[Init] Initial commit - NetMesh terminal manager

electron/preload/stageUploadFile.cjs

@@ -0,0 +1,64 @@
+"use strict";
+
+async function stageRendererFileToTemp(file, localPath, fsImpl, signal = null) {
+  if (!file || typeof file.stream !== "function") {
+    throw new Error("Upload file streaming is unavailable");
+  }
+  let handle = null;
+  let reader = null;
+  let stagedBytes = 0;
+  const cancellationError = () => (
+    signal?.reason instanceof Error ? signal.reason : new Error("Upload staging cancelled")
+  );
+  const onAbort = () => {
+    void Promise.resolve(reader?.cancel?.(cancellationError())).catch(() => {});
+    void handle?.close?.().catch(() => {});
+  };
+  try {
+    handle = await fsImpl.promises.open(localPath, "wx", 0o600);
+    // Stream/getReader can throw synchronously (revoked File, renderer teardown,
+    // or a malformed provider). Initialize them inside the cleanup boundary so
+    // the just-created file handle is never stranded.
+    reader = file.stream().getReader();
+    if (signal?.aborted) throw cancellationError();
+    signal?.addEventListener?.("abort", onAbort, { once: true });
+    while (true) {
+      if (signal?.aborted) throw cancellationError();
+      const { done, value } = await reader.read();
+      if (signal?.aborted) throw cancellationError();
+      if (done) break;
+      if (!value) continue;
+      const chunk = Buffer.from(value.buffer, value.byteOffset, value.byteLength);
+      let chunkOffset = 0;
+      while (chunkOffset < chunk.length) {
+        if (signal?.aborted) throw cancellationError();
+        const remaining = chunk.length - chunkOffset;
+        let result;
+        try {
+          result = await handle.write(chunk, chunkOffset, remaining, stagedBytes);
+        } catch (error) {
+          if (signal?.aborted) throw cancellationError();
+          throw error;
+        }
+        if (signal?.aborted) throw cancellationError();
+        const bytesWritten = result?.bytesWritten;
+        if (!Number.isSafeInteger(bytesWritten) || bytesWritten <= 0 || bytesWritten > remaining) {
+          throw new Error("Unable to stage the complete upload file");
+        }
+        chunkOffset += bytesWritten;
+        stagedBytes += bytesWritten;
+      }
+    }
+    return localPath;
+  } catch (error) {
+    await handle?.close?.().catch(() => {});
+    await fsImpl.promises.unlink(localPath).catch(() => {});
+    throw error;
+  } finally {
+    signal?.removeEventListener?.("abort", onAbort);
+    reader?.releaseLock?.();
+    await handle?.close?.().catch(() => {});
+  }
+}
+
+module.exports = { stageRendererFileToTemp };