The Annoyance Filter.pdf - Fourmilab

§68 ANNOYANCE-FILTER DECODER PARENT CLASS 63
68. Decoder parent class.
This is the abstract parent class of all specific decoders. Albeit abstract in the details, we provide a
variety of services to derived classes.
〈 Class definitions 10 〉 +≡
class MBCSdecoder {
protected:
const string ∗src;
string ::size type p;
mailFolder ∗mf ;
public:
MBCSdecoder(mailFolder ∗m = Λ)
: src(Λ), p(0), mf (Λ) { }
virtual ∼MBCSdecoder( )
{ }
virtual string name (void) = 0; /∗ Name of decoder ∗/
virtual void setSource (const string &s)
{ /∗ Set input source line ∗/
src = &s;
p = 0;
}
virtual void setMailFolder (mailFolder ∗m = Λ)
{
mf = m;
}
virtual void reset (void)
{ /∗ Reset stateful decoder to ground state ∗/
}
virtual int getNextDecodedChar (void) = 0; /∗ Get next decoded character ∗/
virtual int getNextEncodedByte (void)
{
if (p ≥ src ⃗ length ( )) {
return −1;
}
return ((∗src)[p++]) & # FF;
}
protected:
virtual int getNextNBytes (const unsigned int n);
virtual int getNext2Bytes (void)
{
return getNextNBytes (2);
}
virtual int getNext3Bytes (void)
{
return getNextNBytes (3);
}
virtual int getNext4Bytes (void)
{
return getNextNBytes (4);
}