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 A non-malicious use would be to enter "C" to match Charles and Cecilia. 
 A malicious use would be to enter "?:)(^C,[0-9]+?,[0-9]+?$)|(?:" which
 grabs the IPs that made the search.

/* Say this logfile contains:
 * CSV style: search string, time (unix), ip (integer)
 *
 * Alice,1267773881,2147651708
 * Bono,1267774881,2147651708
 * Charles,1267775881,1175563058
 * Cecilia,1267773222,291232332
 *
 * and the CSVLog class has a readLine() method which retrieves a single line from the CSVLog and returns null when at EOF
 */
private CSVLog logfile;
 
// an application repeatedly calls this function that searches through
// the search log for search suggestions for autocompletion
public Set<String> suggestSearches(String search)
{
   Set<String> searches = new HashSet<String>();
    
   // construct regex from user's string   
   // the regex matches valid lines and the grouping characters will limit the 
   // returned regex to the search string
   String regex = "^(" + search + ".*),[0-9]+?,[0-9]+?$";
   Pattern p = Pattern.compile(regex);
   String s;
   while ((s = logfile.readLine()) != null) { //gets a single line from the logfile
       Matcher m = p.matcher(s);
       if (m.find()) {
           String found = m.group(1);
           searches.add(found);
       }
   }
        
   return searches;
}

/* Say this logfile contains:
 * CSV style: search string, time (unix), ip (integer)
 *
 * Alice,1267773881,2147651708
 * Bono,1267774881,2147651708
 * Charles,1267775881,1175563058
 * Cecilia,1267773222,291232332
 *
 * and the CSVLog class has a readLine() method which retrieves a single line from the CSVLog and returns null when at EOF
 */
private CSVLog logfile;
 
// an application repeatedly calls this function that searches through the search log 
// for search suggestions for autocompletion
public Set<String> suggestSearches(String search)
{
   Set<String> searches = new HashSet<String>();

   //filter search
   StringBuilder sb = new StringBuilder(search.length());
   for (int i = 0; i < search.length(); ++i) {
       char ch = search.charAt(i);
       if (Character.isLetterOrDigit(ch))
           sb.append(ch);
   }
   search = sb.toString();
    
   //construct regex from user's string   
   //the regex matches valid lines and the grouping characters will limit the 
   // returned regex to the search string
   String regex = "^(" + search + ".*),[0-9]+?,[0-9]+?$";
   Pattern p = Pattern.compile(regex);
   String s;
   while ((s = logfile.readLine()) != null) { //gets a single line from the logfile
       Matcher m = p.matcher(s);
       if (m.find()) {
           String found = m.group(1);
           searches.add(found);
       }
   }
        
   return searches;
}