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 #include "common/noreturn.h"
  31
  32 using namespace std;
  33
  34 XAPIAN_NORETURN(static void
  35 parameter_error(const char * param, const string & scheme));
  36
  37 static void
  38 parameter_error(const char * msg, const string & scheme)
  39 {
  40     string m(msg);
  41     m += ": '";
  42     m += scheme;
  43     m += "'";
  44     throw m;
  45 }
  46
  47 static bool
  48 double_param(const char ** p, double * ptr_val)
  49 {
  50     char *end;
  51     errno = 0;
  52     double v = strtod(*p, &end);
  53     if (*p == end || errno) return false;
  54     *p = end;
  55     *ptr_val = v;
  56     return true;
  57 }
  58
  59 void
  60 set_expansion_scheme(Xapian::Enquire & enq, const map<string, string> & opt)
  61 {
  62     map<string, string>::const_iterator i = opt.find("expansion");
  63     if (i == opt.end()) return;
  64
  65     const string & scheme = i->second;
  66     if (scheme.empty()) return;
  67
  68     if (startswith(scheme, "trad")) {
  69         const char *p = scheme.c_str() + 4;
  70         if (*p == '\0') {
  71             enq.set_expansion_scheme("trad");
  72             return;
  73         }
  74         if (C_isspace(*p)) {
  75             // Initialise k just to silence compiler warning.
  76             double k = 0.0;
  77             if (!double_param(&p, &k))
  78                 parameter_error("Parameter k is invalid", scheme);
  79             if (*p)
  80                 parameter_error("Extra data after first parameter", scheme);
  81             enq.set_expansion_scheme("trad", k);
  82             return;
  83         }
  84     }
  85
  86     if (startswith(scheme, "bo1")) {
  87         const char *p = scheme.c_str() + 3;
  88         if (*p == '\0') {
  89             enq.set_expansion_scheme("bo1");
  90             return;
  91         }
  92         if (C_isspace(*p)) {
  93             throw "No parameters are required for BO1";
  94         }
  95     }
  96
  97     throw "Unknown $opt{expansion} setting: " + scheme;
  98 }