zmq.hpp

/*
    Copyright (c) 2016-2017 ZeroMQ community
    Copyright (c) 2009-2011 250bpm s.r.o.
    Copyright (c) 2011 Botond Ballo
    Copyright (c) 2007-2009 iMatix Corporation

    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to
    deal in the Software without restriction, including without limitation the
    rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
    sell copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
    IN THE SOFTWARE.
*/

#ifndef __ZMQ_HPP_INCLUDED__
#define __ZMQ_HPP_INCLUDED__

#ifdef _WIN32
#ifndef NOMINMAX
#define NOMINMAX
#endif
#endif

// macros defined if has a specific standard or greater
#if (defined(__cplusplus) && __cplusplus >= 201103L)                                \
  || (defined(_MSC_VER) && _MSC_VER >= 1900)
#define ZMQ_CPP11
#endif
#if (defined(__cplusplus) && __cplusplus >= 201402L)                                \
  || (defined(_HAS_CXX14) && _HAS_CXX14 == 1)                                       \
  || (defined(_HAS_CXX17)                                                           \
      && _HAS_CXX17                                                                 \
           == 1) // _HAS_CXX14 might not be defined when using C++17 on MSVC
#define ZMQ_CPP14
#endif
#if (defined(__cplusplus) && __cplusplus >= 201703L)                                \
  || (defined(_HAS_CXX17) && _HAS_CXX17 == 1)
#define ZMQ_CPP17
#endif

#if defined(ZMQ_CPP14)
#define ZMQ_DEPRECATED(msg) [[deprecated(msg)]]
#elif defined(_MSC_VER)
#define ZMQ_DEPRECATED(msg) __declspec(deprecated(msg))
#elif defined(__GNUC__)
#define ZMQ_DEPRECATED(msg) __attribute__((deprecated(msg)))
#endif

#if defined(ZMQ_CPP17)
#define ZMQ_NODISCARD [[nodiscard]]
#else
#define ZMQ_NODISCARD
#endif

#if defined(ZMQ_CPP11)
#define ZMQ_NOTHROW noexcept
#define ZMQ_EXPLICIT explicit
#define ZMQ_OVERRIDE override
#define ZMQ_NULLPTR nullptr
#define ZMQ_CONSTEXPR_FN constexpr
#define ZMQ_CONSTEXPR_VAR constexpr
#define ZMQ_CPP11_DEPRECATED(msg) ZMQ_DEPRECATED(msg)
#else
#define ZMQ_NOTHROW throw()
#define ZMQ_EXPLICIT
#define ZMQ_OVERRIDE
#define ZMQ_NULLPTR 0
#define ZMQ_CONSTEXPR_FN
#define ZMQ_CONSTEXPR_VAR const
#define ZMQ_CPP11_DEPRECATED(msg)
#endif
#if defined(ZMQ_CPP17)
#define ZMQ_INLINE_VAR inline
#else
#define ZMQ_INLINE_VAR
#endif

#include <zmq.h>

#include <cassert>
#include <cstring>

#include <algorithm>
#include <exception>
#include <iomanip>
#include <sstream>
#include <string>
#include <vector>
#ifdef ZMQ_CPP11
#include <array>
#include <chrono>
#include <tuple>
#include <memory>
#endif
#ifdef ZMQ_CPP17
#ifdef __has_include
#if __has_include(<optional>)
#include <optional>
#define ZMQ_HAS_OPTIONAL 1
#endif
#if __has_include(<string_view>)
#include <string_view>
#define ZMQ_HAS_STRING_VIEW 1
#endif
#endif

#endif

/*  Version macros for compile-time API version detection                     */
#define CPPZMQ_VERSION_MAJOR 4
#define CPPZMQ_VERSION_MINOR 7
#define CPPZMQ_VERSION_PATCH 0

#define CPPZMQ_VERSION                                                              \
    ZMQ_MAKE_VERSION(CPPZMQ_VERSION_MAJOR, CPPZMQ_VERSION_MINOR,                    \
                     CPPZMQ_VERSION_PATCH)

//  Detect whether the compiler supports C++11 rvalue references.
#if (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 2))   \
     && defined(__GXX_EXPERIMENTAL_CXX0X__))
#define ZMQ_HAS_RVALUE_REFS
#define ZMQ_DELETED_FUNCTION = delete
#elif defined(__clang__)
#if __has_feature(cxx_rvalue_references)
#define ZMQ_HAS_RVALUE_REFS
#endif

#if __has_feature(cxx_deleted_functions)
#define ZMQ_DELETED_FUNCTION = delete
#else
#define ZMQ_DELETED_FUNCTION
#endif
#elif defined(_MSC_VER) && (_MSC_VER >= 1900)
#define ZMQ_HAS_RVALUE_REFS
#define ZMQ_DELETED_FUNCTION = delete
#elif defined(_MSC_VER) && (_MSC_VER >= 1600)
#define ZMQ_HAS_RVALUE_REFS
#define ZMQ_DELETED_FUNCTION
#else
#define ZMQ_DELETED_FUNCTION
#endif

#if defined(ZMQ_CPP11) && !defined(__llvm__) && !defined(__INTEL_COMPILER)          \
  && defined(__GNUC__) && __GNUC__ < 5
#define ZMQ_CPP11_PARTIAL
#elif defined(__GLIBCXX__) && __GLIBCXX__ < 20160805
//the date here is the last date of gcc 4.9.4, which
// effectively means libstdc++ from gcc 5.5 and higher won't trigger this branch
#define ZMQ_CPP11_PARTIAL
#endif

#ifdef ZMQ_CPP11
#ifdef ZMQ_CPP11_PARTIAL
#define ZMQ_IS_TRIVIALLY_COPYABLE(T) __has_trivial_copy(T)
#else
#include <type_traits>
#define ZMQ_IS_TRIVIALLY_COPYABLE(T) std::is_trivially_copyable<T>::value
#endif
#endif

#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(3, 3, 0)
#define ZMQ_NEW_MONITOR_EVENT_LAYOUT
#endif

#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 1, 0)
#define ZMQ_HAS_PROXY_STEERABLE
/*  Socket event data  */
typedef struct
{
    uint16_t event; // id of the event as bitfield
    int32_t value;  // value is either error code, fd or reconnect interval
} zmq_event_t;
#endif

// Avoid using deprecated message receive function when possible
#if ZMQ_VERSION < ZMQ_MAKE_VERSION(3, 2, 0)
#define zmq_msg_recv(msg, socket, flags) zmq_recvmsg(socket, msg, flags)
#endif


// In order to prevent unused variable warnings when building in non-debug
// mode use this macro to make assertions.
#ifndef NDEBUG
#define ZMQ_ASSERT(expression) assert(expression)
#else
#define ZMQ_ASSERT(expression) (void) (expression)
#endif

namespace zmq
{
#ifdef ZMQ_CPP11
namespace detail
{
namespace ranges
{
using std::begin;
using std::end;
template<class T> auto begin(T &&r) -> decltype(begin(std::forward<T>(r)))
{
    return begin(std::forward<T>(r));
}
template<class T> auto end(T &&r) -> decltype(end(std::forward<T>(r)))
{
    return end(std::forward<T>(r));
}
} // namespace ranges

template<class T> using void_t = void;

template<class Iter>
using iter_value_t = typename std::iterator_traits<Iter>::value_type;

template<class Range>
using range_iter_t = decltype(
  ranges::begin(std::declval<typename std::remove_reference<Range>::type &>()));

template<class Range> using range_value_t = iter_value_t<range_iter_t<Range>>;

template<class T, class = void> struct is_range : std::false_type
{
};

template<class T>
struct is_range<
  T,
  void_t<decltype(
    ranges::begin(std::declval<typename std::remove_reference<T>::type &>())
    == ranges::end(std::declval<typename std::remove_reference<T>::type &>()))>>
    : std::true_type
{
};

} // namespace detail
#endif

typedef zmq_free_fn free_fn;
typedef zmq_pollitem_t pollitem_t;

class error_t : public std::exception
{
  public:
    error_t() : errnum(zmq_errno()) {}
    virtual const char *what() const ZMQ_NOTHROW ZMQ_OVERRIDE
    {
        return zmq_strerror(errnum);
    }
    int num() const { return errnum; }

  private:
    int errnum;
};

inline int poll(zmq_pollitem_t *items_, size_t nitems_, long timeout_ = -1)
{
    int rc = zmq_poll(items_, static_cast<int>(nitems_), timeout_);
    if (rc < 0)
        throw error_t();
    return rc;
}

ZMQ_DEPRECATED("from 4.3.1, use poll taking non-const items")
inline int poll(zmq_pollitem_t const *items_, size_t nitems_, long timeout_ = -1)
{
    return poll(const_cast<zmq_pollitem_t *>(items_), nitems_, timeout_);
}

#ifdef ZMQ_CPP11
ZMQ_DEPRECATED("from 4.3.1, use poll taking non-const items")
inline int
poll(zmq_pollitem_t const *items, size_t nitems, std::chrono::milliseconds timeout)
{
    return poll(const_cast<zmq_pollitem_t *>(items), nitems,
                static_cast<long>(timeout.count()));
}

ZMQ_DEPRECATED("from 4.3.1, use poll taking non-const items")
inline int poll(std::vector<zmq_pollitem_t> const &items,
                std::chrono::milliseconds timeout)
{
    return poll(const_cast<zmq_pollitem_t *>(items.data()), items.size(),
                static_cast<long>(timeout.count()));
}

ZMQ_DEPRECATED("from 4.3.1, use poll taking non-const items")
inline int poll(std::vector<zmq_pollitem_t> const &items, long timeout_ = -1)
{
    return poll(const_cast<zmq_pollitem_t *>(items.data()), items.size(), timeout_);
}

inline int
poll(zmq_pollitem_t *items, size_t nitems, std::chrono::milliseconds timeout)
{
    return poll(items, nitems, static_cast<long>(timeout.count()));
}

inline int poll(std::vector<zmq_pollitem_t> &items,
                std::chrono::milliseconds timeout)
{
    return poll(items.data(), items.size(), static_cast<long>(timeout.count()));
}

inline int poll(std::vector<zmq_pollitem_t> &items, long timeout_ = -1)
{
    return poll(items.data(), items.size(), timeout_);
}
#endif


inline void version(int *major_, int *minor_, int *patch_)
{
    zmq_version(major_, minor_, patch_);
}

