feat(furvm): add variables

furvm/include/furvm/executor.hpp

@@ -4,6 +4,7 @@
 #include "furvm/fwd.hpp"
 
 #include <stack>
+#include <vector>
 
 namespace furvm {
 
@@ -44,6 +45,8 @@ public:
         mod_p       mod;       /**< Shared pointer to a module with the bytecode. */
         std::size_t position;  /**< Cursor to a current instruction in the bytecode. */
         std::size_t stackBase; /**< Snapshot of the stack size before this frame. */
+
+        std::vector<thing_p> variables; /**< Frame variables. */
     };
 public:
     /**
@@ -139,6 +142,30 @@ public:
      * @return The thing.
      */
     thing_p thing() const;
+public:
+    /**
+     * @brief Stores a thing in a variable.
+     *
+     * @param variable Variable to store the thing in.
+     * @param thing Thing to store.
+     */
+    void store_thing(variable_t variable, const thing_p& thing);
+
+    /**
+     * @brief Stores a thing in a variable.
+     *
+     * @param variable Variable to store the thing in.
+     * @param thing Thing to store.
+     */
+    void store_thing(variable_t variable, thing_p&& thing);
+
+    /**
+     * @brief Returns a thing stored in a variable.
+     *
+     * @param variable Variable where the thing is stored.
+     * @return The thing stored in the variable.
+     */
+    thing_p load_thing(variable_t variable) const;
 public:
     /**
      * @brief Executes next instruction.
@@ -155,4 +182,4 @@ private:
 
 } // namespace furvm
 
-#endif // FURVM_EXECUTOR_HPP
+#endif // FURVM_EXECUTOR_HPP

furvm/include/furvm/fwd.hpp

@@ -132,6 +132,11 @@ using thing_handle = std::uint32_t;
 
 // executor.hpp
 
+/**
+ * @brief A variable index type.
+ */
+using variable_t = std::uint16_t;
+
 /**
  * @enum executor_flags
  * @brief Flags of an executor.
@@ -181,4 +186,4 @@ class stack_underflow;
 
 } // namespace furvm
 
-#endif // FURVM_FWD_HPP
+#endif // FURVM_FWD_HPP

furvm/include/furvm/instruction.hpp

@@ -65,6 +65,20 @@ enum class instruction_t : byte {
      */
     Mod,
 
+    /**
+     * @brief Pushes a variable onto the stack.
+     *
+     * Fetches a variable denoted by next two bytes in little-endian and pushes it onto the stack.
+     */
+    Load,
+
+    /**
+     * @brief Stores an element from the stack in a variable.
+     *
+     * Pops a thing from the stack and stores it in a variable denoted by next two bytes in little-endian.
+     */
+    Store,
+
     /**
      * @brief Calls a function.
      *
@@ -96,4 +110,4 @@ struct instruction {
 
 } // namespace furvm
 
-#endif // FURVM_INSTRUCTION_HPP
+#endif // FURVM_INSTRUCTION_HPP