Fix tests.

bramble-api/src/main/java/org/briarproject/bramble/api/io/BlockSink.java

@@ -0,0 +1,20 @@
+package org.briarproject.bramble.api.io;
+
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.sync.tree.TreeHash;
+
+import java.util.List;
+
+public interface BlockSink {
+
+	/**
+	 * Stores a block of the message with the given temporary ID.
+	 */
+	void putBlock(HashingId h, int blockNumber, byte[] data) throws DbException;
+
+	/**
+	 * Sets the hash tree path of a previously stored block.
+	 */
+	void setPath(HashingId h, int blockNumber, List<TreeHash> path)
+			throws DbException;
+}

bramble-api/src/main/java/org/briarproject/bramble/api/io/HashingId.java

@@ -0,0 +1,27 @@
+package org.briarproject.bramble.api.io;
+
+import org.briarproject.bramble.api.UniqueId;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.Message;
+import org.briarproject.bramble.api.sync.MessageId;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * Type-safe wrapper for a byte array that uniquely identifies a
+ * {@link Message} while it's being hashed and the {@link MessageId} is not
+ * yet known.
+ */
+@ThreadSafe
+@NotNullByDefault
+public class HashingId extends UniqueId {
+
+	public HashingId(byte[] id) {
+		super(id);
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		return o instanceof HashingId && super.equals(o);
+	}
+}

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

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.api.sync;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.tree.TreeHash;
 
 @NotNullByDefault
 public interface MessageFactory {
@@ -10,4 +11,6 @@ public interface MessageFactory {
 	Message createMessage(byte[] raw);
 
 	byte[] getRawMessage(Message m);
+
+	MessageId getMessageId(GroupId g, long timestamp, TreeHash rootHash);
 }

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

@@ -24,6 +24,12 @@ public class MessageId extends UniqueId {
 	public static final String BLOCK_LABEL =
 			"org.briarproject.bramble/MESSAGE_BLOCK";
 
+	/**
+	 * Label for hashing two tree hashes to produce a parent.
+	 */
+	public static final String TREE_LABEL =
+			"org.briarproject.bramble/MESSAGE_TREE";
+
 	public MessageId(byte[] id) {
 		super(id);
 	}

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

@@ -35,4 +35,9 @@ public interface SyncConstants {
 	 * The maximum number of message IDs in an ack, offer or request record.
 	 */
 	int MAX_MESSAGE_IDS = MAX_RECORD_PAYLOAD_BYTES / UniqueId.LENGTH;
+
+	/**
+	 * The maximum length of a message block in bytes.
+	 */
+	int MAX_BLOCK_LENGTH = 32 * 2014; // 32 KiB
 }

bramble-api/src/main/java/org/briarproject/bramble/api/sync/tree/LeafNode.java

@@ -0,0 +1,21 @@
+package org.briarproject.bramble.api.sync.tree;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+@NotNullByDefault
+public class LeafNode extends TreeNode {
+
+	public LeafNode(TreeHash hash, int blockNumber) {
+		super(hash, 0, blockNumber, blockNumber);
+	}
+
+	@Override
+	public TreeNode getLeftChild() {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public TreeNode getRightChild() {
+		throw new UnsupportedOperationException();
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/tree/ParentNode.java

@@ -0,0 +1,26 @@
+package org.briarproject.bramble.api.sync.tree;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+@NotNullByDefault
+public class ParentNode extends TreeNode {
+
+	private final TreeNode left, right;
+
+	public ParentNode(TreeHash hash, TreeNode left, TreeNode right) {
+		super(hash, Math.max(left.getHeight(), right.getHeight()) + 1,
+				left.getFirstBlockNumber(), right.getLastBlockNumber());
+		this.left = left;
+		this.right = right;
+	}
+
+	@Override
+	public TreeNode getLeftChild() {
+		return left;
+	}
+
+	@Override
+	public TreeNode getRightChild() {
+		return right;
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/tree/StreamHasher.java

