feat(furvm): introduce jump and jump not zero instructions

furvm/include/furvm/instruction.hpp

@@ -86,6 +86,21 @@ enum class instruction_t : byte {
      */
     Call,
 
+    /**
+     * @brief Jumps to an instruction relative to the current instruction.
+     *
+     * Jumps to an instruction relative to the current instruction with offset denoted by next byte.
+     */
+    Jump,
+
+    /**
+     * @brief Jumps to an instruction relative to the current instruction if top thing on the stack is not zero.
+     *
+     * Jumps to an instruction relative to the current instruction with offset denoted by next byte if the top thing on
+     * the stack is not zero (is true).
+     */
+    JumpNotZero,
+
     /**
      * @brief Pops the current call frame.
      */

furvm/src/executor.cpp

@@ -139,11 +139,13 @@ void executor::step() {
     case instruction_t::Load: {
         variable_t variable = 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;
         push_thing(load_thing(variable));
     } break;
     case instruction_t::Store: {
         variable_t variable = 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;
         store_thing(variable, std::move(pop_thing()));
     } break;
     case instruction_t::Call: {
@@ -161,6 +163,14 @@ void executor::step() {
         } break;
         }
     } break;
+    case instruction_t::Jump: {
+        frame.position += frame.mod->byte(frame.position++);
+    } break;
+    case instruction_t::JumpNotZero: {
+        byte offset = frame.mod->byte(frame.position++);
+        auto cond   = pop_thing();
+        if (cond->int32() != 0) frame.position += offset;
+    } break;
     case instruction_t::Return: {
         pop_frame();
         if (m_frames.empty()) m_flags = m_flags | executor_flags::Done;