/**
 * Trie file format v4
 *
 * Trie format v4 is very similar to v3. The v4 reader can even read v3 files.
 * The motivation behind v4 is to reduce the cost of storing `.trie` files in git.
 * When a word is added in v3, nearly the entire file is changed due to the absolute
 * references. V4 adds an index sorted by the most frequently used reference to the least.
 * Because git diff is line based, it is important to add line breaks at logical points.
 * V3 added line breaks just to make sure the lines were not too long, V4 takes a different
 * approach. Line breaks are added at two distinct points. First, at the start of each two
 * letter prefix and second after approximately 50 words have been emitted.
 *
 * To improve readability and git diff, at the beginning of each two letter prefix,
 * a comment is emitted.
 *
 * Example:
 *
 * ```
 * /* ab *​/
 * ```
 */
import { Sequence } from 'gensequence';
import { TrieNode, TrieRoot } from '../TrieNode';
export declare const DATA = "__DATA__";
export interface ExportOptions {
    base?: number;
    comment?: string;
    /**
     * This will reduce the size of the `.trie` file by removing references to short suffixes.
     * But it does increase the size of the trie when loaded into memory.
     */
    optimizeSimpleReferences?: boolean;
}
/**
 * Serialize a TrieRoot.
 */
export declare function serializeTrie(root: TrieRoot, options?: ExportOptions | number): Sequence<string>;
interface ReferenceMap {
    /**
     * An array of references to nodes.
     * The most frequently referenced is first in the list.
     * A node must be reference by other nodes to be included.
     */
    refCounts: (readonly [TrieNode, number])[];
}
declare function buildReferenceMap(root: TrieRoot, base: number): ReferenceMap;
export declare function importTrie(linesX: Iterable<string> | string): TrieRoot;
export declare const __testing__: {
    buildReferenceMap: typeof buildReferenceMap;
};
export {};
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