/**
 * @license
 * Copyright 2020 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import { FieldPath } from './path';
/**
 * Provides a set of fields that can be used to partially patch a document.
 * FieldMask is used in conjunction with ObjectValue.
 * Examples:
 *   foo - Overwrites foo entirely with the provided value. If foo is not
 *         present in the companion ObjectValue, the field is deleted.
 *   foo.bar - Overwrites only the field bar of the object foo.
 *             If foo is not an object, foo is replaced with an object
 *             containing foo
 */
export declare class FieldMask {
    readonly fields: FieldPath[];
    constructor(fields: FieldPath[]);
    static empty(): FieldMask;
    /**
     * Returns a new FieldMask object that is the result of adding all the given
     * fields paths to this field mask.
     */
    unionWith(extraFields: FieldPath[]): FieldMask;
    /**
     * Verifies that `fieldPath` is included by at least one field in this field
     * mask.
     *
     * This is an O(n) operation, where `n` is the size of the field mask.
     */
    covers(fieldPath: FieldPath): boolean;
    isEqual(other: FieldMask): boolean;
}
