1 files changed, 58 insertions, 0 deletions

diff --git a/clox/src/vm.c b/clox/src/vm.c
index b728ed5..b11a52a 100644
--- a/clox/src/vm.c
+++ b/clox/src/vm.c
@@ -19,6 +19,7 @@ static Value clockNative(int argCount, Value *args) {
 static void resetStack() {
   vm.stackTop = vm.stack;
   vm.frameCount = 0;
+  vm.openUpvalues = NULL;
 }
 
 static void runtimeError(const char *format, ...) {
@@ -118,6 +119,39 @@ static bool callValue(Value callee, int argCount) {
   return false;
 }
 
+static ObjUpvalue *captureUpvalue(Value *local) {
+  ObjUpvalue *prevUpvalue = NULL;
+  ObjUpvalue *upvalue = vm.openUpvalues;
+  while (upvalue != NULL && upvalue->location > local) {
+    prevUpvalue = upvalue;
+    upvalue = upvalue->next;
+  }
+
+  if (upvalue != NULL && upvalue->location == local) {
+    return upvalue;
+  }
+
+  ObjUpvalue *createdUpvalue = newUpvalue(local);
+  createdUpvalue->next = upvalue;
+
+  if (prevUpvalue == NULL) {
+    vm.openUpvalues = createdUpvalue;
+  } else {
+    prevUpvalue->next = createdUpvalue;
+  }
+
+  return createdUpvalue;
+}
+
+static void closeUpvalues(Value *last) {
+  while (vm.openUpvalues != NULL && vm.openUpvalues->location >= last) {
+    ObjUpvalue *upvalue = vm.openUpvalues;
+    upvalue->closed = *upvalue->location;
+    upvalue->location = &upvalue->closed;
+    vm.openUpvalues = upvalue->next;
+  }
+}
+
 static bool isFalsey(Value value) {
   return IS_NIL(value) || (IS_BOOL(value) && !AS_BOOL(value));
 }
@@ -225,6 +259,16 @@ static InterpretResult run() {
       }
       break;
     }
+    case OP_GET_UPVALUE: {
+      uint8_t slot = READ_BYTE();
+      push(*frame->closure->upvalues[slot]->location);
+      break;
+    }
+    case OP_SET_UPVALUE: {
+      uint8_t slot = READ_BYTE();
+      *frame->closure->upvalues[slot]->location = peek(0);
+      break;
+    }
     case OP_EQUAL: {
       Value b = pop();
       Value a = pop();
@@ -303,10 +347,24 @@ static InterpretResult run() {
       ObjFunction *function = AS_FUNCTION(READ_CONSTANT());
       ObjClosure *closure = newClosure(function);
       push(OBJ_VAL(closure));
+      for (int i = 0; i < closure->upvalueCount; i++) {
+        uint8_t isLocal = READ_BYTE();
+        uint8_t index = READ_BYTE();
+        if (isLocal) {
+          closure->upvalues[i] = captureUpvalue(frame->slots + index);
+        } else {
+          closure->upvalues[i] = frame->closure->upvalues[index];
+        }
+      }
       break;
     }
+    case OP_CLOSE_UPVALUE:
+      closeUpvalues(vm.stackTop - 1);
+      pop();
+      break;
     case OP_RETURN: {
       Value result = pop();
+      closeUpvalues(frame->slots);
       vm.frameCount--;
       if (vm.frameCount == 0) {
         pop();