.idea/codeStyles/Project.xml

@@ -31,15 +31,6 @@
       <option name="PACKAGES_TO_USE_STAR_IMPORTS">
         <value />
       </option>
-      <option name="PACKAGES_IMPORT_LAYOUT">
-        <value>
-          <package name="" alias="false" withSubpackages="true" />
-          <package name="java" alias="false" withSubpackages="true" />
-          <package name="javax" alias="false" withSubpackages="true" />
-          <package name="kotlin" alias="false" withSubpackages="true" />
-          <package name="" alias="true" withSubpackages="true" />
-        </value>
-      </option>
       <option name="NAME_COUNT_TO_USE_STAR_IMPORT" value="2147483647" />
       <option name="NAME_COUNT_TO_USE_STAR_IMPORT_FOR_MEMBERS" value="2147483647" />
       <option name="CODE_STYLE_DEFAULTS" value="KOTLIN_OFFICIAL" />

bramble-api/src/main/java/org/briarproject/bramble/api/client/ClientHelper.java

@@ -35,24 +35,24 @@ public interface ClientHelper {
 
 	Message createMessageForStoringMetadata(GroupId g);
 
-	Message getMessage(MessageId m) throws DbException;
+	Message getSmallMessage(MessageId m) throws DbException;
 
-	Message getMessage(Transaction txn, MessageId m) throws DbException;
+	Message getSmallMessage(Transaction txn, MessageId m) throws DbException;
 
-	BdfList getMessageAsList(MessageId m) throws DbException, FormatException;
+	BdfList getSmallMessageAsList(MessageId m)
+			throws DbException, FormatException;
 
-	BdfList getMessageAsList(Transaction txn, MessageId m) throws DbException,
-			FormatException;
+	BdfList getSmallMessageAsList(Transaction txn, MessageId m)
+			throws DbException, FormatException;
 
-	BdfDictionary getGroupMetadataAsDictionary(GroupId g) throws DbException,
-			FormatException;
+	BdfDictionary getGroupMetadataAsDictionary(GroupId g)
+			throws DbException, FormatException;
 
 	BdfDictionary getGroupMetadataAsDictionary(Transaction txn, GroupId g)
 			throws DbException, FormatException;
 
 	BdfDictionary getMessageMetadataAsDictionary(MessageId m)
-			throws DbException,
-			FormatException;
+			throws DbException, FormatException;
 
 	BdfDictionary getMessageMetadataAsDictionary(Transaction txn, MessageId m)
 			throws DbException, FormatException;
@@ -67,8 +67,8 @@ public interface ClientHelper {
 			BdfDictionary query) throws DbException, FormatException;
 
 	Map<MessageId, BdfDictionary> getMessageMetadataAsDictionary(
-			Transaction txn, GroupId g, BdfDictionary query) throws DbException,
-			FormatException;
+			Transaction txn, GroupId g, BdfDictionary query)
+			throws DbException, FormatException;
 
 	void mergeGroupMetadata(GroupId g, BdfDictionary metadata)
 			throws DbException, FormatException;

bramble-api/src/main/java/org/briarproject/bramble/api/db/DatabaseComponent.java

@@ -163,19 +163,23 @@ public interface DatabaseComponent extends TransactionManager {
 	 * less than or equal to the given length, for transmission over a
 	 * transport with the given maximum latency. Returns null if there are no
 	 * sendable messages that fit in the given length.
+	 *
+	 * @param small True if only single-block messages should be sent
 	 */
 	@Nullable
 	Collection<Message> generateBatch(Transaction txn, ContactId c,
-			int maxLength, int maxLatency) throws DbException;
+			int maxLength, int maxLatency, boolean small) throws DbException;
 
 	/**
 	 * Returns an offer for the given contact for transmission over a
 	 * transport with the given maximum latency, or null if there are no
 	 * messages to offer.
+	 *
+	 * @param small True if only single-block messages should be offered
 	 */
 	@Nullable
 	Offer generateOffer(Transaction txn, ContactId c, int maxMessages,
-			int maxLatency) throws DbException;
+			int maxLatency, boolean small) throws DbException;
 
 	/**
 	 * Returns a request for the given contact, or null if there are no
@@ -272,13 +276,14 @@ public interface DatabaseComponent extends TransactionManager {
 	Collection<Identity> getIdentities(Transaction txn) throws DbException;
 
