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// Copyright (c) 2021 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef BITCOIN_IPC_PROTOCOL_H
#define BITCOIN_IPC_PROTOCOL_H
#include <interfaces/init.h>
#include <functional>
#include <memory>
#include <typeindex>
namespace ipc {
struct Context;
//! IPC protocol interface for calling IPC methods over sockets.
//!
//! There may be different implementations of this interface for different IPC
//! protocols (e.g. Cap'n Proto, gRPC, JSON-RPC, or custom protocols).
class Protocol
{
public:
virtual ~Protocol() = default;
//! Return Init interface that forwards requests over given socket descriptor.
//! Socket communication is handled on a background thread.
//!
//! @note It could be potentially useful in the future to add
//! std::function<void()> on_disconnect callback argument here. But there
//! isn't an immediate need, because the protocol implementation can clean
//! up its own state (calling ProxyServer destructors, etc) on disconnect,
//! and any client calls will just throw ipc::Exception errors after a
//! disconnect.
virtual std::unique_ptr<interfaces::Init> connect(int fd, const char* exe_name) = 0;
//! Listen for connections on provided socket descriptor, accept them, and
//! handle requests on accepted connections. This method doesn't block, and
//! performs I/O on a background thread.
virtual void listen(int listen_fd, const char* exe_name, interfaces::Init& init) = 0;
//! Handle requests on provided socket descriptor, forwarding them to the
//! provided Init interface. Socket communication is handled on the
//! current thread, and this call blocks until the socket is closed.
//!
//! @note: If this method is called, it needs be called before connect() or
//! listen() methods, because for ease of implementation it's inflexible and
//! always runs the event loop in the foreground thread. It can share its
//! event loop with the other methods but can't share an event loop that was
//! created by them. This isn't really a problem because serve() is only
//! called by spawned child processes that call it immediately to
//! communicate back with parent processes.
//
//! The optional `ready_fn` callback will be called after the event loop is
//! created but before it is started. This can be useful in tests to trigger
//! client connections from another thread as soon as the event loop is
//! available, but should not be neccessary in normal code which starts
//! clients and servers independently.
virtual void serve(int fd, const char* exe_name, interfaces::Init& init, const std::function<void()>& ready_fn = {}) = 0;
//! Add cleanup callback to interface that will run when the interface is
//! deleted.
virtual void addCleanup(std::type_index type, void* iface, std::function<void()> cleanup) = 0;
//! Context accessor.
virtual Context& context() = 0;
};
} // namespace ipc
#endif // BITCOIN_IPC_PROTOCOL_H
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