xapian-applications/omega/expand.cc

   1 /** @file
   2  * @brief Set the query expansion scheme for Omega
   3  */
   4 /* Copyright (C) 2009,2013,2014,2015 Olly Betts
   5  * Copyright (C) 2013 Aarsh Shah
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  20  */
  21
  22 #include <config.h>
  23
  24 #include "expand.h"
  25
  26 #include "stringutils.h"
  27
  28 #include <cerrno>
  29 #include <cstdlib>
  30
  31 using namespace std;
  32
  33 [[noreturn]]
  34 static void
  35 parameter_error(const char * msg, const string & scheme)
  36 {
  37     string m(msg);
  38     m += ": '";
  39     m += scheme;
  40     m += "'";
  41     throw m;
  42 }
  43
  44 static bool
  45 double_param(const char ** p, double * ptr_val)
  46 {
  47     char *end;
  48     errno = 0;
  49     double v = strtod(*p, &end);
  50     if (*p == end || errno) return false;
  51     *p = end;
  52     *ptr_val = v;
  53     return true;
  54 }
  55
  56 void
  57 set_expansion_scheme(Xapian::Enquire & enq, const map<string, string> & opt)
  58 {
  59     map<string, string>::const_iterator i = opt.find("expansion");
  60     if (i == opt.end()) return;
  61
  62     const string & scheme = i->second;
  63     if (scheme.empty()) return;
  64
  65     if (startswith(scheme, "trad")) {
  66         const char *p = scheme.c_str() + 4;
  67         if (*p == '\0') {
  68             enq.set_expansion_scheme("trad");
  69             return;
  70         }
  71         if (C_isspace(*p)) {
  72             // Initialise k just to silence compiler warning.
  73             double k = 0.0;
  74             if (!double_param(&p, &k))
  75                 parameter_error("Parameter k is invalid", scheme);
  76             if (*p)
  77                 parameter_error("Extra data after first parameter", scheme);
  78             enq.set_expansion_scheme("trad", k);
  79             return;
  80         }
  81     }
  82
  83     if (startswith(scheme, "bo1")) {
  84         const char *p = scheme.c_str() + 3;
  85         if (*p == '\0') {
  86             enq.set_expansion_scheme("bo1");
  87             return;
  88         }
  89         if (C_isspace(*p)) {
  90             throw "No parameters are required for BO1";
  91         }
  92     }
  93
  94     throw "Unknown $opt{expansion} setting: " + scheme;
  95 }