@@ -0,0 +1,21 @@
+package org.briarproject.bramble.api.sync.tree;
+
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.io.BlockSink;
+import org.briarproject.bramble.api.io.HashingId;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+@NotNullByDefault
+public interface StreamHasher {
+
+	/**
+	 * Reads the given input stream, divides the data into blocks, stores
+	 * the blocks and the resulting hash tree using the given block sink and
+	 * temporary ID, and returns the hash tree.
+	 */
+	TreeNode hash(InputStream in, BlockSink sink, HashingId h)
+			throws IOException, DbException;
+}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/tree/TreeHash.java

@@ -0,0 +1,24 @@
+package org.briarproject.bramble.api.sync.tree;
+
+import org.briarproject.bramble.api.UniqueId;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * Type-safe wrapper for a byte array that uniquely identifies a sequence of
+ * one or more message blocks.
+ */
+@ThreadSafe
+@NotNullByDefault
+public class TreeHash extends UniqueId {
+
+	public TreeHash(byte[] id) {
+		super(id);
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		return o instanceof TreeHash && super.equals(o);
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/tree/TreeHasher.java

@@ -0,0 +1,11 @@
+package org.briarproject.bramble.api.sync.tree;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+@NotNullByDefault
+public interface TreeHasher {
+
+	LeafNode hashBlock(int blockNumber, byte[] data);
+
+	ParentNode mergeTrees(TreeNode left, TreeNode right);
+}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/tree/TreeNode.java

@@ -0,0 +1,38 @@
+package org.briarproject.bramble.api.sync.tree;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+@NotNullByDefault
+public abstract class TreeNode {
+
+	private final TreeHash hash;
+	private final int height, firstBlockNumber, lastBlockNumber;
+
+	TreeNode(TreeHash hash, int height, int firstBlockNumber,
+			int lastBlockNumber) {
+		this.hash = hash;
+		this.height = height;
+		this.firstBlockNumber = firstBlockNumber;
+		this.lastBlockNumber = lastBlockNumber;
+	}
+
+	public TreeHash getHash() {
+		return hash;
+	}
+
+	public int getHeight() {
+		return height;
+	}
+
+	public int getFirstBlockNumber() {
+		return firstBlockNumber;
+	}
+
+	public int getLastBlockNumber() {
+		return lastBlockNumber;
+	}
+
+	public abstract TreeNode getLeftChild();
+
+	public abstract TreeNode getRightChild();
+}

bramble-core/src/main/java/org/briarproject/bramble/sync/MessageFactoryImpl.java

@@ -7,6 +7,7 @@ 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.tree.TreeHash;
 import org.briarproject.bramble.util.ByteUtils;
 
 import javax.annotation.concurrent.Immutable;
@@ -39,13 +40,19 @@ class MessageFactoryImpl implements MessageFactory {
 		if (body.length == 0) throw new IllegalArgumentException();
 		if (body.length > MAX_MESSAGE_BODY_LENGTH)
 			throw new IllegalArgumentException();
-		MessageId id = getMessageId(g, timestamp, body);
+		MessageId id = getMessageIdFromBody(g, timestamp, body);
 		return new Message(id, g, timestamp, body);
 	}
 
-	private MessageId getMessageId(GroupId g, long timestamp, byte[] body) {
+	private MessageId getMessageIdFromBody(GroupId g, long timestamp,
+			byte[] body) {
 		// There's only one block, so the root hash is the hash of the block
 		byte[] rootHash = crypto.hash(BLOCK_LABEL, FORMAT_VERSION_BYTES, body);
+		return getMessageIdFromRootHash(g, timestamp, rootHash);
+	}
+
+	private MessageId getMessageIdFromRootHash(GroupId g, long timestamp,
+			byte[] rootHash) {
 		byte[] timeBytes = new byte[INT_64_BYTES];
 		ByteUtils.writeUint64(timestamp, timeBytes, 0);
 		byte[] idHash = crypto.hash(ID_LABEL, FORMAT_VERSION_BYTES,
@@ -65,7 +72,7 @@ class MessageFactoryImpl implements MessageFactory {
 		long timestamp = ByteUtils.readUint64(raw, UniqueId.LENGTH);
 		byte[] body = new byte[raw.length - MESSAGE_HEADER_LENGTH];
 		System.arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
-		MessageId id = getMessageId(g, timestamp, body);
+		MessageId id = getMessageIdFromBody(g, timestamp, body);
 		return new Message(id, g, timestamp, body);
 	}
 