 	/**
-	 * Returns the message with the given ID.
+	 * Returns the single-block message with the given ID.
 	 * <p/>
 	 * Read-only.
 	 *
 	 * @throws MessageDeletedException if the message has been deleted
+	 * @throws MessageTooLargeException if the message has more than one block
 	 */
-	Message getMessage(Transaction txn, MessageId m) throws DbException;
+	Message getSmallMessage(Transaction txn, MessageId m) throws DbException;
 
 	/**
 	 * Returns the IDs of all delivered messages in the given group.

bramble-api/src/main/java/org/briarproject/bramble/api/db/MessageTooLargeException.java

+package org.briarproject.bramble.api.db;
+
+/**
+ * Thrown when a multi-block message is requested from the database via a
+ * method that is only suitable for requesting single-block messages.
+ */
+public class MessageTooLargeException extends DbException {
+}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncConstants.java

@@ -29,10 +29,15 @@ public interface SyncConstants {
 	 */
 	int MESSAGE_HEADER_LENGTH = UniqueId.LENGTH + 8;
 
+	/**
+	 * The maximum length of a block in bytes.
+	 */
+	int MAX_BLOCK_LENGTH = 32 * 1024; // 32 KiB
+
 	/**
 	 * The maximum length of a message body in bytes.
 	 */
-	int MAX_MESSAGE_BODY_LENGTH = 32 * 1024; // 32 KiB
+	int MAX_MESSAGE_BODY_LENGTH = MAX_BLOCK_LENGTH;
 
 	/**
 	 * The maximum length of a message in bytes.

bramble-core/src/main/java/org/briarproject/bramble/client/ClientHelperImpl.java

@@ -116,25 +116,27 @@ class ClientHelperImpl implements ClientHelper {
 	}
 
 	@Override
-	public Message getMessage(MessageId m) throws DbException {
-		return db.transactionWithResult(true, txn -> getMessage(txn, m));
+	public Message getSmallMessage(MessageId m) throws DbException {
+		return db.transactionWithResult(true, txn -> getSmallMessage(txn, m));
 	}
 
 	@Override
-	public Message getMessage(Transaction txn, MessageId m) throws DbException {
-		return db.getMessage(txn, m);
+	public Message getSmallMessage(Transaction txn, MessageId m)
+			throws DbException {
+		return db.getSmallMessage(txn, m);
 	}
 
 	@Override
-	public BdfList getMessageAsList(MessageId m) throws DbException,
-			FormatException {
-		return db.transactionWithResult(true, txn -> getMessageAsList(txn, m));
+	public BdfList getSmallMessageAsList(MessageId m)
+			throws DbException, FormatException {
+		return db.transactionWithResult(true, txn ->
+				getSmallMessageAsList(txn, m));
 	}
 
 	@Override
-	public BdfList getMessageAsList(Transaction txn, MessageId m)
+	public BdfList getSmallMessageAsList(Transaction txn, MessageId m)
 			throws DbException, FormatException {
-		return toList(db.getMessage(txn, m).getBody());
+		return toList(db.getSmallMessage(txn, m).getBody());
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/db/Database.java

@@ -12,6 +12,7 @@ import org.briarproject.bramble.api.db.DataTooOldException;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.MessageDeletedException;
+import org.briarproject.bramble.api.db.MessageTooLargeException;
 import org.briarproject.bramble.api.db.Metadata;
 import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.identity.Author;
@@ -332,13 +333,14 @@ interface Database<T> {
 	Collection<Identity> getIdentities(T txn) throws DbException;
 
 	/**
-	 * Returns the message with the given ID.
+	 * Returns the single-block message with the given ID.
 	 * <p/>
 	 * Read-only.
 	 *
 	 * @throws MessageDeletedException if the message has been deleted
+	 * @throws MessageTooLargeException if the message has more than one block
 	 */
-	Message getMessage(T txn, MessageId m) throws DbException;
+	Message getSmallMessage(T txn, MessageId m) throws DbException;
 
 	/**
 	 * Returns the IDs and states of all dependencies of the given message.
@@ -456,6 +458,15 @@ interface Database<T> {
 	Collection<MessageId> getMessagesToOffer(T txn, ContactId c,
 			int maxMessages, int maxLatency) throws DbException;
 
