Fix #2173 with a no_trailing_dot_policy

no_trailing_dot_policy rejects parsing exp, exp_n, nan, inf
and rejects parsing a fractional part if detects ".Fmt".
For Fmt = 'j', 's', 'o', 'n':
 42.foo    rule parses 42.
 42.json   rule parses 42
 42..json  rule parses 42.

Reference:
- https://github.com/Project-OSRM/osrm-backend/pull/2222#issuecomment-206206239

include/server/api/base_parameters_grammar.hpp

@@ -29,10 +29,51 @@ namespace api
 {
 
 namespace qi = boost::spirit::qi;
+
+template <typename T, char... Fmt>
+struct no_trailing_dot_policy : qi::real_policies<T> {
+
+    template <typename Iterator>
+    static bool parse_dot(Iterator& first, Iterator const& last) {
+        if (first == last || *first != '.')
+            return false;
+
+        static const constexpr char fmt[sizeof...(Fmt)] = {Fmt...};
+
+        if (first + sizeof(fmt) < last
+            && std::equal(fmt, fmt + sizeof(fmt), first + 1u))
+            return false;
+
+        ++first;
+        return true;
+    }
+
+    template <typename Iterator>
+    static bool parse_exp(Iterator&, const Iterator&) {
+        return false;
+    }
+
+    template <typename Iterator, typename Attribute>
+    static bool parse_exp_n(Iterator&, const Iterator&, Attribute&) {
+        return false;
+    }
+
+    template <typename Iterator, typename Attribute>
+    static bool parse_nan(Iterator&, const Iterator&, Attribute&) {
+        return false;
+    }
+
+    template <typename Iterator, typename Attribute>
+    static bool parse_inf(Iterator&, const Iterator&, Attribute&) {
+        return false;
+    }
+};
+
 struct BaseParametersGrammar : boost::spirit::qi::grammar<std::string::iterator>
 {
     using Iterator = std::string::iterator;
     using RadiusesT = std::vector<boost::optional<double>>;
+    using json_policy = no_trailing_dot_policy<double, 'j', 's', 'o', 'n'>;
 
     BaseParametersGrammar(qi::rule<Iterator> &root_rule_, engine::api::BaseParameters &parameters_)
         : BaseParametersGrammar::base_type(root_rule_), base_parameters(parameters_)
@@ -82,7 +123,7 @@ struct BaseParametersGrammar : boost::spirit::qi::grammar<std::string::iterator>
             qi::lit("bearings=") >> (-(qi::short_ >> ',' >> qi::short_))[add_bearing] % ";";
         polyline_rule = qi::as_string[qi::lit("polyline(") >> +polyline_chars >>
                                       qi::lit(")")][polyline_to_coordinates];
-        location_rule = (qi::double_ >> qi::lit(',') >> qi::double_)[add_coordinate];
+        location_rule = (double_ >> qi::lit(',') >> double_)[add_coordinate];
         query_rule = (location_rule % ';') | polyline_rule;
 
         base_rule = bearings_rule | radiuses_rule[set_radiuses] | hints_rule;
@@ -100,6 +141,7 @@ struct BaseParametersGrammar : boost::spirit::qi::grammar<std::string::iterator>
     qi::rule<Iterator, RadiusesT()> radiuses_rule;
     qi::rule<Iterator, unsigned char()> base64_char;
     qi::rule<Iterator, std::string()> alpha_numeral, polyline_chars;
+    qi::real_parser<double, json_policy> double_;
 };
 }
 }

include/server/api/match_parameter_grammar.hpp

@@ -62,8 +62,7 @@ struct MatchParametersGrammar final : public BaseParametersGrammar
         timestamps_rule = qi::lit("timestamps=") >> qi::uint_ % ";";
         match_rule = steps_rule[set_steps] | geometries_rule | overview_rule |
                      timestamps_rule[set_timestamps];
-        root_rule = query_rule >> -qi::lit(".") >> -qi::lit("json") >>
-                    -(qi::lit("?") >> (match_rule | base_rule) % '&');
+        root_rule = query_rule >> -qi::lit(".json") >> -(qi::lit("?") >> (match_rule | base_rule) % '&');
     }
 
     engine::api::MatchParameters parameters;

include/server/api/nearest_parameter_grammar.hpp

@@ -31,8 +31,7 @@ struct NearestParametersGrammar final : public BaseParametersGrammar
             parameters.number_of_results = number;
         };
         nearest_rule = (qi::lit("number=") >> qi::uint_)[set_number];
-        root_rule = query_rule >> -qi::lit(".") >> -qi::lit("json") >>
-                    -(qi::lit("?") >> (nearest_rule | base_rule) % '&');
+        root_rule = query_rule >> -qi::lit(".json") >> -(qi::lit("?") >> (nearest_rule | base_rule) % '&');
     }
 
     engine::api::NearestParameters parameters;

include/server/api/route_parameters_grammar.hpp

@@ -65,8 +65,7 @@ struct RouteParametersGrammar : public BaseParametersGrammar
         route_rule = steps_rule[set_steps] | alternatives_rule[set_alternatives] | geometries_rule |
                      overview_rule | uturns_rule;
 
-        root_rule = query_rule >> -qi::lit(".") >> -qi::lit("json") >>
-                    -(qi::lit("?") >> (route_rule | base_rule) % '&');
+        root_rule = query_rule >> -qi::lit(".json") >> -(qi::lit("?") >> (route_rule | base_rule) % '&');
     }
 
     engine::api::RouteParameters parameters;

include/server/api/table_parameter_grammar.hpp

@@ -41,8 +41,7 @@ struct TableParametersGrammar final : public BaseParametersGrammar
             (qi::lit("sources=") >> (qi::ulong_ % ";")[set_sources]) | qi::lit("sources=all");
         table_rule = destinations_rule | sources_rule;
 
-        root_rule = query_rule >> -qi::lit(".") >> -qi::lit("json") >>
-                    -(qi::lit("?") >> (table_rule | base_rule) % '&');
+        root_rule = query_rule >> -qi::lit(".json") >> -(qi::lit("?") >> (table_rule | base_rule) % '&');
     }
 
     engine::api::TableParameters parameters;

include/server/api/trip_parameter_grammar.hpp

@@ -57,8 +57,7 @@ struct TripParametersGrammar final : public BaseParametersGrammar
                         qi::lit("overview=false")[set_false_type];
         trip_rule = steps_rule[set_steps] | geometries_rule | overview_rule;
 
-        root_rule = query_rule >> -qi::lit(".") >> -qi::lit("json") >>
-                    -(qi::lit("?") >> (trip_rule | base_rule) % '&');
+        root_rule = query_rule >> -qi::lit(".json") >> -(qi::lit("?") >> (trip_rule | base_rule) % '&');
     }
 
     engine::api::TripParameters parameters;