better networked model loading

src/App.vue

@@ -25,7 +25,7 @@ let sData: Ref<SceneManagerData> = SceneMgr.newData();
 // Set up the load model event listener
 let networkMgr = new NetworkManager();
 networkMgr.addEventListener('update', (model: NetworkUpdateEvent) => {
-  sData.value.viewerSrc = model.url;
+  SceneMgr.loadModel(sData.value, model.name, model.url);
 });
 // Start loading all configured models ASAP
 for (let model of settings.preloadModels) {

src/misc/network.ts

@@ -1,6 +1,7 @@
 export class NetworkUpdateEvent extends Event {
     name: string;
     url: string;
+
     constructor(name: string, url: string) {
         super("update");
         this.name = name;
@@ -27,15 +28,11 @@ export class NetworkManager extends EventTarget {
             // Get the last part of the URL as the "name" of the model
             let name = url.split("/").pop();
             name = name?.split(".")[0] || `unknown-${Math.random()}`;
-            let prevHash = this.knownObjectHashes[name];
             // Use a head request to get the hash of the file
-            let response = await fetch(url, { method: "HEAD" });
+            let response = await fetch(url, {method: "HEAD"});
             let hash = response.headers.get("etag");
             // Only trigger an update if the hash has changed
-            if (hash !== prevHash) {
-                this.knownObjectHashes[name] = hash;
-                this.dispatchEvent(new NetworkUpdateEvent(name, url));
-            }
+            this.foundModel(name, hash, url);
         }
     }
 
@@ -44,13 +41,7 @@ export class NetworkManager extends EventTarget {
         ws.onmessage = (event) => {
             let data = JSON.parse(event.data);
             console.debug("WebSocket message", data);
-            let name = data.name;
-            let prevHash = this.knownObjectHashes[name];
-            let hash = data.hash;
-            if (hash !== prevHash) {
-                this.knownObjectHashes[name] = hash;
-                this.dispatchEvent(new NetworkUpdateEvent(name, data.url));
-            }
+            this.foundModel(data.name, data.hash, data.url);
         };
         ws.onerror = (event) => {
             console.error("WebSocket error", event);
@@ -60,4 +51,12 @@ export class NetworkManager extends EventTarget {
             setTimeout(() => this.monitorWebSocket(url), 500);
         }
     }
+
+    private foundModel(name: string, hash: string, url: string) {
+        let prevHash = this.knownObjectHashes[name];
+        if (hash !== prevHash) {
+            this.knownObjectHashes[name] = hash;
+            this.dispatchEvent(new NetworkUpdateEvent(name, url));
+        }
+    }
 }

src/misc/scene.ts

@@ -3,6 +3,7 @@ import type {ModelScene} from "@google/model-viewer/lib/three-components/ModelSc
 import {ref, Ref} from 'vue';
 import {Document} from '@gltf-transform/core';
 import {ModelViewerInfo} from "./viewer/ModelViewerWrapper.vue";
+import {splitGlbs} from "../models/glb/glbs";
 
 type SceneManagerData = {
     /** When updated, forces the viewer to load a new model replacing the current one */
@@ -32,6 +33,22 @@ export class SceneMgr {
         });
     }
 
+    /** Loads a GLB/GLBS model from a URL and adds it to the viewer or replaces it if the names match */
+    static async loadModel(data: SceneManagerData, name: string, url: string) {
+        let response = await fetch(url);
+        if (!response.ok) throw new Error("Failed to fetch model: " + response.statusText);
+        let glbsSplitter = splitGlbs(response.body!);
+        let {value: numChunks} = await glbsSplitter.next();
+        console.log("Loading model with", numChunks, "chunks");
+        while (true) {
+            let {value: chunk, done} = await glbsSplitter.next();
+            if (done) break;
+            console.log("Got chunk", chunk);
+            // Override the current model with the new one
+            data.viewerSrc = URL.createObjectURL(new Blob([chunk], {type: 'model/gltf-binary'}));
+        }
+    }
+
     /** Should be called any model finishes loading successfully (after a viewerSrc update) */
     static onload(data: SceneManagerData, info: typeof ModelViewerInfo) {
         console.log("ModelViewer loaded", info);

src/models/glb/glbs.ts

@@ -1,79 +1,67 @@
-export type SplitGlbsResult = {
-    numChunks: number;
-    glbReader: ReadableStream<Uint8Array>;
-}
+const textDecoder = new TextDecoder();
 
