[Init] Initial commit - NetMesh terminal manager

electron/plugins/terminalInterceptorTransport.cjs

@@ -0,0 +1,70 @@
+"use strict";
+
+const schema = require("./generated/plugin-contract.schema.json");
+const { assertTerminalInterceptorFrameSchema } = require("./contractValidator.cjs");
+
+const limits = schema.$defs.TerminalInterceptorLimits.const;
+const TERMINAL_INTERCEPTOR_MAX_CHUNK_BYTES = limits.maxChunkBytes;
+const TERMINAL_INTERCEPTOR_MAX_WINDOW_BYTES = limits.maxWindowBytes;
+const arrayBufferByteLength = Object.getOwnPropertyDescriptor(
+  ArrayBuffer.prototype,
+  "byteLength",
+)?.get;
+
+function copyOwnDataRecord(value, label) {
+  if (value === null || typeof value !== "object" || Array.isArray(value)) {
+    throw new TypeError(`${label} must be a plain object`);
+  }
+  const copy = {};
+  for (const key of Object.keys(value)) {
+    const descriptor = Object.getOwnPropertyDescriptor(value, key);
+    if (!descriptor || !("value" in descriptor)) {
+      throw new TypeError(`${label} must contain data properties only`);
+    }
+    copy[key] = descriptor.value;
+  }
+  return copy;
+}
+
+function transferredByteLength(value) {
+  if (!arrayBufferByteLength) throw new TypeError("ArrayBuffer byteLength getter is unavailable");
+  try {
+    const byteLength = arrayBufferByteLength.call(value);
+    // The intrinsic getter reports zero for a detached zero-length buffer as
+    // well as for a valid empty buffer. Constructing a view distinguishes the
+    // two and also works for ArrayBuffers created in another realm.
+    new Uint8Array(value);
+    return byteLength;
+  } catch {
+    throw new TypeError("Terminal interceptor transfer requires a real, attached ArrayBuffer");
+  }
+}
+
+function createTerminalInterceptorEnvelope(frameValue, transfer) {
+  const frame = copyOwnDataRecord(frameValue, "Terminal interceptor frame");
+  assertTerminalInterceptorFrameSchema(frame);
+  const requiresTransfer = frame.type === "netcatty:terminal-interceptor:chunk"
+    || (frame.type === "netcatty:terminal-interceptor:result" && frame.status === "ok");
+  if (!requiresTransfer) {
+    if (transfer !== undefined) {
+      throw new TypeError("This terminal interceptor frame must not include a transferred buffer");
+    }
+    return Object.freeze({ frame: Object.freeze(frame) });
+  }
+  if (transfer === undefined) {
+    throw new TypeError("This terminal interceptor frame requires a transferred ArrayBuffer");
+  }
+  const byteLength = transferredByteLength(transfer);
+  if (byteLength !== frame.byteLength) {
+    throw new RangeError(
+      `Terminal interceptor byteLength mismatch: declared ${frame.byteLength}, received ${byteLength}`,
+    );
+  }
+  return Object.freeze({ frame: Object.freeze(frame), transfer });
+}
+
+module.exports = {
+  TERMINAL_INTERCEPTOR_MAX_CHUNK_BYTES,
+  TERMINAL_INTERCEPTOR_MAX_WINDOW_BYTES,
+  createTerminalInterceptorEnvelope,
+};