xapian-core/net/progclient.h

   1 /** @file
   2  *  @brief Implementation of RemoteDatabase using a spawned server.
   3  */
   4 /* Copyright (C) 2007,2010,2011,2014,2019,2023,2024 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation; either version 2 of the
   9  * License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  19  */
  20
  21 #ifndef XAPIAN_INCLUDED_PROGCLIENT_H
  22 #define XAPIAN_INCLUDED_PROGCLIENT_H
  23
  24 #include <string>
  25 #include <string_view>
  26
  27 #include <sys/types.h>
  28
  29 #include "backends/remote/remote-database.h"
  30
  31 /** Implementation of RemoteDatabase using a spawned server.
  32  *
  33  *  ProgClient spawns a child process to connect to the server - for example,
  34  *  an ssh command to run the server on a remote host.  Communication with the
  35  *  child process is via a pipe.
  36  */
  37 class ProgClient : public RemoteDatabase {
  38     /// Don't allow assignment.
  39     ProgClient& operator=(const ProgClient&) = delete;
  40
  41     /// Don't allow copying.
  42     ProgClient(const ProgClient&) = delete;
  43
  44 #ifndef __WIN32__
  45     /// Process id of the child process.
  46     pid_t child;
  47 #else
  48     /// HANDLE of the child process.
  49     HANDLE child;
  50 #endif
  51
  52     /** Start the child process.
  53      *
  54      *  @param progname The program used to create the connection.
  55      *  @param args     Any arguments to the program.
  56      *  @param child    Reference to store the child process pid/HANDLE in.
  57      *
  58      *  @return A std::pair containing the file descriptor for the connection
  59      *          to the child process and a context string to return with any
  60      *          error messages.
  61      *
  62      *  Note: this method is called early on during class construction before
  63      *  any member variables or even the base class have been initialised.
  64      *  To help avoid accidentally trying to use member variables, this method
  65      *  has been deliberately made "static".
  66      */
  67     static std::pair<int, std::string> run_program(std::string_view progname,
  68                                                    std::string_view args,
  69 #ifndef __WIN32__
  70                                                    pid_t& child
  71 #else
  72                                                    HANDLE& child
  73 #endif
  74                                                    );
  75
  76   public:
  77     /** Constructor.
  78      *
  79      *  @param progname The program used to create the connection.
  80      *  @param args     Any arguments to the program.
  81      *  @param timeout_ Timeout for communication (in seconds).
  82      *  @param writable Is this a WritableDatabase?
  83      *  @param flags    Xapian::DB_RETRY_LOCK or 0.
  84      */
  85     ProgClient(std::string_view progname,
  86                std::string_view args,
  87                double timeout_,
  88                bool writable,
  89                int flags)
  90         : RemoteDatabase(run_program(progname, args, child),
  91                          timeout_,
  92                          writable,
  93                          flags)
  94     {}
  95
  96     /** Destructor. */
  97     ~ProgClient();
  98 };
  99
 100 #endif // XAPIAN_INCLUDED_PROGCLIENT_H