more likely in complex
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systems where events cause other events to be generated.
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An example scenario is where you create an Type1Event and call
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EventSender<Type1Event>::send(Type1Event). This call to send() in turn
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calls the processEvent() method of a listener of Type1Event's.
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If this listener's method creates another Type1Event and calls
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EventSender<Type1Event>::send(Type1Event) on it, this will cause that
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listener's processEvent() to be called once more, and the
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process repeats. This is likely to trigger an infinite loop of
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event generation. The only case where this would not happen is if
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the listener keeps state information that changes between successive
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calls to processEvent(), such that it does not generate an event
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during one of those calls (the recursion ends), or if this listener
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deregister's itself from listening.
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Since an infinite recursion is likely to cause a program crash, and
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since it is quite easy to make that kind of mistake, EventSender<EvType>
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forbids calling send() while a send() (for that event type) is
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in progress. It will throw a EventSender<EvType>::IllegalSendError if
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such a situation occurs.
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\author Oliver Schoenborn
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\since Sept 2002
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*/
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template<typename EvType>
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class EventSender<EvType>::IllegalSendError
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: public std::logic_error
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{
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public:
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/// Create the exception
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IllegalSendError() : std::logic_error( msg() ) {}
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private:
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/// Prefix for each new line
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static std::string nl() throw() { return "\n!!! "; }
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/// The message to give to std::logic_error constructor.
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static std::string msg()
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{
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std::ostringstream ss;
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ss << nl() << "BUG alert (Recursive send forbidden): "
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<< nl() << "Method send() of " << typeid(EventSender<EvType>).name()
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<< nl() << "calls itself indirectly through listeners"
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<< nl() << "(forbidden since could lead to infinite loop).";
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return ss.str();
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}
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};
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#endif // ILLEGAL_SEND_ERROR_H
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