/**
 * @copyright Sister Software
 * @license AGPL-3.0
 * @author Teffen Ellis, et al.
 * @file A fixed-capacity set of 128-bit fingerprints in one flat `Uint32Array`.
 *
 *   The adapter runner deduplicates by holding every key it has seen. A V8 `Set` refuses its 16,777,217th
 *   entry outright, so the runner capped itself at 10,000,000 keys. Three adapters passed that cap in
 *   `v0.7.0-de-holdout`. The duplicate census over that build measured what the cap costs: of the
 *   2,491,399 duplicate rows the three adapters wrote, 1,490,992 duplicate a key first seen after the cap.
 *   A membership test on a capped set cannot refuse those rows.
 *
 *   This holds the keys as fingerprints instead. Each slot uses four 32-bit words and open addressing with linear
 *   probing. The allocation happens once at construction. The entry count is bounded by the array
 *   the caller sized rather than by a V8 limit. A 2^27-slot table holds 57,570,829 keys at load 0.43 in
 *   2.0 GiB outside the V8 heap.
 *
 *   **A fingerprint collision drops a legitimate row.** Two distinct keys sharing all 128 bits are read as
 *   one and the second row is dropped. Over 57,847,619 keys the expected number of colliding pairs is
 *   about 4.9e-24, so the table trades that for the 1,490,992 duplicates a capped set admits. A caller
 *   that cannot accept any false drop keeps the `Set`.
 */
/**
 * The load factor at which linear probing's expected probe count stays low enough to ignore.
 *
 * Above this the table refuses further keys rather than degrading, because a build whose
 * dedup slows by an order of magnitude partway through reports no cause.
 */
export declare const FINGERPRINT_MAX_LOAD = 0.7;
/**
 * The largest slot count this accepts, as a base-2 logarithm.
 *
 * 2^30 slots hold 751,619,276 keys at the load limit and occupy 16 GiB.
 * Past that the backing `Uint32Array` exceeds what one allocation can hold on a 30.5 GB host,
 * A run that asks for it aborts on the allocation rather than on the key that overflowed.
 */
export declare const MAX_SLOTS_LOG2 = 30;
/**
 * A fingerprint set sized once, holding 128-bit values outside the V8 heap.
 */
export declare class FingerprintSet {
    #private;
    /**
     * @param slotsLog2 Base-2 logarithm of the slot count, so the mask is exact.
     * 27 gives 134,217,728 slots in 2.0 GiB.
     */
    constructor(slotsLog2: number);
    get size(): number;
    /**
     * How many keys this table accepts before {@linkcode add} throws.
     */
    get limit(): number;
    get slots(): number;
    /**
     * Bytes the table occupies outside the V8 heap.
     * They are absent from `--max-old-space-size`.
     */
    get bytes(): number;
    /**
     * Add a key's fingerprint.
     *
     * @returns `true` when the key is new, `false` when this table already holds its fingerprint.
     * @throws When the table is at {@linkcode FINGERPRINT_MAX_LOAD}.
     * A silent degradation would make a build slow down partway through with no cause to read.
     */
    add(key: string): boolean;
}
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