+	/**
+	 * Returns the IDs of some single-block messages that are eligible to be
+	 * offered to the given contact, up to the given number of messages.
+	 * <p/>
+	 * Read-only.
+	 */
+	Collection<MessageId> getSmallMessagesToOffer(T txn, ContactId c,
+			int maxMessages, int maxLatency) throws DbException;
+
 	/**
 	 * Returns the IDs of some messages that are eligible to be requested from
 	 * the given contact, up to the given number of messages.
@@ -474,6 +485,15 @@ interface Database<T> {
 	Collection<MessageId> getMessagesToSend(T txn, ContactId c, int maxLength,
 			int maxLatency) throws DbException;
 
+	/**
+	 * Returns the IDs of some single-block messages that are eligible to be
+	 * sent to the given contact, up to the given total length.
+	 * <p/>
+	 * Read-only.
+	 */
+	Collection<MessageId> getSmallMessagesToSend(T txn, ContactId c,
+			int maxLength, int maxLatency) throws DbException;
+
 	/**
 	 * Returns the IDs of any messages that need to be validated.
 	 * <p/>

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java

@@ -406,16 +406,19 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	@Nullable
 	@Override
 	public Collection<Message> generateBatch(Transaction transaction,
-			ContactId c, int maxLength, int maxLatency) throws DbException {
+			ContactId c, int maxLength, int maxLatency, boolean small)
+			throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		Collection<MessageId> ids =
-				db.getMessagesToSend(txn, c, maxLength, maxLatency);
+		Collection<MessageId> ids;
+		if (small)
+			ids = db.getSmallMessagesToSend(txn, c, maxLength, maxLatency);
+		else ids = db.getMessagesToSend(txn, c, maxLength, maxLatency);
 		List<Message> messages = new ArrayList<>(ids.size());
 		for (MessageId m : ids) {
-			messages.add(db.getMessage(txn, m));
+			messages.add(db.getSmallMessage(txn, m));
 			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
 		}
 		if (ids.isEmpty()) return null;
@@ -427,13 +430,15 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	@Nullable
 	@Override
 	public Offer generateOffer(Transaction transaction, ContactId c,
-			int maxMessages, int maxLatency) throws DbException {
+			int maxMessages, int maxLatency, boolean small) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		Collection<MessageId> ids =
-				db.getMessagesToOffer(txn, c, maxMessages, maxLatency);
+		Collection<MessageId> ids;
+		if (small)
+			ids = db.getSmallMessagesToOffer(txn, c, maxMessages, maxLatency);
+		else ids = db.getMessagesToOffer(txn, c, maxMessages, maxLatency);
 		if (ids.isEmpty()) return null;
 		for (MessageId m : ids)
 			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
@@ -448,8 +453,8 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		Collection<MessageId> ids = db.getMessagesToRequest(txn, c,
-				maxMessages);
+		Collection<MessageId> ids =
+				db.getMessagesToRequest(txn, c, maxMessages);
 		if (ids.isEmpty()) return null;
 		db.removeOfferedMessages(txn, c, ids);
 		return new Request(ids);
@@ -467,7 +472,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 				db.getRequestedMessagesToSend(txn, c, maxLength, maxLatency);
 		List<Message> messages = new ArrayList<>(ids.size());
 		for (MessageId m : ids) {
-			messages.add(db.getMessage(txn, m));
+			messages.add(db.getSmallMessage(txn, m));
 			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
 		}
 		if (ids.isEmpty()) return null;
@@ -559,12 +564,12 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	@Override
-	public Message getMessage(Transaction transaction, MessageId m)
+	public Message getSmallMessage(Transaction transaction, MessageId m)
 			throws DbException {
 		T txn = unbox(transaction);
 		if (!db.containsMessage(txn, m))
 			throw new NoSuchMessageException();
-		return db.getMessage(txn, m);
+		return db.getSmallMessage(txn, m);
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseModule.java

@@ -6,7 +6,6 @@ import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventExecutor;
 import org.briarproject.bramble.api.lifecycle.ShutdownManager;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 
 import java.sql.Connection;
@@ -22,9 +21,8 @@ public class DatabaseModule {
 
 	@Provides
 	@Singleton
-	Database<Connection> provideDatabase(DatabaseConfig config,
-			MessageFactory messageFactory, Clock clock) {
-		return new H2Database(config, messageFactory, clock);
+	Database<Connection> provideDatabase(DatabaseConfig config, Clock clock) {
+		return new H2Database(config, clock);
 	}
 
