Move offset mapping entirely into the parser

experiments/modern/src/maki-interpreter/parser.js

@@ -10,6 +10,22 @@ const PRIMITIVE_TYPES = {
   6: "STRING",
 };
 
+// TODO: Don't depend upon COMMANDS
+function opcodeToArgType(opcode) {
+  const argType = COMMANDS[opcode].arg;
+  switch (argType) {
+    case "func":
+    case "line":
+      return "COMMAND_OFFSET";
+    case "var":
+    case "objFunc":
+    case "obj":
+      return "VARIABLE_OFFSET";
+    default:
+      return "NONE";
+  }
+}
+
 // Holds a buffer and a pointer. Consumers can consume bytesoff the end of the
 // file. When we want to run in the browser, we can refactor this class to use a
 // typed array: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Typed_arrays
@@ -232,23 +248,20 @@ function parseComand({ start, makiFile, length, pos }) {
     pos,
     opcode,
     arg: null,
+    argType: opcodeToArgType(opcode),
   };
 
-  const argType = COMMANDS[opcode].arg;
-  if (argType == null) {
+  if (command.argType == "NONE") {
     return command;
   }
 
   let arg = null;
-  switch (argType) {
-    case "func":
-    case "line":
+  switch (command.argType) {
+    case "COMMAND_OFFSET":
       // Note in the perl code here: "todo, something strange going on here..."
       arg = makiFile.readInt32LE() + 5 + pos;
       break;
-    case "var":
-    case "objFunc":
-    case "obj":
+    case "VARIABLE_OFFSET":
       arg = makiFile.readUInt32LE();
       break;
     default:
@@ -314,16 +327,22 @@ function parse(buffer) {
       binaryOffset: undefined,
     });
   });
+
+  const resolvedCommands = commands.map(command => {
+    if (command.argType === "COMMAND_OFFSET") {
+      return Object.assign({}, command, { arg: offsetToCommand[command.arg] });
+    }
+    return command;
+  });
   return {
     magic,
     classes,
     methods,
     variables,
     bindings: resolvedBindings,
-    commands,
+    commands: resolvedCommands,
     version,
     extraVersion,
-    offsetToCommand,
   };
 }
 

experiments/modern/src/maki-interpreter/virtualMachine.js

@@ -11,7 +11,7 @@ function coerceTypes(var1, var2, val1, val2) {
 }
 
 async function interpret(start, program, stack = [], { logger = null }) {
-  const { commands, methods, variables, classes, offsetToCommand } = program;
+  const { commands, methods, variables, classes } = program;
 
   function twoArgCoercingOperator(operator) {
     const a = stack.pop();
@@ -32,11 +32,6 @@ async function interpret(start, program, stack = [], { logger = null }) {
     stack.push(operator(bValue, aValue));
   }
 
-  function jumpToOffset(offset) {
-    const nextCommandIndex = offsetToCommand[offset];
-    return nextCommandIndex - 1;
-  }
-
   let i = start;
   while (i < commands.length) {
     const command = commands[i];
@@ -105,7 +100,7 @@ async function interpret(start, program, stack = [], { logger = null }) {
         if (value) {
           break;
         }
-        i = jumpToOffset(command.arg);
+        i = command.arg - 1;
         break;
       }
       // jumpIfNot
@@ -115,12 +110,12 @@ async function interpret(start, program, stack = [], { logger = null }) {
         if (!value) {
           break;
         }
-        i = jumpToOffset(command.arg);
+        i = command.arg - 1;
         break;
       }
       // jump
       case 18: {
-        i = jumpToOffset(command.arg);
+        i = command.arg - 1;
         break;
       }
       // call
@@ -149,10 +144,9 @@ async function interpret(start, program, stack = [], { logger = null }) {
       // callGlobal
       case 25: {
         const offset = command.arg;
-        const nextCommandIndex = offsetToCommand[offset];
         // Remove this await when we can run the VM synchronously.
         // See GitHub issue #814
-        const value = await interpret(nextCommandIndex, program, stack, {
+        const value = await interpret(offset, program, stack, {
           logger,
         });
         stack.push(value);