src.com.android.server.backup.encryption.chunking.InlineLengthsEncryptedChunkEncoder 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, prepending the length of the chunk.
*
* This allows us to decode the backup file during restore without any extra information about
* the boundaries of the chunks. The backup file should contain a chunk ordering in mode {@link
* ChunksMetadataProto#INLINE_LENGTHS}.
*
*
We use this implementation during key value backup.
*/
public class InlineLengthsEncryptedChunkEncoder implements EncryptedChunkEncoder {
public static final int BYTES_LENGTH = Integer.SIZE / Byte.SIZE;
private final LengthlessEncryptedChunkEncoder mLengthlessEncryptedChunkEncoder =
new LengthlessEncryptedChunkEncoder();
@Override
public void writeChunkToWriter(BackupWriter writer, EncryptedChunk chunk) throws IOException {
int length = mLengthlessEncryptedChunkEncoder.getEncodedLengthOfChunk(chunk);
writer.writeBytes(toByteArray(length));
mLengthlessEncryptedChunkEncoder.writeChunkToWriter(writer, chunk);
}
@Override
public int getEncodedLengthOfChunk(EncryptedChunk chunk) {
return BYTES_LENGTH + mLengthlessEncryptedChunkEncoder.getEncodedLengthOfChunk(chunk);
}
@Override
@ChunkOrderingType
public int getChunkOrderingType() {
return ChunksMetadataProto.INLINE_LENGTHS;
}
/**
* Returns a big-endian representation of {@code value} in a 4-element byte array; equivalent to
* {@code ByteBuffer.allocate(4).putInt(value).array()}. For example, the input value {@code
* 0x12131415} would yield the byte array {@code {0x12, 0x13, 0x14, 0x15}}.
*
*
Equivalent to guava's Ints.toByteArray.
*/
static byte[] toByteArray(int value) {
return new byte[] {
(byte) (value >> 24), (byte) (value >> 16), (byte) (value >> 8), (byte) value
};
}
}