1// Copyright (c) 2022-present 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#include <util/signalinterrupt.h>
6
7#ifdef WIN32
8#include <mutex>
9#else
10#include <util/tokenpipe.h>
11#endif
12
13#include <ios>
14#include <optional>
15
16namespace util {
17
18SignalInterrupt::SignalInterrupt() : m_flag{false}
19{
20#ifndef WIN32
21    std::optional<TokenPipe> pipe = TokenPipe::Make();
22    if (!pipe) throw std::ios_base::failure("Could not create TokenPipe");
23    m_pipe_r = pipe->TakeReadEnd();
24    m_pipe_w = pipe->TakeWriteEnd();
25#endif
26}
27
28SignalInterrupt::operator bool() const
29{
30    return m_flag;
31}
32
33bool SignalInterrupt::reset()
34{
35    // Cancel existing interrupt by waiting for it, this will reset condition flags and remove
36    // the token from the pipe.
37    if (*this && !wait()) return false;
38    m_flag = false;
39    return true;
40}
41
42bool SignalInterrupt::operator()()
43{
44#ifdef WIN32
45    std::unique_lock<std::mutex> lk(m_mutex);
46    m_flag = true;
47    m_cv.notify_one();
48#else
49    // This must be reentrant and safe for calling in a signal handler, so using a condition variable is not safe.
50    // Make sure that the token is only written once even if multiple threads call this concurrently or in
51    // case of a reentrant signal.
52    if (!m_flag.exchange(true)) {
53        // Write an arbitrary byte to the write end of the pipe.
54        int res = m_pipe_w.TokenWrite('x');
55        if (res != 0) {
56            return false;
57        }
58    }
59#endif
60    return true;
61}
62
63bool SignalInterrupt::wait()
64{
65#ifdef WIN32
66    std::unique_lock<std::mutex> lk(m_mutex);
67    m_cv.wait(lk, [this] { return m_flag.load(); });
68#else
69    int res = m_pipe_r.TokenRead();
70    if (res != 'x') {
71        return false;
72    }
73#endif
74    return true;
75}
76
77} // namespace util
78