The Annoyance Filter.pdf - Fourmilab

76 INTERPRETER PARENT CLASS ANNOYANCE-FILTER §89
89. We provide this default implementation of getNextDecodedChar for derived classes. They’re free
to override it, but this may do the job for most. A logical character is obtained from the decoder.
If its character code is less than or equal to 256, it is taken as a single byte character and returned
directly. Otherwise, a character name is concocted by concatenating the character set name and the
hexadecimal character code, with the prefix and suffix at either end. Character sets in which each
ideograph is logically a word will typically use a prefix and suffix of a single blank, while sets in which
characters behave like letters will use a void prefix and suffix.
〈 Class implementations 11 〉 +≡
string MBCSinterpreter ::getNextDecodedChar (void)
{
assert(dp ≠ Λ);
}
int dc = dp ⃗ getNextDecodedChar ( );
if (dc < 0) {
return ""; /∗ End of input stream ∗/
}
if (dc < 256) {
string r(1, static cast〈char〉(dc));
}
return r;
ostringstream os ;
os .setf (ios ::uppercase );
os ≪ prefix ≪ name ( ) ≪ "−" ≪ hex ≪ dc ≪ dec ≪ suffix ;
return os .str ( );
90. The default implementation of decodeLine sets the source to the argument string, then assembles
a line by concatenating the results of successive calls to getNextDecodedChar .
〈 Class implementations 11 〉 +≡
string MBCSinterpreter ::decodeLine (const string &s)
{
string r = "", t;
}
setSource (s);
while ((t = getNextDecodedChar ( )) ≠ "") {
r += t;
}
return r;