Dropping cppzmq dependency; adding some zmq utils

src/net/zmq.cpp

@@ -0,0 +1,188 @@
+// Copyright (c) 2019, The Monero Project
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "net/zmq.h"
+
+#include <cassert>
+#include <cerrno>
+#include <limits>
+#include <utility>
+
+namespace net
+{
+namespace zmq
+{
+    const std::error_category& error_category() noexcept
+    {
+        struct category final : std::error_category
+        {
+            virtual const char* name() const noexcept override final
+            {
+                return "error::error_category()";
+            }
+
+            virtual std::string message(int value) const override final
+            {
+                char const* const msg = zmq_strerror(value);
+                if (msg)
+                    return msg;
+                return "zmq_strerror failure";
+            }
+
+            virtual std::error_condition default_error_condition(int value) const noexcept override final
+            {
+                // maps specific errors to generic `std::errc` cases.
+                switch (value)
+                {
+                case EFSM:
+                case ETERM:
+                    break;
+                default:
+                    /* zmq is using cerrno errors. C++ spec indicates that
+                       `std::errc` values must be identical to the cerrno value.
+                       So just map every zmq specific error to the generic errc
+                       equivalent. zmq extensions must be in the switch or they
+                       map to a non-existent errc enum value. */
+                    return std::errc(value);
+                }
+                return std::error_condition{value, *this};
+            }
+
+        };
+        static const category instance{};
+        return instance;
+    }
+
+    void terminate::call(void* ptr) noexcept
+    {
+        assert(ptr != nullptr); // see header
+        while (zmq_term(ptr))
+        {
+            if (zmq_errno() != EINTR)
+                break;
+        }
+    }
+
+    namespace
+    {
+        //! RAII wrapper for `zmq_msg_t`.
+        class message
+        {
+            zmq_msg_t handle_;
+
+        public:
+            message() noexcept
+              : handle_()
+            {
+                zmq_msg_init(handle());
+            }
+
+            message(message&& rhs) = delete;
+            message(const message& rhs) = delete;
+            message& operator=(message&& rhs) = delete;
+            message& operator=(const message& rhs) = delete;
+
+            ~message() noexcept
+            {
+                zmq_msg_close(handle());
+            }
+
+            zmq_msg_t* handle() noexcept
+            {
+                return std::addressof(handle_);
+            }
+
+            const char* data() noexcept
+            {
+                return static_cast<const char*>(zmq_msg_data(handle()));
+            }
+
+            std::size_t size() noexcept
+            {
+                return zmq_msg_size(handle());
+            }
+        };
+
+        struct do_receive
+        {
+            /* ZMQ documentation states that message parts are atomic - either
+               all are received or none are. Looking through ZMQ code and
+               Github discussions indicates that after part 1 is returned,
+               `EAGAIN` cannot be returned to meet these guarantees. Unit tests
+               verify (for the `inproc://` case) that this is the behavior. 
+               Therefore, read errors after the first part are treated as a
+               failure for the entire message (probably `ETERM`). */
+            int operator()(std::string& payload, void* const socket, const int flags) const
+            {
+                static constexpr const int max_out = std::numeric_limits<int>::max();
+                const std::string::size_type initial = payload.size();
+                message part{};
+                for (;;)
+                {
+                    int last = 0;
+                    if ((last = zmq_msg_recv(part.handle(), socket, flags)) < 0)
+                        return last;
+
+                    payload.append(part.data(), part.size());
+                    if (!zmq_msg_more(part.handle()))
+                        break;
+                }
+                const std::string::size_type added = payload.size() - initial;
+                return unsigned(max_out) < added ? max_out : int(added);
+            }
+        };
+
+        template<typename F, typename... T>
+        expect<void> retry_op(F op, T&&... args) noexcept(noexcept(op(args...)))
+        {
+            for (;;)
+            {
+                if (0 <= op(args...))
+                    return success();
+
+                const int error = zmq_errno();
+                if (error != EINTR)
+                    return make_error_code(error);
+            }
+        }
+    } // anonymous
+
+    expect<std::string> receive(void* const socket, const int flags)
+    {
+        std::string payload{};
+        MONERO_CHECK(retry_op(do_receive{}, payload, socket, flags));
+        return {std::move(payload)};
+    }
+
+    expect<void> send(const epee::span<const std::uint8_t> payload, void* const socket, const int flags) noexcept
+    {
+        return retry_op(zmq_send, socket, payload.data(), payload.size(), flags);
+    }
+} // zmq
+} // net
+