fix(map): override length values appropriately when reading map chunks

src/lib/map/MapArea.ts

@@ -77,7 +77,7 @@ class MapArea {
 
       // Normalize all MCAL splats into 8-bit depth splats
       let splat: Uint8Array;
-      if (!alpha) {
+      if (!alpha || alpha.length === 0) {
         splat = null;
       } else if (this.#layerSplatDepth === 4) {
         const rawSplat = new Uint8Array(

src/lib/map/io/McnkIo.ts

@@ -0,0 +1,73 @@
+import { IoContext, IoSource, IoType, IoMode, IoStream, openStream } from '@wowserhq/io';
+import * as mcnkIo from './mcnk.js';
+
+/**
+ * An IoType to read MCNK data from ADT files.
+ *
+ * While MCNK is nominally a headered TLV format, a number of presumed bugs in Blizzard's authoring
+ * tools lead to multiple tags with invalid lengths. The game client uses alternative length values
+ * specified in the header for these tags.
+ */
+class McnkIo implements IoType {
+  getSize() {
+    return 0;
+  }
+
+  #readChunk(stream: IoStream, context: IoContext, header: Record<string, any>) {
+    const tagValue = mcnkIo.chunkTag.read(stream);
+
+    let lengthValue = stream.readUint32Le();
+    if (tagValue === 'MCAL') {
+      lengthValue = header.mcalSize - 8;
+    } else if (tagValue === 'MCLQ') {
+      lengthValue = header.mclqSize - 8;
+    } else if (tagValue === 'MCSH') {
+      lengthValue = header.mcshSize;
+    }
+
+    const valueType = mcnkIo.chunks[tagValue];
+    const valueBytes = stream.readBytes(lengthValue);
+
+    let valueValue = valueBytes;
+    if (valueType && valueType.read) {
+      const valueStream = openStream(valueBytes, IoMode.Read);
+      valueValue = valueType.read(valueStream, context);
+    }
+
+    // If tag is padded, adjust offset accordingly
+    const padding = mcnkIo.padding[tagValue] ?? 0;
+    stream.offset += padding;
+
+    return {
+      tag: tagValue,
+      length: lengthValue,
+      value: valueValue,
+    };
+  }
+
+  #readChunks(stream: IoStream, context: IoContext, header: Record<string, any>) {
+    const chunks = [];
+
+    while (!stream.eof) {
+      chunks.push(this.#readChunk(stream, context, header));
+    }
+
+    return chunks;
+  }
+
+  read(source: IoSource, context: IoContext = {}) {
+    const stream = openStream(source, IoMode.Read);
+    const value: Record<string, any> = {};
+
+    context.local = null;
+    context.root = context.root ?? null;
+
+    const header = mcnkIo.header.read(source);
+    value.header = header;
+    value.data = this.#readChunks(stream, context, header);
+
+    return value;
+  }
+}
+
+export default McnkIo;

src/lib/map/io/adt.ts

@@ -1,7 +1,7 @@
 import * as io from '@wowserhq/io';
-import { mver } from './common.js';
-import { MAP_CHUNK_VERTEX_COUNT } from '../const.js';
 import { IoType } from '@wowserhq/io';
+import { mver } from './common.js';
+import McnkIo from './McnkIo.js';
 
 const mapChunkInfo = io.struct({
   offset: io.uint32le,
@@ -10,69 +10,7 @@ const mapChunkInfo = io.struct({
   padding: io.uint32le,
 });
 
