comments

contracts/ERC20Mixer.sol

@@ -47,7 +47,7 @@ contract ERC20Mixer is Mixer {
     (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0x23b872dd /* transferFrom */, _from, _to, _amount));
     require(success, "not enough allowed tokens");
 
-    // if contract returns some data let's make sure that is `true` according to standard
+    // if contract returns some data lets make sure that is `true` according to standard
     if (data.length > 0) {
       require(data.length == 32, "data length should be either 0 or 32 bytes");
       success = abi.decode(data, (bool));
@@ -59,7 +59,7 @@ contract ERC20Mixer is Mixer {
     (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0xa9059cbb /* transfer */, _to, _amount));
     require(success, "not enough tokens");
 
-    // if contract returns some data let's make sure that is `true` according to standard
+    // if contract returns some data lets make sure that is `true` according to standard
     if (data.length > 0) {
       require(data.length == 32, "data length should be either 0 or 32 bytes");
       success = abi.decode(data, (bool));

contracts/ETHMixer.sol

@@ -22,6 +22,10 @@ contract ETHMixer is Mixer {
   ) Mixer(_verifier, _denomination, _merkleTreeHeight, _operator) public {
   }
 
+  function _processDeposit() internal {
+    require(msg.value == denomination, "Please send `mixDenomination` ETH along with transaction");
+  }
+
   function _processWithdraw(address payable _receiver, address payable _relayer, uint256 _fee, uint256 _refund) internal {
     // sanity checks
     require(msg.value == 0, "Message value is supposed to be zero for ETH mixer");
@@ -32,8 +36,4 @@ contract ETHMixer is Mixer {
       _relayer.transfer(_fee);
     }
   }
-
-  function _processDeposit() internal {
-    require(msg.value == denomination, "Please send `mixDenomination` ETH along with transaction");
-  }
 }

contracts/MerkleTreeWithHistory.sol

@@ -19,11 +19,13 @@ contract MerkleTreeWithHistory {
   uint256 public constant FIELD_SIZE = 21888242871839275222246405745257275088548364400416034343698204186575808495617;
   uint256 public constant ZERO_VALUE = 5702960885942360421128284892092891246826997279710054143430547229469817701242; // = MiMC("tornado")
 
+  uint256 public levels;
+
+  // the following variables are made public for easier testing and debugging and
+  // are not supposed to be accessed in regular code
   uint256 public constant ROOT_HISTORY_SIZE = 100;
   uint256[ROOT_HISTORY_SIZE] public roots;
   uint256 public currentRootIndex = 0;
-
-  uint256 public levels;
   uint32 public nextIndex = 0;
   uint256[] public filledSubtrees;
   uint256[] public zeros;
@@ -45,9 +47,10 @@ contract MerkleTreeWithHistory {
     roots[0] = hashLeftRight(currentZero, currentZero);
   }
 
+  /**
+    @dev Hash 2 tree leaves, returns MiMC(_left, _right)
+  */
   function hashLeftRight(uint256 _left, uint256 _right) public pure returns (uint256 hash) {
-    // those checks should never trigger in practice, because they're already performed by the snark verifier
-    // added for convenience if someone decides to call this function directly
     require(_left < FIELD_SIZE, "_left should be inside the field");
     require(_right < FIELD_SIZE, "_right should be inside the field");
     uint256 R = _left;
@@ -90,6 +93,9 @@ contract MerkleTreeWithHistory {
     return nextIndex - 1;
   }
 
+  /**
+    @dev Whether the root is present in the root history
+  */
   function isKnownRoot(uint256 _root) public view returns(bool) {
     if (_root == 0) {
       return false;
@@ -123,6 +129,9 @@ contract MerkleTreeWithHistory {
     //   } while (i != currentRootIndex);
   }
 
+  /**
+    @dev Returns the last root
+  */
   function getLastRoot() public view returns(uint256) {
     return roots[currentRootIndex];
   }

contracts/Mixer.sol

@@ -25,7 +25,6 @@ contract Mixer is MerkleTreeWithHistory {
   IVerifier public verifier;
 
   // operator can
-  //  - receive a relayer fee
   //  - disable new deposits in case of emergency
   //  - update snark verification key until this ability is permanently disabled
   address public operator;
@@ -42,8 +41,9 @@ contract Mixer is MerkleTreeWithHistory {
   /**
     @dev The constructor
     @param _verifier the address of SNARK verifier for this contract
+    @param _denomination transfer amount for each deposit
     @param _merkleTreeHeight the height of deposits' Merkle Tree
-    @param _operator operator address (see operator above)
+    @param _operator operator address (see operator comment above)
   */
   constructor(
     IVerifier _verifier,
@@ -75,7 +75,7 @@ contract Mixer is MerkleTreeWithHistory {
   function _processDeposit() internal;
 
   /**
-    @dev Withdraw deposit from the mixer. `proof` is a zkSNARK proof data, and input is an array of circuit public inputs
+    @dev Withdraw a deposit from the mixer. `proof` is a zkSNARK proof data, and input is an array of circuit public inputs
     `input` array consists of:
       - merkle root of all deposits in the mixer
       - hash of unique deposit nullifier to prevent double spends