Function eTag

http/etag.ts:151–166

(
  entity: string | ReturnType<TextEncoder["encode"]> | FileInfo,
  options: ETagOptions = {},
)

  options?: ETagOptions,
): Promise<string | undefined>;
export async function eTag(
  entity: string | ReturnType<TextEncoder["encode"]> | FileInfo,
  options: ETagOptions = {},
): Promise<string | undefined> {
  const weak = options.weak ?? isFileInfo(entity);
  const tag =
    await (isFileInfo(entity)
      ? calcFileInfo(entity, options)
      : calcEntity(entity, options));

  if (!tag) {
    return undefined;
  }

  return weak ? `W/"${tag}"` : `"${tag}"`;
}

const STAR_REGEXP = /^\s*\*\s*$/;
const COMMA_REGEXP = /\s*,\s*/;