Merge branch 'v2-prototype' into feature/combinatorial-testing

* v2-prototype: (26 commits)
  Rename _coverageCollector -> _profilerCollector in TraceCollectionSubprovider
  Refactor sol-cov to de-duplicate code for coverage and profiling
  Rename popByte and popAddress
  Hard code test addresses/bytes32 instead of generating pseudorandom ones
  Update artifacts
  Rename computeCoverageAsync -> computeSingleTraceCoverageAsync
  Fix linter errors
  Refactor sol-cov to avoid keeping traceInfo in memory
  Unpop byte rather than making deep copy
  Pass gas in to marketBuyOrdersNoThrow
  Looks up the memory location of makerAssetData/takerAssetData
  Make ZRX_PROXY_ID constant rather than popping it from ZRX_ASSET_DATA
  Add tests for deepCopyBytes and missing write methods from LibBytes
  Pop id from assetData before dispatching to AssetProxies
  Upgrade solidity-parser-entlr 0.2.11 => 0.2.12
  Fix import order
  Fix typos
  Add CHANGELOGs
  Speed-up sol-cov
  Increase delay when sending transactions during devnet startup
  ...

19 files changed, 200 insertions, 205 deletions

diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
index dd25bf41a..ddcd78e93 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
@@ -47,16 +47,7 @@ contract ERC20Proxy is
         internal
     {
         // Decode asset data.
-        (
-            uint8 proxyId,
-            address token
-        ) = decodeERC20AssetData(assetData);
-
-        // Data must be intended for this proxy.
-        require(
-            proxyId == PROXY_ID,
-            ASSET_PROXY_ID_MISMATCH
-        );
+        address token = readAddress(assetData, 0);
 
         // Transfer tokens.
         bool success = IERC20Token(token).transferFrom(from, to, amount);
@@ -75,30 +66,4 @@ contract ERC20Proxy is
     {
         return PROXY_ID;
     }
-
-    /// @dev Decodes ERC20 Asset data.
-    /// @param assetData Encoded byte array.
-    /// @return proxyId Intended ERC20 proxy id.
-    /// @return token ERC20 token address.
-    function decodeERC20AssetData(bytes memory assetData)
-        internal
-        pure
-        returns (
-            uint8 proxyId,
-            address token
-        )
-    {
-        // Validate encoded data length
-        uint256 length = assetData.length;
-        require(
-            length == 21,
-            LENGTH_21_REQUIRED
-        );
-
-        // Decode data
-        token = readAddress(assetData, 0);
-        proxyId = uint8(assetData[length - 1]);
-
-        return (proxyId, token);
-    }
 }
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
index 25136133d..861fac2c1 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
@@ -46,30 +46,22 @@ contract ERC721Proxy is
     )
         internal
     {
+        // There exists only 1 of each token.
+        require(
+            amount == 1,
+            INVALID_AMOUNT
+        );
+    
         // Decode asset data.
         (
-            uint8 proxyId,
             address token,
             uint256 tokenId,
             bytes memory receiverData
         ) = decodeERC721AssetData(assetData);
 
-
-        // Data must be intended for this proxy.
-        require(
-            proxyId == PROXY_ID,
-            ASSET_PROXY_ID_MISMATCH
-        );
-
-        // There exists only 1 of each token.
-        require(
-            amount == 1,
-            INVALID_AMOUNT
-        );
-
         // Transfer token. Saves gas by calling safeTransferFrom only
         // when there is receiverData present. Either succeeds or throws.
-        if(receiverData.length > 0) {
+        if (receiverData.length > 0) {
             ERC721Token(token).safeTransferFrom(from, to, tokenId, receiverData);
         } else {
             ERC721Token(token).transferFrom(from, to, tokenId);
@@ -97,29 +89,19 @@ contract ERC721Proxy is
         internal
         pure
         returns (
-            uint8 proxyId,
             address token,
             uint256 tokenId,
             bytes memory receiverData
         )
     {
-        // Validate encoded data length
-        uint256 length = assetData.length;
-        require(
-            length >= 53,
-            LENGTH_AT_LEAST_53_REQUIRED
-        );
-
         // Decode asset data.
         token = readAddress(assetData, 0);
         tokenId = readUint256(assetData, 20);
-        if (length > 53) {
+        if (assetData.length > 52) {
             receiverData = readBytes(assetData, 52);
         }
-        proxyId = uint8(assetData[length - 1]);
 
         return (
-            proxyId,
             token,
             tokenId,
             receiverData
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/libs/LibAssetProxyErrors.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/libs/LibAssetProxyErrors.sol
index 80180a0d9..65bdacdb7 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/libs/LibAssetProxyErrors.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/libs/LibAssetProxyErrors.sol
@@ -27,11 +27,6 @@ contract LibAssetProxyErrors {
     string constant AUTHORIZED_ADDRESS_MISMATCH = "AUTHORIZED_ADDRESS_MISMATCH";  // Address at index does not match given target address.
 