@@ -78,4 +85,10 @@ class MessageFactoryImpl implements MessageFactory {
 		System.arraycopy(body, 0, raw, MESSAGE_HEADER_LENGTH, body.length);
 		return raw;
 	}
+
+	@Override
+	public MessageId getMessageId(GroupId g, long timestamp,
+			TreeHash rootHash) {
+		return getMessageIdFromRootHash(g, timestamp, rootHash.getBytes());
+	}
 }

bramble-core/src/main/java/org/briarproject/bramble/sync/tree/HashTree.java

@@ -0,0 +1,16 @@
+package org.briarproject.bramble.sync.tree;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.tree.LeafNode;
+import org.briarproject.bramble.api.sync.tree.TreeNode;
+
+import javax.annotation.concurrent.NotThreadSafe;
+
+@NotThreadSafe
+@NotNullByDefault
+interface HashTree {
+
+	void addLeaf(LeafNode leaf);
+
+	TreeNode getRoot();
+}

bramble-core/src/main/java/org/briarproject/bramble/sync/tree/HashTreeImpl.java

@@ -0,0 +1,46 @@
+package org.briarproject.bramble.sync.tree;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.tree.LeafNode;
+import org.briarproject.bramble.api.sync.tree.TreeHasher;
+import org.briarproject.bramble.api.sync.tree.TreeNode;
+
+import java.util.Deque;
+import java.util.LinkedList;
+
+import javax.inject.Inject;
+
+@NotNullByDefault
+class HashTreeImpl implements HashTree {
+
+	private final TreeHasher treeHasher;
+	private final Deque<TreeNode> nodes = new LinkedList<>();
+
+	@Inject
+	HashTreeImpl(TreeHasher treeHasher) {
+		this.treeHasher = treeHasher;
+	}
+
+	@Override
+	public void addLeaf(LeafNode leaf) {
+		TreeNode add = leaf;
+		int height = leaf.getHeight();
+		TreeNode last = nodes.peekLast();
+		while (last != null && last.getHeight() == height) {
+			add = treeHasher.mergeTrees(last, add);
+			height = add.getHeight();
+			nodes.removeLast();
+			last = nodes.peekLast();
+		}
+		nodes.addLast(add);
+	}
+
+	@Override
+	public TreeNode getRoot() {
+		TreeNode root = nodes.removeLast();
+		while (!nodes.isEmpty()) {
+			root = treeHasher.mergeTrees(nodes.removeLast(), root);
+		}
+		return root;
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/sync/tree/StreamHasherImpl.java

