The Annoyance Filter.pdf - Fourmilab

§164 ANNOYANCE-FILTER MAIL FOLDER 137
164. To facilitate parsing of header fields, this static method performs a case-insensitive test for
header field target and, if it is found, stores its argument into arg , set to canonical lower case.
〈 Class implementations 11 〉 +≡
bool mailFolder ::compareHeaderField (string &s, const string target , string &arg )
{
if (s.length ( ) > target .length ( )) {
string sc = s;
stringCanonicalise (sc);
if ((sc.substr (0, target .length ( )) ≡ target ) ∧ (sc[target .length ( )] ≡ ’:’)) {
unsigned int i;
for (i = target .length ( ) + 1; i < sc.length ( ); i++) {
if (¬isISOspace (sc[i])) {
break;
}
}
if (i < sc.length ( )) {
int n = 0;
while ((i + n) < sc.length ( )) {
if (isISOspace (sc[i + n]) ∨ (sc[i + n] ≡ ’;’)) {
break;
}
n++;
}
arg = sc.substr (i, n);
}
else {
arg = "";
}
return true ;
}
}
return false ;
}