     /// AssetProxy errors ///
-    string constant ASSET_PROXY_ID_MISMATCH = "ASSET_PROXY_ID_MISMATCH";          // Proxy id in metadata does not match this proxy id.
     string constant INVALID_AMOUNT = "INVALID_AMOUNT";                            // Transfer amount must equal 1.
     string constant TRANSFER_FAILED = "TRANSFER_FAILED";                          // Transfer failed.
-
-    /// Length validation errors ///
-    string constant LENGTH_21_REQUIRED = "LENGTH_21_REQUIRED";                    // Byte array must have a length of 21.
-    string constant LENGTH_AT_LEAST_53_REQUIRED = "LENGTH_AT_LEAST_53_REQUIRED";  // Byte array must have a length of at least 53.
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
index e77d81c06..9e0246303 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
@@ -19,12 +19,14 @@
 pragma solidity ^0.4.24;
 
 import "../../utils/Ownable/Ownable.sol";
+import "../../utils/LibBytes/LibBytes.sol";
 import "./libs/LibExchangeErrors.sol";
 import "./mixins/MAssetProxyDispatcher.sol";
 import "../AssetProxy/interfaces/IAssetProxy.sol";
 
 contract MixinAssetProxyDispatcher is
     Ownable,
+    LibBytes,
     LibExchangeErrors,
     MAssetProxyDispatcher
 {
@@ -81,11 +83,13 @@ contract MixinAssetProxyDispatcher is
 
     /// @dev Forwards arguments to assetProxy and calls `transferFrom`. Either succeeds or throws.
     /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param assetProxyId Id of assetProxy to dispach to.
     /// @param from Address to transfer token from.
     /// @param to Address to transfer token to.
     /// @param amount Amount of token to transfer.
     function dispatchTransferFrom(
         bytes memory assetData,
+        uint8 assetProxyId,
         address from,
         address to,
         uint256 amount
@@ -94,16 +98,8 @@ contract MixinAssetProxyDispatcher is
     {
         // Do nothing if no amount should be transferred.
         if (amount > 0) {
-
-            // Lookup asset proxy
-            uint256 length = assetData.length;
-            require(
-                length > 0,
-                LENGTH_GREATER_THAN_0_REQUIRED
-            );
-            uint8 assetProxyId = uint8(assetData[length - 1]);
+            // Lookup assetProxy
             IAssetProxy assetProxy = assetProxies[assetProxyId];
-
             // transferFrom will either succeed or throw.
             assetProxy.transferFrom(assetData, from, to, amount);
         }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol
index 12b57d99f..0a0f0209a 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol
@@ -108,9 +108,6 @@ contract MixinExchangeCore is
         // Compute proportional fill amounts
         fillResults = calculateFillResults(order, takerAssetFilledAmount);
 
-        // Settle order
-        settleOrder(order, takerAddress, fillResults);
-
         // Update exchange internal state
         updateFilledState(
             order,
@@ -119,6 +116,10 @@ contract MixinExchangeCore is
             orderInfo.orderTakerAssetFilledAmount,
             fillResults
         );
+    
+        // Settle order
+        settleOrder(order, takerAddress, fillResults);
+
         return fillResults;
     }
 
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinMatchOrders.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinMatchOrders.sol
index ed76287e0..517b743fe 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinMatchOrders.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinMatchOrders.sol
@@ -14,7 +14,6 @@
 pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
-import "../../utils/LibBytes/LibBytes.sol";
 import "./libs/LibMath.sol";
 import "./libs/LibOrder.sol";
 import "./libs/LibFillResults.sol";
@@ -25,7 +24,6 @@ import "./mixins/MSettlement.sol";
 import "./mixins/MTransactions.sol";
 
 contract MixinMatchOrders is
-    LibBytes,
     LibMath,
     LibExchangeErrors,
     MExchangeCore,
@@ -94,14 +92,6 @@ contract MixinMatchOrders is
             rightSignature
         );
 
