import { DataBufferBuilder } from './buffer.js';
import { Builder, BuilderOptions } from '../builder.js';
import { Union, SparseUnion, DenseUnion } from '../type.js';
export interface UnionBuilderOptions<T extends Union = any, TNull = any> extends BuilderOptions<T, TNull> {
    valueToChildTypeId?: (builder: UnionBuilder<T, TNull>, value: any, offset: number) => number;
}
/** @ignore */
export declare abstract class UnionBuilder<T extends Union, TNull = any> extends Builder<T, TNull> {
    protected _typeIds: DataBufferBuilder<Int8Array>;
    constructor(options: UnionBuilderOptions<T, TNull>);
    get typeIdToChildIndex(): {
        [key: number]: number;
    };
    append(value: T['TValue'] | TNull, childTypeId?: number): this;
    set(index: number, value: T['TValue'] | TNull, childTypeId?: number): this;
    setValue(index: number, value: T['TValue'], childTypeId?: number): void;
    addChild(child: Builder, name?: string): number;
    /** @ignore */
    protected _valueToChildTypeId(builder: UnionBuilder<T, TNull>, value: any, offset: number): number;
}
/** @ignore */
export declare class SparseUnionBuilder<T extends SparseUnion, TNull = any> extends UnionBuilder<T, TNull> {
}
/** @ignore */
export declare class DenseUnionBuilder<T extends DenseUnion, TNull = any> extends UnionBuilder<T, TNull> {
    protected _offsets: DataBufferBuilder<Int32Array>;
    constructor(options: UnionBuilderOptions<T, TNull>);
    /** @ignore */
    setValue(index: number, value: T['TValue'], childTypeId?: number): void;
}