-const mapChunkHeader = io.struct({
-  flags: io.uint32le,
-  indexX: io.uint32le,
-  indexY: io.uint32le,
-  layerCount: io.uint32le,
-  doodadRefCount: io.uint32le,
-  mcvtOffset: io.uint32le,
-  mcnrOffset: io.uint32le,
-  mclyOffset: io.uint32le,
-  mcrfOffset: io.uint32le,
-  mcalOffset: io.uint32le,
-  mcalSize: io.uint32le,
-  mcshOffset: io.uint32le,
-  mcshSize: io.uint32le,
-  areaId: io.uint32le,
-  mapObjRefCount: io.uint32le,
-  holes: io.uint16le,
-  padding: io.uint16le,
-  predTex: io.array(io.uint16le, { size: 8 }),
-  noEffectDoodad: io.array(io.uint8, { size: 8 }),
-  mcseOffset: io.uint32le,
-  soundEmitterCount: io.uint32le,
-  mclqOffset: io.uint32le,
-  mclqSize: io.uint32le,
-  position: io.array(io.float32le, { size: 3 }),
-  mccvOffset: io.uint32le,
-  padding2: io.array(io.uint32le, { size: 2 }),
-});
-
-const mapLayer = io.struct({
-  textureId: io.uint32le,
-  properties: io.uint32le,
-  alphaOffset: io.uint32le,
-  effectId: io.uint32le,
-});
-
-const mcvt = io.typedArray(io.float32le, { size: MAP_CHUNK_VERTEX_COUNT });
-
-const mcly = io.array(mapLayer);
-
-const mcnr = io.typedArray(io.int8, { size: 3 * MAP_CHUNK_VERTEX_COUNT });
-
-const mcnkChunks = {
-  MCVT: mcvt,
-  MCLY: mcly,
-  MCNR: mcnr,
-};
-
-const mcnkPadding = {
-  MCNR: 13,
-};
-
-const mcnkChunk = io.tlv(
-  io.string({ size: 4, reverse: true, terminate: false }),
-  io.uint32le,
-  mcnkChunks,
-  { padding: mcnkPadding },
-);
-
-const mcnk = io.struct({
-  header: mapChunkHeader,
-  data: io.array(mcnkChunk),
-});
+const mcnk = new McnkIo();
 
 const mhdr = io.struct({
   flags: io.uint32le,

src/lib/map/io/mcnk.ts

@@ -0,0 +1,59 @@
+import * as io from '@wowserhq/io';
+import { IoType } from '@wowserhq/io';
+import { MAP_CHUNK_VERTEX_COUNT } from '../const.js';
+
+const header: IoType = io.struct({
+  flags: io.uint32le,
+  indexX: io.uint32le,
+  indexY: io.uint32le,
+  layerCount: io.uint32le,
+  doodadRefCount: io.uint32le,
+  mcvtOffset: io.uint32le,
+  mcnrOffset: io.uint32le,
+  mclyOffset: io.uint32le,
+  mcrfOffset: io.uint32le,
+  mcalOffset: io.uint32le,
+  mcalSize: io.uint32le,
+  mcshOffset: io.uint32le,
+  mcshSize: io.uint32le,
+  areaId: io.uint32le,
+  mapObjRefCount: io.uint32le,
+  holes: io.uint16le,
+  padding: io.uint16le,
+  predTex: io.array(io.uint16le, { size: 8 }),
+  noEffectDoodad: io.array(io.uint8, { size: 8 }),
+  mcseOffset: io.uint32le,
+  soundEmitterCount: io.uint32le,
+  mclqOffset: io.uint32le,
+  mclqSize: io.uint32le,
+  position: io.array(io.float32le, { size: 3 }),
+  mccvOffset: io.uint32le,
+  padding2: io.array(io.uint32le, { size: 2 }),
+});
+
+const layer = io.struct({
+  textureId: io.uint32le,
+  properties: io.uint32le,
+  alphaOffset: io.uint32le,
+  effectId: io.uint32le,
+});
+
+const chunkTag: IoType = io.string({ size: 4, reverse: true, terminate: false });
+
+const mcvt = io.typedArray(io.float32le, { size: MAP_CHUNK_VERTEX_COUNT });
+
+const mcly = io.array(layer);
+
+const mcnr = io.typedArray(io.int8, { size: 3 * MAP_CHUNK_VERTEX_COUNT });
+
+const chunks: Record<string, IoType> = {
+  MCVT: mcvt,
+  MCLY: mcly,
+  MCNR: mcnr,
+};
+
+const padding = {
+  MCNR: 13,
+};
+
+export { header, chunkTag, chunks, padding };

src/spec/map/MapArea.spec.ts

@@ -13,5 +13,15 @@ describe('MapArea', () => {
         expect(mapArea.chunks.length).toBe(16 * 16);
       });
     });
+
+    describe('pvpzone', () => {
+      test('should load map area from valid file', () => {
+        const map = new Map().load('./fixture/map/pvpzone.wdt');
+        const mapArea = new MapArea(map.layerSplatDepth).load('./fixture/map/pvpzone3430.adt');
+
+        expect(mapArea.version).toBe(18);
+        expect(mapArea.chunks.length).toBe(16 * 16);
+      });
+    });
   });
 });