-        // Settle matched orders. Succeeds or throws.
-        settleMatchedOrders(
-            leftOrder,
-            rightOrder,
-            takerAddress,
-            matchedFillResults
-        );
-
         // Update exchange state
         updateFilledState(
             leftOrder,
@@ -117,6 +107,14 @@ contract MixinMatchOrders is
             rightOrderInfo.orderTakerAssetFilledAmount,
             matchedFillResults.right
         );
+    
+        // Settle matched orders. Succeeds or throws.
+        settleMatchedOrders(
+            leftOrder,
+            rightOrder,
+            takerAddress,
+            matchedFillResults
+        );
 
         return matchedFillResults;
     }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol
index 83e9dfdf4..29a9c87bd 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol
@@ -19,6 +19,7 @@
 pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
+import "../../utils/LibBytes/LibBytes.sol";
 import "./libs/LibMath.sol";
 import "./libs/LibFillResults.sol";
 import "./libs/LibOrder.sol";
@@ -28,25 +29,18 @@ import "./mixins/MSettlement.sol";
 import "./mixins/MAssetProxyDispatcher.sol";
 
 contract MixinSettlement is
+    LibBytes,
     LibMath,
     LibExchangeErrors,
     MMatchOrders,
     MSettlement,
     MAssetProxyDispatcher
 {
-    // ZRX metadata used for fee transfers.
+    // ZRX address encoded as a byte array.
     // This will be constant throughout the life of the Exchange contract,
     // since ZRX will always be transferred via the ERC20 AssetProxy.
-    bytes internal ZRX_PROXY_DATA;
-
-    /// @dev Gets the ZRX metadata used for fee transfers.
-    function zrxAssetData()
-        external
-        view
-        returns (bytes memory)
-    {
-        return ZRX_PROXY_DATA;
-    }
+    bytes internal ZRX_ASSET_DATA;
+    uint8 constant ZRX_PROXY_ID = 1;
 
     /// TODO: _zrxAssetData should be a constant in production.
     /// @dev Constructor sets the metadata that will be used for paying ZRX fees.
@@ -54,7 +48,7 @@ contract MixinSettlement is
     constructor (bytes memory _zrxAssetData)
         public
     {
-        ZRX_PROXY_DATA = _zrxAssetData;
+        ZRX_ASSET_DATA = _zrxAssetData;
     }
 
     /// @dev Settles an order by transferring assets between counterparties.
@@ -68,26 +62,33 @@ contract MixinSettlement is
     )
         internal
     {
+        uint8 makerAssetProxyId = uint8(popLastByte(order.makerAssetData));
+        uint8 takerAssetProxyId = uint8(popLastByte(order.takerAssetData));
+        bytes memory zrxAssetData = ZRX_ASSET_DATA;
         dispatchTransferFrom(
             order.makerAssetData,
+            makerAssetProxyId,
             order.makerAddress,
             takerAddress,
             fillResults.makerAssetFilledAmount
         );
         dispatchTransferFrom(
             order.takerAssetData,
+            takerAssetProxyId,
             takerAddress,
             order.makerAddress,
             fillResults.takerAssetFilledAmount
         );
         dispatchTransferFrom(
-            ZRX_PROXY_DATA,
+            zrxAssetData,
+            ZRX_PROXY_ID,
             order.makerAddress,
             order.feeRecipientAddress,
             fillResults.makerFeePaid
         );
         dispatchTransferFrom(
-            ZRX_PROXY_DATA,
+            zrxAssetData,
+            ZRX_PROXY_ID,
             takerAddress,
             order.feeRecipientAddress,
             fillResults.takerFeePaid
@@ -107,21 +108,27 @@ contract MixinSettlement is
     )
         internal
     {
+        uint8 leftMakerAssetProxyId = uint8(popLastByte(leftOrder.makerAssetData));
+        uint8 rightMakerAssetProxyId = uint8(popLastByte(rightOrder.makerAssetData));
+        bytes memory zrxAssetData = ZRX_ASSET_DATA;
         // Order makers and taker
         dispatchTransferFrom(
             leftOrder.makerAssetData,
+            leftMakerAssetProxyId,
             leftOrder.makerAddress,
             rightOrder.makerAddress,
             matchedFillResults.right.takerAssetFilledAmount
         );
         dispatchTransferFrom(
             rightOrder.makerAssetData,
+            rightMakerAssetProxyId,
             rightOrder.makerAddress,
             leftOrder.makerAddress,
             matchedFillResults.left.takerAssetFilledAmount
         );
         dispatchTransferFrom(
             leftOrder.makerAssetData,
+            leftMakerAssetProxyId,
             leftOrder.makerAddress,
             takerAddress,
             matchedFillResults.leftMakerAssetSpreadAmount
@@ -129,13 +136,15 @@ contract MixinSettlement is
 