@@ -0,0 +1,85 @@
+package org.briarproject.bramble.sync.tree;
+
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.io.BlockSink;
+import org.briarproject.bramble.api.io.HashingId;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.tree.StreamHasher;
+import org.briarproject.bramble.api.sync.tree.TreeHash;
+import org.briarproject.bramble.api.sync.tree.TreeHasher;
+import org.briarproject.bramble.api.sync.tree.TreeNode;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.LinkedList;
+
+import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+import javax.inject.Provider;
+
+import static java.util.Arrays.copyOfRange;
+import static org.briarproject.bramble.api.sync.SyncConstants.MAX_BLOCK_LENGTH;
+
+@Immutable
+@NotNullByDefault
+class StreamHasherImpl implements StreamHasher {
+
+	private final TreeHasher treeHasher;
+	private final Provider<HashTree> hashTreeProvider;
+
+	@Inject
+	StreamHasherImpl(TreeHasher treeHasher,
+			Provider<HashTree> hashTreeProvider) {
+		this.treeHasher = treeHasher;
+		this.hashTreeProvider = hashTreeProvider;
+	}
+
+	@Override
+	public TreeNode hash(InputStream in, BlockSink sink, HashingId h)
+			throws IOException, DbException {
+		HashTree tree = hashTreeProvider.get();
+		byte[] block = new byte[MAX_BLOCK_LENGTH];
+		int read;
+		for (int blockNumber = 0; (read = read(in, block)) > 0; blockNumber++) {
+			byte[] data;
+			if (read == block.length) data = block;
+			else data = copyOfRange(block, 0, read);
+			sink.putBlock(h, blockNumber, data);
+			tree.addLeaf(treeHasher.hashBlock(blockNumber, data));
+		}
+		TreeNode root = tree.getRoot();
+		setPaths(sink, h, root, new LinkedList<>());
+		return root;
+	}
+
+	/**
+	 * Reads a block from the given input stream and returns the number of
+	 * bytes read, or 0 if no bytes were read before reaching the end of the
+	 * stream.
+	 */
+	private int read(InputStream in, byte[] block) throws IOException {
+		int offset = 0;
+		while (offset < block.length) {
+			int read = in.read(block, offset, block.length - offset);
+			if (read == -1) return offset;
+			offset += read;
+		}
+		return offset;
+	}
+
+	private void setPaths(BlockSink sink, HashingId h, TreeNode node,
+			LinkedList<TreeHash> path) throws DbException {
+		if (node.getHeight() == 0) {
+			// We've reached a leaf - store the path
+			sink.setPath(h, node.getFirstBlockNumber(), path);
+		} else {
+			// Add the right child's hash to the path and traverse the left
+			path.addFirst(node.getRightChild().getHash());
+			setPaths(sink, h, node.getLeftChild(), path);
+			// Add the left child's hash to the path and traverse the right
+			path.removeFirst();
+			path.addFirst(node.getLeftChild().getHash());
+			setPaths(sink, h, node.getRightChild(), path);
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/sync/tree/TreeHasherImpl.java

@@ -0,0 +1,44 @@
+package org.briarproject.bramble.sync.tree;
+
+import org.briarproject.bramble.api.crypto.CryptoComponent;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.tree.LeafNode;
+import org.briarproject.bramble.api.sync.tree.ParentNode;
+import org.briarproject.bramble.api.sync.tree.TreeHash;
+import org.briarproject.bramble.api.sync.tree.TreeHasher;
+import org.briarproject.bramble.api.sync.tree.TreeNode;
+
+import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+
+import static org.briarproject.bramble.api.sync.Message.FORMAT_VERSION;
+import static org.briarproject.bramble.api.sync.MessageId.BLOCK_LABEL;
+import static org.briarproject.bramble.api.sync.MessageId.TREE_LABEL;
+
+@Immutable
+@NotNullByDefault
+class TreeHasherImpl implements TreeHasher {
+
+	private static final byte[] FORMAT_VERSION_BYTES =
+			new byte[] {FORMAT_VERSION};
+
+	private final CryptoComponent crypto;
+
+	@Inject
+	TreeHasherImpl(CryptoComponent crypto) {
+		this.crypto = crypto;
+	}
+
+	@Override
+	public LeafNode hashBlock(int blockNumber, byte[] data) {
+		byte[] hash = crypto.hash(BLOCK_LABEL, FORMAT_VERSION_BYTES, data);
+		return new LeafNode(new TreeHash(hash), blockNumber);
+	}
+
+	@Override
+	public ParentNode mergeTrees(TreeNode left, TreeNode right) {
+		byte[] hash = crypto.hash(TREE_LABEL, FORMAT_VERSION_BYTES,
+				left.getHash().getBytes(), right.getHash().getBytes());
+		return new ParentNode(new TreeHash(hash), left, right);
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/test/TestMessageFactory.java

@@ -4,6 +4,8 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 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.tree.TreeHash;
 
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
 
@@ -27,4 +29,10 @@ public class TestMessageFactory implements MessageFactory {
 		System.arraycopy(body, 0, raw, MESSAGE_HEADER_LENGTH, body.length);
 		return raw;
 	}
+
+	@Override
+	public MessageId getMessageId(GroupId g, long timestamp,
+			TreeHash rootHash) {
+		throw new UnsupportedOperationException();
+	}
 }