/*
* Copyright 2011 Google Inc.
*
* 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.
*/
package com.google.ipc.invalidation.ticl;
import java.util.Collection;
/**
* Interface for a store that allows objects to be added/removed along with
* the ability to get the digest for the whole or partial set of those objects.
*
* @param <ElementType> the type of the element stored in this
*
*/
public interface DigestStore<ElementType> {
/** Returns the number of elements. */
int size();
/** Returns whether {@code element} is in the store. */
boolean contains(ElementType element);
/**
* Returns a digest of the desired objects.
* <p>
* NOTE: the digest computations <b>MUST NOT</b> depend on the order in which the elements
* were added.
*/
byte[] getDigest();
/**
* Returns the elements whose digest prefixes begin with the bit prefix {@code digestPrefix}.
* {@code prefixLen} is the length of {@code digestPrefix} in bits, which may be less than
* {@code digestPrefix.length} (and may be 0). The implementing class can return *more* objects
* than what has been specified by {@code digestPrefix}, e.g., it could return all the objects
* in the store.
*/
Collection<ElementType> getElements(byte[] digestPrefix, int prefixLen);
/**
* Adds {@code element} to the store. No-op if {@code element} is already present.
* @return whether the element was added
*/
boolean add(ElementType element);
/**
* Adds {@code elements} to the store. If any element in {@code elements} is already present,
* the addition is a no-op for that element.
* @return the elements that were added
*/
Collection<ElementType> add(Collection<ElementType> elements);
/**
* Removes {@code element} from the store. No-op if {@code element} is not present.
* @return whether the element was removed
*/
boolean remove(ElementType element);
/**
* Remove {@code elements} to the store. If any element in {@code elements} is not present, the
* removal is a no-op for that element.
* @return the elements that were removed
*/
Collection<ElementType> remove(Collection<ElementType> elements);
/** Removes all elements in this and returns them. */
Collection<ElementType> removeAll();
}