added a simple message bus

source/core/utils/message_bus.cpp

@@ -0,0 +1,97 @@
+#include "matador/utils/message_bus.hpp"
+
+namespace matador::utils {
+message::message()
+: ptr_(nullptr)
+, owner_(nullptr)
+, type_(typeid(void)) {}
+
+bool message::empty() const {
+  return ptr_ == nullptr && !owner_;
+}
+
+std::type_index message::type() const {
+  return type_;
+}
+
+const void * message::msg_ptr() const {
+  return owner_ ? owner_.get() : ptr_;
+}
+
+subscription::subscription(message_bus *bus, const std::type_index type, const uint64_t id)
+: bus_(bus)
+, type_(type)
+, id_(id) {}
+
+subscription::subscription(subscription &&other) noexcept
+: bus_(other.bus_)
+, type_(other.type_)
+, id_(other.id_) {
+  other.bus_ = nullptr;
+}
+
+subscription& subscription::operator=(subscription &&other) noexcept {
+  if (this != &other) {
+    unsubscribe();
+    bus_ = other.bus_;
+    type_ = other.type_;
+    id_ = other.id_;
+    other.bus_ = nullptr;
+  }
+  return *this;
+}
+
+subscription::~subscription() {
+  unsubscribe();
+}
+
+bool subscription::valid() const {
+  return bus_ != nullptr;
+}
+
+void message_bus::unsubscribe(const std::type_index type, HandlerId id) {
+  std::unique_lock writeLock(mutex_);
+  const auto it = handlers_.find(type);
+  if (it == handlers_.end()) {
+    return;
+  }
+  auto &handler_vector = it->second;
+  handler_vector.erase(std::remove_if(handler_vector.begin(), handler_vector.end(),
+                           [id](const Entry &e) { return e.id == id; }),
+            handler_vector.end());
+  if (handler_vector.empty()) {
+    handlers_.erase(it);
+  }
+}
+
+void message_bus::unsubscribe(HandlerId id) {
+  std::unique_lock writeLock(mutex_);
+  for (auto it = handlers_.begin(); it != handlers_.end(); ) {
+    auto &handler_vector = it->second;
+    handler_vector.erase(std::remove_if(handler_vector.begin(), handler_vector.end(),
+                             [id](const Entry &e) { return e.id == id; }),
+              handler_vector.end());
+    if (handler_vector.empty()) it = handlers_.erase(it);
+    else ++it;
+  }
+}
+
+void message_bus::publish(const message &msg) const {
+  if (msg.empty()) {
+    return;
+  }
+  std::vector<Entry> snapshot;
+  {
+    std::shared_lock readLock(mutex_);
+    const auto it = handlers_.find(msg.type());
+    if (it == handlers_.end()) {
+      return;
+    }
+    snapshot = it->second;
+  }
+  const void* p = msg.msg_ptr();
+  for (const auto &e : snapshot) {
+    if (!e.filter || e.filter(p)) e.handler(p);
+  }
+}
+}