core.hpp

//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012- OpenVPN Inc.
//
//    SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//

// Linux methods for enumerating the number of cores on machine,
// and binding a thread to a particular core.

#pragma once

#include <thread>

#include <openvpn/common/platform.hpp>

#if defined(__APPLE__)
#include <sys/types.h>
#include <sys/sysctl.h>
#elif defined(OPENVPN_PLATFORM_LINUX)
#include <unistd.h>
#elif defined(OPENVPN_PLATFORM_WIN)
#include <windows.h>
#endif

namespace openvpn {

inline int n_cores()
{
    int count = std::thread::hardware_concurrency();
    // C++11 allows thread::hardware_concurrency() to return 0, fall back
    // to specific solution if we detect this
    if (count > 0)
        return count;

#if defined(__APPLE__)
    size_t count_len = sizeof(count);
    if (::sysctlbyname("hw.logicalcpu", &count, &count_len, NULL, 0) != 0)
        count = 1;
    return count;
#elif defined(OPENVPN_PLATFORM_LINUX)
    long ret = ::sysconf(_SC_NPROCESSORS_ONLN);
    if (ret <= 0)
        ret = 1;
    return static_cast<int>(ret);
#elif defined(OPENVPN_PLATFORM_WIN)
    SYSTEM_INFO si;
    ::GetSystemInfo(&si);
    return si.dwNumberOfProcessors;
#else
    return 1;
#endif
}

} // namespace openvpn