[Under Audit] Add Bucket-Lender

contracts/external/weth/README.md

@@ -0,0 +1,3 @@
+All contracts in this folder are taken from the official MakerDao GitHub.
+They have been upgraded to a more recent Solidity version without changing functionality.
+They are only included for testing purposes.

contracts/external/weth/WETH9.sol

@@ -0,0 +1,63 @@
+pragma solidity 0.4.24;
+
+
+contract WETH9 {
+    string public name     = "Wrapped Ether";
+    string public symbol   = "WETH";
+    uint8  public decimals = 18;
+
+    event Approval(address indexed src, address indexed guy, uint wad);
+    event Transfer(address indexed src, address indexed dst, uint wad);
+    event Deposit(address indexed dst, uint wad);
+    event Withdrawal(address indexed src, uint wad);
+
+    mapping (address => uint)                       public  balanceOf;
+    mapping (address => mapping (address => uint))  public  allowance;
+
+    function() public payable {
+        deposit();
+    }
+    function deposit() public payable {
+        balanceOf[msg.sender] += msg.value;
+        emit Deposit(msg.sender, msg.value);
+    }
+    function withdraw(uint wad) public {
+        require(balanceOf[msg.sender] >= wad);
+        balanceOf[msg.sender] -= wad;
+        msg.sender.transfer(wad);
+        emit Withdrawal(msg.sender, wad);
+    }
+
+    function totalSupply() public view returns (uint) {
+        return address(this).balance;
+    }
+
+    function approve(address guy, uint wad) public returns (bool) {
+        allowance[msg.sender][guy] = wad;
+        emit Approval(msg.sender, guy, wad);
+        return true;
+    }
+
+    function transfer(address dst, uint wad) public returns (bool) {
+        return transferFrom(msg.sender, dst, wad);
+    }
+
+    function transferFrom(address src, address dst, uint wad)
+        public
+        returns (bool)
+    {
+        require(balanceOf[src] >= wad);
+
+        if (src != msg.sender && allowance[src][msg.sender] != uint(-1)) {
+            require(allowance[src][msg.sender] >= wad);
+            allowance[src][msg.sender] -= wad;
+        }
+
+        balanceOf[src] -= wad;
+        balanceOf[dst] += wad;
+
+        emit Transfer(src, dst, wad);
+
+        return true;
+    }
+}

contracts/lib/MathHelpers.sol

@@ -107,6 +107,20 @@ library MathHelpers {
         return 2 ** 256 - 1;
     }
 
+    /**
+     * Calculates and returns the maximum value for a uint256 in solidity
+     *
+     * @return  The maximum value for uint256
+     */
+    function maxUint32(
+    )
+        internal
+        pure
+        returns (uint32)
+    {
+        return 2 ** 32 - 1;
+    }
+
     /**
      * Returns the number of bits in a uint256. That is, the lowest number, x, such that n >> x == 0
      *