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/*
* Copyright (C) 2016 The Android Open Source Project
*
* 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.android.apkzlib.sign.v2;
import java.io.IOException;
import java.security.MessageDigest;
import javax.annotation.Nonnull;
/**
* Source of data which is fed into {@link MessageDigest} instances.
*
* <p>This abstraction serves two purposes:
* <ul>
* <li>Transparent digesting of different types of sources, such as {@code byte[]},
* {@code ZFile}, {@link java.nio.ByteBuffer} and/or memory-mapped file.</li>
* <li>Support sources larger than 2 GB. If all sources were smaller than 2 GB, {@code ByteBuffer}
* would have worked as the unifying abstraction.</li>
* </ul>
*/
public interface DigestSource {
/**
* Returns the amount of data (in bytes) contained in this data source.
*/
long size();
/**
* Feeds the specified chunk from this data source into each of the provided
* {@link MessageDigest} instances. Each {@code MessageDigest} instance receives the specified
* chunk of data in full.
*
* @param offset index (in bytes) at which the chunk starts relative to the start of this data
* source.
* @param size size (in bytes) of the chunk.
*/
void feedDigests(long offset, int size, @Nonnull MessageDigest[] digests) throws IOException;
}
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