UrlSource: Deal gracefully with servers that cap unbounded range requests (fixes #231)

src/source.ts

@@ -234,14 +234,9 @@ export class BlobSource extends Source {
 				const { done, value } = await reader.read();
 				if (done) {
 					this._orchestrator.forgetWorker(worker);
-
-					if (worker.currentPos < worker.targetPos) { // I think this `if` should always hit?
 					throw new Error('Blob reader stopped unexpectedly before all requested data was read.');
 				}
 
-					break;
-				}
-
 				if (worker.aborted) {
 					break;
 				}
@@ -441,7 +436,7 @@ export class UrlSource extends Source {
 		let fileSize: number;
 
 		if (response.status === 206) {
-			fileSize = this._getPartialLengthFromRangeResponse(response);
+			fileSize = this._getTotalLengthFromRangeResponse(response);
 			worker = this._orchestrator.createWorker(0, Math.min(fileSize, URL_SOURCE_MIN_LOAD_AMOUNT));
 		} else {
 			// Server probably returned a 200.
@@ -515,14 +510,6 @@ export class UrlSource extends Source {
 				);
 			}
 
-			const length = this._getPartialLengthFromRangeResponse(response);
-			const required = worker.targetPos - worker.currentPos;
-			if (length < required) {
-				throw new Error(
-					`HTTP response unexpectedly too short: Needed at least ${required} bytes, got only ${length}.`,
-				);
-			}
-
 			if (!response.body) {
 				throw new Error(
 					'Missing HTTP response body stream. The used fetch function must provide the response body as a'
@@ -568,18 +555,19 @@ export class UrlSource extends Source {
 				const { done, value } = readResult;
 
 				if (done) {
+					if (worker.currentPos >= worker.targetPos) {
+						// All data was delivered, we're good
 						this._orchestrator.forgetWorker(worker);
-
-					if (worker.currentPos < worker.targetPos) {
-						throw new Error(
-							'Response stream reader stopped unexpectedly before all requested data was read.',
-						);
-					}
-
 						worker.running = false;
 						return;
 					}
 
+					// The response stopped early, before the target. This can happen if server decides to cap range
+					// requests arbitrarily, even if the request had an uncapped end. In this case, let's fetch the rest
+					// of the data using a new request.
+					break;
+				}
+
 				this.onread?.(worker.currentPos, worker.currentPos + value.length);
 				this._orchestrator.supplyWorkerData(worker, value);
 			}
@@ -597,16 +585,15 @@ export class UrlSource extends Source {
 	}
 
 	/** @internal */
-	private _getPartialLengthFromRangeResponse(response: Response) {
+	private _getTotalLengthFromRangeResponse(response: Response) {
 		const contentRange = response.headers.get('Content-Range');
 		if (contentRange) {
 			const match = /\/(\d+)/.exec(contentRange);
 			if (match) {
 				return Number(match[1]);
-			} else {
-				throw new Error(`Invalid Content-Range header: ${contentRange}`);
 			}
-		} else {
+		}
+
 		const contentLength = response.headers.get('Content-Length');
 		if (contentLength) {
 			return Number(contentLength);
@@ -617,7 +604,6 @@ export class UrlSource extends Source {
 			);
 		}
 	}
-	}
 
 	/** @internal */
 	_dispose() {