 /**
  * Given a stream of binary data (e.g. from a fetch response), splits a GLBS file into its component GLB files and
- * returns them as a stream of Uint8Arrays with known lengths. It also supports simple GLB files by returning itself.
+ * returns them as a generator of Uint8Arrays (that starts with the expected length).
+ * It also supports simple GLB files (no splitting needed).
  */
-export async function splitGlbs(reader: ReadableStream<Uint8Array>): Promise<SplitGlbsResult> {
-    // Create a transform stream that splits the GLBS file into its component GLB files by reading the length of each
-    // chunk and then reading that many bytes from the input stream.
-    let buffer4Bytes = new Uint8Array(4);
-    let readerImpl = reader.getReader({mode: 'byob'});
-    await readerImpl.read(buffer4Bytes);
-    if (buffer4Bytes[0] === '{'.charCodeAt(0) || Array.from(buffer4Bytes) === "glTF".split('').map(c => c.charCodeAt(0))) {
-        return {numChunks: 1, glbReader: await singleBlob(reader)}
-    }
-    let isGlbs = Array.from(buffer4Bytes) === "GLBS".split('').map(c => c.charCodeAt(0));
-    if (!isGlbs) throw new Error('Invalid magic numbers for expected GLBS file: ' + buffer4Bytes);
-    // Create a new readable stream that splits the GLBS file into its component GLB files by reading the length of each
-    // chunk and then reading that many bytes from the input stream.
-    // - But first, we read the number of chunks (can be 0xFFFFFFFF if the number of chunks is unknown).
-    await readerImpl.read(buffer4Bytes);
+export async function* splitGlbs(readerSrc: ReadableStream<Uint8Array>): AsyncGenerator<number | Uint8Array> {
+    let reader = readerSrc.getReader();
+    let [buffer4Bytes, buffered] = await readN(reader, new Uint8Array(), 4);
+    console.assert(buffer4Bytes.length === 4, 'Expected 4 bytes for magic numbers')
+    let magic = textDecoder.decode(buffer4Bytes)
+    if (magic === 'glTF' /* GLB */ || magic[0] == '{' /* glTF */) {
+        yield 1
+        let remaining = await readAll(reader, buffered);
+        // Add back the header to the beginning of the document
+        let finalBuffer = new Uint8Array(buffer4Bytes.length + remaining.length);
+        finalBuffer.set(buffer4Bytes);
+        finalBuffer.set(remaining, buffer4Bytes.length);
+        yield finalBuffer
+    } else if (magic !== "GLBS") {
+        // First, we read the number of chunks (can be 0xFFFFFFFF if the number of chunks is unknown).
+        [buffer4Bytes, buffered] = await readN(reader, buffered, 4);
         let numChunks = new DataView(buffer4Bytes.buffer).getUint32(0, true);
-    return {
-        numChunks,
-        // - Then, we read the length of each chunk followed by the chunk itself.
-        glbReader: new ReadableStream<Uint8Array>({
-            async start(controller) {
+        yield numChunks
+        // Then, we read the length of each chunk followed by the chunk itself.
         for (let i = 0; i < numChunks; i++) {
             // - Read length
-                    let {done} = await readerImpl.read(buffer4Bytes);
-                    if (done) {
+            [buffer4Bytes, buffered] = await readN(reader, buffered, 4);
+            if (buffer4Bytes.length === 0) {
                 if (numChunks != 0xFFFFFFFF) throw new Error('Unexpected end of stream while reading chunk length');
                 else break // We reached the end of the stream of unknown length, so we stop reading chunks.
             }
             let length = new DataView(buffer4Bytes.buffer).getUint32(0, true);
             // - Read chunk
-                    let chunkReader = await singleBlob(reader, length);
-                    let {value: fullChunk} = await chunkReader.getReader().read();
-                    controller.enqueue(fullChunk);
+            let chunk: Uint8Array
+            [chunk, buffered] = await readN(reader, buffered, length);
+            yield chunk
         }
-                controller.close();
-            }
-        })
-    };
+    } else throw new Error('Invalid magic numbers for expected GLB/GLBS file: ' + magic);
+    reader.releaseLock()
 }
 
-async function singleBlob(reader: ReadableStream<Uint8Array>, stopAfter: number | null = null): Promise<ReadableStream<Uint8Array>> {
-    // Make sure the reader reads the entire stream at once.
-    const readerImpl = reader.getReader();
-    let bufferedChunks: Uint8Array = new Uint8Array();
-    let done = false;
-    let length = 0;
-    while (!done) {
-        let {value, done: d} = await readerImpl.read();
-        if (value) {
-            // TODO: This is inefficient. We should be able to avoid copying the buffer each time. byob?
-            let oldBuffer = bufferedChunks;
-            let newLength = bufferedChunks.length + value.length;
-            if (stopAfter !== null && newLength > stopAfter) {
-                newLength = stopAfter;
-                value = value.slice(0, stopAfter - bufferedChunks.length);
+/** Reads exactly `n` bytes from the reader and returns them as a Uint8Array.
+ * An over-read is possible, in which case the returned array will still have `n` bytes and the over-read bytes will be
+ * returned. They should be provided to the next call to `readN` to avoid losing data.
+ */
+async function readN(reader: ReadableStreamDefaultReader<Uint8Array>, buffered: Uint8Array, n: number | null = null): Promise<[Uint8Array, Uint8Array]> {
+    let buffer = buffered;
+    while (n === null || buffer.length < n) {
+        let {done, value} = await reader.read();
+        if (done) break;
+        let newBuffer = new Uint8Array(buffer.length + value.length);
+        newBuffer.set(buffer);
+        newBuffer.set(value, buffer.length);
+        buffer = newBuffer;
     }
-            bufferedChunks = new Uint8Array(newLength);
-            bufferedChunks.set(oldBuffer);
-            bufferedChunks.set(value, length);
-            length += value.length;
+    if (n !== null) {
+        return [buffer.slice(0, n), buffer.slice(n)]
+    } else {
+        return [buffer, new Uint8Array()];
     }
-        done = d;
-    }
-    return new ReadableStream<Uint8Array>({
-        start(controller) {
-            controller.enqueue(bufferedChunks);
-            controller.close();
-        }
-    });
+}
+
+async function readAll(reader: ReadableStreamDefaultReader<Uint8Array>, buffered: Uint8Array): Promise<Uint8Array> {
+    return (await readN(reader, buffered, null))[0];
 }

tsconfig.json

@@ -1,5 +1,5 @@
 {
   "compilerOptions": {
-    "lib": ["ES2020", "DOM"]
+    "lib": ["es2015", "DOM"]
   }
 }