         // Maker fees
         dispatchTransferFrom(
-            ZRX_PROXY_DATA,
+            zrxAssetData,
+            ZRX_PROXY_ID,
             leftOrder.makerAddress,
             leftOrder.feeRecipientAddress,
             matchedFillResults.left.makerFeePaid
         );
         dispatchTransferFrom(
-            ZRX_PROXY_DATA,
+            zrxAssetData,
+            ZRX_PROXY_ID,
             rightOrder.makerAddress,
             rightOrder.feeRecipientAddress,
             matchedFillResults.right.makerFeePaid
@@ -144,7 +153,8 @@ contract MixinSettlement is
         // Taker fees
         if (leftOrder.feeRecipientAddress == rightOrder.feeRecipientAddress) {
             dispatchTransferFrom(
-                ZRX_PROXY_DATA,
+                zrxAssetData,
+                ZRX_PROXY_ID,
                 takerAddress,
                 leftOrder.feeRecipientAddress,
                 safeAdd(
@@ -154,13 +164,15 @@ contract MixinSettlement is
             );
         } else {
             dispatchTransferFrom(
-                ZRX_PROXY_DATA,
+                zrxAssetData,
+                ZRX_PROXY_ID,
                 takerAddress,
                 leftOrder.feeRecipientAddress,
                 matchedFillResults.left.takerFeePaid
             );
             dispatchTransferFrom(
-                ZRX_PROXY_DATA,
+                zrxAssetData,
+                ZRX_PROXY_ID,
                 takerAddress,
                 rightOrder.feeRecipientAddress,
                 matchedFillResults.right.takerFeePaid
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
index 48a0c5552..1a556dfe2 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
@@ -93,7 +93,7 @@ contract MixinSignatureValidator is
         );
 
         // Pop last byte off of signature byte array.
-        SignatureType signatureType = SignatureType(uint8(popByte(signature)));
+        SignatureType signatureType = SignatureType(uint8(popLastByte(signature)));
 
         // Variables are not scoped in Solidity.
         uint8 v;
@@ -183,7 +183,7 @@ contract MixinSignatureValidator is
         // | 0x14 + x | 1      | Signature type is always "\x06" |
         } else if (signatureType == SignatureType.Validator) {
             // Pop last 20 bytes off of signature byte array.
-            address validator = popAddress(signature);
+            address validator = popLast20Bytes(signature);
             // Ensure signer has approved validator.
             if (!allowedValidators[signer][validator]) {
                 return false;
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol
index e09f80bcc..a7849f4cb 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol
@@ -19,7 +19,6 @@
 pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
-import "../../utils/LibBytes/LibBytes.sol";
 import "./libs/LibMath.sol";
 import "./libs/LibOrder.sol";
 import "./libs/LibFillResults.sol";
@@ -27,7 +26,6 @@ import "./libs/LibExchangeErrors.sol";
 import "./mixins/MExchangeCore.sol";
 
 contract MixinWrapperFunctions is
-    LibBytes,
     LibMath,
     LibFillResults,
     LibExchangeErrors,
@@ -174,6 +172,7 @@ contract MixinWrapperFunctions is
             mstore(add(dataAreaStart, mul(10, 0x20)), sub(dataAreaEnd, dataAreaStart))
 
             // Calculate length of <order.makerAssetData>
+            sourceOffset := mload(add(order, 0x140)) // makerAssetData
             arrayLenBytes := mload(sourceOffset)
             sourceOffset := add(sourceOffset, 0x20)
             arrayLenWords := div(add(arrayLenBytes, 0x1F), 0x20)
@@ -193,6 +192,7 @@ contract MixinWrapperFunctions is
             mstore(add(dataAreaStart, mul(11, 0x20)), sub(dataAreaEnd, dataAreaStart))
 
