fin: feature complete, all tests pass ready to merge

CMakeLists.txt

@@ -11,6 +11,7 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 # Core library
 add_library(core
     src/core/SysfsRead.cxx
+    src/core/UnixIpcBridge.cxx
     src/core/Producer.cxx
 )
 

README.md

@@ -25,3 +25,12 @@ The reader never throws on I/O errors; every outcome is expressed through the en
 ## Producer class / thread
 
 `Producer` ([include/Producer.hpp](include/Producer.hpp), [src/core/Producer.cxx](src/core/Producer.cxx)) runs a worker `std::thread` that periodically polls the `SysfsReader` and, when the status is `Enabled`, generates a random integer and forwards it through an injected `send_fn` callback. The polling interval is 1 second under normal conditions and 7 seconds when the sysfs file reports `ErrorTempTooHigh` (cool-down).
+
+## UnixIpcBridge
+
+>[!note]
+>why unix domain sockets? Because I have more experience with them under linux than with posix shared memmory and semaphore, and I find them easier to unit-test.
+
+`UnixIpcBridge` ([include/UnixIpcBridge.hpp](include/UnixIpcBridge.hpp), [src/core/UnixIpcBridge.cxx](src/core/UnixIpcBridge.cxx)) is a small helper that connects to a UNIX domain socket and sends a single `int` per call. It opens a new connection for each value, which keeps the protocol stateless and simple.
+
+**Tests:** [tests/test_unix_ipc.cxx](tests/test_unix_ipc.cxx) — spins up a fake socket server, sends values through the bridge, and asserts they arrive correctly.

include/UnixIpcBridge.hpp

@@ -0,0 +1,31 @@
+// UnixIpcBridge.hpp
+// SPDX-License-Identifier: GPL-3.0-only
+// Author: Unai Blazquez <unaibg2000@gmail.com>
+
+#pragma once
+#include <fcntl.h>  // non‑blocking
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>  // close()
+
+#include <string>
+
+///@brief Small bridge to allow the producer class to send data over UNIX domain
+/// sockets
+class UnixIpcBridge
+{
+ public:
+  ///@brief constructor
+  ///@param socket path pointing the socket
+  explicit UnixIpcBridge(const std::string& socket_path);
+
+  ///@brief sending function, this goes into the producer
+  ///@param integer to send over the socket
+  void send(int value);
+
+ private:
+  std::string m_socket_path;
+  int m_socket_fd = -1;
+
+  void connect_to_consumer();
+};

tests/CMakeLists.txt

@@ -25,3 +25,15 @@ target_link_libraries(test_producer
 
 add_test(NAME test_producer COMMAND test_producer)
 
+add_executable(test_ipc
+    test_unix_ipc.cxx
+)
+
+target_link_libraries(test_ipc
+    PRIVATE
+        core
+        gtest
+        gtest_main
+)
+
+add_test(NAME test_ipc COMMAND test_ipc)