#ifdef ZMQ_CPP11
inline std::tuple<int, int, int> version()
{
    std::tuple<int, int, int> v;
    zmq_version(&std::get<0>(v), &std::get<1>(v), &std::get<2>(v));
    return v;
}
#endif

class message_t
{
  public:
    message_t() ZMQ_NOTHROW
    {
        int rc = zmq_msg_init(&msg);
        ZMQ_ASSERT(rc == 0);
    }

    explicit message_t(size_t size_)
    {
        int rc = zmq_msg_init_size(&msg, size_);
        if (rc != 0)
            throw error_t();
    }

    template<class ForwardIter> message_t(ForwardIter first, ForwardIter last)
    {
        typedef typename std::iterator_traits<ForwardIter>::value_type value_t;

        assert(std::distance(first, last) >= 0);
        size_t const size_ =
          static_cast<size_t>(std::distance(first, last)) * sizeof(value_t);
        int const rc = zmq_msg_init_size(&msg, size_);
        if (rc != 0)
            throw error_t();
        std::copy(first, last, data<value_t>());
    }

    message_t(const void *data_, size_t size_)
    {
        int rc = zmq_msg_init_size(&msg, size_);
        if (rc != 0)
            throw error_t();
        if (size_)
        {
            // this constructor allows (nullptr, 0),
            // memcpy with a null pointer is UB
            memcpy(data(), data_, size_);
        }
    }

    message_t(void *data_, size_t size_, free_fn *ffn_, void *hint_ = ZMQ_NULLPTR)
    {
        int rc = zmq_msg_init_data(&msg, data_, size_, ffn_, hint_);
        if (rc != 0)
            throw error_t();
    }

#if defined(ZMQ_CPP11) && !defined(ZMQ_CPP11_PARTIAL)
    template<class Range,
             typename = typename std::enable_if<
               detail::is_range<Range>::value
               && ZMQ_IS_TRIVIALLY_COPYABLE(detail::range_value_t<Range>)
               && !std::is_same<Range, message_t>::value>::type>
    explicit message_t(const Range &rng) :
        message_t(detail::ranges::begin(rng), detail::ranges::end(rng))
    {
    }
#endif

#ifdef ZMQ_HAS_RVALUE_REFS
    message_t(message_t &&rhs) ZMQ_NOTHROW : msg(rhs.msg)
    {
        int rc = zmq_msg_init(&rhs.msg);
        ZMQ_ASSERT(rc == 0);
    }

    message_t &operator=(message_t &&rhs) ZMQ_NOTHROW
    {
        std::swap(msg, rhs.msg);
        return *this;
    }
#endif

    ~message_t() ZMQ_NOTHROW
    {
        int rc = zmq_msg_close(&msg);
        ZMQ_ASSERT(rc == 0);
    }

    void rebuild()
    {
        int rc = zmq_msg_close(&msg);
        if (rc != 0)
            throw error_t();
        rc = zmq_msg_init(&msg);
        ZMQ_ASSERT(rc == 0);
    }

    void rebuild(size_t size_)
    {
        int rc = zmq_msg_close(&msg);
        if (rc != 0)
            throw error_t();
        rc = zmq_msg_init_size(&msg, size_);
        if (rc != 0)
            throw error_t();
    }

    void rebuild(const void *data_, size_t size_)
    {
        int rc = zmq_msg_close(&msg);
        if (rc != 0)
            throw error_t();
        rc = zmq_msg_init_size(&msg, size_);
        if (rc != 0)
            throw error_t();
        memcpy(data(), data_, size_);
    }

    void rebuild(void *data_, size_t size_, free_fn *ffn_, void *hint_ = ZMQ_NULLPTR)
    {
        int rc = zmq_msg_close(&msg);
        if (rc != 0)
            throw error_t();
        rc = zmq_msg_init_data(&msg, data_, size_, ffn_, hint_);
        if (rc != 0)
            throw error_t();
    }

    ZMQ_DEPRECATED("from 4.3.1, use move taking non-const reference instead")
    void move(message_t const *msg_)
    {
        int rc = zmq_msg_move(&msg, const_cast<zmq_msg_t *>(msg_->handle()));
        if (rc != 0)
            throw error_t();
    }

    void move(message_t &msg_)
    {
        int rc = zmq_msg_move(&msg, msg_.handle());
        if (rc != 0)
            throw error_t();
    }

    ZMQ_DEPRECATED("from 4.3.1, use copy taking non-const reference instead")
    void copy(message_t const *msg_)
    {
        int rc = zmq_msg_copy(&msg, const_cast<zmq_msg_t *>(msg_->handle()));
        if (rc != 0)
            throw error_t();
    }

    void copy(message_t &msg_)
    {
        int rc = zmq_msg_copy(&msg, msg_.handle());
        if (rc != 0)
            throw error_t();
    }

    bool more() const ZMQ_NOTHROW
    {
        int rc = zmq_msg_more(const_cast<zmq_msg_t *>(&msg));
        return rc != 0;
    }

    void *data() ZMQ_NOTHROW { return zmq_msg_data(&msg); }

    const void *data() const ZMQ_NOTHROW
    {
        return zmq_msg_data(const_cast<zmq_msg_t *>(&msg));
    }

    size_t size() const ZMQ_NOTHROW
    {
        return zmq_msg_size(const_cast<zmq_msg_t *>(&msg));
    }

    ZMQ_NODISCARD bool empty() const ZMQ_NOTHROW { return size() == 0u; }

    template<typename T> T *data() ZMQ_NOTHROW { return static_cast<T *>(data()); }

    template<typename T> T const *data() const ZMQ_NOTHROW
    {
        return static_cast<T const *>(data());
    }

    ZMQ_DEPRECATED("from 4.3.0, use operator== instead")
    bool equal(const message_t *other) const ZMQ_NOTHROW { return *this == *other; }

    bool operator==(const message_t &other) const ZMQ_NOTHROW
    {
        const size_t my_size = size();
        return my_size == other.size() && 0 == memcmp(data(), other.data(), my_size);
    }

    bool operator!=(const message_t &other) const ZMQ_NOTHROW
    {
        return !(*this == other);
    }

#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(3, 2, 0)
    int get(int property_)
    {
        int value = zmq_msg_get(&msg, property_);
        if (value == -1)
            throw error_t();
        return value;
    }
#endif

#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 1, 0)
    const char *gets(const char *property_)
    {
        const char *value = zmq_msg_gets(&msg, property_);
        if (value == ZMQ_NULLPTR)
            throw error_t();
        return value;
    }
#endif

#if defined(ZMQ_BUILD_DRAFT_API) && ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 0)
    uint32_t routing_id() const
    {
        return zmq_msg_routing_id(const_cast<zmq_msg_t *>(&msg));
    }

    void set_routing_id(uint32_t routing_id)
    {
        int rc = zmq_msg_set_routing_id(&msg, routing_id);
        if (rc != 0)
            throw error_t();
    }

    const char *group() const
    {
        return zmq_msg_group(const_cast<zmq_msg_t *>(&msg));
    }

    void set_group(const char *group)
    {
        int rc = zmq_msg_set_group(&msg, group);
        if (rc != 0)
            throw error_t();
    }
#endif

    // interpret message content as a string
    std::string to_string() const
    {
        return std::string(static_cast<const char *>(data()), size());
    }
#ifdef ZMQ_CPP17
    // interpret message content as a string
    std::string_view to_string_view() const noexcept
    {
        return std::string_view(static_cast<const char *>(data()), size());
    }
#endif

    /** Dump content to string for debugging.
    *   Ascii chars are readable, the rest is printed as hex.
    *   Probably ridiculously slow.
    *   Use to_string() or to_string_view() for
    *   interpreting the message as a string.
    */
    std::string str() const
    {
        // Partly mutuated from the same method in zmq::multipart_t
        std::stringstream os;

        const unsigned char *msg_data = this->data<unsigned char>();
        unsigned char byte;
        size_t size = this->size();
        int is_ascii[2] = {0, 0};

        os << "zmq::message_t [size " << std::dec << std::setw(3)
           << std::setfill('0') << size << "] (";
        // Totally arbitrary
        if (size >= 1000) {
            os << "... too big to print)";
        } else {
            while (size--) {
                byte = *msg_data++;

                is_ascii[1] = (byte >= 32 && byte < 127);
                if (is_ascii[1] != is_ascii[0])
                    os << " "; // Separate text/non text

                if (is_ascii[1]) {
                    os << byte;
                } else {
                    os << std::hex << std::uppercase << std::setw(2)
                       << std::setfill('0') << static_cast<short>(byte);
                }
                is_ascii[0] = is_ascii[1];
            }
            os << ")";
        }
        return os.str();
    }

    void swap(message_t &other) ZMQ_NOTHROW
    {
        // this assumes zmq::msg_t from libzmq is trivially relocatable
        std::swap(msg, other.msg);
    }

    ZMQ_NODISCARD zmq_msg_t *handle() ZMQ_NOTHROW { return &msg; }
    ZMQ_NODISCARD const zmq_msg_t *handle() const ZMQ_NOTHROW { return &msg; }

  private:
    //  The underlying message
    zmq_msg_t msg;

    //  Disable implicit message copying, so that users won't use shared
    //  messages (less efficient) without being aware of the fact.
    message_t(const message_t &) ZMQ_DELETED_FUNCTION;
    void operator=(const message_t &) ZMQ_DELETED_FUNCTION;
};

inline void swap(message_t &a, message_t &b) ZMQ_NOTHROW
{
    a.swap(b);
}

#ifdef ZMQ_CPP11
enum class ctxopt
{
#ifdef ZMQ_BLOCKY
    blocky = ZMQ_BLOCKY,
#endif
#ifdef ZMQ_IO_THREADS
    io_threads = ZMQ_IO_THREADS,
#endif
#ifdef ZMQ_THREAD_SCHED_POLICY
    thread_sched_policy = ZMQ_THREAD_SCHED_POLICY,
#endif
#ifdef ZMQ_THREAD_PRIORITY
    thread_priority = ZMQ_THREAD_PRIORITY,
#endif
#ifdef ZMQ_THREAD_AFFINITY_CPU_ADD
    thread_affinity_cpu_add = ZMQ_THREAD_AFFINITY_CPU_ADD,
#endif
#ifdef ZMQ_THREAD_AFFINITY_CPU_REMOVE
    thread_affinity_cpu_remove = ZMQ_THREAD_AFFINITY_CPU_REMOVE,
#endif
#ifdef ZMQ_THREAD_NAME_PREFIX
    thread_name_prefix = ZMQ_THREAD_NAME_PREFIX,
#endif
#ifdef ZMQ_MAX_MSGSZ
    max_msgsz = ZMQ_MAX_MSGSZ,
#endif
#ifdef ZMQ_ZERO_COPY_RECV
    zero_copy_recv = ZMQ_ZERO_COPY_RECV,
#endif
#ifdef ZMQ_MAX_SOCKETS
    max_sockets = ZMQ_MAX_SOCKETS,
#endif
#ifdef ZMQ_SOCKET_LIMIT
    socket_limit = ZMQ_SOCKET_LIMIT,
#endif
#ifdef ZMQ_IPV6
    ipv6 = ZMQ_IPV6,
#endif
#ifdef ZMQ_MSG_T_SIZE
    msg_t_size = ZMQ_MSG_T_SIZE
#endif
};
#endif

class context_t
{
  public:
    context_t()
    {
        ptr = zmq_ctx_new();
        if (ptr == ZMQ_NULLPTR)
            throw error_t();
    }


    explicit context_t(int io_threads_, int max_sockets_ = ZMQ_MAX_SOCKETS_DFLT)
    {
        ptr = zmq_ctx_new();
        if (ptr == ZMQ_NULLPTR)
            throw error_t();

        int rc = zmq_ctx_set(ptr, ZMQ_IO_THREADS, io_threads_);
        ZMQ_ASSERT(rc == 0);

        rc = zmq_ctx_set(ptr, ZMQ_MAX_SOCKETS, max_sockets_);
        ZMQ_ASSERT(rc == 0);
    }