 	@Provides

bramble-core/src/main/java/org/briarproject/bramble/db/H2Database.java

@@ -6,7 +6,6 @@ import org.briarproject.bramble.api.db.DbClosedException;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.util.StringUtils;
 
@@ -51,9 +50,8 @@ class H2Database extends JdbcDatabase {
 	private volatile SecretKey key = null;
 
 	@Inject
-	H2Database(DatabaseConfig config, MessageFactory messageFactory,
-			Clock clock) {
-		super(dbTypes, messageFactory, clock);
+	H2Database(DatabaseConfig config, Clock clock) {
+		super(dbTypes, clock);
 		this.config = config;
 		File dir = config.getDatabaseDirectory();
 		String path = new File(dir, "db").getAbsolutePath();

bramble-core/src/main/java/org/briarproject/bramble/db/HyperSqlDatabase.java

@@ -6,7 +6,6 @@ import org.briarproject.bramble.api.db.DbClosedException;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.util.StringUtils;
 
@@ -51,9 +50,8 @@ class HyperSqlDatabase extends JdbcDatabase {
 	private volatile SecretKey key = null;
 
 	@Inject
-	HyperSqlDatabase(DatabaseConfig config, MessageFactory messageFactory,
-			Clock clock) {
-		super(dbTypes, messageFactory, clock);
+	HyperSqlDatabase(DatabaseConfig config, Clock clock) {
+		super(dbTypes, clock);
 		this.config = config;
 		File dir = config.getDatabaseDirectory();
 		String path = new File(dir, "db").getAbsolutePath();

bramble-core/src/main/java/org/briarproject/bramble/db/JdbcDatabase.java

@@ -16,6 +16,7 @@ import org.briarproject.bramble.api.db.DataTooOldException;
 import org.briarproject.bramble.api.db.DbClosedException;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.MessageDeletedException;
+import org.briarproject.bramble.api.db.MessageTooLargeException;
 import org.briarproject.bramble.api.db.Metadata;
 import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.identity.Author;
@@ -30,7 +31,6 @@ import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.Group.Visibility;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.MessageStatus;
 import org.briarproject.bramble.api.sync.validation.MessageState;
@@ -76,6 +76,7 @@ import static org.briarproject.bramble.api.db.Metadata.REMOVE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.Group.Visibility.VISIBLE;
+import static org.briarproject.bramble.api.sync.SyncConstants.MAX_BLOCK_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
 import static org.briarproject.bramble.api.sync.validation.MessageState.DELIVERED;
 import static org.briarproject.bramble.api.sync.validation.MessageState.PENDING;
@@ -98,7 +99,7 @@ import static org.briarproject.bramble.util.LogUtils.now;
 abstract class JdbcDatabase implements Database<Connection> {
 
 	// Package access for testing
-	static final int CODE_SCHEMA_VERSION = 47;
+	static final int CODE_SCHEMA_VERSION = 48;
 
 	// Time period offsets for incoming transport keys
 	private static final int OFFSET_PREV = -1;
@@ -180,8 +181,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " state INT NOT NULL,"
 					+ " shared BOOLEAN NOT NULL,"
 					+ " temporary BOOLEAN NOT NULL,"
-					+ " length INT NOT NULL,"
-					+ " raw BLOB," // Null if message has been deleted
+					+ " length INT NOT NULL," // Includes message header
+					+ " deleted BOOLEAN NOT NULL,"
+					+ " blockCount INT NOT NULL,"
 					+ " PRIMARY KEY (messageId),"
 					+ " FOREIGN KEY (groupId)"
 					+ " REFERENCES groups (groupId)"
@@ -227,6 +229,17 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES contacts (contactId)"
 					+ " ON DELETE CASCADE)";
 
+	private static final String CREATE_BLOCKS =
+			"CREATE TABLE blocks"
+					+ " (messageId _HASH NOT NULL,"
+					+ " blockNumber INT NOT NULL,"
+					+ " blockLength INT NOT NULL," // Excludes block header
+					+ " data BLOB," // Null if message has been deleted
+					+ " PRIMARY KEY (messageId, blockNumber),"
+					+ " FOREIGN KEY (messageId)"
+					+ " REFERENCES messages (messageId)"
+					+ " ON DELETE CASCADE)";
+
 	private static final String CREATE_STATUSES =
 			"CREATE TABLE statuses"
 					+ " (messageId _HASH NOT NULL,"
@@ -339,7 +352,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 	private static final Logger LOG =
 			getLogger(JdbcDatabase.class.getName());
 
