Add Unpack Method

src/builder.ts

@@ -5,6 +5,7 @@ import { Span } from './span';
 import * as transform from './transform';
 
 export { code, node, transform, Property, PropertyType, Span };
+export { Endianess } from "./code";
 export { Edge } from './edge';
 export { LoopChecker } from './loop-checker';
 export { ISpanAllocatorResult, SpanAllocator } from './span-allocator';
@@ -72,6 +73,8 @@ export class Builder {
                 otherwise?: node.Node): node.Invoke {
     let res: node.Invoke;
 
+    // TODO: (Vizonex) Should we add a check for non-existant unpack properties here? 
+
     // `.invoke(name)`
     if (map === undefined) {
       res = new node.Invoke(fn, {});

src/code/creator.ts

@@ -181,4 +181,20 @@ export class Creator {
   public test(field: string, value: number): code.Test {
     return new code.Test(field, value);
   }
+
+  /** 
+   * Intrinsic operation.
+   * 
+   *  state[field] <<= 8 or >>= 8 (depending on endianess)  
+   *  state[field] |= value
+   *  return (state[field] < (property size limit)) ? 0 : -1;
+   * 
+   * @param field Property Name
+   * @param endianness Endianness Enum to determine if big 
+   * or little endianness should be accounted for.
+   * defaults to `Endianess.Little`
+   */
+  public unpack(field: string, endianness?: code.Endianess) : code.Unpack {
+    return new code.Unpack(field, endianness);
+  }
 }

src/code/index.ts

@@ -13,3 +13,4 @@ export { Store } from './store';
 export { Test } from './test';
 export { Update } from './update';
 export { Value } from './value';
+export { Unpack, Endianess } from './unpack';

src/code/unpack.ts

@@ -0,0 +1,32 @@
+import { Field } from "./field";
+
+/** Options for `code.unpack()` */
+export enum Endianess {
+    Little = 0,
+    Big = 1
+};
+
+/** Helps with making unpacking protocols.
+ * It unpacks variables via left & right shifting 
+ * based on a given endianness argument
+ */
+export class Unpack extends Field {
+    public readonly bigEndian:boolean;
+    /**
+     * @param field Name of the property that should be unpacked to
+     * @param endianness determines how to unpack the value provided
+     * Default Value: `Endianess.Little`.
+     */
+
+    constructor (field: string, endianness?:Endianess){
+        if (endianness === undefined){
+            endianness = Endianess.Little;
+        } 
+        super(
+            'match', 
+            endianness == Endianess.Little ? 'unpack_le' : 'unpack_be',  
+            field
+        );
+        this.bigEndian = endianness == Endianess.Big;
+    }
+}

test/builder.test.ts

@@ -1,5 +1,5 @@
 import { beforeEach, describe, it, type TestContext } from 'node:test';
-import { Builder } from '../src/builder';
+import { Builder, Endianess } from '../src/builder';
 
 describe('LLParse/Builder', () => {
   let b: Builder;
@@ -88,4 +88,18 @@ describe('LLParse/Builder', () => {
       10,
     ]);
   });
+
+  it('should create an unpack for Invoke'), (t: TestContext) => {
+    const start = b.node('start');
+    b.property('i16', 'unpack_value');
+    const unpack_error = b.error(0, 'failed to unpack value');
+    const invoke = b.invoke(
+      b.code.unpack('unpack_value', Endianess.Little),
+      start, unpack_error
+    );
+    const otherwise = invoke.getOtherwiseEdge();
+    t.assert.deepStrictEqual(
+      otherwise?.node, unpack_error
+    );
+  }
 });