#ifdef ZMQ_HAS_RVALUE_REFS
    context_t(context_t &&rhs) ZMQ_NOTHROW : ptr(rhs.ptr) { rhs.ptr = ZMQ_NULLPTR; }
    context_t &operator=(context_t &&rhs) ZMQ_NOTHROW
    {
        close();
        std::swap(ptr, rhs.ptr);
        return *this;
    }
#endif

    ~context_t() ZMQ_NOTHROW { close(); }

    ZMQ_CPP11_DEPRECATED("from 4.7.0, use set taking zmq::ctxopt instead")
    int setctxopt(int option_, int optval_)
    {
        int rc = zmq_ctx_set(ptr, option_, optval_);
        ZMQ_ASSERT(rc == 0);
        return rc;
    }

    ZMQ_CPP11_DEPRECATED("from 4.7.0, use get taking zmq::ctxopt instead")
    int getctxopt(int option_) { return zmq_ctx_get(ptr, option_); }

#ifdef ZMQ_CPP11
    void set(ctxopt option, int optval)
    {
        int rc = zmq_ctx_set(ptr, static_cast<int>(option), optval);
        if (rc == -1)
            throw error_t();
    }

    ZMQ_NODISCARD int get(ctxopt option)
    {
        int rc = zmq_ctx_get(ptr, static_cast<int>(option));
        // some options have a default value of -1
        // which is unfortunate, and may result in errors
        // that don't make sense
        if (rc == -1)
            throw error_t();
        return rc;
    }
#endif

    // Terminates context (see also shutdown()).
    void close() ZMQ_NOTHROW
    {
        if (ptr == ZMQ_NULLPTR)
            return;

        int rc;
        do {
            rc = zmq_ctx_destroy(ptr);
        } while (rc == -1 && errno == EINTR);

        ZMQ_ASSERT(rc == 0);
        ptr = ZMQ_NULLPTR;
    }

    // Shutdown context in preparation for termination (close()).
    // Causes all blocking socket operations and any further
    // socket operations to return with ETERM.
    void shutdown() ZMQ_NOTHROW
    {
        if (ptr == ZMQ_NULLPTR)
            return;
        int rc = zmq_ctx_shutdown(ptr);
        ZMQ_ASSERT(rc == 0);
    }

    //  Be careful with this, it's probably only useful for
    //  using the C api together with an existing C++ api.
    //  Normally you should never need to use this.
    ZMQ_EXPLICIT operator void *() ZMQ_NOTHROW { return ptr; }

    ZMQ_EXPLICIT operator void const *() const ZMQ_NOTHROW { return ptr; }

    operator bool() const ZMQ_NOTHROW { return ptr != ZMQ_NULLPTR; }

    void swap(context_t &other) ZMQ_NOTHROW { std::swap(ptr, other.ptr); }

  private:
    void *ptr;

    context_t(const context_t &) ZMQ_DELETED_FUNCTION;
    void operator=(const context_t &) ZMQ_DELETED_FUNCTION;
};

inline void swap(context_t &a, context_t &b) ZMQ_NOTHROW
{
    a.swap(b);
}

#ifdef ZMQ_CPP11

struct recv_buffer_size
{
    size_t size;             // number of bytes written to buffer
    size_t untruncated_size; // untruncated message size in bytes

    ZMQ_NODISCARD bool truncated() const noexcept
    {
        return size != untruncated_size;
    }
};

#if defined(ZMQ_HAS_OPTIONAL) && (ZMQ_HAS_OPTIONAL > 0)

using send_result_t = std::optional<size_t>;
using recv_result_t = std::optional<size_t>;
using recv_buffer_result_t = std::optional<recv_buffer_size>;

#else

namespace detail
{
// A C++11 type emulating the most basic
// operations of std::optional for trivial types
template<class T> class trivial_optional
{
  public:
    static_assert(std::is_trivial<T>::value, "T must be trivial");
    using value_type = T;

    trivial_optional() = default;
    trivial_optional(T value) noexcept : _value(value), _has_value(true) {}

    const T *operator->() const noexcept
    {
        assert(_has_value);
        return &_value;
    }
    T *operator->() noexcept
    {
        assert(_has_value);
        return &_value;
    }

    const T &operator*() const noexcept
    {
        assert(_has_value);
        return _value;
    }
    T &operator*() noexcept
    {
        assert(_has_value);
        return _value;
    }

    T &value()
    {
        if (!_has_value)
            throw std::exception();
        return _value;
    }
    const T &value() const
    {
        if (!_has_value)
            throw std::exception();
        return _value;
    }

    explicit operator bool() const noexcept { return _has_value; }
    bool has_value() const noexcept { return _has_value; }

  private:
    T _value{};
    bool _has_value{false};
};
} // namespace detail

using send_result_t = detail::trivial_optional<size_t>;
using recv_result_t = detail::trivial_optional<size_t>;
using recv_buffer_result_t = detail::trivial_optional<recv_buffer_size>;

#endif

namespace detail
{
template<class T> constexpr T enum_bit_or(T a, T b) noexcept
{
    static_assert(std::is_enum<T>::value, "must be enum");
    using U = typename std::underlying_type<T>::type;
    return static_cast<T>(static_cast<U>(a) | static_cast<U>(b));
}
template<class T> constexpr T enum_bit_and(T a, T b) noexcept
{
    static_assert(std::is_enum<T>::value, "must be enum");
    using U = typename std::underlying_type<T>::type;
    return static_cast<T>(static_cast<U>(a) & static_cast<U>(b));
}
template<class T> constexpr T enum_bit_xor(T a, T b) noexcept
{
    static_assert(std::is_enum<T>::value, "must be enum");
    using U = typename std::underlying_type<T>::type;
    return static_cast<T>(static_cast<U>(a) ^ static_cast<U>(b));
}
template<class T> constexpr T enum_bit_not(T a) noexcept
{
    static_assert(std::is_enum<T>::value, "must be enum");
    using U = typename std::underlying_type<T>::type;
    return static_cast<T>(~static_cast<U>(a));
}
} // namespace detail

// partially satisfies named requirement BitmaskType
enum class send_flags : int
{
    none = 0,
    dontwait = ZMQ_DONTWAIT,
    sndmore = ZMQ_SNDMORE
};

constexpr send_flags operator|(send_flags a, send_flags b) noexcept
{
    return detail::enum_bit_or(a, b);
}
constexpr send_flags operator&(send_flags a, send_flags b) noexcept
{
    return detail::enum_bit_and(a, b);
}
constexpr send_flags operator^(send_flags a, send_flags b) noexcept
{
    return detail::enum_bit_xor(a, b);
}
constexpr send_flags operator~(send_flags a) noexcept
{
    return detail::enum_bit_not(a);
}

// partially satisfies named requirement BitmaskType
enum class recv_flags : int
{
    none = 0,
    dontwait = ZMQ_DONTWAIT
};

constexpr recv_flags operator|(recv_flags a, recv_flags b) noexcept
{
    return detail::enum_bit_or(a, b);
}
constexpr recv_flags operator&(recv_flags a, recv_flags b) noexcept
{
    return detail::enum_bit_and(a, b);
}
constexpr recv_flags operator^(recv_flags a, recv_flags b) noexcept
{
    return detail::enum_bit_xor(a, b);
}
constexpr recv_flags operator~(recv_flags a) noexcept
{
    return detail::enum_bit_not(a);
}


// mutable_buffer, const_buffer and buffer are based on
// the Networking TS specification, draft:
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/n4771.pdf

class mutable_buffer
{
  public:
    constexpr mutable_buffer() noexcept : _data(nullptr), _size(0) {}
    constexpr mutable_buffer(void *p, size_t n) noexcept : _data(p), _size(n)
    {
#ifdef ZMQ_CPP14
        assert(p != nullptr || n == 0);
#endif
    }

    constexpr void *data() const noexcept { return _data; }
    constexpr size_t size() const noexcept { return _size; }
    mutable_buffer &operator+=(size_t n) noexcept
    {
        // (std::min) is a workaround for when a min macro is defined
        const auto shift = (std::min)(n, _size);
        _data = static_cast<char *>(_data) + shift;
        _size -= shift;
        return *this;
    }

  private:
    void *_data;
    size_t _size;
};

inline mutable_buffer operator+(const mutable_buffer &mb, size_t n) noexcept
{
    return mutable_buffer(static_cast<char *>(mb.data()) + (std::min)(n, mb.size()),
                          mb.size() - (std::min)(n, mb.size()));
}
inline mutable_buffer operator+(size_t n, const mutable_buffer &mb) noexcept
{
    return mb + n;
}

class const_buffer
{
  public:
    constexpr const_buffer() noexcept : _data(nullptr), _size(0) {}
    constexpr const_buffer(const void *p, size_t n) noexcept : _data(p), _size(n)
    {
#ifdef ZMQ_CPP14
        assert(p != nullptr || n == 0);
#endif
    }
    constexpr const_buffer(const mutable_buffer &mb) noexcept :
        _data(mb.data()), _size(mb.size())
    {
    }

    constexpr const void *data() const noexcept { return _data; }
    constexpr size_t size() const noexcept { return _size; }
    const_buffer &operator+=(size_t n) noexcept
    {
        const auto shift = (std::min)(n, _size);
        _data = static_cast<const char *>(_data) + shift;
        _size -= shift;
        return *this;
    }

  private:
    const void *_data;
    size_t _size;
};

inline const_buffer operator+(const const_buffer &cb, size_t n) noexcept
{
    return const_buffer(static_cast<const char *>(cb.data())
                          + (std::min)(n, cb.size()),
                        cb.size() - (std::min)(n, cb.size()));
}
inline const_buffer operator+(size_t n, const const_buffer &cb) noexcept
{
    return cb + n;
}

