fix(trpc): stream backpressure via pull-driven pause and RFC range edge cases

packages/trpc/src/services/stream.service.ts

@@ -8,6 +8,33 @@ export type RemoteFileStream = {
     body: ReadableStream<Uint8Array> | null;
 };
 
+type ParsedRange = { start: number; end: number } | "unsatisfiable" | null;
+
+/**
+ * 解析单段 bytes Range（RFC 9110）：
+ * - null = 语法非法/不支持的形态 → 调用方忽略并回退 200 全量
+ * - "unsatisfiable" = 语义不可满足 → 416
+ */
+function parseBytesRange(header: string, size: number): ParsedRange {
+    const m = /^bytes=(\d*)-(\d*)$/i.exec(header.trim());
+    if (!m) return null;
+    const first = m[1] ?? "";
+    const second = m[2] ?? "";
+    if (!first && !second) return null;
+    if (!first) {
+        // 后缀语法 bytes=-N：最后 N 字节；N=0 不可满足
+        const suffix = Number(second);
+        if (suffix === 0) return "unsatisfiable";
+        return { start: Math.max(0, size - suffix), end: size - 1 };
+    }
+    const start = Number(first);
+    if (start >= size) return "unsatisfiable";
+    if (!second) return { start, end: size - 1 };
+    const end = Number(second);
+    if (end < start) return "unsatisfiable";
+    return { start, end: Math.min(end, size - 1) };
+}
+
 /** 打开远端媒体的 Range 流；webdav 细节只在本层出现，web 只拿 Headers + ReadableStream。 */
 export async function openRemoteFileStream(
     userId: string,
@@ -36,15 +63,21 @@ export async function openRemoteFileStream(
     let end = item.size > 0 ? item.size - 1 : 0;
 
     if (rangeHeader && item.size > 0) {
-        const m = /bytes=(\d*)-(\d*)/.exec(rangeHeader);
-        if (m) {
-            if (m[1]) start = Number(m[1]);
-            if (m[2]) end = Math.min(Number(m[2]), item.size - 1);
+        const parsed = parseBytesRange(rangeHeader, item.size);
+        if (parsed === "unsatisfiable") {
+            headers.set("Content-Range", `bytes */${item.size}`);
+            return { status: 416, headers, body: null };
+        }
+        if (parsed) {
+            start = parsed.start;
+            end = parsed.end;
             status = 206;
             headers.set("Content-Range", `bytes ${start}-${end}/${item.size}`);
             headers.set("Content-Length", String(end - start + 1));
         }
-    } else if (item.size > 0) {
+        // parsed === null（非法 Range）：忽略并回退 200，下方补 Content-Length
+    }
+    if (status === 200 && item.size > 0) {
         headers.set("Content-Length", String(item.size));
     }
 
@@ -53,17 +86,24 @@ export async function openRemoteFileStream(
         item.size > 0
             ? client.createReadStream(abs, { range: { start, end } })
             : client.createReadStream(abs);
+    // ReadableLike 类型未声明 pause/resume，但实现是 Node Readable（data 监听后进入 flowing 模式）
+    const src = nodeStream as typeof nodeStream & { pause(): void; resume(): void };
 
+    // pull 驱动 + desiredSize 背压：队列满时 pause，pull（消费者取走）时 resume
     const body = new ReadableStream<Uint8Array>({
         start(controller) {
-            nodeStream.on("data", (chunk: Buffer | string) => {
+            src.on("data", (chunk: Buffer | string) => {
                 controller.enqueue(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk));
+                if ((controller.desiredSize ?? 1) <= 0) src.pause();
             });
-            nodeStream.on("end", () => controller.close());
-            nodeStream.on("error", (err: unknown) => controller.error(err));
+            src.on("end", () => controller.close());
+            src.on("error", (err: unknown) => controller.error(err));
+        },
+        pull() {
+            src.resume();
         },
         cancel() {
-            nodeStream.destroy();
+            src.destroy();
         },
     });