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contracts/TornadoTrees.sol

@@ -4,7 +4,7 @@ pragma solidity ^0.6.0;
 pragma experimental ABIEncoderV2;
 
 import "./interfaces/ITornadoTreesV1.sol";
-import "./interfaces/IVerifier.sol";
+import "./interfaces/IBatchTreeUpdateVerifier.sol";
 
 contract TornadoTrees {
   address public immutable governance;
@@ -13,7 +13,7 @@ contract TornadoTrees {
   bytes32 public withdrawalRoot;
   bytes32 public previousWithdrawalRoot;
   address public tornadoProxy;
-  IVerifier public treeUpdateVerifier;
+  IBatchTreeUpdateVerifier public treeUpdateVerifier;
   ITornadoTreesV1 public immutable tornadoTreesV1;
 
   // make sure CHUNK_TREE_HEIGHT has the same value in BatchTreeUpdate.circom
@@ -70,7 +70,7 @@ contract TornadoTrees {
     address _governance,
     address _tornadoProxy,
     ITornadoTreesV1 _tornadoTreesV1,
-    IVerifier _treeUpdateVerifier,
+    IBatchTreeUpdateVerifier _treeUpdateVerifier,
     SearchParams memory _searchParams
   ) public {
     governance = _governance;
@@ -110,6 +110,9 @@ contract TornadoTrees {
     uint256 _from, // most likely array length after the proposal has passed
     uint256 _step // optimal step size to find first match, approximately equals dispersion
   ) public view returns (uint256) {
+    if (_from == 0 && _step == 0) {
+      return 0; // for tests
+    }
     // Find the segment with correct array length
     bool direction = elementExists(_tornadoTreesV1, _type, _from);
     do {
@@ -271,7 +274,7 @@ contract TornadoTrees {
     tornadoProxy = _tornadoProxy;
   }
 
-  function setVerifierContract(IVerifier _treeUpdateVerifier) external onlyGovernance {
+  function setVerifierContract(IBatchTreeUpdateVerifier _treeUpdateVerifier) external onlyGovernance {
     treeUpdateVerifier = _treeUpdateVerifier;
   }
 

contracts/interfaces/IBatchTreeUpdateVerifier.sol

@@ -2,6 +2,6 @@
 
 pragma solidity ^0.6.0;
 
-interface IVerifier {
+interface IBatchTreeUpdateVerifier {
   function verifyProof(bytes calldata proof, uint256[1] calldata input) external view returns (bool);
 }

contracts/mocks/TornadoTreesMock.sol

@@ -5,7 +5,7 @@ pragma experimental ABIEncoderV2;
 
 import "../TornadoTrees.sol";
 import "../interfaces/ITornadoTreesV1.sol";
-import "../interfaces/IVerifier.sol";
+import "../interfaces/IBatchTreeUpdateVerifier.sol";
 
 contract TornadoTreesMock is TornadoTrees {
   uint256 public currentBlock;
@@ -14,7 +14,7 @@ contract TornadoTreesMock is TornadoTrees {
     address _governance,
     address _tornadoProxy,
     ITornadoTreesV1 _tornadoTreesV1,
-    IVerifier _treeUpdateVerifier,
+    IBatchTreeUpdateVerifier _treeUpdateVerifier,
     SearchParams memory _searchParams
   ) public TornadoTrees(_governance, _tornadoProxy, _tornadoTreesV1, _treeUpdateVerifier, _searchParams) {}
 
@@ -40,6 +40,11 @@ contract TornadoTreesMock is TornadoTrees {
     registerWithdrawal(_instance, _nullifier);
   }
 
+  function updateRoots(bytes32 _depositRoot, bytes32 _withdrawalRoot) public {
+    depositRoot = _depositRoot;
+    withdrawalRoot = _withdrawalRoot;
+  }
+
   function updateDepositTreeMock(
     bytes32 _oldRoot,
     bytes32 _newRoot,

package.json

@@ -1,6 +1,6 @@
 {
   "name": "tornado-trees",
-  "version": "0.0.2",
+  "version": "0.0.4",
   "main": "src/index.js",
   "repository": "https://github.com/tornadocash/tornado-trees.git",
   "author": "Tornadocash team <hello@tornado.cash>",

test/binarySearch.test.js

@@ -37,6 +37,13 @@ describe('findArrayLength', () => {
     expect(depositsLength).to.be.equal(depositsEven.length)
   })
 
+  it('should work for empty array', async () => {
+    publicArray = await PublicArray.deploy()
+    // will throw out of gas if you pass non zero params
+    const depositsLength = await tornadoTrees.findArrayLength(publicArray.address, 'deposits(uint256)', 0, 0)
+    expect(depositsLength).to.be.equal(0)
+  })
+
   it('should work for odd array', async () => {
     publicArray = await PublicArray.deploy()
     await publicArray.setDeposits(depositsOdd)