// buffer creation

constexpr mutable_buffer buffer(void *p, size_t n) noexcept
{
    return mutable_buffer(p, n);
}
constexpr const_buffer buffer(const void *p, size_t n) noexcept
{
    return const_buffer(p, n);
}
constexpr mutable_buffer buffer(const mutable_buffer &mb) noexcept
{
    return mb;
}
inline mutable_buffer buffer(const mutable_buffer &mb, size_t n) noexcept
{
    return mutable_buffer(mb.data(), (std::min)(mb.size(), n));
}
constexpr const_buffer buffer(const const_buffer &cb) noexcept
{
    return cb;
}
inline const_buffer buffer(const const_buffer &cb, size_t n) noexcept
{
    return const_buffer(cb.data(), (std::min)(cb.size(), n));
}

namespace detail
{
template<class T> struct is_buffer
{
    static constexpr bool value =
      std::is_same<T, const_buffer>::value || std::is_same<T, mutable_buffer>::value;
};

template<class T> struct is_pod_like
{
    // NOTE: The networking draft N4771 section 16.11 requires
    // T in the buffer functions below to be
    // trivially copyable OR standard layout.
    // Here we decide to be conservative and require both.
    static constexpr bool value =
      ZMQ_IS_TRIVIALLY_COPYABLE(T) && std::is_standard_layout<T>::value;
};

template<class C> constexpr auto seq_size(const C &c) noexcept -> decltype(c.size())
{
    return c.size();
}
template<class T, size_t N>
constexpr size_t seq_size(const T (&/*array*/)[N]) noexcept
{
    return N;
}

template<class Seq>
auto buffer_contiguous_sequence(Seq &&seq) noexcept
  -> decltype(buffer(std::addressof(*std::begin(seq)), size_t{}))
{
    using T = typename std::remove_cv<
      typename std::remove_reference<decltype(*std::begin(seq))>::type>::type;
    static_assert(detail::is_pod_like<T>::value, "T must be POD");

    const auto size = seq_size(seq);
    return buffer(size != 0u ? std::addressof(*std::begin(seq)) : nullptr,
                  size * sizeof(T));
}
template<class Seq>
auto buffer_contiguous_sequence(Seq &&seq, size_t n_bytes) noexcept
  -> decltype(buffer_contiguous_sequence(seq))
{
    using T = typename std::remove_cv<
      typename std::remove_reference<decltype(*std::begin(seq))>::type>::type;
    static_assert(detail::is_pod_like<T>::value, "T must be POD");

    const auto size = seq_size(seq);
    return buffer(size != 0u ? std::addressof(*std::begin(seq)) : nullptr,
                  (std::min)(size * sizeof(T), n_bytes));
}

} // namespace detail

// C array
template<class T, size_t N> mutable_buffer buffer(T (&data)[N]) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, size_t N>
mutable_buffer buffer(T (&data)[N], size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
template<class T, size_t N> const_buffer buffer(const T (&data)[N]) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, size_t N>
const_buffer buffer(const T (&data)[N], size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
// std::array
template<class T, size_t N> mutable_buffer buffer(std::array<T, N> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, size_t N>
mutable_buffer buffer(std::array<T, N> &data, size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
template<class T, size_t N>
const_buffer buffer(std::array<const T, N> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, size_t N>
const_buffer buffer(std::array<const T, N> &data, size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
template<class T, size_t N>
const_buffer buffer(const std::array<T, N> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, size_t N>
const_buffer buffer(const std::array<T, N> &data, size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
// std::vector
template<class T, class Allocator>
mutable_buffer buffer(std::vector<T, Allocator> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, class Allocator>
mutable_buffer buffer(std::vector<T, Allocator> &data, size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
template<class T, class Allocator>
const_buffer buffer(const std::vector<T, Allocator> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, class Allocator>
const_buffer buffer(const std::vector<T, Allocator> &data, size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
// std::basic_string
template<class T, class Traits, class Allocator>
mutable_buffer buffer(std::basic_string<T, Traits, Allocator> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, class Traits, class Allocator>
mutable_buffer buffer(std::basic_string<T, Traits, Allocator> &data,
                      size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
template<class T, class Traits, class Allocator>
const_buffer buffer(const std::basic_string<T, Traits, Allocator> &data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, class Traits, class Allocator>
const_buffer buffer(const std::basic_string<T, Traits, Allocator> &data,
                    size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}

#if defined(ZMQ_HAS_STRING_VIEW) && (ZMQ_HAS_STRING_VIEW > 0)
// std::basic_string_view
template<class T, class Traits>
const_buffer buffer(std::basic_string_view<T, Traits> data) noexcept
{
    return detail::buffer_contiguous_sequence(data);
}
template<class T, class Traits>
const_buffer buffer(std::basic_string_view<T, Traits> data, size_t n_bytes) noexcept
{
    return detail::buffer_contiguous_sequence(data, n_bytes);
}
#endif

// Buffer for a string literal (null terminated)
// where the buffer size excludes the terminating character.
// Equivalent to zmq::buffer(std::string_view("...")).
template<class Char, size_t N>
constexpr const_buffer str_buffer(const Char (&data)[N]) noexcept
{
    static_assert(detail::is_pod_like<Char>::value, "Char must be POD");
#ifdef ZMQ_CPP14
    assert(data[N - 1] == Char{0});
#endif
    return const_buffer(static_cast<const Char *>(data), (N - 1) * sizeof(Char));
}

namespace literals
{
constexpr const_buffer operator"" _zbuf(const char *str, size_t len) noexcept
{
    return const_buffer(str, len * sizeof(char));
}
constexpr const_buffer operator"" _zbuf(const wchar_t *str, size_t len) noexcept
{
    return const_buffer(str, len * sizeof(wchar_t));
}
constexpr const_buffer operator"" _zbuf(const char16_t *str, size_t len) noexcept
{
    return const_buffer(str, len * sizeof(char16_t));
}
constexpr const_buffer operator"" _zbuf(const char32_t *str, size_t len) noexcept
{
    return const_buffer(str, len * sizeof(char32_t));
}
}

#endif // ZMQ_CPP11


#ifdef ZMQ_CPP11
namespace sockopt
{
// There are two types of options,
// integral type with known compiler time size (int, bool, int64_t, uint64_t)
// and arrays with dynamic size (strings, binary data).

// BoolUnit: if true accepts values of type bool (but passed as T into libzmq)
template<int Opt, class T, bool BoolUnit = false> struct integral_option
{
};

// NullTerm:
// 0: binary data
// 1: null-terminated string (`getsockopt` size includes null)
// 2: binary (size 32) or Z85 encoder string of size 41 (null included)
template<int Opt, int NullTerm = 1> struct array_option
{
};

#define ZMQ_DEFINE_INTEGRAL_OPT(OPT, NAME, TYPE)                                    \
    using NAME##_t = integral_option<OPT, TYPE, false>;                             \
    ZMQ_INLINE_VAR ZMQ_CONSTEXPR_VAR NAME##_t NAME{}
#define ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(OPT, NAME, TYPE)                          \
    using NAME##_t = integral_option<OPT, TYPE, true>;                              \
    ZMQ_INLINE_VAR ZMQ_CONSTEXPR_VAR NAME##_t NAME{}
#define ZMQ_DEFINE_ARRAY_OPT(OPT, NAME)                                             \
    using NAME##_t = array_option<OPT>;                                             \
    ZMQ_INLINE_VAR ZMQ_CONSTEXPR_VAR NAME##_t NAME{}
#define ZMQ_DEFINE_ARRAY_OPT_BINARY(OPT, NAME)                                      \
    using NAME##_t = array_option<OPT, 0>;                                          \
    ZMQ_INLINE_VAR ZMQ_CONSTEXPR_VAR NAME##_t NAME{}
#define ZMQ_DEFINE_ARRAY_OPT_BIN_OR_Z85(OPT, NAME)                                  \
    using NAME##_t = array_option<OPT, 2>;                                          \
    ZMQ_INLINE_VAR ZMQ_CONSTEXPR_VAR NAME##_t NAME{}

// duplicate definition from libzmq 4.3.3
#if defined _WIN32
#if defined _WIN64
typedef unsigned __int64 cppzmq_fd_t;
#else
typedef unsigned int cppzmq_fd_t;
#endif
#else
typedef int cppzmq_fd_t;
#endif