-	private final MessageFactory messageFactory;
 	private final Clock clock;
 	private final DatabaseTypes dbTypes;
 
@@ -359,10 +371,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 
 	protected abstract void compactAndClose() throws DbException;
 
-	JdbcDatabase(DatabaseTypes databaseTypes, MessageFactory messageFactory,
-			Clock clock) {
+	JdbcDatabase(DatabaseTypes databaseTypes, Clock clock) {
 		this.dbTypes = databaseTypes;
-		this.messageFactory = messageFactory;
 		this.clock = clock;
 	}
 
@@ -440,10 +450,12 @@ abstract class JdbcDatabase implements Database<Connection> {
 				if (LOG.isLoggable(INFO))
 					LOG.info("Migrating from schema " + start + " to " + end);
 				if (listener != null) listener.onDatabaseMigration();
+				long startTime = now();
 				// Apply the migration
 				m.migrate(txn);
 				// Store the new schema version
 				storeSchemaVersion(txn, end);
+				logDuration(LOG, "Migration", startTime);
 				dataSchemaVersion = end;
 			}
 		}
@@ -463,7 +475,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 				new Migration43_44(dbTypes),
 				new Migration44_45(),
 				new Migration45_46(),
-				new Migration46_47(dbTypes)
+				new Migration46_47(dbTypes),
+				new Migration47_48(dbTypes)
 		);
 	}
 