             // Calculate length of <order.takerAssetData>
+            sourceOffset := mload(add(order, 0x160)) // takerAssetData
             arrayLenBytes := mload(sourceOffset)
             sourceOffset := add(sourceOffset, 0x20)
             arrayLenWords := div(add(arrayLenBytes, 0x1F), 0x20)
@@ -333,14 +333,13 @@ contract MixinWrapperFunctions is
         public
         returns (FillResults memory totalFillResults)
     {
+        bytes memory takerAssetData = orders[0].takerAssetData;
+    
         for (uint256 i = 0; i < orders.length; i++) {
 
-            // Token being sold by taker must be the same for each order
-            // TODO: optimize by only using takerAssetData for first order.
-            require(
-                areBytesEqual(orders[i].takerAssetData, orders[0].takerAssetData),
-                ASSET_DATA_MISMATCH
-            );
+            // We assume that asset being sold by taker is the same for each order.
+            // Rather than passing this in as calldata, we use the takerAssetData from the first order in all later orders.
+            orders[i].takerAssetData = takerAssetData;
 
             // Calculate the remaining amount of takerAsset to sell
             uint256 remainingTakerAssetFillAmount = safeSub(takerAssetFillAmount, totalFillResults.takerAssetFilledAmount);
@@ -352,6 +351,14 @@ contract MixinWrapperFunctions is
                 signatures[i]
             );
 
+            // HACK: the proxyId is "popped" from the byte array before a fill is settled
+            // by subtracting from the length of the array. Since the popped byte is 
+            // still in memory, we can "unpop" it by incrementing the length of the byte array.
+            assembly {
+                let len := mload(takerAssetData)
+                mstore(takerAssetData, add(len, 1))
+            }
+
             // Update amounts filled and fees paid by maker and taker
             addFillResults(totalFillResults, singleFillResults);
 
@@ -377,14 +384,13 @@ contract MixinWrapperFunctions is
         public
         returns (FillResults memory totalFillResults)
     {
+        bytes memory takerAssetData = orders[0].takerAssetData;
+
         for (uint256 i = 0; i < orders.length; i++) {
 
-            // Token being sold by taker must be the same for each order
-            // TODO: optimize by only using takerAssetData for first order.
-            require(
-                areBytesEqual(orders[i].takerAssetData, orders[0].takerAssetData),
-                ASSET_DATA_MISMATCH
-            );
+            // We assume that asset being sold by taker is the same for each order.
+            // Rather than passing this in as calldata, we use the takerAssetData from the first order in all later orders.
+            orders[i].takerAssetData = takerAssetData;
 
             // Calculate the remaining amount of takerAsset to sell
             uint256 remainingTakerAssetFillAmount = safeSub(takerAssetFillAmount, totalFillResults.takerAssetFilledAmount);
@@ -420,14 +426,13 @@ contract MixinWrapperFunctions is
         public
         returns (FillResults memory totalFillResults)
     {
+        bytes memory makerAssetData = orders[0].makerAssetData;
+
         for (uint256 i = 0; i < orders.length; i++) {
 
-            // Token being bought by taker must be the same for each order
-            // TODO: optimize by only using makerAssetData for first order.
-            require(
-                areBytesEqual(orders[i].makerAssetData, orders[0].makerAssetData),
-                ASSET_DATA_MISMATCH
-            );
+            // We assume that asset being bought by taker is the same for each order.
+            // Rather than passing this in as calldata, we copy the makerAssetData from the first order onto all later orders.
+            orders[i].makerAssetData = makerAssetData;
 
             // Calculate the remaining amount of makerAsset to buy
             uint256 remainingMakerAssetFillAmount = safeSub(makerAssetFillAmount, totalFillResults.makerAssetFilledAmount);
@@ -447,6 +452,14 @@ contract MixinWrapperFunctions is
                 signatures[i]
             );
 
+            // HACK: the proxyId is "popped" from the byte array before a fill is settled
+            // by subtracting from the length of the array. Since the popped byte is 
+            // still in memory, we can "unpop" it by incrementing the length of the byte array.
+            assembly {
+                let len := mload(makerAssetData)
+                mstore(makerAssetData, add(len, 1))
+            }
+
             // Update amounts filled and fees paid by maker and taker
             addFillResults(totalFillResults, singleFillResults);
 
