feat(furvm): add call instruction

furvm/include/furvm/function.hpp

@@ -14,7 +14,7 @@ enum class function_t : std::uint8_t {
     Native,     /**< A native function implemented through furvm API. */
 };
 
-using native_function = std::function<void(const executor_p&)>;
+using native_function = std::function<void(executor&)>;
 
 class function {
 private:

furvm/include/furvm/instruction.hpp

@@ -65,6 +65,13 @@ enum class instruction_t : byte {
      */
     Mod,
 
+    /**
+     * @brief Calls a function.
+     *
+     * Calls a function denoted by next two bytes in little-endian from current frame's module.
+     */
+    Call,
+
     /**
      * @brief Pops the current call frame.
      */

furvm/include/furvm/module.hpp

@@ -51,6 +51,14 @@ public:
      * @return The byte.
      */
     constexpr byte byte(std::size_t offset) const { return m_bytecode.at(offset); }
+public:
+    /**
+     * @brief Returns a function from this module.
+     *
+     * @param id Id of the function.
+     * @return The function.
+     */
+    constexpr const function_p& function_at(function_handle id) const { return m_functions.at(id); }
 private:
     module_handle           m_id;
     bytecode_t              m_bytecode;

furvm/src/executor.cpp

@@ -109,6 +109,17 @@ void executor::step() {
         auto lhs = pop_thing();
         push_thing(lhs % rhs);
     } break;
+    case instruction_t::Call: {
+        function_handle funcId = static_cast<std::uint16_t>(frame.mod->byte(frame.position)) |
+                                 (static_cast<std::uint16_t>(frame.mod->byte(frame.position + 1)) << 8);
+        frame.position        += 2;
+
+        const function_p& function = frame.mod->function_at(funcId);
+        switch (function->type()) {
+        case function_t::Normal: push_frame(function); break;
+        case function_t::Native: function->native()(*this); break;
+        }
+    } break;
     case instruction_t::Return: {
         pop_frame();
         if (m_frames.empty()) m_flags = m_flags | executor_flags::Done;

furvm/src/main.cpp

@@ -11,17 +11,19 @@
 #include <iostream>
 #include <memory>
 
-static constexpr std::array<furvm::byte, 6> s_bytecode = {
+static constexpr std::array<furvm::byte, 8> s_bytecode = {
     furvm::byte(furvm::instruction_t::PushB2I),
     67,
     furvm::byte(furvm::instruction_t::Clone),
     furvm::byte(furvm::instruction_t::Add),
-    furvm::byte(furvm::instruction_t::Drop),
+    furvm::byte(furvm::instruction_t::Call),
+    1,
+    0,
     furvm::byte(furvm::instruction_t::Return),
 };
 
-void print(const furvm::executor_p& exec) {
-    std::cout << exec->pop_thing()->int32() << '\n';
+void print(furvm::executor& exec) {
+    std::cout << exec.pop_thing()->int32() << '\n';
 }
 
 int main(void) {