The Annoyance Filter.pdf - Fourmilab

138 MAIL FOLDER ANNOYANCE-FILTER §165
165. This static method tests for an argument to a header field and stores the argument, if present,
into arg . The argument name is canonicalised to lower case, but the argument is left as-is. Quotes are
deleted from quoted arguments.
〈 Class implementations 11 〉 +≡
bool mailFolder ::parseHeaderArgument (string &s, const string target , string &arg )
{
if (s.length ( ) > target .length ( )) {
string sc = s;
string ::size type p, p1 ;
stringCanonicalise (sc);
if (((p = sc.find (target )) ≠ string ::npos ) ∧ (sc.length ( ) >
(p + target .length ( ))) ∧ (sc[p + target .length ( )] ≡ ’=’)) {
p += target .length ( ) + 1;
if (p < s.length ( )) {
if (s[p] ≡ ’"’) {
if ((p1 = s.find (’"’, p + 1)) ≠ string ::npos ) {
arg = s.substr (p + 1, p1 − (p + 1));
return true ;
}
}
else {
string ::size type i = p;
for ( ; i < s.length ( ); i++) {
if (¬isISOspace (s[i])) {
break;
}
}
if (i < s.length ( )) {
int n = 0;
while ((i + n) < s.length ( )) {
if ((isISOspace (s[i + n])) ∨ (s[i + n] ≡ ’;’)) {
break;
}
n++;
}
arg = s.substr (i, n);
}
else {
arg = "";
}
return true ;
}
}
}
}
return false ;
}