Static channel (#69)

* Add static channel
* Add CPP_CHANNEL_SANITIZE_THREADS
* Simplify conditions
* Extract nodiscard
* Set version

Author: andreiavrammsd

.github/workflows/cmake.yml

@@ -76,11 +76,11 @@ jobs:
 
       - name: Build
         working-directory: ${{github.workspace}}/build
-        run: cmake --build . --config ${{ matrix.config.build_type }} --target tests -j
+        run: cmake --build . --config ${{ matrix.config.build_type }} --target channel_tests -j
 
       - name: Test
         working-directory: ${{github.workspace}}/build
-        run: ctest -C ${{ matrix.config.build_type }} --verbose -R channel_test --output-on-failure -j
+        run: ctest -C ${{ matrix.config.build_type }} --verbose -L channel_tests --output-on-failure -j
 
       - name: Run examples
         working-directory: ${{github.workspace}}/build
@@ -102,11 +102,11 @@ jobs:
 
       - name: Build
         working-directory: ${{github.workspace}}/build
-        run: cmake --build . --config Debug --target tests -j
+        run: cmake --build . --config Debug --target channel_tests -j
 
       - name: Test
         working-directory: ${{github.workspace}}/build
-        run: ctest -C Debug --verbose -R channel_test -j
+        run: ctest -C Debug --verbose -L channel_tests -j
 
       - name: Upload coverage reports to Codecov
         uses: codecov/codecov-action@v5

.vscode/settings.json

@@ -4,6 +4,7 @@
         "-DCPP_CHANNEL_BUILD_TESTS=ON",
         "-DCPP_CHANNEL_COVERAGE=ON",
         "-DCPP_CHANNEL_SANITIZERS=ON",
+        "-DCPP_CHANNEL_SANITIZE_THREADS=OFF",
         "-DCMAKE_CXX_STANDARD=11",
         "-DCMAKE_INSTALL_PREFIX=${workspaceFolder}/install",
     ],

CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.12)
 project(cpp_channel)
-set(PROJECT_VERSION 1.0.1)
+set(PROJECT_VERSION 1.1.0)
 
 set(CMAKE_CXX_STANDARD 11 CACHE STRING "C++ standard")
 set(CMAKE_CXX_STANDARD_REQUIRED YES)
@@ -18,6 +18,7 @@ option(CPP_CHANNEL_BUILD_TESTS "Build all of cpp_channel's own tests." OFF)
 option(CPP_CHANNEL_BUILD_EXAMPLES "Build cpp_channel's example programs." OFF)
 option(CPP_CHANNEL_COVERAGE "Generate test coverage." OFF)
 option(CPP_CHANNEL_SANITIZERS "Build with sanitizers." OFF)
+option(CPP_CHANNEL_SANITIZE_THREADS "Build with thread sanitizer." OFF)
 
 if (CPP_CHANNEL_BUILD_TESTS)
     enable_testing()

README.md

@@ -13,6 +13,7 @@
 * Close to prevent pushing and stop waiting to fetch.
 * Integrates well with STL algorithms in some cases. Eg: std::move(ch.begin(), ch.end(), ...).
 * Tested with GCC, Clang, and MSVC.
+* Includes stack-based, exception-free alternative (static channel).
 
 ## Requirements
 
@@ -26,7 +27,7 @@ Choose one of the methods:
 * [CMake FetchContent](https://github.com/andreiavrammsd/cpp-channel/tree/master/examples/cmake-project)
 * [CMake install](https://cmake.org/cmake/help/latest/command/install.html)
 ```shell
-VERSION=1.0.1 \
+VERSION=1.1.0 \
     && wget https://github.com/andreiavrammsd/cpp-channel/archive/refs/tags/v$VERSION.zip \
     && unzip v$VERSION.zip \
     && cd cpp-channel-$VERSION \
@@ -111,6 +112,26 @@ int main() {
 }
 ```
 
+```c++
+#include <msd/static_channel.hpp>
+
+int main() {
+    msd::static_channel<int, 2> chan{};  // always buffered
+
+    int in = 1;
+    int out = 0;
+
+    // Send to channel
+    chan.write(in);
+    chan.write(in);
+
+    // Read from channel
+    chan.read(out);
+    chan.read(out);
+    chan.read(out);  // blocking because channel is empty (and no one writes on it)
+}
+```
+
 See [examples](https://github.com/andreiavrammsd/cpp-channel/tree/master/examples) and [documentation](https://andreiavrammsd.github.io/cpp-channel/).
 