@@ -472,14 +485,13 @@ contract MixinWrapperFunctions is
         public
         returns (FillResults memory totalFillResults)
     {
+        bytes memory makerAssetData = orders[0].makerAssetData;
+
         for (uint256 i = 0; i < orders.length; i++) {
 
-            // Token being bought by taker must be the same for each order
-            // TODO: optimize by only using makerAssetData for first order.
-            require(
-                areBytesEqual(orders[i].makerAssetData, orders[0].makerAssetData),
-                ASSET_DATA_MISMATCH
-            );
+            // We assume that asset being bought by taker is the same for each order.
+            // Rather than passing this in as calldata, we copy the makerAssetData from the first order onto all later orders.
+            orders[i].makerAssetData = makerAssetData;
 
             // Calculate the remaining amount of makerAsset to buy
             uint256 remainingMakerAssetFillAmount = safeSub(makerAssetFillAmount, totalFillResults.makerAssetFilledAmount);
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol
index 2b4bbeec4..48dd0f8be 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol
@@ -25,7 +25,6 @@ contract LibExchangeErrors {
     string constant INVALID_TAKER = "INVALID_TAKER";                        // Invalid takerAddress.
     string constant INVALID_SENDER = "INVALID_SENDER";                      // Invalid `msg.sender`.
     string constant INVALID_ORDER_SIGNATURE = "INVALID_ORDER_SIGNATURE";    // Signature validation failed. 
-    string constant ASSET_DATA_MISMATCH = "ASSET_DATA_MISMATCH";            // Asset data must be the same for each order. 
     
     /// fillOrder validation errors ///
     string constant INVALID_TAKER_AMOUNT = "INVALID_TAKER_AMOUNT";          // takerAssetFillAmount cannot equal 0.
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
index 82eafb529..d16a830f4 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
@@ -34,11 +34,13 @@ contract MAssetProxyDispatcher is
 
     /// @dev Forwards arguments to assetProxy and calls `transferFrom`. Either succeeds or throws.
     /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param assetProxyId Id of assetProxy to dispach to.
     /// @param from Address to transfer token from.
     /// @param to Address to transfer token to.
     /// @param amount Amount of token to transfer.
     function dispatchTransferFrom(
         bytes memory assetData,
+        uint8 assetProxyId,
         address from,
         address to,
         uint256 amount
diff --git a/packages/contracts/src/contracts/current/test/TestAssetDataDecoders/TestAssetDataDecoders.sol b/packages/contracts/src/contracts/current/test/TestAssetDataDecoders/TestAssetDataDecoders.sol
index 2c6a8fdb0..5987291d2 100644
--- a/packages/contracts/src/contracts/current/test/TestAssetDataDecoders/TestAssetDataDecoders.sol
+++ b/packages/contracts/src/contracts/current/test/TestAssetDataDecoders/TestAssetDataDecoders.sol
@@ -23,26 +23,8 @@ import "../../protocol/AssetProxy/ERC20Proxy.sol";
 import "../../protocol/AssetProxy/ERC721Proxy.sol";
 
 contract TestAssetDataDecoders is
-    ERC20Proxy,
     ERC721Proxy
 {
-
-    /// @dev Decodes ERC20 Asset data.
-    /// @param assetData Encoded byte array.
-    /// @return proxyId Intended ERC20 proxy id.
-    /// @return token ERC20 token address.
-    function publicDecodeERC20Data(bytes memory assetData)
-        public
-        pure
-        returns (
-            uint8 proxyId,
-            address token
-        )
-    {
-        (proxyId, token) = decodeERC20AssetData(assetData);
-        return (proxyId, token);
-    }
-
     /// @dev Decodes ERC721 Asset data.
     /// @param assetData Encoded byte array.
     /// @return proxyId Intended ERC721 proxy id.
@@ -54,21 +36,18 @@ contract TestAssetDataDecoders is
         public
         pure
         returns (
-            uint8 proxyId,
             address token,
             uint256 tokenId,
             bytes memory receiverData
         )
     {
         (
-            proxyId,
             token,
             tokenId,
             receiverData
         ) = decodeERC721AssetData(assetData);
 
