Add parser, vm, objects

Big ol thing. You should check it out sometime

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/vm/machine.rs

@@ -0,0 +1,69 @@
+use crate::object::*;
+use crate::vm::error::*;
+use std::cell::RefCell;
+use std::rc::Rc;
+
+#[derive(Default)]
+pub struct MachineBuilder {
+    max_stack_size: Option<usize>,
+    max_arena_objects: Option<usize>,
+}
+
+impl MachineBuilder {
+    pub fn max_stack_size(mut self, max_stack_size: Option<usize>) -> Self {
+        self.max_stack_size = max_stack_size;
+        self
+    }
+
+    pub fn max_arena_objects(mut self, max_arena_objects: Option<usize>) -> Self {
+        self.max_arena_objects = max_arena_objects;
+        self
+    }
+
+    pub fn finish(self) -> Machine {
+        Machine::new(self.max_stack_size, Arena::new(self.max_arena_objects))
+    }
+}
+
+/// The current state of a VM.
+#[derive(Debug)]
+pub struct Machine {
+    stack: Vec<Value>,
+    max_stack_size: Option<usize>,
+    arena: Rc<RefCell<Arena>>,
+}
+
+impl Machine {
+    pub fn new(max_stack_size: Option<usize>, arena: Arena) -> Self {
+        Machine {
+            stack: Default::default(),
+            max_stack_size,
+            arena: Rc::new(RefCell::new(arena)),
+        }
+    }
+
+    pub fn max_stack_size(&self) -> Option<usize> {
+        self.max_stack_size
+    }
+
+    pub fn stack(&self) -> &Vec<Value> {
+        &self.stack
+    }
+    pub fn stack_mut(&mut self) -> &mut Vec<Value> {
+        &mut self.stack
+    }
+
+    pub fn stack_push(&mut self, value: Value) -> Result<()> {
+        if let Some(max) = self.max_stack_size() {
+            if self.stack.len() >= max {
+                return Err(RuntimeError::StackOverflow);
+            }
+        }
+        self.stack_mut().push(value);
+        Ok(())
+    }
+
+    pub fn stack_pop(&mut self) -> Option<Value> {
+        self.stack_mut().pop()
+    }
+}