How to use the capnp-ts.Uint64 function in capnp-ts

export function generateCapnpImport(ctx: CodeGeneratorFileContext): void {
  // Look for the special importPath annotation on the file to see if we need a different import path for capnp-ts.

  const fileNode = lookupNode(ctx, ctx.file);
  const tsFileId = capnp.Uint64.fromHexString(TS_FILE_ID);
  // This may be undefined if ts.capnp is not imported; fine, we'll just use the default.
  const tsAnnotationFile = ctx.nodes.find(n => n.getId().equals(tsFileId));
  // We might not find the importPath annotation; that's definitely a bug but let's move on.
  const tsImportPathAnnotation =
    tsAnnotationFile &&
    tsAnnotationFile.getNestedNodes().find(n => n.getName() === "importPath");
  // There may not necessarily be an import path annotation on the file node. That's fine.
  const importAnnotation =
    tsImportPathAnnotation &&
    fileNode
      .getAnnotations()
      .find(a => a.getId().equals(tsImportPathAnnotation.getId()));
  const importPath =
    importAnnotation === undefined
      ? "capnp-ts"
      : importAnnotation.getValue().getText();

export function lookupNode(
  ctx: CodeGeneratorFileContext,
  lookup: { getId(): capnp.Uint64 } | capnp.Uint64
): s.Node {
  const id = lookup instanceof capnp.Uint64 ? lookup : lookup.getId();
  const node = ctx.nodes.find(n => n.getId().equals(id));

  if (node === undefined) throw new Error(format(E.GEN_NODE_LOOKUP_FAIL, id));

  return node;
}