remoteconnection.h

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/* Copyright (C) 2006-2026 Olly Betts
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see
 * <https://www.gnu.org/licenses/>.
 */
 
#ifndef XAPIAN_INCLUDED_REMOTECONNECTION_H
#define XAPIAN_INCLUDED_REMOTECONNECTION_H
 
#include <string>
 
#include "remoteprotocol.h"
 
#ifdef __WIN32__
# include "safewinsock2.h"
#else
# include "safesyssocket.h"
#endif
 
class RemoteConnection {
    void operator=(const RemoteConnection &);
 
    RemoteConnection(const RemoteConnection &);
 
    int fdin;
 
    int fdout;
 
#ifndef __WIN32__
    // On Unix-like platforms we want to avoid generating SIGPIPE when writing
    // to a socket when the other end has been closed since signals break the
    // encapsulation of what we're doing inside the library - either user code
    // would need to handle the SIGPIPE, or we set a signal handler for SIGPIPE
    // but that would handle *any* SIGPIPE in the process, not just those we
    // might trigger, and that could break user code which expects to trigger
    // and handle SIGPIPE.
    //
    // We don't need SIGPIPE since we can check errno==EPIPE instead (which is
    // actually simpler to do).
    //
    // We support using SO_NOSIGPIPE (not standardised) or MSG_NOSIGNAL
    // (specified by POSIX but more awkward to use) which seems to cover all
    // modern Unix-like platforms.  For platforms without either we currently
    // just set the SIGPIPE signal handler to SIG_IGN.
# if defined(SO_NOSIGPIPE) && !defined(__NetBSD__)
    // Prefer using SO_NOSIGPIPE and write(), except on NetBSD where we seem to
    // still get SIGPIPE despite using it.
#  define USE_SO_NOSIGPIPE
# elif defined MSG_NOSIGNAL
    // Use send(..., MSG_NOSIGNAL).
    int send_flags = MSG_NOSIGNAL;
#  define USE_MSG_NOSIGNAL
# endif
#endif
 
    std::string buffer;
 
    size_t chunked_data_left;
 
    bool read_at_least(size_t min_len, double end_time);
 
#ifdef __WIN32__
    WSAOVERLAPPED overlapped;
 
    DWORD calc_read_wait_msecs(double end_time);
#else
    ssize_t send_or_write(const void* p, size_t n);
#endif
 
  protected:
    std::string context;
 
  public:
    RemoteConnection(int fdin_, int fdout_,
                     const std::string & context_ = std::string());
 
#ifdef __WIN32__
    ~RemoteConnection();
#endif
 
    int get_read_fd() const { return fdin; }
 
    int sniff_next_message_type(double end_time);
 
    int get_message(std::string &result, double end_time);
 
    int get_message_chunked(double end_time);
 
    int get_message_chunk(std::string &result, size_t at_least,
                          double end_time);
 
    int receive_file(const std::string &file, double end_time);
 
    void send_message(char type, std::string_view s, double end_time);
 
    void send_file(char type, int fd, double end_time);
 
    void shutdown();
 
    void do_close();
 
    const std::string& get_context() const { return context; }
};
 
class OwnedRemoteConnection : public RemoteConnection {
  public:
    OwnedRemoteConnection(int fdin_, int fdout_,
                          const std::string& context_ = std::string())
        : RemoteConnection(fdin_, fdout_, context_) { }
 
    ~OwnedRemoteConnection() {
        do_close();
    }
};
 
#endif // XAPIAN_INCLUDED_REMOTECONNECTION_H