#ifdef ZMQ_AFFINITY
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_AFFINITY, affinity, uint64_t);
#endif
#ifdef ZMQ_BACKLOG
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_BACKLOG, backlog, int);
#endif
#ifdef ZMQ_BINDTODEVICE
ZMQ_DEFINE_ARRAY_OPT_BINARY(ZMQ_BINDTODEVICE, bindtodevice);
#endif
#ifdef ZMQ_CONFLATE
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_CONFLATE, conflate, int);
#endif
#ifdef ZMQ_CONNECT_ROUTING_ID
ZMQ_DEFINE_ARRAY_OPT(ZMQ_CONNECT_ROUTING_ID, connect_routing_id);
#endif
#ifdef ZMQ_CONNECT_TIMEOUT
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_CONNECT_TIMEOUT, connect_timeout, int);
#endif
#ifdef ZMQ_CURVE_PUBLICKEY
ZMQ_DEFINE_ARRAY_OPT_BIN_OR_Z85(ZMQ_CURVE_PUBLICKEY, curve_publickey);
#endif
#ifdef ZMQ_CURVE_SECRETKEY
ZMQ_DEFINE_ARRAY_OPT_BIN_OR_Z85(ZMQ_CURVE_SECRETKEY, curve_secretkey);
#endif
#ifdef ZMQ_CURVE_SERVER
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_CURVE_SERVER, curve_server, int);
#endif
#ifdef ZMQ_CURVE_SERVERKEY
ZMQ_DEFINE_ARRAY_OPT_BIN_OR_Z85(ZMQ_CURVE_SERVERKEY, curve_serverkey);
#endif
#ifdef ZMQ_EVENTS
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_EVENTS, events, int);
#endif
#ifdef ZMQ_FD
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_FD, fd, cppzmq_fd_t);
#endif
#ifdef ZMQ_GSSAPI_PLAINTEXT
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_GSSAPI_PLAINTEXT, gssapi_plaintext, int);
#endif
#ifdef ZMQ_GSSAPI_SERVER
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_GSSAPI_SERVER, gssapi_server, int);
#endif
#ifdef ZMQ_GSSAPI_SERVICE_PRINCIPAL
ZMQ_DEFINE_ARRAY_OPT(ZMQ_GSSAPI_SERVICE_PRINCIPAL, gssapi_service_principal);
#endif
#ifdef ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE,
                        gssapi_service_principal_nametype,
                        int);
#endif
#ifdef ZMQ_GSSAPI_PRINCIPAL
ZMQ_DEFINE_ARRAY_OPT(ZMQ_GSSAPI_PRINCIPAL, gssapi_principal);
#endif
#ifdef ZMQ_GSSAPI_PRINCIPAL_NAMETYPE
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_GSSAPI_PRINCIPAL_NAMETYPE,
                        gssapi_principal_nametype,
                        int);
#endif
#ifdef ZMQ_HANDSHAKE_IVL
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_HANDSHAKE_IVL, handshake_ivl, int);
#endif
#ifdef ZMQ_HEARTBEAT_IVL
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_HEARTBEAT_IVL, heartbeat_ivl, int);
#endif
#ifdef ZMQ_HEARTBEAT_TIMEOUT
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_HEARTBEAT_TIMEOUT, heartbeat_timeout, int);
#endif
#ifdef ZMQ_HEARTBEAT_TTL
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_HEARTBEAT_TTL, heartbeat_ttl, int);
#endif
#ifdef ZMQ_IMMEDIATE
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_IMMEDIATE, immediate, int);
#endif
#ifdef ZMQ_INVERT_MATCHING
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_INVERT_MATCHING, invert_matching, int);
#endif
#ifdef ZMQ_IPV6
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_IPV6, ipv6, int);
#endif
#ifdef ZMQ_LAST_ENDPOINT
ZMQ_DEFINE_ARRAY_OPT(ZMQ_LAST_ENDPOINT, last_endpoint);
#endif
#ifdef ZMQ_LINGER
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_LINGER, linger, int);
#endif
#ifdef ZMQ_MAXMSGSIZE
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_MAXMSGSIZE, maxmsgsize, int64_t);
#endif
#ifdef ZMQ_MECHANISM
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_MECHANISM, mechanism, int);
#endif
#ifdef ZMQ_METADATA
ZMQ_DEFINE_ARRAY_OPT(ZMQ_METADATA, metadata);
#endif
#ifdef ZMQ_MULTICAST_HOPS
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_MULTICAST_HOPS, multicast_hops, int);
#endif
#ifdef ZMQ_MULTICAST_LOOP
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_MULTICAST_LOOP, multicast_loop, int);
#endif
#ifdef ZMQ_MULTICAST_MAXTPDU
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_MULTICAST_MAXTPDU, multicast_maxtpdu, int);
#endif
#ifdef ZMQ_PLAIN_SERVER
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_PLAIN_SERVER, plain_server, int);
#endif
#ifdef ZMQ_PLAIN_PASSWORD
ZMQ_DEFINE_ARRAY_OPT(ZMQ_PLAIN_PASSWORD, plain_password);
#endif
#ifdef ZMQ_PLAIN_USERNAME
ZMQ_DEFINE_ARRAY_OPT(ZMQ_PLAIN_USERNAME, plain_username);
#endif
#ifdef ZMQ_USE_FD
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_USE_FD, use_fd, int);
#endif
#ifdef ZMQ_PROBE_ROUTER
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_PROBE_ROUTER, probe_router, int);
#endif
#ifdef ZMQ_RATE
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_RATE, rate, int);
#endif
#ifdef ZMQ_RCVBUF
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_RCVBUF, rcvbuf, int);
#endif
#ifdef ZMQ_RCVHWM
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_RCVHWM, rcvhwm, int);
#endif
#ifdef ZMQ_RCVMORE
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_RCVMORE, rcvmore, int);
#endif
#ifdef ZMQ_RCVTIMEO
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_RCVTIMEO, rcvtimeo, int);
#endif
#ifdef ZMQ_RECONNECT_IVL
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_RECONNECT_IVL, reconnect_ivl, int);
#endif
#ifdef ZMQ_RECONNECT_IVL_MAX
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_RECONNECT_IVL_MAX, reconnect_ivl_max, int);
#endif
#ifdef ZMQ_RECOVERY_IVL
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_RECOVERY_IVL, recovery_ivl, int);
#endif
#ifdef ZMQ_REQ_CORRELATE
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_REQ_CORRELATE, req_correlate, int);
#endif
#ifdef ZMQ_REQ_RELAXED
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_REQ_RELAXED, req_relaxed, int);
#endif
#ifdef ZMQ_ROUTER_HANDOVER
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_ROUTER_HANDOVER, router_handover, int);
#endif
#ifdef ZMQ_ROUTER_MANDATORY
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_ROUTER_MANDATORY, router_mandatory, int);
#endif
#ifdef ZMQ_ROUTER_NOTIFY
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_ROUTER_NOTIFY, router_notify, int);
#endif
#ifdef ZMQ_ROUTING_ID
ZMQ_DEFINE_ARRAY_OPT_BINARY(ZMQ_ROUTING_ID, routing_id);
#endif
#ifdef ZMQ_SNDBUF
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_SNDBUF, sndbuf, int);
#endif
#ifdef ZMQ_SNDHWM
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_SNDHWM, sndhwm, int);
#endif
#ifdef ZMQ_SNDTIMEO
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_SNDTIMEO, sndtimeo, int);
#endif
#ifdef ZMQ_SOCKS_PROXY
ZMQ_DEFINE_ARRAY_OPT(ZMQ_SOCKS_PROXY, socks_proxy);
#endif
#ifdef ZMQ_STREAM_NOTIFY
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_STREAM_NOTIFY, stream_notify, int);
#endif
#ifdef ZMQ_SUBSCRIBE
ZMQ_DEFINE_ARRAY_OPT(ZMQ_SUBSCRIBE, subscribe);
#endif
#ifdef ZMQ_TCP_KEEPALIVE
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_TCP_KEEPALIVE, tcp_keepalive, int);
#endif
#ifdef ZMQ_TCP_KEEPALIVE_CNT
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_TCP_KEEPALIVE_CNT, tcp_keepalive_cnt, int);
#endif
#ifdef ZMQ_TCP_KEEPALIVE_IDLE
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_TCP_KEEPALIVE_IDLE, tcp_keepalive_idle, int);
#endif
#ifdef ZMQ_TCP_KEEPALIVE_INTVL
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_TCP_KEEPALIVE_INTVL, tcp_keepalive_intvl, int);
#endif
#ifdef ZMQ_TCP_MAXRT
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_TCP_MAXRT, tcp_maxrt, int);
#endif
#ifdef ZMQ_THREAD_SAFE
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_THREAD_SAFE, thread_safe, int);
#endif
#ifdef ZMQ_TOS
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_TOS, tos, int);
#endif
#ifdef ZMQ_TYPE
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_TYPE, type, int);
#endif
#ifdef ZMQ_UNSUBSCRIBE
ZMQ_DEFINE_ARRAY_OPT(ZMQ_UNSUBSCRIBE, unsubscribe);
#endif
#ifdef ZMQ_VMCI_BUFFER_SIZE
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_VMCI_BUFFER_SIZE, vmci_buffer_size, uint64_t);
#endif
#ifdef ZMQ_VMCI_BUFFER_MIN_SIZE
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_VMCI_BUFFER_MIN_SIZE, vmci_buffer_min_size, uint64_t);
#endif
#ifdef ZMQ_VMCI_BUFFER_MAX_SIZE
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_VMCI_BUFFER_MAX_SIZE, vmci_buffer_max_size, uint64_t);
#endif
#ifdef ZMQ_VMCI_CONNECT_TIMEOUT
ZMQ_DEFINE_INTEGRAL_OPT(ZMQ_VMCI_CONNECT_TIMEOUT, vmci_connect_timeout, int);
#endif
#ifdef ZMQ_XPUB_VERBOSE
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_XPUB_VERBOSE, xpub_verbose, int);
#endif
#ifdef ZMQ_XPUB_VERBOSER
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_XPUB_VERBOSER, xpub_verboser, int);
#endif
#ifdef ZMQ_XPUB_MANUAL
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_XPUB_MANUAL, xpub_manual, int);
#endif
#ifdef ZMQ_XPUB_NODROP
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_XPUB_NODROP, xpub_nodrop, int);
#endif
#ifdef ZMQ_XPUB_WELCOME_MSG
ZMQ_DEFINE_ARRAY_OPT(ZMQ_XPUB_WELCOME_MSG, xpub_welcome_msg);
#endif
#ifdef ZMQ_ZAP_ENFORCE_DOMAIN
ZMQ_DEFINE_INTEGRAL_BOOL_UNIT_OPT(ZMQ_ZAP_ENFORCE_DOMAIN, zap_enforce_domain, int);
#endif
#ifdef ZMQ_ZAP_DOMAIN
ZMQ_DEFINE_ARRAY_OPT(ZMQ_ZAP_DOMAIN, zap_domain);
#endif

} // namespace sockopt
#endif // ZMQ_CPP11


namespace detail
{
class socket_base
{
  public:
    socket_base() ZMQ_NOTHROW : _handle(ZMQ_NULLPTR) {}
    ZMQ_EXPLICIT socket_base(void *handle) ZMQ_NOTHROW : _handle(handle) {}

    template<typename T>
    ZMQ_CPP11_DEPRECATED("from 4.7.0, use `set` taking option from zmq::sockopt")
    void setsockopt(int option_, T const &optval)
    {
        setsockopt(option_, &optval, sizeof(T));
    }

    ZMQ_CPP11_DEPRECATED("from 4.7.0, use `set` taking option from zmq::sockopt")
    void setsockopt(int option_, const void *optval_, size_t optvallen_)
    {
        int rc = zmq_setsockopt(_handle, option_, optval_, optvallen_);
        if (rc != 0)
            throw error_t();
    }

