Updated contracts and README

ethify · Aug 1, 2019 · e4a94e8 · e4a94e8
1 parent 3420efb
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diff --git a/README.md b/README.md
@@ -640,10 +640,6 @@ With Ganache running, execute:
 truffle migrate --network development --reset
 ```
 
-## Workshop Exercises
+## Hackathon Bounties
 
-#### 1. Create a smart contract that splits ETH into 3 different tokens. In the constructor, specify the 3 different tokens and percentage distribution of each token.
-
-#### 2. Launch an Automated Price Reserve with your own custom token.
-
-#### 3. Integrate token swaps in your own solidity project.
+For our hackathon bounties, please visit https://kyber.network/hack.
diff --git a/contracts/ExpectedRate.sol b/contracts/ExpectedRate.sol
@@ -55,27 +55,10 @@ contract ExpectedRate is Withdrawable, ExpectedRateInterface, Utils2 {
 
         if (srcQty == 0) srcQty = 1;
 
-        uint bestReserve;
-        uint worstCaseSlippageRate;
+        bool didRevert = false;
 
-        if (usePermissionless) {
-            (bestReserve, expectedRate) = kyberNetwork.findBestRate(src, dest, srcQty);
-
-            if (quantityFactor != 1) {
-                (bestReserve, slippageRate) = kyberNetwork.findBestRate(src, dest, (srcQty * quantityFactor));
-            } else {
-                slippageRate = expectedRate;
-            }
-        } else {
-            (bestReserve, expectedRate) = kyberNetwork.findBestRateOnlyPermission(src, dest, srcQty);
-
-            if (quantityFactor != 1) {
-                (bestReserve, slippageRate) = kyberNetwork.findBestRateOnlyPermission(src, dest,
-                    (srcQty * quantityFactor));
-            } else {
-                slippageRate = expectedRate;
-            }
-        }
+        (didRevert, expectedRate, slippageRate) = safeFindBestRate(src, dest, srcQty, usePermissionless);
+        if (didRevert) return (0, 0);
 
         if (expectedRate == 0) {
             expectedRate = expectedRateSmallQty(src, dest, srcQty, usePermissionless);
@@ -88,9 +71,9 @@ contract ExpectedRate is Withdrawable, ExpectedRateInterface, Utils2 {
             if (checkKncArbitrageRate(expectedRate)) expectedRate = 0;
         }
 
-        require(expectedRate <= MAX_RATE);
+        if (expectedRate > MAX_RATE) return (0, 0);
 
-        worstCaseSlippageRate = ((10000 - worstCaseRateFactorInBps) * expectedRate) / 10000;
+        uint worstCaseSlippageRate = ((10000 - worstCaseRateFactorInBps) * expectedRate) / 10000;
         if (slippageRate >= worstCaseSlippageRate) {
             slippageRate = worstCaseSlippageRate;
         }
@@ -101,7 +84,11 @@ contract ExpectedRate is Withdrawable, ExpectedRateInterface, Utils2 {
     function checkKncArbitrageRate(uint currentKncToEthRate) public view returns(bool) {
         uint converseRate;
         uint slippage;
-	(converseRate, slippage) = getExpectedRate(ETH_TOKEN_ADDRESS, knc, UNIT_QTY_FOR_FEE_BURNER, true);
+    	(converseRate, slippage) = getExpectedRate(ETH_TOKEN_ADDRESS, knc, UNIT_QTY_FOR_FEE_BURNER, true);
+
+        // if returned rate is 0, can't trust this arb test. assume we have arb
+        if(converseRate == 0) return true;
+
         require(converseRate <= MAX_RATE && currentKncToEthRate <= MAX_RATE);
         return ((converseRate * currentKncToEthRate) > (PRECISION ** 2));
     }
@@ -121,4 +108,55 @@ contract ExpectedRate is Withdrawable, ExpectedRateInterface, Utils2 {
         (reserve, rateEthToDest) = kyberNetwork.searchBestRate(ETH_TOKEN_ADDRESS, dest, ethQty, usePermissionless);
         return rateSrcToEth * rateEthToDest / PRECISION;
     }
+
+    function safeFindBestRate(ERC20 src, ERC20 dest, uint srcQty, bool usePermissionless)
+        internal view
+        returns (bool didRevert, uint expectedRate, uint slippageRate)
+    {
+        bytes4 sig = usePermissionless ?
+            bytes4(keccak256("findBestRate(address,address,uint256)")) :
+            bytes4(keccak256("findBestRateOnlyPermission(address,address,uint256)")); //Function signatures
+
+        (didRevert, expectedRate) = assemblyFindBestRate(src, dest, srcQty, sig);
+
+        if (didRevert) return (true, 0, 0);
+
+        if (quantityFactor != 1) {
+            (didRevert, slippageRate) = assemblyFindBestRate(src, dest, (srcQty * quantityFactor), sig);
+        } else {
+            slippageRate = expectedRate;
+        }
+    }
+
+    function assemblyFindBestRate(ERC20 src, ERC20 dest, uint srcQty, bytes4 sig)
+        internal view
+        returns (bool didRevert, uint rate)
+    {
+        address addr = address(kyberNetwork);  // kyber address
+        uint success;
+
+        assembly {
+            let x := mload(0x40)        // "free memory pointer"
+            mstore(x,sig)               // function signature
+            mstore(add(x,0x04),src)     // src address padded to 32 bytes
+            mstore(add(x,0x24),dest)    // dest padded to 32 bytes
+            mstore(add(x,0x44),srcQty)  // uint 32 bytes
+            mstore(0x40,add(x,0xa4))    // set free storage pointer to empty space after output
+
+            // input size = sig + ERC20 (address) + ERC20 + uint
+            // = 4 + 32 + 32 + 32 = 100 = 0x64
+            success := staticcall(
+                gas,  // gas
+                addr, // Kyber addr
+                x,    // Inputs at location x
+                0x64, // Inputs size bytes
+                add(x, 0x64),    // output storage after input
+                0x40) // Output size are (uint, uint) = 64 bytes
+
+            rate := mload(add(x,0x84))  //Assign 2nd output to rate, first output not used,
+            mstore(0x40,x)    // Set empty storage pointer back to start position
+        }
+
+        if (success != 1) didRevert = true;
+    }
 }