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       1              : // Copyright (c) 2021 The Bitcoin Core developers
       2              : // Distributed under the MIT software license, see the accompanying
       3              : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       4              : 
       5              : #ifndef BITCOIN_IPC_PROTOCOL_H
       6              : #define BITCOIN_IPC_PROTOCOL_H
       7              : 
       8              : #include <interfaces/init.h>
       9              : 
      10              : #include <functional>
      11              : #include <memory>
      12              : #include <typeindex>
      13              : 
      14              : namespace ipc {
      15              : struct Context;
      16              : 
      17              : //! IPC protocol interface for calling IPC methods over sockets.
      18              : //!
      19              : //! There may be different implementations of this interface for different IPC
      20              : //! protocols (e.g. Cap'n Proto, gRPC, JSON-RPC, or custom protocols).
      21            2 : class Protocol
      22              : {
      23              : public:
      24            2 :     virtual ~Protocol() = default;
      25              : 
      26              :     //! Return Init interface that forwards requests over given socket descriptor.
      27              :     //! Socket communication is handled on a background thread.
      28              :     //!
      29              :     //! @note It could be potentially useful in the future to add
      30              :     //! std::function<void()> on_disconnect callback argument here. But there
      31              :     //! isn't an immediate need, because the protocol implementation can clean
      32              :     //! up its own state (calling ProxyServer destructors, etc) on disconnect,
      33              :     //! and any client calls will just throw ipc::Exception errors after a
      34              :     //! disconnect.
      35              :     virtual std::unique_ptr<interfaces::Init> connect(int fd, const char* exe_name) = 0;
      36              : 
      37              :     //! Listen for connections on provided socket descriptor, accept them, and
      38              :     //! handle requests on accepted connections. This method doesn't block, and
      39              :     //! performs I/O on a background thread.
      40              :     virtual void listen(int listen_fd, const char* exe_name, interfaces::Init& init) = 0;
      41              : 
      42              :     //! Handle requests on provided socket descriptor, forwarding them to the
      43              :     //! provided Init interface. Socket communication is handled on the
      44              :     //! current thread, and this call blocks until the socket is closed.
      45              :     //!
      46              :     //! @note: If this method is called, it needs be called before connect() or
      47              :     //! listen() methods, because for ease of implementation it's inflexible and
      48              :     //! always runs the event loop in the foreground thread. It can share its
      49              :     //! event loop with the other methods but can't share an event loop that was
      50              :     //! created by them. This isn't really a problem because serve() is only
      51              :     //! called by spawned child processes that call it immediately to
      52              :     //! communicate back with parent processes.
      53              :     //
      54              :     //! The optional `ready_fn` callback will be called after the event loop is
      55              :     //! created but before it is started. This can be useful in tests to trigger
      56              :     //! client connections from another thread as soon as the event loop is
      57              :     //! available, but should not be necessary in normal code which starts
      58              :     //! clients and servers independently.
      59              :     virtual void serve(int fd, const char* exe_name, interfaces::Init& init, const std::function<void()>& ready_fn = {}) = 0;
      60              : 
      61              :     //! Disconnect any incoming connections that are still connected.
      62              :     virtual void disconnectIncoming() = 0;
      63              : 
      64              :     //! Add cleanup callback to interface that will run when the interface is
      65              :     //! deleted.
      66              :     virtual void addCleanup(std::type_index type, void* iface, std::function<void()> cleanup) = 0;
      67              : 
      68              :     //! Context accessor.
      69              :     virtual Context& context() = 0;
      70              : };
      71              : } // namespace ipc
      72              : 
      73              : #endif // BITCOIN_IPC_PROTOCOL_H