Import ChunkListingMap

/*

 * Copyright (C) 2019 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.chunk;

import android.annotation.Nullable;

import com.android.server.backup.encryption.protos.nano.ChunksMetadataProto;

import java.util.HashMap;

import java.util.Map;

/**

 * Chunk listing in a format optimized for quick look up of chunks via their hash keys. This is

 * useful when building an incremental backup. After a chunk has been produced, the algorithm can

 * quickly look up whether the chunk existed in the previous backup by checking this chunk listing.

 * It can then tell the server to use that chunk, through telling it the position and length of the

 * chunk in the previous backup's blob.

 */

public class ChunkListingMap {

    private final Map<ChunkHash, Entry> mChunksByHash;

    /** Construct a map from a {@link ChunksMetadataProto.ChunkListing} protobuf */

    public static ChunkListingMap fromProto(ChunksMetadataProto.ChunkListing chunkListingProto) {

        Map<ChunkHash, Entry> entries = new HashMap<>();

        long start = 0;

        for (ChunksMetadataProto.Chunk chunk : chunkListingProto.chunks) {

            entries.put(new ChunkHash(chunk.hash), new Entry(start, chunk.length));

            start += chunk.length;

        }

        return new ChunkListingMap(entries);

    }

    private ChunkListingMap(Map<ChunkHash, Entry> chunksByHash) {

        // This is only called from the {@link #fromProto} method, so we don't

        // need to take a copy.

        this.mChunksByHash = chunksByHash;

    }

    /** Returns {@code true} if there is a chunk with the given SHA-256 MAC key in the listing. */

    public boolean hasChunk(ChunkHash hash) {

        return mChunksByHash.containsKey(hash);

    }

    /**

     * Returns the entry for the chunk with the given hash.

     *

     * @param hash The SHA-256 MAC of the plaintext of the chunk.

     * @return The entry, containing position and length of the chunk in the backup blob, or null if

     *     it does not exist.

     */

    @Nullable

    public Entry getChunkEntry(ChunkHash hash) {

        return mChunksByHash.get(hash);

    }

    /** Information about a chunk entry in a backup blob - i.e., its position and length. */

    public static final class Entry {

        private final int mLength;

        private final long mStart;

        private Entry(long start, int length) {

            mLength = length;

            mStart = start;

        }

        /** Returns the length of the chunk in bytes. */

        public int getLength() {

            return mLength;

        }

        /** Returns the start position of the chunk in the backup blob, in bytes. */

        public long getStart() {

            return mStart;

        }

    }

}

/*

 * Copyright (C) 2019 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.chunk;

import static com.google.common.truth.Truth.assertThat;

import android.platform.test.annotations.Presubmit;

import com.android.server.backup.encryption.protos.nano.ChunksMetadataProto;

import com.google.common.base.Charsets;

import org.junit.Before;

import org.junit.Test;

import org.junit.runner.RunWith;

import org.robolectric.RobolectricTestRunner;

import java.util.Arrays;

@RunWith(RobolectricTestRunner.class)

@Presubmit

public class ChunkListingMapTest {

    private static final ChunkHash CHUNK_A_HASH = getHash("CHUNK_A");

    private static final ChunkHash CHUNK_B_HASH = getHash("CHUNK_B");

    private static final ChunkHash CHUNK_C_HASH = getHash("CHUNK_C");

    private static final int CHUNK_A_LENGTH = 256;

    private static final int CHUNK_B_LENGTH = 1024;

    private static final int CHUNK_C_LENGTH = 4055;

    private static final int CHUNK_A_START = 0;

    private static final int CHUNK_B_START = CHUNK_A_START + CHUNK_A_LENGTH;

    private static final int CHUNK_C_START = CHUNK_B_START + CHUNK_B_LENGTH;

    private ChunkListingMap mChunkListingMap;

    @Before

    public void setUp() {

        mChunkListingMap = createFromFixture();

    }

    @Test

    public void hasChunk_isTrueForExistingChunks() {

        assertThat(mChunkListingMap.hasChunk(CHUNK_A_HASH)).isTrue();

        assertThat(mChunkListingMap.hasChunk(CHUNK_B_HASH)).isTrue();

        assertThat(mChunkListingMap.hasChunk(CHUNK_C_HASH)).isTrue();

    }

    @Test

    public void hasChunk_isFalseForNonexistentChunks() {

        assertThat(mChunkListingMap.hasChunk(getHash("CHUNK_D"))).isFalse();

        assertThat(mChunkListingMap.hasChunk(getHash(""))).isFalse();

    }

    @Test

    public void getChunkListing_hasCorrectLengths() {

        assertThat(mChunkListingMap.getChunkEntry(CHUNK_A_HASH).getLength())

                .isEqualTo(CHUNK_A_LENGTH);

        assertThat(mChunkListingMap.getChunkEntry(CHUNK_B_HASH).getLength())

                .isEqualTo(CHUNK_B_LENGTH);

        assertThat(mChunkListingMap.getChunkEntry(CHUNK_C_HASH).getLength())

                .isEqualTo(CHUNK_C_LENGTH);

    }

    @Test

    public void getChunkListing_hasCorrectStarts() {

        assertThat(mChunkListingMap.getChunkEntry(CHUNK_A_HASH).getStart())

                .isEqualTo(CHUNK_A_START);

        assertThat(mChunkListingMap.getChunkEntry(CHUNK_B_HASH).getStart())

                .isEqualTo(CHUNK_B_START);

        assertThat(mChunkListingMap.getChunkEntry(CHUNK_C_HASH).getStart())

                .isEqualTo(CHUNK_C_START);

    }

    @Test

    public void getChunkListing_isNullForNonExistentChunks() {

        assertThat(mChunkListingMap.getChunkEntry(getHash("Hey"))).isNull();

    }

    private static ChunkListingMap createFromFixture() {

        ChunksMetadataProto.ChunkListing chunkListing = new ChunksMetadataProto.ChunkListing();

        chunkListing.chunks = new ChunksMetadataProto.Chunk[3];

        chunkListing.chunks[0] = newChunk(CHUNK_A_HASH.getHash(), CHUNK_A_LENGTH);

        chunkListing.chunks[1] = newChunk(CHUNK_B_HASH.getHash(), CHUNK_B_LENGTH);

        chunkListing.chunks[2] = newChunk(CHUNK_C_HASH.getHash(), CHUNK_C_LENGTH);

        return ChunkListingMap.fromProto(chunkListing);

    }

    private static ChunkHash getHash(String name) {

        return new ChunkHash(

                Arrays.copyOf(name.getBytes(Charsets.UTF_8), ChunkHash.HASH_LENGTH_BYTES));

    }

    public static ChunksMetadataProto.Chunk newChunk(byte[] hash, int length) {

        ChunksMetadataProto.Chunk newChunk = new ChunksMetadataProto.Chunk();

        newChunk.hash = Arrays.copyOf(hash, hash.length);

        newChunk.length = length;

        return newChunk;

    }

}