The Annoyance Filter.pdf - Fourmilab

74 UTF-16 UNICODE DECODER ANNOYANCE-FILTER §86
86. Decode the next logical character. We return −1 when the end of the encoded line is encountered.
〈 Class implementations 11 〉 +≡
int UTF 16 Unicode MBCSdecoder ::getNextDecodedChar (void)
{
string ::size type nwydes = 0;
int w1 , w2 , result ;
w1 = getNextUTF 16Word ( );
if (w1 < 0) {
return w1 ;
}
if ((w1 ≤ # D800) ∨ (w1 > # DFFF)) {
result = w1 ;
nwydes = 1;
}
else if ((w1 ≥ # D800) ∧ (w1 ≤ # DBFF)) {
w2 = getNextUTF 16Word ( );
if (w2 < 0) {
ostringstream os ;
os ≪ name ( ) ≪ "_MBCSdecoder:␣Premature␣end␣of␣line␣in␣UTF−16␣two␣word␣char\
acter.";
reportDecoderDiagnostic(os );
return −1;
}
nwydes = 2;
if ((w2 < # DC00) ∨ (w2 > # DFFF)) {
ostringstream os ;
os ≪ name ( ) ≪ "_MBCSdecoder:␣Invalid␣second␣word␣surrogate␣" ≪ "0x" ≪
setiosflags (ios ::uppercase ) ≪ hex ≪ w2 ≪ "␣in␣UTF−16␣encoded␣string.";
reportDecoderDiagnostic(os );
return −1;
}
result = (((w1 & # 3FF) ≪ 10) | (w2 & # 3FF)) + # 10000;
}
else {
ostringstream os ;
os ≪ name ( ) ≪ "_MBCSdecoder:␣Invalid␣first␣word␣surrogate␣" ≪ "0x" ≪
setiosflags (ios ::uppercase ) ≪ hex ≪ w1 ≪ "␣in␣UTF−16␣encoded␣string.";
reportDecoderDiagnostic(os );
return −1;
}
return result ;
}