@@ -509,6 +522,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_MESSAGE_METADATA));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_MESSAGE_DEPENDENCIES));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_OFFERS));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_BLOCKS));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_STATUSES));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_TRANSPORTS));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_PENDING_CONTACTS));
@@ -726,7 +740,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		ResultSet rs = null;
 		try {
 			String sql = "SELECT messageId, timestamp, state, shared,"
-					+ " length, raw IS NULL"
+					+ " length, deleted"
 					+ " FROM messages"
 					+ " WHERE groupId = ?";
 			ps = txn.prepareStatement(sql);
@@ -788,8 +802,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		try {
 			String sql = "INSERT INTO messages (messageId, groupId, timestamp,"
-					+ " state, shared, temporary, length, raw)"
-					+ " VALUES (?, ?, ?, ?, ?, ?, ?, ?)";
+					+ " state, shared, temporary, length, deleted, blockCount)"
+					+ " VALUES (?, ?, ?, ?, ?, ?, ?, FALSE, 1)";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getId().getBytes());
 			ps.setBytes(2, m.getGroupId().getBytes());
@@ -797,12 +811,20 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setInt(4, state.getValue());
 			ps.setBoolean(5, shared);
 			ps.setBoolean(6, temporary);
-			byte[] raw = messageFactory.getRawMessage(m);
-			ps.setInt(7, raw.length);
-			ps.setBytes(8, raw);
+			ps.setInt(7, m.getRawLength());
 			int affected = ps.executeUpdate();
 			if (affected != 1) throw new DbStateException();
 			ps.close();
+			sql = "INSERT INTO blocks (messageId, blockNumber, blockLength,"
+					+ " data)"
+					+ " VALUES (?, 0, ?, ?)";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, m.getId().getBytes());
+			ps.setInt(2, m.getBody().length);
+			ps.setBytes(3, m.getBody());
+			affected = ps.executeUpdate();
+			if (affected != 1) throw new DbStateException();
+			ps.close();
 			// Create a status row for each contact that can see the group
 			Map<ContactId, Boolean> visibility =
 					getGroupVisibility(txn, m.getGroupId());
@@ -811,7 +833,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 				boolean offered = removeOfferedMessage(txn, c, m.getId());
 				boolean seen = offered || c.equals(sender);
 				addStatus(txn, m.getId(), c, m.getGroupId(), m.getTimestamp(),
-						raw.length, state, e.getValue(), shared, false, seen);
+						m.getRawLength(), state, e.getValue(), shared, false,
+						seen);
 			}
 			// Update denormalised column in messageDependencies if dependency
 			// is in same group as dependent
@@ -1290,12 +1313,18 @@ abstract class JdbcDatabase implements Database<Connection> {
 	public void deleteMessage(Connection txn, MessageId m) throws DbException {
 		PreparedStatement ps = null;
 		try {
-			String sql = "UPDATE messages SET raw = NULL WHERE messageId = ?";
+			String sql = "UPDATE messages SET deleted = TRUE"
+					+ " WHERE messageId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getBytes());
 			int affected = ps.executeUpdate();
+			if (affected < 0 || affected > 1) throw new DbStateException();
+			ps.close();
+			sql = "UPDATE blocks SET data = NULL WHERE messageId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, m.getBytes());
+			affected = ps.executeUpdate();
 			if (affected < 0) throw new DbStateException();
-			if (affected > 1) throw new DbStateException();
 			ps.close();
 			// Update denormalised column in statuses
 			sql = "UPDATE statuses SET deleted = TRUE WHERE messageId = ?";
@@ -1688,11 +1717,13 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public Message getMessage(Connection txn, MessageId m) throws DbException {
+	public Message getSmallMessage(Connection txn, MessageId m)
+			throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT groupId, timestamp, raw FROM messages"
+			String sql = "SELECT groupId, timestamp, deleted, blockCount"
+					+ " FROM messages"
 					+ " WHERE messageId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getBytes());
@@ -1700,15 +1731,25 @@ abstract class JdbcDatabase implements Database<Connection> {
 			if (!rs.next()) throw new DbStateException();
 			GroupId g = new GroupId(rs.getBytes(1));
 			long timestamp = rs.getLong(2);
-			byte[] raw = rs.getBytes(3);
+			boolean deleted = rs.getBoolean(3);
+			int blockCount = rs.getInt(4);
+			if (rs.next()) throw new DbStateException();
+			rs.close();
+			ps.close();
+			if (deleted) throw new MessageDeletedException();
+			if (blockCount > 1) throw new MessageTooLargeException();
+			sql = "SELECT data FROM blocks"
+					+ " WHERE messageId = ? AND blockNumber = 0";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, m.getBytes());
+			rs = ps.executeQuery();
+			if (!rs.next()) throw new DbStateException();
+			byte[] data = rs.getBytes(1);
+			if (data == null) throw new DbStateException();
 			if (rs.next()) throw new DbStateException();
 			rs.close();
 			ps.close();
-			if (raw == null) throw new MessageDeletedException();
-			if (raw.length <= MESSAGE_HEADER_LENGTH) throw new AssertionError();
-			byte[] body = new byte[raw.length - MESSAGE_HEADER_LENGTH];
-			System.arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
-			return new Message(m, g, timestamp, body);
+			return new Message(m, g, timestamp, data);
 		} catch (SQLException e) {
 			tryToClose(rs, LOG, WARNING);
 			tryToClose(ps, LOG, WARNING);
@@ -2100,6 +2141,42 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public Collection<MessageId> getSmallMessagesToOffer(Connection txn,
+			ContactId c, int maxMessages, int maxLatency) throws DbException {
+		long now = clock.currentTimeMillis();
+		long eta = now + maxLatency;
+		PreparedStatement ps = null;
+		ResultSet rs = null;
+		try {
+			String sql = "SELECT messageId FROM statuses"
+					+ " WHERE contactId = ? AND state = ?"
+					+ " AND length <= ?"
+					+ " AND groupShared = TRUE AND messageShared = TRUE"
+					+ " AND deleted = FALSE"
+					+ " AND seen = FALSE AND requested = FALSE"
+					+ " AND (expiry <= ? OR eta > ?)"
+					+ " ORDER BY timestamp LIMIT ?";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, c.getInt());
+			ps.setInt(2, DELIVERED.getValue());
+			ps.setInt(3, MESSAGE_HEADER_LENGTH + MAX_BLOCK_LENGTH);
+			ps.setLong(4, now);
+			ps.setLong(5, eta);
+			ps.setInt(6, maxMessages);
+			rs = ps.executeQuery();
+			List<MessageId> ids = new ArrayList<>();
+			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
+			rs.close();
+			ps.close();
+			return ids;
+		} catch (SQLException e) {
+			tryToClose(rs, LOG, WARNING);
+			tryToClose(ps, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public Collection<MessageId> getMessagesToRequest(Connection txn,
 			ContactId c, int maxMessages) throws DbException {
@@ -2164,6 +2241,47 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public Collection<MessageId> getSmallMessagesToSend(Connection txn,
+			ContactId c, int maxLength, int maxLatency) throws DbException {
+		long now = clock.currentTimeMillis();
+		long eta = now + maxLatency;
+		PreparedStatement ps = null;
+		ResultSet rs = null;
+		try {
+			String sql = "SELECT length, messageId FROM statuses"
+					+ " WHERE contactId = ? AND state = ?"
+					+ " AND length <= ?"
+					+ " AND groupShared = TRUE AND messageShared = TRUE"
+					+ " AND deleted = FALSE"
+					+ " AND seen = FALSE"
+					+ " AND (expiry <= ? OR eta > ?)"
+					+ " ORDER BY timestamp";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, c.getInt());
+			ps.setInt(2, DELIVERED.getValue());
+			ps.setInt(3, MESSAGE_HEADER_LENGTH + MAX_BLOCK_LENGTH);
+			ps.setLong(4, now);
+			ps.setLong(5, eta);
+			rs = ps.executeQuery();
+			List<MessageId> ids = new ArrayList<>();
+			int total = 0;
+			while (rs.next()) {
+				int length = rs.getInt(1);
+				if (total + length > maxLength) break;
+				ids.add(new MessageId(rs.getBytes(2)));
+				total += length;
+			}
+			rs.close();
+			ps.close();
+			return ids;
+		} catch (SQLException e) {
+			tryToClose(rs, LOG, WARNING);
+			tryToClose(ps, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public Collection<MessageId> getMessagesToValidate(Connection txn)
 			throws DbException {
@@ -2182,7 +2300,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		ResultSet rs = null;
 		try {
 			String sql = "SELECT messageId FROM messages"
-					+ " WHERE state = ? AND raw IS NOT NULL";
+					+ " WHERE state = ? AND deleted = FALSE";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, state.getValue());
 			rs = ps.executeQuery();

