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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_INTERFACES_IPC_H
6 : : #define BITCOIN_INTERFACES_IPC_H
7 : :
8 : : #include <functional>
9 : : #include <memory>
10 : : #include <typeindex>
11 : :
12 : : namespace ipc {
13 : : struct Context;
14 : : } // namespace ipc
15 : :
16 : : namespace interfaces {
17 : : class Init;
18 : :
19 : : //! Interface providing access to interprocess-communication (IPC)
20 : : //! functionality. The IPC implementation is responsible for establishing
21 : : //! connections between a controlling process and a process being controlled.
22 : : //! When a connection is established, the process being controlled returns an
23 : : //! interfaces::Init pointer to the controlling process, which the controlling
24 : : //! process can use to get access to other interfaces and functionality.
25 : : //!
26 : : //! When spawning a new process, the steps are:
27 : : //!
28 : : //! 1. The controlling process calls interfaces::Ipc::spawnProcess(), which
29 : : //! calls ipc::Process::spawn(), which spawns a new process and returns a
30 : : //! socketpair file descriptor for communicating with it.
31 : : //! interfaces::Ipc::spawnProcess() then calls ipc::Protocol::connect()
32 : : //! passing the socketpair descriptor, which returns a local proxy
33 : : //! interfaces::Init implementation calling remote interfaces::Init methods.
34 : : //! 2. The spawned process calls interfaces::Ipc::startSpawnProcess(), which
35 : : //! calls ipc::Process::checkSpawned() to read command line arguments and
36 : : //! determine whether it is a spawned process and what socketpair file
37 : : //! descriptor it should use. It then calls ipc::Protocol::serve() to handle
38 : : //! incoming requests from the socketpair and invoke interfaces::Init
39 : : //! interface methods, and exit when the socket is closed.
40 : : //! 3. The controlling process calls local proxy interfaces::Init object methods
41 : : //! to make other proxy objects calling other remote interfaces. It can also
42 : : //! destroy the initial interfaces::Init object to close the connection and
43 : : //! shut down the spawned process.
44 : : //!
45 : : //! When connecting to an existing process, the steps are similar to spawning a
46 : : //! new process, except a socket is created instead of a socketpair, and
47 : : //! destroying an Init interface doesn't end the process, since there can be
48 : : //! multiple connections.
49 : : class Ipc
50 : : {
51 : : public:
52 : : virtual ~Ipc() = default;
53 : :
54 : : //! Spawn a child process returning pointer to its Init interface.
55 : : virtual std::unique_ptr<Init> spawnProcess(const char* exe_name) = 0;
56 : :
57 : : //! If this is a spawned process, block and handle requests from the parent
58 : : //! process by forwarding them to this process's Init interface, then return
59 : : //! true. If this is not a spawned child process, return false.
60 : : virtual bool startSpawnedProcess(int argc, char* argv[], int& exit_status) = 0;
61 : :
62 : : //! Connect to a socket address and make a client interface proxy object
63 : : //! using provided callback. connectAddress returns an interface pointer if
64 : : //! the connection was established, returns null if address is empty ("") or
65 : : //! disabled ("0") or if a connection was refused but not required ("auto"),
66 : : //! and throws an exception if there was an unexpected error.
67 : : virtual std::unique_ptr<Init> connectAddress(std::string& address) = 0;
68 : :
69 : : //! Connect to a socket address and make a client interface proxy object
70 : : //! using provided callback. Throws an exception if there was an error.
71 : : virtual void listenAddress(std::string& address) = 0;
72 : :
73 : : //! Add cleanup callback to remote interface that will run when the
74 : : //! interface is deleted.
75 : : template<typename Interface>
76 : 0 : void addCleanup(Interface& iface, std::function<void()> cleanup)
77 : : {
78 [ # # ]: 0 : addCleanup(typeid(Interface), &iface, std::move(cleanup));
79 : 0 : }
80 : :
81 : : //! IPC context struct accessor (see struct definition for more description).
82 : : virtual ipc::Context& context() = 0;
83 : :
84 : : protected:
85 : : //! Internal implementation of public addCleanup method (above) as a
86 : : //! type-erased virtual function, since template functions can't be virtual.
87 : : virtual void addCleanup(std::type_index type, void* iface, std::function<void()> cleanup) = 0;
88 : : };
89 : :
90 : : //! Return implementation of Ipc interface.
91 : : std::unique_ptr<Ipc> MakeIpc(const char* exe_name, const char* process_argv0, Init& init);
92 : : } // namespace interfaces
93 : :
94 : : #endif // BITCOIN_INTERFACES_IPC_H
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