tests/test_unix_ipc.cxx

@@ -0,0 +1,220 @@
+#include <gtest/gtest.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+#include <atomic>
+#include <chrono>
+#include <cstring>
+#include <stdexcept>
+#include <string>
+#include <thread>
+#include <vector>
+
+#include "UnixIpcBridge.hpp"
+
+// ---------------------------------------------------------------------------
+// Helper: a minimal UNIX-domain socket server that accepts one connection,
+// reads `count` ints, then tears down cleanly.  Uses a ready-flag so the
+// client never races against bind/listen.
+// ---------------------------------------------------------------------------
+class FakeConsumer
+{
+ public:
+  explicit FakeConsumer(const std::string& path, int count = 1)
+      : m_path(path), m_count(count)
+  {
+    // Remove stale socket from any previous failed run
+    unlink(m_path.c_str());
+  }
+
+  /// Start the server on a background thread.
+  void start()
+  {
+    m_thread = std::thread([this] { run(); });
+
+    // Spin until the server signals it is listening (bounded wait).
+    auto deadline = std::chrono::steady_clock::now() + std::chrono::seconds(5);
+    while (!m_ready.load(std::memory_order_acquire))
+    {
+      if (std::chrono::steady_clock::now() > deadline)
+      {
+        throw std::runtime_error("FakeConsumer: server failed to start");
+      }
+      std::this_thread::sleep_for(std::chrono::milliseconds(1));
+    }
+  }
+
+  /// Block until the server thread finishes.
+  void join() { m_thread.join(); }
+
+  /// Values received in order.
+  const std::vector<int>& received() const { return m_received; }
+
+  ~FakeConsumer() { unlink(m_path.c_str()); }
+
+ private:
+  void run()
+  {
+    m_server_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+    ASSERT_GE(m_server_fd, 0) << "socket() failed: " << strerror(errno);
+
+    struct sockaddr_un addr = {};
+    addr.sun_family = AF_UNIX;
+    std::strncpy(addr.sun_path, m_path.c_str(), sizeof(addr.sun_path) - 1);
+
+    ASSERT_EQ(
+        bind(m_server_fd, reinterpret_cast<sockaddr*>(&addr), sizeof(addr)), 0)
+        << "bind() failed: " << strerror(errno);
+    ASSERT_EQ(listen(m_server_fd, 1), 0)
+        << "listen() failed: " << strerror(errno);
+
+    // Signal that we are ready to accept connections.
+    m_ready.store(true, std::memory_order_release);
+
+    int client_fd = accept(m_server_fd, nullptr, nullptr);
+    ASSERT_GE(client_fd, 0) << "accept() failed: " << strerror(errno);
+
+    for (int i = 0; i < m_count; ++i)
+    {
+      int value = 0;
+      ssize_t n = recv(client_fd, &value, sizeof(value), MSG_WAITALL);
+      ASSERT_EQ(n, static_cast<ssize_t>(sizeof(value)))
+          << "recv() short read on message " << i;
+      m_received.push_back(value);
+    }
+
+    close(client_fd);
+    close(m_server_fd);
+  }
+
+  std::string m_path;
+  int m_count;
+  int m_server_fd = -1;
+  std::atomic<bool> m_ready{false};
+  std::thread m_thread;
+  std::vector<int> m_received;
+};
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+/// Sends a single integer value and verifies the consumer receives it.
+TEST(UnixIpcBridgeTest, SendsSingleInt)
+{
+  const std::string sock = "/tmp/test_ipc_single.sock";
+
+  FakeConsumer consumer(sock, /*count=*/1);
+  consumer.start();
+
+  UnixIpcBridge bridge(sock);
+  bridge.send(42);
+
+  consumer.join();
+
+  ASSERT_EQ(consumer.received().size(), 1u);
+  EXPECT_EQ(consumer.received()[0], 42);
+}
+
+/// Sends zero and a negative value — makes sure sign bits survive.
+TEST(UnixIpcBridgeTest, SendsZeroAndNegativeValues)
+{
+  // Zero
+  {
+    const std::string sock = "/tmp/test_ipc_zero.sock";
+    FakeConsumer consumer(sock, 1);
+    consumer.start();
+
+    UnixIpcBridge bridge(sock);
+    bridge.send(0);
+
+    consumer.join();
+    ASSERT_EQ(consumer.received().size(), 1u);
+    EXPECT_EQ(consumer.received()[0], 0);
+  }
+
+  // Negative
+  {
+    const std::string sock = "/tmp/test_ipc_neg.sock";
+    FakeConsumer consumer(sock, 1);
+    consumer.start();
+
+    UnixIpcBridge bridge(sock);
+    bridge.send(-1);
+
+    consumer.join();
+    ASSERT_EQ(consumer.received().size(), 1u);
+    EXPECT_EQ(consumer.received()[0], -1);
+  }
+}
+
+/// Sends INT_MAX / INT_MIN to check for truncation or overflow.
+TEST(UnixIpcBridgeTest, SendsExtremeBoundaryValues)
+{
+  {
+    const std::string sock = "/tmp/test_ipc_max.sock";
+    FakeConsumer consumer(sock, 1);
+    consumer.start();
+
+    UnixIpcBridge bridge(sock);
+    bridge.send(std::numeric_limits<int>::max());
+
+    consumer.join();
+    ASSERT_EQ(consumer.received().size(), 1u);
+    EXPECT_EQ(consumer.received()[0], std::numeric_limits<int>::max());
+  }
+
+  {
+    const std::string sock = "/tmp/test_ipc_min.sock";
+    FakeConsumer consumer(sock, 1);
+    consumer.start();
+
+    UnixIpcBridge bridge(sock);
+    bridge.send(std::numeric_limits<int>::min());
+
+    consumer.join();
+    ASSERT_EQ(consumer.received().size(), 1u);
+    EXPECT_EQ(consumer.received()[0], std::numeric_limits<int>::min());
+  }
+}
+
+/// Connecting to a non-existent socket must throw, not silently fail.
+TEST(UnixIpcBridgeTest, ThrowsWhenNoConsumerListening)
+{
+  const std::string sock = "/tmp/test_ipc_noserver.sock";
+  unlink(sock.c_str());  // make sure nothing is there
+
+  UnixIpcBridge bridge(sock);
+  EXPECT_THROW(bridge.send(99), std::runtime_error);
+}
+
+/// Multiple sequential sends (each reopens the connection).
+TEST(UnixIpcBridgeTest, MultipleSendsSequentially)
+{
+  const std::string sock = "/tmp/test_ipc_multi.sock";
+  constexpr int kMessages = 5;
+
+  // Server expects exactly kMessages ints from kMessages connections.
+  // Because the bridge reconnects every send(), we run kMessages
+  // single-message consumers sequentially.
+  std::vector<int> all_received;
+  for (int i = 0; i < kMessages; ++i)
+  {
+    FakeConsumer consumer(sock, 1);
+    consumer.start();
+
+    UnixIpcBridge bridge(sock);
+    bridge.send(i * 10);
+
+    consumer.join();
+    ASSERT_EQ(consumer.received().size(), 1u);
+    all_received.push_back(consumer.received()[0]);
+  }
+
+  ASSERT_EQ(all_received.size(), static_cast<size_t>(kMessages));
+  for (int i = 0; i < kMessages; ++i)
+  {
+    EXPECT_EQ(all_received[i], i * 10);
+  }
+}