feat: setup runtime vm

runtime/src/lib.rs

@@ -2,6 +2,7 @@ pub mod object;
 
 mod bytecode;
 mod compiler;
+mod vm;
 
 #[cfg(test)]
 mod test;

runtime/src/object.rs

@@ -6,4 +6,5 @@ pub enum Object {
     Float(f64),
     Boolean(bool),
     String(Rc<String>),
+    Null,
 }

runtime/src/test/mod.rs

@@ -0,0 +1 @@
+mod compiler;

runtime/src/vm.rs

@@ -0,0 +1,47 @@
+use crate::{bytecode::Bytecode, object::Object};
+
+const STACK_SIZE: usize = 4096;
+
+#[derive(Debug)]
+pub struct VirtualMachine {
+    stack: Vec<Object>,
+    // StackPointer which points to the next value.
+    // Top of the stack is stack[sp-1]
+    sp: usize,
+}
+
+impl VirtualMachine {
+    pub fn new() -> Self {
+        Self {
+            stack: vec![Object::Null; STACK_SIZE],
+            sp: 0,
+        }
+    }
+
+    fn push(&mut self, obj: Object) {
+        if self.sp >= self.stack.len() {
+            panic!("stack overflow");
+        }
+
+        self.stack[self.sp] = obj;
+        self.sp += 1;
+    }
+
+    fn pop(&mut self) -> Object {
+        self.sp -= 1;
+        self.stack[self.sp].clone()
+    }
+
+    pub fn run(&mut self, bytecode: &Bytecode) {
+        for inst in &bytecode.instructions {
+            match inst {
+                crate::bytecode::Instruction::Constant(idx) => {
+                    self.push(bytecode.constants[*idx].clone())
+                }
+                crate::bytecode::Instruction::Pop => {
+                    self.pop();
+                }
+            }
+        }
+    }
+}