    ZMQ_CPP11_DEPRECATED("from 4.7.0, use `get` taking option from zmq::sockopt")
    void getsockopt(int option_, void *optval_, size_t *optvallen_) const
    {
        int rc = zmq_getsockopt(_handle, option_, optval_, optvallen_);
        if (rc != 0)
            throw error_t();
    }

    template<typename T>
    ZMQ_CPP11_DEPRECATED("from 4.7.0, use `get` taking option from zmq::sockopt")
    T getsockopt(int option_) const
    {
        T optval;
        size_t optlen = sizeof(T);
        getsockopt(option_, &optval, &optlen);
        return optval;
    }

#ifdef ZMQ_CPP11
    // Set integral socket option, e.g.
    // `socket.set(zmq::sockopt::linger, 0)`
    template<int Opt, class T, bool BoolUnit>
    void set(sockopt::integral_option<Opt, T, BoolUnit>, const T &val)
    {
        static_assert(std::is_integral<T>::value, "T must be integral");
        set_option(Opt, &val, sizeof val);
    }

    // Set integral socket option from boolean, e.g.
    // `socket.set(zmq::sockopt::immediate, false)`
    template<int Opt, class T>
    void set(sockopt::integral_option<Opt, T, true>, bool val)
    {
        static_assert(std::is_integral<T>::value, "T must be integral");
        T rep_val = val;
        set_option(Opt, &rep_val, sizeof rep_val);
    }

    // Set array socket option, e.g.
    // `socket.set(zmq::sockopt::plain_username, "foo123")`
    template<int Opt, int NullTerm>
    void set(sockopt::array_option<Opt, NullTerm>, const char *buf)
    {
        set_option(Opt, buf, std::strlen(buf));
    }

    // Set array socket option, e.g.
    // `socket.set(zmq::sockopt::routing_id, zmq::buffer(id))`
    template<int Opt, int NullTerm>
    void set(sockopt::array_option<Opt, NullTerm>, const_buffer buf)
    {
        set_option(Opt, buf.data(), buf.size());
    }

    // Set array socket option, e.g.
    // `socket.set(zmq::sockopt::routing_id, id_str)`
    template<int Opt, int NullTerm>
    void set(sockopt::array_option<Opt, NullTerm>, const std::string &buf)
    {
        set_option(Opt, buf.data(), buf.size());
    }

#ifdef ZMQ_CPP17
    // Set array socket option, e.g.
    // `socket.set(zmq::sockopt::routing_id, id_str)`
    template<int Opt, int NullTerm>
    void set(sockopt::array_option<Opt, NullTerm>, std::string_view buf)
    {
        set_option(Opt, buf.data(), buf.size());
    }
#endif

    // Get scalar socket option, e.g.
    // `auto opt = socket.get(zmq::sockopt::linger)`
    template<int Opt, class T, bool BoolUnit>
    ZMQ_NODISCARD T get(sockopt::integral_option<Opt, T, BoolUnit>) const
    {
        static_assert(std::is_integral<T>::value, "T must be integral");
        T val;
        size_t size = sizeof val;
        get_option(Opt, &val, &size);
        assert(size == sizeof val);
        return val;
    }

    // Get array socket option, writes to buf, returns option size in bytes, e.g.
    // `size_t optsize = socket.get(zmq::sockopt::routing_id, zmq::buffer(id))`
    template<int Opt, int NullTerm>
    ZMQ_NODISCARD size_t get(sockopt::array_option<Opt, NullTerm>,
                             mutable_buffer buf) const
    {
        size_t size = buf.size();
        get_option(Opt, buf.data(), &size);
        return size;
    }

    // Get array socket option as string (initializes the string buffer size to init_size) e.g.
    // `auto s = socket.get(zmq::sockopt::routing_id)`
    // Note: removes the null character from null-terminated string options,
    // i.e. the string size excludes the null character.
    template<int Opt, int NullTerm>
    ZMQ_NODISCARD std::string get(sockopt::array_option<Opt, NullTerm>,
                                  size_t init_size = 1024) const
    {
        if (NullTerm == 2 && init_size == 1024) {
            init_size = 41; // get as Z85 string
        }
        std::string str(init_size, '\0');
        size_t size = get(sockopt::array_option<Opt>{}, buffer(str));
        if (NullTerm == 1) {
            if (size > 0) {
                assert(str[size - 1] == '\0');
                --size;
            }
        } else if (NullTerm == 2) {
            assert(size == 32 || size == 41);
            if (size == 41) {
                assert(str[size - 1] == '\0');
                --size;
            }
        }
        str.resize(size);
        return str;
    }
#endif

    void bind(std::string const &addr) { bind(addr.c_str()); }

    void bind(const char *addr_)
    {
        int rc = zmq_bind(_handle, addr_);
        if (rc != 0)
            throw error_t();
    }

    void unbind(std::string const &addr) { unbind(addr.c_str()); }

    void unbind(const char *addr_)
    {
        int rc = zmq_unbind(_handle, addr_);
        if (rc != 0)
            throw error_t();
    }

    void connect(std::string const &addr) { connect(addr.c_str()); }

    void connect(const char *addr_)
    {
        int rc = zmq_connect(_handle, addr_);
        if (rc != 0)
            throw error_t();
    }

    void disconnect(std::string const &addr) { disconnect(addr.c_str()); }

    void disconnect(const char *addr_)
    {
        int rc = zmq_disconnect(_handle, addr_);
        if (rc != 0)
            throw error_t();
    }

    bool connected() const ZMQ_NOTHROW { return (_handle != ZMQ_NULLPTR); }

    ZMQ_CPP11_DEPRECATED("from 4.3.1, use send taking a const_buffer and send_flags")
    size_t send(const void *buf_, size_t len_, int flags_ = 0)
    {
        int nbytes = zmq_send(_handle, buf_, len_, flags_);
        if (nbytes >= 0)
            return static_cast<size_t>(nbytes);
        if (zmq_errno() == EAGAIN)
            return 0;
        throw error_t();
    }

    ZMQ_CPP11_DEPRECATED("from 4.3.1, use send taking message_t and send_flags")
    bool send(message_t &msg_,
              int flags_ = 0) // default until removed
    {
        int nbytes = zmq_msg_send(msg_.handle(), _handle, flags_);
        if (nbytes >= 0)
            return true;
        if (zmq_errno() == EAGAIN)
            return false;
        throw error_t();
    }

    template<typename T>
    ZMQ_CPP11_DEPRECATED(
      "from 4.4.1, use send taking message_t or buffer (for contiguous "
      "ranges), and send_flags")
    bool send(T first, T last, int flags_ = 0)
    {
        zmq::message_t msg(first, last);
        int nbytes = zmq_msg_send(msg.handle(), _handle, flags_);
        if (nbytes >= 0)
            return true;
        if (zmq_errno() == EAGAIN)
            return false;
        throw error_t();
    }

#ifdef ZMQ_HAS_RVALUE_REFS
    ZMQ_CPP11_DEPRECATED("from 4.3.1, use send taking message_t and send_flags")
    bool send(message_t &&msg_,
              int flags_ = 0) // default until removed
    {
#ifdef ZMQ_CPP11
        return send(msg_, static_cast<send_flags>(flags_)).has_value();
#else
        return send(msg_, flags_);
#endif
    }
#endif

#ifdef ZMQ_CPP11
    send_result_t send(const_buffer buf, send_flags flags = send_flags::none)
    {
        const int nbytes =
          zmq_send(_handle, buf.data(), buf.size(), static_cast<int>(flags));
        if (nbytes >= 0)
            return static_cast<size_t>(nbytes);
        if (zmq_errno() == EAGAIN)
            return {};
        throw error_t();
    }

    send_result_t send(message_t &msg, send_flags flags)
    {
        int nbytes = zmq_msg_send(msg.handle(), _handle, static_cast<int>(flags));
        if (nbytes >= 0)
            return static_cast<size_t>(nbytes);
        if (zmq_errno() == EAGAIN)
            return {};
        throw error_t();
    }

    send_result_t send(message_t &&msg, send_flags flags)
    {
        return send(msg, flags);
    }
#endif

    ZMQ_CPP11_DEPRECATED(
      "from 4.3.1, use recv taking a mutable_buffer and recv_flags")
    size_t recv(void *buf_, size_t len_, int flags_ = 0)
    {
        int nbytes = zmq_recv(_handle, buf_, len_, flags_);
        if (nbytes >= 0)
            return static_cast<size_t>(nbytes);
        if (zmq_errno() == EAGAIN)
            return 0;
        throw error_t();
    }

    ZMQ_CPP11_DEPRECATED(
      "from 4.3.1, use recv taking a reference to message_t and recv_flags")
    bool recv(message_t *msg_, int flags_ = 0)
    {
        int nbytes = zmq_msg_recv(msg_->handle(), _handle, flags_);
        if (nbytes >= 0)
            return true;
        if (zmq_errno() == EAGAIN)
            return false;
        throw error_t();
    }

#ifdef ZMQ_CPP11
    ZMQ_NODISCARD
    recv_buffer_result_t recv(mutable_buffer buf,
                              recv_flags flags = recv_flags::none)
    {
        const int nbytes =
          zmq_recv(_handle, buf.data(), buf.size(), static_cast<int>(flags));
        if (nbytes >= 0) {
            return recv_buffer_size{
              (std::min)(static_cast<size_t>(nbytes), buf.size()),
              static_cast<size_t>(nbytes)};
        }
        if (zmq_errno() == EAGAIN)
            return {};
        throw error_t();
    }

    ZMQ_NODISCARD
    recv_result_t recv(message_t &msg, recv_flags flags = recv_flags::none)
    {
        const int nbytes =
          zmq_msg_recv(msg.handle(), _handle, static_cast<int>(flags));
        if (nbytes >= 0) {
            assert(msg.size() == static_cast<size_t>(nbytes));
            return static_cast<size_t>(nbytes);
        }
        if (zmq_errno() == EAGAIN)
            return {};
        throw error_t();
    }
#endif

#if defined(ZMQ_BUILD_DRAFT_API) && ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 0)
    void join(const char *group)
    {
        int rc = zmq_join(_handle, group);
        if (rc != 0)
            throw error_t();
    }

    void leave(const char *group)
    {
        int rc = zmq_leave(_handle, group);
        if (rc != 0)
            throw error_t();
    }
#endif

    ZMQ_NODISCARD void *handle() ZMQ_NOTHROW { return _handle; }
    ZMQ_NODISCARD const void *handle() const ZMQ_NOTHROW { return _handle; }

