Add sets

src/main/java/it/cavallium/dbengine/database/collections/DatabaseEmpty.java

@@ -0,0 +1,42 @@
+package it.cavallium.dbengine.database.collections;
+
+import it.cavallium.dbengine.database.LLDictionary;
+import it.cavallium.dbengine.database.serialization.Serializer;
+import org.jetbrains.annotations.NotNull;
+
+public class DatabaseEmpty {
+
+	@SuppressWarnings("unused")
+	public static final Nothing NOTHING = new Nothing();
+	private static final byte[] NOTHING_BYTES = new byte[0];
+	private static final Serializer<Nothing, byte[]> NOTHING_SERIALIZER = new Serializer<>() {
+		@Override
+		public @NotNull Nothing deserialize(byte @NotNull [] serialized) {
+			return NOTHING;
+		}
+
+		@Override
+		public byte @NotNull [] serialize(@NotNull Nothing deserialized) {
+			return NOTHING_BYTES;
+		}
+	};
+	private static final SubStageGetter<Nothing, DatabaseStageEntry<Nothing>> NOTHING_SUB_STAGE_GETTER = new SubStageGetterSingle<>(NOTHING_SERIALIZER);
+
+	private DatabaseEmpty() {
+	}
+
+	public static DatabaseStageEntry<Nothing> create(LLDictionary dictionary, byte[] key) {
+		return new DatabaseSingle<>(dictionary, key, NOTHING_SERIALIZER);
+	}
+
+	public static SubStageGetter<Nothing, DatabaseStageEntry<Nothing>> createSubStageGetter() {
+		return NOTHING_SUB_STAGE_GETTER;
+	}
+
+	public static final class Nothing {
+
+		private Nothing() {
+
+		}
+	}
+}

src/main/java/it/cavallium/dbengine/database/collections/DatabaseSetDictionary.java

@@ -0,0 +1,47 @@
+package it.cavallium.dbengine.database.collections;
+
+import it.cavallium.dbengine.client.CompositeSnapshot;
+import it.cavallium.dbengine.database.LLDictionary;
+import it.cavallium.dbengine.database.collections.DatabaseEmpty.Nothing;
+import it.cavallium.dbengine.database.serialization.SerializerFixedBinaryLength;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+import org.jetbrains.annotations.Nullable;
+import reactor.core.publisher.Mono;
+
+public class DatabaseSetDictionary<T> extends DatabaseMapDictionaryDeep<T, Nothing, DatabaseStageEntry<Nothing>> {
+
+	protected DatabaseSetDictionary(LLDictionary dictionary,
+			byte[] prefixKey,
+			SerializerFixedBinaryLength<T, byte[]> keySuffixSerializer) {
+		super(dictionary, prefixKey, keySuffixSerializer, DatabaseEmpty.createSubStageGetter(), 0);
+	}
+
+	public static <T> DatabaseSetDictionary<T> simple(LLDictionary dictionary,
+			SerializerFixedBinaryLength<T, byte[]> keySerializer) {
+		return new DatabaseSetDictionary<>(dictionary, EMPTY_BYTES, keySerializer);
+	}
+
+	public static <T> DatabaseSetDictionary<T> tail(LLDictionary dictionary,
+			byte[] prefixKey,
+			SerializerFixedBinaryLength<T, byte[]> keySuffixSerializer) {
+		return new DatabaseSetDictionary<>(dictionary, prefixKey, keySuffixSerializer);
+	}
+
+	public Mono<Set<T>> getKeySet(@Nullable CompositeSnapshot snapshot) {
+		return get(snapshot).map(Map::keySet);
+	}
+
+	public Mono<Set<T>> setAndGetPreviousKeySet(Set<T> value) {
+		var hm = new HashMap<T, Nothing>();
+		for (T t : value) {
+			hm.put(t, DatabaseEmpty.NOTHING);
+		}
+		return setAndGetPrevious(hm).map(Map::keySet);
+	}
+
+	public Mono<Set<T>> clearAndGetPreviousKeySet() {
+		return clearAndGetPrevious().map(Map::keySet);
+	}
+}

src/main/java/it/cavallium/dbengine/database/collections/SubStageGetterSet.java

@@ -0,0 +1,56 @@
+package it.cavallium.dbengine.database.collections;
+
+import it.cavallium.dbengine.client.CompositeSnapshot;
+import it.cavallium.dbengine.database.LLDictionary;
+import it.cavallium.dbengine.database.collections.DatabaseEmpty.Nothing;
+import it.cavallium.dbengine.database.serialization.SerializerFixedBinaryLength;
+import java.util.Map;
+import org.jetbrains.annotations.Nullable;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+public class SubStageGetterSet<T> implements SubStageGetter<Map<T, Nothing>, DatabaseSetDictionary<T>> {
+
+	private static final boolean assertsEnabled;
+	static {
+		boolean assertsEnabledTmp = false;
+		//noinspection AssertWithSideEffects
+		assert assertsEnabledTmp = true;
+		//noinspection ConstantConditions
+		assertsEnabled = assertsEnabledTmp;
+	}
+
+	private final SerializerFixedBinaryLength<T, byte[]> keySerializer;
+
+	public SubStageGetterSet(SerializerFixedBinaryLength<T, byte[]> keySerializer) {
+		this.keySerializer = keySerializer;
+	}
+
+	@Override
+	public Mono<DatabaseSetDictionary<T>> subStage(LLDictionary dictionary,
+			@Nullable CompositeSnapshot snapshot,
+			byte[] prefixKey,
+			Flux<byte[]> keyFlux) {
+		Mono<DatabaseSetDictionary<T>> result = Mono.just(DatabaseSetDictionary.tail(dictionary, prefixKey, keySerializer));
+		if (assertsEnabled) {
+			return checkKeyFluxConsistency(prefixKey, keyFlux).then(result);
+		} else {
+			return result;
+		}
+	}
+
+	@Override
+	public boolean needsKeyFlux() {
+		return assertsEnabled;
+	}
+
+	private Mono<Void> checkKeyFluxConsistency(byte[] prefixKey, Flux<byte[]> keyFlux) {
+		return keyFlux.doOnNext(key -> {
+			assert key.length == prefixKey.length + getKeyBinaryLength();
+		}).then();
+	}
+
+	public int getKeyBinaryLength() {
+		return keySerializer.getSerializedBinaryLength();
+	}
+}