include/GaudiKernel/IFileAccess.h

0001 /***********************************************************************************\
0002 * (c) Copyright 1998-2019 CERN for the benefit of the LHCb and ATLAS collaborations *
0003 *                                                                                   *
0004 * This software is distributed under the terms of the Apache version 2 licence,     *
0005 * copied verbatim in the file "LICENSE".                                            *
0006 *                                                                                   *
0007 * In applying this licence, CERN does not waive the privileges and immunities       *
0008 * granted to it by virtue of its status as an Intergovernmental Organization        *
0009 * or submit itself to any jurisdiction.                                             *
0010 \***********************************************************************************/
0011 #ifndef GaudiKernel_IFileAccess_H
0012 #define GaudiKernel_IFileAccess_H
0013
0014 // Include Files
0015 #include "GaudiKernel/IInterface.h"
0016 #include <istream>
0017 #include <memory>
0018 #include <optional>
0019 #include <string>
0020 #include <vector>
0021
0022 /** @class IFileAccess IFileAccess.h GaudiKernel/IFileAccess.h
0023  *
0024  * Abstract interface for a service or tool implementing a read access to files.
0025  *
0026  * @author Marco Clemencic
0027  * @date   2008-01-18
0028  */
0029 class GAUDI_API IFileAccess : virtual public IInterface {
0030 public:
0031   /// InterfaceID
0032   DeclareInterfaceID( IFileAccess, 3, 1 );
0033
0034   /// Find the URL and returns a unique_ptr to an input stream interface of an
0035   /// object that can be used to read from the file the URL is pointing to.
0036   /// Returns an empty pointer if the URL cannot be resolved.
0037   virtual std::unique_ptr<std::istream> open( std::string const& url ) = 0;
0038
0039   /// Find the URL and returns an optional<string> to the content of
0040   /// the file the URL is pointing to.
0041   /// Returns an 'unengaged' optional if the URL cannot be resolved.
0042   virtual std::optional<std::string> read( std::string const& url ) {
0043     auto is = open( url );
0044     if ( !is || !is->good() ) return std::nullopt;
0045     return std::string{ std::istreambuf_iterator<char>{ *is }, std::istreambuf_iterator<char>{} };
0046   }
0047
0048   /// Protocols supported by the instance.
0049   virtual const std::vector<std::string>& protocols() const = 0;
0050 };
0051
0052 #endif // GaudiKernel_IFileAccess_H