The Annoyance Filter.pdf - Fourmilab

§219 ANNOYANCE-FILTER POP3 PROXY SERVER IMPLEMENTATION 179
219. The popFilter function handles the actual filtering of messages retrieved by the POP proxy
server. It takes the text of each message, creates mail folder to read it as an istringstream, then
classifies the message, generating a transcript annotated with the classification, which is returned to the
client in lieu of the raw message received from the server.
〈 Utility functions 219 〉 ≡
#ifdef POP3_PROXY_SERVER
void popFilter (const string command , const string argument , char ∗replyBuffer , int
∗replyLength , string &reply )
{
if ((command ≡ "retr") ∧ ((∗replyLength ) > 0) ∧ (replyBuffer [0] ≡ ’+’)) {
〈 Create mail folder to read reply from POP3 server 220 〉;
〈 Classify the message, generating an in-memory transcript of the results 221 〉;
#define not POPFILTER TRACE
#ifdef POPFILTER_TRACE
cerr ≪ "Classification␣done." ≪ endl ;
#endif
#ifdef OLDWAY
ostringstream os ;
#else
unsigned int mtl = mf .sizeMessageTranscript ( );
#ifdef POPFILTER_TRACE
cerr ≪ "Message␣transcript␣predicted␣size:␣" ≪ mtl ≪ endl ;
#endif
char ∗mtbuf = new char[mtl + 16];
ostrstream os (mtbuf , mtl + 16);
#endif
mf .writeMessageTranscript (os );
#ifdef POPFILTER_TRACE
cerr ≪ "Transcript␣written." ≪ endl ;
#endif
mf .clearMessageTranscript ( );
#ifdef POPFILTER_TRACE
cerr ≪ "Transcript␣cleared." ≪ endl ;
cerr ≪ "Message␣transcript␣actual␣size:␣" ≪ os .tellp( ) ≪ endl ;
#endif
reply .erase ( );
#ifndef OLDWAY
os ≪ ’\0’;
#endif
reply = os .str ( );
#ifdef POPFILTER_TRACE
cerr ≪ "Reply␣string␣length:␣" ≪ reply .length ( ) ≪ endl ;
#endif
#ifndef OLDWAY
delete mtbuf ;
#endif
#ifdef POPFILTER_TRACE
cerr ≪ "Reply␣created." ≪ endl ;
#endif
〈 Modify POP3 reply message to reflect change in text length 222 〉;
#ifdef POPFILTER_TRACE