Strictless Output Persistence

#31
#51

https://lifesigns1.bandcamp.com/album/lifesigns

Funny how in the first issue, I wasn't liking the new GitHub UI at the time, now I don't mind it, and it does look really nice :D

This first one is specifically for the persistence of the read offset when `strict` mode is disabled. It is only accessible with a getter on the NBTData object, and it will return `null` otherwise, when strict mode is enabled (still on by default).

This is initially to set up allowing for easier test-parsing of files with adjacent content, like Bedrock's LevelDB entries. With NBTify currently not easily making the previous offset accessible, it makes it hard to deduce where the next reading step should start from. This simply adds that transparency on it's own.

I may rework the method by how the NBTData object handles this, make it a little tidier.

4664e4c

Author: Offroaders123

src/format.ts

@@ -23,6 +23,7 @@ export class NBTData<T extends RootTagLike = RootTag> implements Format {
   endian: Endian;
   compression: Compression;
   bedrockLevel: BedrockLevel;
+  #byteOffset: typeof this.byteOffset = null;
 
   constructor(data: T | NBTData<T>, options: NBTDataOptions = {}) {
     if (data instanceof NBTData) {
@@ -50,6 +51,17 @@ export class NBTData<T extends RootTagLike = RootTag> implements Format {
     this.bedrockLevel = bedrockLevel;
   }
 
+  get byteOffset(): number | null {
+    return this.#byteOffset;
+  }
+
+  /**
+   * @internal
+   */
+  set byteOffset(value: typeof this.byteOffset) {
+    this.#byteOffset = value;
+  }
+
   get [Symbol.toStringTag](): "NBTData" {
     return "NBTData";
   }

src/read.ts

@@ -185,7 +185,13 @@ class NBTReader {
       throw new Error(`Encountered unexpected End tag at byte offset ${this.#byteOffset}, ${remaining} unread bytes remaining`);
     }
 
-    return new NBTData(root, { rootName: rootNameV, endian, compression, bedrockLevel });
+    const result: NBTData<T> = new NBTData<T>(root, { rootName: rootNameV, endian, compression, bedrockLevel });
+
+    if (!strict) {
+      result.byteOffset = this.#byteOffset;
+    }
+
+    return result;
   }
 
   #readTag<T extends Tag>(type: TAG): T;

test/index.test.ts

@@ -1,5 +1,5 @@
 import { describe, it } from "node:test";
-import { rejects, strictEqual, throws } from "node:assert";
+import assert, { rejects, strictEqual, throws } from "node:assert";
 import { readFile, readdir } from "node:fs/promises";
 import * as NBT from "../src/index.js";
 
@@ -29,8 +29,8 @@ describe("Read, Stringify, Parse and Write", () => {
       /** Determines if the test is for checking empty list handling. */
       const emptyList: boolean = name.startsWith("empty");
 
-      /** Disables strict mode for the Legacy Console Edition player data files. */
-      const strict: boolean = !name.includes("_280dfc");
+      /** Disables strict mode for Bedrock LevelDB and Legacy Console Edition player data files. */
+      const strict: boolean = !/^BlockEntity|^chunk91|_280dfc/.test(name);
 
       /** Reads the NBT file buffer by auto-detecting the file format. */
       const result: void | NBT.RootTag | NBT.NBTData = (snbt)
@@ -40,6 +40,10 @@ describe("Read, Stringify, Parse and Write", () => {
         : await NBT.read<NBT.RootTag>(buffer, { strict });
       if (result === undefined) return;
 
+      if (!strict && result instanceof NBT.NBTData) {
+        assert(result.byteOffset !== null, `'${name}' should have bytes remaining because it shouldn't be parseable with strict mode`);
+      }
+
       /** Stringifies the NBTData result to an SNBT string. */
       const stringified: string | void = (listItemAssertion)
         ? throws(() => NBT.stringify(result), `'${name}' stringifies to SNBT when it shouldn't`)