[FEATURE][spatialite] Add a REGEXP function to use for SQL filter et cie

Author: nirvn

src/providers/spatialite/qgsspatialiteconnection.cpp

@@ -640,6 +640,24 @@ bool QgsSpatiaLiteConnection::isDeclaredHidden( sqlite3 *handle, const QString &
 
 
 
+static void fcnRegexp( sqlite3_context *ctx, int /*argc*/, sqlite3_value *argv[] )
+{
+  // Get arguments and check their values
+  QRegExp arg1( reinterpret_cast<const char *>( sqlite3_value_text( argv[0] ) ) );
+  QString arg2( reinterpret_cast<const char *>( sqlite3_value_text( argv[1] ) ) );
+  if ( !arg1.isValid() )
+    return sqlite3_result_error( ctx, "invalid operand", -1 );
+
+  // Set the pattern matching syntax to a Perl-like one. This is the default in Qt 4.x but Qt 5
+  // changes this to a greedy one (QRegExp::RegExp2). To make sure the behaviour of our application
+  // doesn't change depending on the build environment, we make sure to always set the same pattern
+  // matching syntax.
+  arg1.setPatternSyntax( QRegExp::RegExp );
+  // Perform the actual matching and return the result. Note that Qt's QRegExp returns -1 if the regex
+  // doesn't match and the position in the string otherwise; SQLite expects a 0 for not found and a 1 for found.
+  sqlite3_result_int( ctx, arg1.indexIn( arg2 ) >= 0 );
+}
+
 
 
 
@@ -702,6 +720,10 @@ QgsSqliteHandle *QgsSqliteHandle::openDb( const QString &dbPath, bool shared )
     QgsDebugMsg( QStringLiteral( "Failure while connecting to: %1\n\ninvalid metadata tables" ).arg( dbPath ) );
     return nullptr;
   }
+
+  // add REGEXP function
+  sqlite3_create_function( database.get(), "REGEXP", 2, SQLITE_UTF8, nullptr, fcnRegexp, nullptr, nullptr );
+
   // activating Foreign Key constraints
   ( void )sqlite3_exec( database.get(), "PRAGMA foreign_keys = 1", nullptr, nullptr, nullptr );