    ZMQ_EXPLICIT operator bool() const ZMQ_NOTHROW { return _handle != ZMQ_NULLPTR; }
    // note: non-const operator bool can be removed once
    // operator void* is removed from socket_t
    ZMQ_EXPLICIT operator bool() ZMQ_NOTHROW { return _handle != ZMQ_NULLPTR; }

  protected:
    void *_handle;

  private:
    void set_option(int option_, const void *optval_, size_t optvallen_)
    {
        int rc = zmq_setsockopt(_handle, option_, optval_, optvallen_);
        if (rc != 0)
            throw error_t();
    }

    void get_option(int option_, void *optval_, size_t *optvallen_) const
    {
        int rc = zmq_getsockopt(_handle, option_, optval_, optvallen_);
        if (rc != 0)
            throw error_t();
    }
};
} // namespace detail

#ifdef ZMQ_CPP11
enum class socket_type : int
{
    req = ZMQ_REQ,
    rep = ZMQ_REP,
    dealer = ZMQ_DEALER,
    router = ZMQ_ROUTER,
    pub = ZMQ_PUB,
    sub = ZMQ_SUB,
    xpub = ZMQ_XPUB,
    xsub = ZMQ_XSUB,
    push = ZMQ_PUSH,
    pull = ZMQ_PULL,
#if defined(ZMQ_BUILD_DRAFT_API) && ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 0)
    server = ZMQ_SERVER,
    client = ZMQ_CLIENT,
    radio = ZMQ_RADIO,
    dish = ZMQ_DISH,
#endif
#if ZMQ_VERSION_MAJOR >= 4
    stream = ZMQ_STREAM,
#endif
    pair = ZMQ_PAIR
};
#endif

struct from_handle_t
{
    struct _private
    {
    }; // disabling use other than with from_handle
    ZMQ_CONSTEXPR_FN ZMQ_EXPLICIT from_handle_t(_private /*p*/) ZMQ_NOTHROW {}
};

ZMQ_CONSTEXPR_VAR from_handle_t from_handle =
  from_handle_t(from_handle_t::_private());

// A non-owning nullable reference to a socket.
// The reference is invalidated on socket close or destruction.
class socket_ref : public detail::socket_base
{
  public:
    socket_ref() ZMQ_NOTHROW : detail::socket_base() {}
#ifdef ZMQ_CPP11
    socket_ref(std::nullptr_t) ZMQ_NOTHROW : detail::socket_base() {}
#endif
    socket_ref(from_handle_t /*fh*/, void *handle) ZMQ_NOTHROW
        : detail::socket_base(handle)
    {
    }
};

#ifdef ZMQ_CPP11
inline bool operator==(socket_ref sr, std::nullptr_t /*p*/) ZMQ_NOTHROW
{
    return sr.handle() == nullptr;
}
inline bool operator==(std::nullptr_t /*p*/, socket_ref sr) ZMQ_NOTHROW
{
    return sr.handle() == nullptr;
}
inline bool operator!=(socket_ref sr, std::nullptr_t /*p*/) ZMQ_NOTHROW
{
    return !(sr == nullptr);
}
inline bool operator!=(std::nullptr_t /*p*/, socket_ref sr) ZMQ_NOTHROW
{
    return !(sr == nullptr);
}
#endif

inline bool operator==(socket_ref a, socket_ref b) ZMQ_NOTHROW
{
    return std::equal_to<void *>()(a.handle(), b.handle());
}
inline bool operator!=(socket_ref a, socket_ref b) ZMQ_NOTHROW
{
    return !(a == b);
}
inline bool operator<(socket_ref a, socket_ref b) ZMQ_NOTHROW
{
    return std::less<void *>()(a.handle(), b.handle());
}
inline bool operator>(socket_ref a, socket_ref b) ZMQ_NOTHROW
{
    return b < a;
}
inline bool operator<=(socket_ref a, socket_ref b) ZMQ_NOTHROW
{
    return !(a > b);
}
inline bool operator>=(socket_ref a, socket_ref b) ZMQ_NOTHROW
{
    return !(a < b);
}

} // namespace zmq

#ifdef ZMQ_CPP11
namespace std
{
template<> struct hash<zmq::socket_ref>
{
    size_t operator()(zmq::socket_ref sr) const ZMQ_NOTHROW
    {
        return hash<void *>()(sr.handle());
    }
};
} // namespace std
#endif

namespace zmq
{
class socket_t : public detail::socket_base
{
    friend class monitor_t;

  public:
    socket_t() ZMQ_NOTHROW : detail::socket_base(ZMQ_NULLPTR), ctxptr(ZMQ_NULLPTR) {}

    socket_t(context_t &context_, int type_) :
        detail::socket_base(zmq_socket(static_cast<void *>(context_), type_)),
        ctxptr(static_cast<void *>(context_))
    {
        if (_handle == ZMQ_NULLPTR)
            throw error_t();
    }

#ifdef ZMQ_CPP11
    socket_t(context_t &context_, socket_type type_) :
        socket_t(context_, static_cast<int>(type_))
    {
    }
#endif

#ifdef ZMQ_HAS_RVALUE_REFS
    socket_t(socket_t &&rhs) ZMQ_NOTHROW : detail::socket_base(rhs._handle),
                                           ctxptr(rhs.ctxptr)
    {
        rhs._handle = ZMQ_NULLPTR;
        rhs.ctxptr = ZMQ_NULLPTR;
    }
    socket_t &operator=(socket_t &&rhs) ZMQ_NOTHROW
    {
        close();
        std::swap(_handle, rhs._handle);
        return *this;
    }
#endif

    ~socket_t() ZMQ_NOTHROW { close(); }

    operator void *() ZMQ_NOTHROW { return _handle; }

    operator void const *() const ZMQ_NOTHROW { return _handle; }

    void close() ZMQ_NOTHROW
    {
        if (_handle == ZMQ_NULLPTR)
            // already closed
            return;
        int rc = zmq_close(_handle);
        ZMQ_ASSERT(rc == 0);
        _handle = ZMQ_NULLPTR;
    }

    void swap(socket_t &other) ZMQ_NOTHROW
    {
        std::swap(_handle, other._handle);
        std::swap(ctxptr, other.ctxptr);
    }

    operator socket_ref() ZMQ_NOTHROW { return socket_ref(from_handle, _handle); }

  private:
    void *ctxptr;

    socket_t(const socket_t &) ZMQ_DELETED_FUNCTION;
    void operator=(const socket_t &) ZMQ_DELETED_FUNCTION;

    // used by monitor_t
    socket_t(void *context_, int type_) :
        detail::socket_base(zmq_socket(context_, type_)), ctxptr(context_)
    {
        if (_handle == ZMQ_NULLPTR)
            throw error_t();
    }
};

inline void swap(socket_t &a, socket_t &b) ZMQ_NOTHROW
{
    a.swap(b);
}

ZMQ_DEPRECATED("from 4.3.1, use proxy taking socket_t objects")
inline void proxy(void *frontend, void *backend, void *capture)
{
    int rc = zmq_proxy(frontend, backend, capture);
    if (rc != 0)
        throw error_t();
}

inline void
proxy(socket_ref frontend, socket_ref backend, socket_ref capture = socket_ref())
{
    int rc = zmq_proxy(frontend.handle(), backend.handle(), capture.handle());
    if (rc != 0)
        throw error_t();
}

#ifdef ZMQ_HAS_PROXY_STEERABLE
ZMQ_DEPRECATED("from 4.3.1, use proxy_steerable taking socket_t objects")
inline void
proxy_steerable(void *frontend, void *backend, void *capture, void *control)
{
    int rc = zmq_proxy_steerable(frontend, backend, capture, control);
    if (rc != 0)
        throw error_t();
}

inline void proxy_steerable(socket_ref frontend,
                            socket_ref backend,
                            socket_ref capture,
                            socket_ref control)
{
    int rc = zmq_proxy_steerable(frontend.handle(), backend.handle(),
                                 capture.handle(), control.handle());
    if (rc != 0)
        throw error_t();
}
#endif

class monitor_t
{
  public:
    monitor_t() : _socket(), _monitor_socket() {}

    virtual ~monitor_t() { close(); }

#ifdef ZMQ_HAS_RVALUE_REFS
    monitor_t(monitor_t &&rhs) ZMQ_NOTHROW : _socket(), _monitor_socket()
    {
        std::swap(_socket, rhs._socket);
        std::swap(_monitor_socket, rhs._monitor_socket);
    }

    monitor_t &operator=(monitor_t &&rhs) ZMQ_NOTHROW
    {
        close();
        _socket = socket_ref();
        std::swap(_socket, rhs._socket);
        std::swap(_monitor_socket, rhs._monitor_socket);
        return *this;
    }
#endif


    void
    monitor(socket_t &socket, std::string const &addr, int events = ZMQ_EVENT_ALL)
    {
        monitor(socket, addr.c_str(), events);
    }

    void monitor(socket_t &socket, const char *addr_, int events = ZMQ_EVENT_ALL)
    {
        init(socket, addr_, events);
        while (true) {
            check_event(-1);
        }
    }

    void init(socket_t &socket, std::string const &addr, int events = ZMQ_EVENT_ALL)
    {
        init(socket, addr.c_str(), events);
    }

    void init(socket_t &socket, const char *addr_, int events = ZMQ_EVENT_ALL)
    {
        int rc = zmq_socket_monitor(socket.handle(), addr_, events);
        if (rc != 0)
            throw error_t();

        _socket = socket;
        _monitor_socket = socket_t(socket.ctxptr, ZMQ_PAIR);
        _monitor_socket.connect(addr_);

        on_monitor_started();
    }

    operator void *() ZMQ_NOTHROW { return handle(); }

    operator void const *() const ZMQ_NOTHROW { return handle(); }

    ZMQ_NODISCARD void *handle() ZMQ_NOTHROW { return _monitor_socket.handle(); }

    ZMQ_NODISCARD const void *handle() const ZMQ_NOTHROW { return _monitor_socket.handle(); }

    operator socket_ref() ZMQ_NOTHROW { return (zmq::socket_ref) _monitor_socket; }

#if ZMQ_VERSION_MAJOR >= 4
    bool get_event(zmq_event_t& eventMsg, std::string& address, zmq::recv_flags flags = zmq::recv_flags::none)
    {
        assert(_monitor_socket);

        eventMsg.event = 0;
        eventMsg.value = 0;
        address = std::string();