 <br>

examples/CMakeLists.txt

@@ -36,3 +36,6 @@ add_example(example_multithreading multithreading.cpp)
 
 add_example(example_streaming streaming.cpp)
 run_example(example_streaming)
+
+add_example(example_multithreading_static_channel multithreading_static_channel.cpp)
+run_example(example_multithreading_static_channel)

examples/multithreading_static_channel.cpp

@@ -0,0 +1,47 @@
+#include <future>
+#include <iostream>
+#include <sstream>
+#include <thread>
+
+#include "msd/static_channel.hpp"
+
+int main()
+{
+    msd::static_channel<int, 50> chan{};  // always buffered
+
+    // Send to channel
+    const auto writer = [&chan](int begin, int end) {
+        for (int i = begin; i <= end; ++i) {
+            chan.write(i);
+
+            std::stringstream msg;
+            msg << "Sent " << i << " from " << std::this_thread::get_id() << "\n";
+            std::cout << msg.str();
+
+            std::this_thread::sleep_for(std::chrono::milliseconds(10));  // simulate work
+        }
+        chan.close();
+    };
+
+    const auto reader = [&chan]() {
+        for (const auto out : chan) {  // blocking until channel is drained (closed and empty)
+            std::stringstream msg;
+            msg << "Received " << out << " on " << std::this_thread::get_id() << "\n";
+            std::cout << msg.str();
+
+            std::this_thread::sleep_for(std::chrono::milliseconds(200));  // simulate work
+        }
+    };
+
+    const auto reader_1 = std::async(std::launch::async, reader);
+    const auto reader_2 = std::async(std::launch::async, reader);
+    const auto reader_3 = std::async(std::launch::async, reader);
+    const auto writer_1 = std::async(std::launch::async, writer, 1, 50);
+    const auto writer_2 = std::async(std::launch::async, writer, 51, 100);
+
+    reader_1.wait();
+    reader_2.wait();
+    reader_3.wait();
+    writer_1.wait();
+    writer_2.wait();
+}

include/msd/blocking_iterator.hpp

@@ -64,7 +64,7 @@ class blocking_iterator {
      */
     reference operator*()
     {
-        chan_ >> value_;
+        chan_.read(value_);
 
         return value_;
     }

include/msd/channel.hpp

@@ -11,15 +11,10 @@
 #include <type_traits>
 
 #include "blocking_iterator.hpp"
+#include "nodiscard.hpp"
 
 namespace msd {
 
-#if (__cplusplus >= 201703L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L))
-#define NODISCARD [[nodiscard]]
-#else
-#define NODISCARD
-#endif
-
 /**
  * @brief Exception thrown if trying to write on closed channel.
  */
@@ -134,11 +129,9 @@ class channel {
                 return false;
             }
 
-            if (!(size_ == 0)) {
-                out = std::move(queue_.front());
-                queue_.pop();
-                --size_;
-            }
+            out = std::move(queue_.front());
+            queue_.pop();
+            --size_;
         }
 
         cnd_.notify_one();
@@ -202,7 +195,7 @@ class channel {
     NODISCARD bool drained() noexcept
     {
         std::unique_lock<std::mutex> lock{mtx_};
-        return is_closed_ && size_ == 0;
+        return size_ == 0 && is_closed_;
     }
 
     /**
@@ -238,7 +231,7 @@ class channel {
 
     void waitBeforeRead(std::unique_lock<std::mutex>& lock)
     {
-        cnd_.wait(lock, [this]() { return !(size_ == 0) || is_closed_; });
+        cnd_.wait(lock, [this]() { return size_ > 0 || is_closed_; });
     };
 
     void waitBeforeWrite(std::unique_lock<std::mutex>& lock)
@@ -247,8 +240,6 @@ class channel {
             cnd_.wait(lock, [this]() { return size_ < cap_; });
         }
     }
-
-    friend class blocking_iterator<channel>;
 };
 
 template <typename T>

include/msd/nodiscard.hpp

@@ -0,0 +1,16 @@
+// Copyright (C) 2020-2025 Andrei Avram
+
+#ifndef MSD_NODISCARD_HPP_
+#define MSD_NODISCARD_HPP_
+
+namespace msd {
+
+#if (__cplusplus >= 201703L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L))
+#define NODISCARD [[nodiscard]]
+#else
+#define NODISCARD
+#endif
+
+}  // namespace msd
+
+#endif  // MSD_NODISCARD_HPP_