/**
 * Mutable B+ tree used by BTreeIndex for sorted value buckets. Keys use the
 * supplied comparator, which must return a number that is not NaN; BTreeIndex
 * checks every comparator result. Point operations cost O(log size). This fork has
 * no copy-on-write sharing, cloning, optional-value storage, early-exit range
 * callbacks, or in-place range edits: only the operations BTreeIndex uses,
 * plus `has()` and the `get()` fallback that the Map oracle observes
 * (tests/btree-map-oracle.test.ts).
 * @author David Piepgrass
 */
export declare class BTree<K = any, V = any> {
    private _root;
    _size: number;
    _maxNodeSize: number;
    /**
     * provides a total order over keys (and a strict partial order over the type K)
     * @returns a negative value if a < b, 0 if a === b and a positive value if a > b
     */
    _compare: (a: K, b: K) => number;
    /**
     * Initializes an empty B+ tree.
     * @param compare Custom function to compare pairs of elements in the tree.
     * @param maxNodeSize Branching factor (maximum items or children per node)
     *   Must be in range 4..256. If undefined or <4 then default is used; if >256 then 256.
     */
    constructor(compare: (a: K, b: K) => number, maxNodeSize?: number);
    /** Gets the number of key-value pairs in the tree. */
    get size(): number;
    /** Releases the tree so that its size is 0. */
    clear(): void;
    /**
     * Finds a pair in the tree and returns the associated value.
     * @param defaultValue a value to return if the key was not found.
     * @returns the value, or defaultValue if the key was not found.
     * @description Computational complexity: O(log size)
     */
    get(key: K, defaultValue?: V): V | undefined;
    /** Returns true if the key exists in the B+ tree. */
    has(key: K): boolean;
    /**
     * Adds or overwrites a key-value pair in the B+ tree. Overwriting also
     * replaces the stored key.
     * @returns true if a new key-value pair was added.
     * @description Computational complexity: O(log size)
     */
    set(key: K, value: V): boolean;
    /**
     * Removes a single key-value pair from the B+ tree.
     * @returns true if a pair was found and removed, false otherwise.
     * @description Computational complexity: O(log size)
     */
    delete(key: K): boolean;
    /** Gets the lowest key in the tree. Complexity: O(log size) */
    minKey(): K | undefined;
    /** Gets the highest key in the tree. Complexity: O(1) */
    maxKey(): K | undefined;
    /** Returns the next pair whose key is larger than the specified key (or undefined if there is none).
     * If key === undefined, this function returns the lowest pair.
     */
    nextHigherPair(key: K | undefined): [K, V] | undefined;
    /** Returns the next pair whose key is smaller than the specified key (or undefined if there is none).
     *  If key === undefined, this function returns the highest pair.
     */
    nextLowerPair(key: K | undefined): [K, V] | undefined;
    /**
     * Scans the specified range of keys, in ascending order by key.
     * Note: the callback `onFound` must not insert or remove items in the
     * collection. Doing so may cause incorrect data to be sent to the
     * callback afterward.
     * @param low The first key scanned will be greater than or equal to `low`.
     * @param high Scanning stops when a key larger than this is reached.
     * @param includeHigh If the `high` key is present, `onFound` is called for
     *        that final pair if and only if this parameter is true.
     * @description Computational complexity: O(number of items scanned + log size)
     */
    forRange(low: K, high: K, includeHigh: boolean, onFound: (k: K, v: V) => void): void;
}