The Annoyance Filter.pdf - Fourmilab

174 POP3 PROXY SERVER CLASS DEFINITION ANNOYANCE-FILTER §210
210. If the status from the server is positive and the command is one which elicits a multiple-line
reply, read the reply from the server until the terminating sentinel, a single period followed by the
CR/LF line terminator. Any line in the reply which begins with a period is quoted by prefixing a
period.
We concatenate replies from the server into the reply string until the end sentinel is encountered.
〈 Read multi-line reply from server if present 210 〉 ≡
reply = "";
if ((serverBuffer [0] ≡ ’+’) ∧ ((multiLine .find (command ) ≠ multiLine .end ( )) ∨ ((argument ≡
"") ∧ (cMultiLine .find (command ) ≠ cMultiLine .end ( ))))) {
int bll ;
char bp[POP_BUFFER];
if (popProxyTrace ) {
cerr ≪ "POP3:␣Reading␣multi−line␣reply␣from␣server." ≪ endl ;
}
do {
bll = recv (serverSocket , bp, POP_MAX_MESSAGE, 0);
if (bll < 0) {
perror ("POP3Proxy␣reading␣multi−line␣reply␣to␣request␣from␣server");
break;
}
#ifdef POP3_TRACE_TRANSFER_DETAIL
if (popProxyTrace ) {
cerr ≪ "POP3:␣Appending␣" ≪ bll ≪ "␣bytes␣to␣multi−line␣reply." ≪ endl ;
}
#endif
reply += string(bp, bll );
} while ((reply .length ( ) < 3) ∨ ((reply ≠ ".\r\n") ∧ (reply .substr (reply .length ( ) − 5) ≠
"\r\n.\r\n")));
}
This code is used in section 204.
211. Here’s where we permit the filterFunction to get into the act. If there’s a filterFunction , we
hand it everything it needs to modify the status line and reply from the server. Note that even though
we go to the effort to pass the canonicalised and parsed command and argument, it’s up to the filter
function to compose the rough-and-ready status string in the serverBuffer string, which must be zero
terminated.
〈 Fiddle with the reply from the server as required 211 〉 ≡
if (popProxyTrace ) {
cerr ≪ "POP3:␣Calling␣filter␣function." ≪ endl ;
}
if (filterFunction ≠ Λ) {
serverBuffer [serverLength ] = 0;
filterFunction (command , argument , serverBuffer , &serverLength , reply );
}
if (popProxyTrace ) {
cerr ≪ "POP3:␣Returned␣from␣filter␣function." ≪ endl ;
}
This code is used in section 204.