feat(furvm): introduce executor

furvm/include/furvm/context.hpp

@@ -13,8 +13,10 @@ namespace furvm {
 class context {
 public:
     using value_type = std::unique_ptr<mod>; /**< An alias to unique pointer of module. */
+
+    friend class executor;
 public:
-    context()  = default;
+    context();
     ~context() = default;
 
     /**
@@ -92,7 +94,8 @@ public:
      */
     constexpr size_t size() const { return m_modules.size(); }
 private:
-    std::vector<std::unique_ptr<mod>> m_modules;
+    std::vector<std::unique_ptr<mod>>      m_modules;
+    std::vector<std::shared_ptr<executor>> m_executors;
 };
 
 } // namespace furvm

furvm/include/furvm/executor.hpp

@@ -0,0 +1,88 @@
+#ifndef FURVM_EXECUTOR_HPP
+#define FURVM_EXECUTOR_HPP
+
+#include "furvm/fwd.hpp"
+
+#include <memory>
+
+namespace furvm {
+
+enum class executor_flags : std::uint32_t {
+    Suspended = (1 << 0), /**< Execution suspended. */
+};
+
+static inline executor_flags operator|(executor_flags lhs, executor_flags rhs) {
+    return executor_flags(static_cast<std::uint32_t>(lhs) | static_cast<std::uint32_t>(rhs));
+}
+
+static inline executor_flags operator&(executor_flags lhs, executor_flags rhs) {
+    return executor_flags(static_cast<std::uint32_t>(lhs) & static_cast<std::uint32_t>(rhs));
+}
+
+static inline executor_flags operator~(executor_flags flags) {
+    return executor_flags(~static_cast<std::uint32_t>(flags));
+}
+
+class executor {
+private:
+    /**
+     * @brief A private token for the private constructor.
+     *
+     * Also `egzekutor` in Polish translates to `executor` I think.
+     */
+    struct egzekutor {
+        explicit egzekutor() = default;
+    };
+public:
+    /**
+     * @brief Private constructor.
+     *
+     * @param id
+     * @param context
+     */
+    executor(egzekutor, executor_handle id, const std::shared_ptr<context>& context);
+
+    ~executor();
+
+    /**
+     * @brief Move constructor.
+     */
+    executor(executor&&) = default;
+
+    /**
+     * @brief Move constructor.
+     */
+    executor& operator=(executor&&) = default;
+
+    executor(const executor&)            = delete;
+    executor& operator=(const executor&) = delete;
+public:
+    /**
+     * @brief Returns a new executor.
+     *
+     * @param context Furvm context.
+     */
+    static std::shared_ptr<executor> create(const std::shared_ptr<context>& context);
+public:
+    /**
+     * @brief Returns an id of this executor.
+     *
+     * @return The id.
+     */
+    executor_handle id() const { return m_id; }
+
+    /**
+     * @brief Returns flags of this executor.
+     *
+     * @return The flags.
+     */
+    executor_flags flags() const { return m_flags; }
+private:
+    executor_handle          m_id;
+    executor_flags           m_flags{}; // NOLINT(bugprone-invalid-enum-default-initialization)
+    std::shared_ptr<context> m_context;
+};
+
+} // namespace furvm
+
+#endif // FURVM_EXECUTOR_HPP

furvm/include/furvm/fwd.hpp

@@ -61,6 +61,27 @@ class mod;
  */
 using module_handle = std::uint32_t;
 
+// executor.hpp
+
+/**
+ * @enum executor_flags
+ * @brief Flags of an executor.
+ */
+enum class executor_flags : std::uint32_t;
+
+/**
+ * @class executor
+ * @brief Furvm executor.
+ *
+ * Furvm executors are like threads.
+ */
+class executor;
+
+/**
+ * @brief Furvm executor's index.
+ */
+using executor_handle = std::uint32_t;
+
 // context.hpp
 
 /**