        {
            message_t msg;
            int rc = zmq_msg_recv(msg.handle(), _monitor_socket.handle(),
                static_cast<int>(flags));

            if (rc == -1)
            {
                if (zmq_errno() == ETERM || zmq_errno() == EAGAIN)
                    return false;
                else
                    throw error_t();
            }

            const char *data = msg.data<char>();
            memcpy(&eventMsg.event, data, sizeof(uint16_t));
            data += sizeof(uint16_t);
            memcpy(&eventMsg.value, data, sizeof(int32_t));
        }

        message_t addrMsg;
        int rc = zmq_msg_recv(addrMsg.handle(), _monitor_socket.handle(),
            static_cast<int>(flags));

        if (rc == -1)
        {
            if (zmq_errno() == ETERM)
                return false;
            else
                throw error_t();
        }

        const char *str = addrMsg.data<char>();
        address = std::string(str, str + addrMsg.size());

        return true;
    }
#endif

    bool check_event(int timeout = 0)
    {
        assert(_monitor_socket);

        zmq_msg_t eventMsg;
        zmq_msg_init(&eventMsg);

        zmq::pollitem_t items[] = {
          {_monitor_socket.handle(), 0, ZMQ_POLLIN, 0},
        };

        zmq::poll(&items[0], 1, timeout);

        if (items[0].revents & ZMQ_POLLIN) {
            int rc = zmq_msg_recv(&eventMsg, _monitor_socket.handle(), 0);
            if (rc == -1 && zmq_errno() == ETERM)
                return false;
            assert(rc != -1);

        } else {
            zmq_msg_close(&eventMsg);
            return false;
        }

#if ZMQ_VERSION_MAJOR >= 4
        const char *data = static_cast<const char *>(zmq_msg_data(&eventMsg));
        zmq_event_t msgEvent;
        memcpy(&msgEvent.event, data, sizeof(uint16_t));
        data += sizeof(uint16_t);
        memcpy(&msgEvent.value, data, sizeof(int32_t));
        zmq_event_t *event = &msgEvent;
#else
        zmq_event_t *event = static_cast<zmq_event_t *>(zmq_msg_data(&eventMsg));
#endif

#ifdef ZMQ_NEW_MONITOR_EVENT_LAYOUT
        zmq_msg_t addrMsg;
        zmq_msg_init(&addrMsg);
        int rc = zmq_msg_recv(&addrMsg, _monitor_socket.handle(), 0);
        if (rc == -1 && zmq_errno() == ETERM) {
            zmq_msg_close(&eventMsg);
            return false;
        }

        assert(rc != -1);
        const char *str = static_cast<const char *>(zmq_msg_data(&addrMsg));
        std::string address(str, str + zmq_msg_size(&addrMsg));
        zmq_msg_close(&addrMsg);
#else
        // Bit of a hack, but all events in the zmq_event_t union have the same layout so this will work for all event types.
        std::string address = event->data.connected.addr;
#endif

#ifdef ZMQ_EVENT_MONITOR_STOPPED
        if (event->event == ZMQ_EVENT_MONITOR_STOPPED) {
            zmq_msg_close(&eventMsg);
            return false;
        }

#endif

        switch (event->event) {
            case ZMQ_EVENT_CONNECTED:
                on_event_connected(*event, address.c_str());
                break;
            case ZMQ_EVENT_CONNECT_DELAYED:
                on_event_connect_delayed(*event, address.c_str());
                break;
            case ZMQ_EVENT_CONNECT_RETRIED:
                on_event_connect_retried(*event, address.c_str());
                break;
            case ZMQ_EVENT_LISTENING:
                on_event_listening(*event, address.c_str());
                break;
            case ZMQ_EVENT_BIND_FAILED:
                on_event_bind_failed(*event, address.c_str());
                break;
            case ZMQ_EVENT_ACCEPTED:
                on_event_accepted(*event, address.c_str());
                break;
            case ZMQ_EVENT_ACCEPT_FAILED:
                on_event_accept_failed(*event, address.c_str());
                break;
            case ZMQ_EVENT_CLOSED:
                on_event_closed(*event, address.c_str());
                break;
            case ZMQ_EVENT_CLOSE_FAILED:
                on_event_close_failed(*event, address.c_str());
                break;
            case ZMQ_EVENT_DISCONNECTED:
                on_event_disconnected(*event, address.c_str());
                break;
#ifdef ZMQ_BUILD_DRAFT_API
#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 3)
            case ZMQ_EVENT_HANDSHAKE_FAILED_NO_DETAIL:
                on_event_handshake_failed_no_detail(*event, address.c_str());
                break;
            case ZMQ_EVENT_HANDSHAKE_FAILED_PROTOCOL:
                on_event_handshake_failed_protocol(*event, address.c_str());
                break;
            case ZMQ_EVENT_HANDSHAKE_FAILED_AUTH:
                on_event_handshake_failed_auth(*event, address.c_str());
                break;
            case ZMQ_EVENT_HANDSHAKE_SUCCEEDED:
                on_event_handshake_succeeded(*event, address.c_str());
                break;
#elif ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 1)
            case ZMQ_EVENT_HANDSHAKE_FAILED:
                on_event_handshake_failed(*event, address.c_str());
                break;
            case ZMQ_EVENT_HANDSHAKE_SUCCEED:
                on_event_handshake_succeed(*event, address.c_str());
                break;
#endif
#endif
            default:
                on_event_unknown(*event, address.c_str());
                break;
        }
        zmq_msg_close(&eventMsg);

        return true;
    }

#ifdef ZMQ_EVENT_MONITOR_STOPPED
    void abort()
    {
        if (_socket)
            zmq_socket_monitor(_socket.handle(), ZMQ_NULLPTR, 0);

        _socket = socket_ref();
    }
#endif

    void close() ZMQ_NOTHROW
    {
#ifdef ZMQ_EVENT_MONITOR_STOPPED
        abort();
#endif
        _monitor_socket = socket_t();
    }

    virtual void on_monitor_started() {}
    virtual void on_event_connected(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_connect_delayed(const zmq_event_t &event_,
                                          const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_connect_retried(const zmq_event_t &event_,
                                          const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_listening(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_bind_failed(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_accepted(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_accept_failed(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_closed(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_close_failed(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_disconnected(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 3)
    virtual void on_event_handshake_failed_no_detail(const zmq_event_t &event_,
                                                     const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_handshake_failed_protocol(const zmq_event_t &event_,
                                                    const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_handshake_failed_auth(const zmq_event_t &event_,
                                                const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_handshake_succeeded(const zmq_event_t &event_,
                                              const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
#elif ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 1)
    virtual void on_event_handshake_failed(const zmq_event_t &event_,
                                           const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
    virtual void on_event_handshake_succeed(const zmq_event_t &event_,
                                            const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }
#endif
    virtual void on_event_unknown(const zmq_event_t &event_, const char *addr_)
    {
        (void) event_;
        (void) addr_;
    }

  private:
    monitor_t(const monitor_t &) ZMQ_DELETED_FUNCTION;
    void operator=(const monitor_t &) ZMQ_DELETED_FUNCTION;

    socket_ref _socket;
    socket_t _monitor_socket;
};

#if defined(ZMQ_BUILD_DRAFT_API) && defined(ZMQ_CPP11) && defined(ZMQ_HAVE_POLLER)

// polling events
enum class event_flags : short
{
    none = 0,
    pollin = ZMQ_POLLIN,
    pollout = ZMQ_POLLOUT,
    pollerr = ZMQ_POLLERR,
    pollpri = ZMQ_POLLPRI
};

constexpr event_flags operator|(event_flags a, event_flags b) noexcept
{
    return detail::enum_bit_or(a, b);
}
constexpr event_flags operator&(event_flags a, event_flags b) noexcept
{
    return detail::enum_bit_and(a, b);
}
constexpr event_flags operator^(event_flags a, event_flags b) noexcept
{
    return detail::enum_bit_xor(a, b);
}
constexpr event_flags operator~(event_flags a) noexcept
{
    return detail::enum_bit_not(a);
}

struct no_user_data;

// layout compatible with zmq_poller_event_t
template<class T = no_user_data> struct poller_event
{
    socket_ref socket;
#ifdef _WIN32
    SOCKET fd;
#else
    int fd;
#endif
    T *user_data;
    event_flags events;
};

template<typename T = no_user_data> class poller_t
{
  public:
    using event_type = poller_event<T>;

    poller_t() : poller_ptr(zmq_poller_new())
    {
        if (!poller_ptr)
            throw error_t();
    }

    template<
      typename Dummy = void,
      typename =
        typename std::enable_if<!std::is_same<T, no_user_data>::value, Dummy>::type>
    void add(zmq::socket_ref socket, event_flags events, T *user_data)
    {
        add_impl(socket, events, user_data);
    }

    void add(zmq::socket_ref socket, event_flags events)
    {
        add_impl(socket, events, nullptr);
    }

    void remove(zmq::socket_ref socket)
    {
        if (0 != zmq_poller_remove(poller_ptr.get(), socket.handle())) {
            throw error_t();
        }
    }

    void modify(zmq::socket_ref socket, event_flags events)
    {
        if (0
            != zmq_poller_modify(poller_ptr.get(), socket.handle(),
                                 static_cast<short>(events))) {
            throw error_t();
        }
    }

    size_t wait_all(std::vector<event_type> &poller_events,
                    const std::chrono::milliseconds timeout)
    {
        int rc = zmq_poller_wait_all(
          poller_ptr.get(),
          reinterpret_cast<zmq_poller_event_t *>(poller_events.data()),
          static_cast<int>(poller_events.size()),
          static_cast<long>(timeout.count()));
        if (rc > 0)
            return static_cast<size_t>(rc);

#if ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 3)
        if (zmq_errno() == EAGAIN)
#else
        if (zmq_errno() == ETIMEDOUT)
#endif
            return 0;

        throw error_t();
    }

  private:
    struct destroy_poller_t
    {
        void operator()(void *ptr) noexcept
        {
            int rc = zmq_poller_destroy(&ptr);
            ZMQ_ASSERT(rc == 0);
        }
    };

    std::unique_ptr<void, destroy_poller_t> poller_ptr;

    void add_impl(zmq::socket_ref socket, event_flags events, T *user_data)
    {
        if (0
            != zmq_poller_add(poller_ptr.get(), socket.handle(), user_data,
                              static_cast<short>(events))) {
            throw error_t();
        }
    }
};
#endif //  defined(ZMQ_BUILD_DRAFT_API) && defined(ZMQ_CPP11) && defined(ZMQ_HAVE_POLLER)

inline std::ostream &operator<<(std::ostream &os, const message_t &msg)
{
    return os << msg.str();
}

} // namespace zmq

#endif // __ZMQ_HPP_INCLUDED__