bramble-core/src/main/java/org/briarproject/bramble/db/Migration38_39.java

@@ -37,6 +37,7 @@ class Migration38_39 implements Migration<Connection> {
 			s.execute("ALTER TABLE incomingKeys"
 					+ " ALTER COLUMN contactId"
 					+ " SET NOT NULL");
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration39_40.java

@@ -36,6 +36,7 @@ class Migration39_40 implements Migration<Connection> {
 			s.execute("ALTER TABLE statuses"
 					+ " ALTER COLUMN eta"
 					+ " SET NOT NULL");
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration40_41.java

@@ -38,6 +38,7 @@ class Migration40_41 implements Migration<Connection> {
 			s = txn.createStatement();
 			s.execute("ALTER TABLE contacts"
 					+ dbTypes.replaceTypes(" ADD alias _STRING"));
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration41_42.java

@@ -89,6 +89,7 @@ class Migration41_42 implements Migration<Connection> {
 					+ " FOREIGN KEY (keySetId)"
 					+ " REFERENCES outgoingHandshakeKeys (keySetId)"
 					+ " ON DELETE CASCADE)"));
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration42_43.java

@@ -44,6 +44,7 @@ class Migration42_43 implements Migration<Connection> {
 					+ " ADD COLUMN handshakePublicKey _BINARY"));
 			s.execute("ALTER TABLE contacts"
 					+ " DROP COLUMN active");
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration43_44.java

@@ -50,6 +50,7 @@ class Migration43_44 implements Migration<Connection> {
 					+ " ADD COLUMN rootKey _SECRET"));
 			s.execute("ALTER TABLE outgoingKeys"
 					+ " ADD COLUMN alice BOOLEAN");
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration44_45.java

@@ -31,6 +31,7 @@ class Migration44_45 implements Migration<Connection> {
 		try {
 			s = txn.createStatement();
 			s.execute("ALTER TABLE pendingContacts DROP COLUMN state");
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration45_46.java

@@ -32,6 +32,7 @@ class Migration45_46 implements Migration<Connection> {
 			s = txn.createStatement();
 			s.execute("ALTER TABLE messages"
 					+ " ADD COLUMN temporary BOOLEAN DEFAULT FALSE NOT NULL");
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);