src.com.android.server.backup.encryption.chunking.LengthlessEncryptedChunkEncoder Maven / Gradle / Ivy
/*
* Copyright (C) 2018 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.server.backup.encryption.chunking;
import com.android.server.backup.encryption.chunk.ChunkOrderingType;
import com.android.server.backup.encryption.chunk.ChunksMetadataProto;
import java.io.IOException;
/**
* Encodes an {@link EncryptedChunk} as bytes without including any information about the length of
* the chunk.
*
* In order for us to decode the backup file during restore it must include a chunk ordering in
* mode {@link ChunksMetadataProto#EXPLICIT_STARTS}, which contains the boundaries of the chunks in
* the encrypted file. This information allows us to decode the backup file and divide it into
* chunks without including the length of each chunk inline.
*
*
We use this implementation during full backup.
*/
public class LengthlessEncryptedChunkEncoder implements EncryptedChunkEncoder {
@Override
public void writeChunkToWriter(BackupWriter writer, EncryptedChunk chunk) throws IOException {
writer.writeBytes(chunk.nonce());
writer.writeBytes(chunk.encryptedBytes());
}
@Override
public int getEncodedLengthOfChunk(EncryptedChunk chunk) {
return chunk.nonce().length + chunk.encryptedBytes().length;
}
@Override
@ChunkOrderingType
public int getChunkOrderingType() {
return ChunksMetadataProto.EXPLICIT_STARTS;
}
}