I have a set of loadable data decoders for a specific type of data and a stream to read containing data. Now I want the program to select the correct decoder in a reliable way so I want to use a trial-and-error algorithm. It seems resonable to create a decoder and connect it to the stream using a constructor:
// C++ code
// codecs is an array of structs containing function pointers loaded from a dll
FileIn src("foo.wav");
for(size_t i=0; i<N_CODECS; ++i)
{
try
{
WaveIn wavein(codecs[i],src);
//Process data
return;
}
catch(...) //Swallow error. It's likly that another codec works. But if it were another error??
{
src.reset();
}
}
//no codec found (definitly an error)
Here, there is probably no true error before we have tried all codecs in the list. The reason to try-catch here is that it is not possible to get return code from the ctor. Would it be better to use zombie objects in this case?
EDIT: What the constructor does, is the following
WaveIn::WaveIn(Vtable& vt, FileIn& src):m_vt(vt)
{
m_handle=m_vt.create(src);
if(m_handle==NULL) //Resources allocated in DLL were released in this case.
{throw "Bad file";}
}
The dtor:
WaveIn::~WaveIn()
{
m_vt.destroy(m_handle);
}
