/**
 * In-memory FIFO used by transport layers that must not drop ordering
 * (EventBuffer, GoogleTagGateway pending captures).
 *
 * - Optional capacity: when full, {@link FifoQueue.enqueue} returns false
 *   and the item is not stored (same semantics as the previous hand-rolled
 *   `length < max` checks).
 * - Default capacity is unbounded (`Number.POSITIVE_INFINITY`).
 */
export declare class FifoQueue<T> {
    private readonly _maxItems;
    private _items;
    constructor(_maxItems?: number);
    get length(): number;
    /** Append one item when under capacity. */
    enqueue(item: T): boolean;
    /**
     * Atomically remove every item in arrival order. Returns a new array
     * reference owned by the caller; the queue is empty after this call.
     */
    takeAll(): T[];
    clear(): void;
}