         return (
-            proxyId,
             token,
             tokenId,
             receiverData
diff --git a/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol
index 2ae69e0ef..d469a07f0 100644
--- a/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol
@@ -24,11 +24,12 @@ import "../../protocol/Exchange/MixinAssetProxyDispatcher.sol";
 contract TestAssetProxyDispatcher is MixinAssetProxyDispatcher {
     function publicDispatchTransferFrom(
         bytes memory assetData,
+        uint8 assetProxyId,
         address from,
         address to,
         uint256 amount)
         public
     {
-        dispatchTransferFrom(assetData, from, to, amount);
+        dispatchTransferFrom(assetData, assetProxyId, from, to, amount);
     }
 }
diff --git a/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol b/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol
index 22c84504c..6f1898acd 100644
--- a/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol
+++ b/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol
@@ -28,24 +28,24 @@ contract TestLibBytes is
     /// @dev Pops the last byte off of a byte array by modifying its length.
     /// @param b Byte array that will be modified.
     /// @return The byte that was popped off.
-    function publicPopByte(bytes memory b)
+    function publicPopLastByte(bytes memory b)
         public
         pure
         returns (bytes memory, bytes1 result)
     {
-        result = popByte(b);
+        result = popLastByte(b);
         return (b, result);
     }
 
     /// @dev Pops the last 20 bytes off of a byte array by modifying its length.
     /// @param b Byte array that will be modified.
     /// @return The 20 byte address that was popped off.
-    function publicPopAddress(bytes memory b)
+    function publicPopLast20Bytes(bytes memory b)
         public
         pure
         returns (bytes memory, address result)
     {
-        result = popAddress(b);
+        result = popLast20Bytes(b);
         return (b, result);
     }
 
@@ -62,6 +62,21 @@ contract TestLibBytes is
         return equal;
     }
 
+    /// @dev Performs a deep copy of a byte array onto another byte array of greater than or equal length.
+    /// @param dest Byte array that will be overwritten with source bytes.
+    /// @param source Byte array to copy onto dest bytes.
+    function publicDeepCopyBytes(
+        bytes memory dest,
+        bytes memory source
+    )
+        public
+        pure
+        returns (bytes memory)
+    {
+        deepCopyBytes(dest, source);
+        return dest;
+    }
+
     /// @dev Reads an address from a position in a byte array.
     /// @param b Byte array containing an address.
     /// @param index Index in byte array of address.
diff --git a/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol b/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
index d1d10476f..10d7ce41a 100644
--- a/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
+++ b/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
@@ -30,11 +30,12 @@ contract LibBytes is
     string constant GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED = "GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED";
     string constant GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED = "GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED";
     string constant GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED = "GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED";
+    string constant GREATER_OR_EQUAL_TO_SOURCE_BYTES_LENGTH_REQUIRED = "GREATER_OR_EQUAL_TO_SOURCE_BYTES_LENGTH_REQUIRED";
 
     /// @dev Pops the last byte off of a byte array by modifying its length.
     /// @param b Byte array that will be modified.
     /// @return The byte that was popped off.
-    function popByte(bytes memory b)
+    function popLastByte(bytes memory b)
         internal
         pure
         returns (bytes1 result)
@@ -58,7 +59,7 @@ contract LibBytes is
     /// @dev Pops the last 20 bytes off of a byte array by modifying its length.
     /// @param b Byte array that will be modified.
     /// @return The 20 byte address that was popped off.
-    function popAddress(bytes memory b)
+    function popLast20Bytes(bytes memory b)
         internal
         pure
         returns (address result)
@@ -79,41 +80,6 @@ contract LibBytes is
         return result;
     }
 
-    /// @dev Tests equality of two byte arrays.
-    /// @param lhs First byte array to compare.
-    /// @param rhs Second byte array to compare.
-    /// @return True if arrays are the same. False otherwise.
-    function areBytesEqual(
-        bytes memory lhs,
-        bytes memory rhs
-    )
-        internal
-        pure
-        returns (bool equal)
-    {
-        assembly {
-            // Get the number of words occupied by <lhs>
-            let lenFullWords := div(add(mload(lhs), 0x1F), 0x20)
-
-            // Add 1 to the number of words, to account for the length field
-            lenFullWords := add(lenFullWords, 0x1)
-
-            // Test equality word-by-word.
-            // Terminates early if there is a mismatch.
-            for {let i := 0} lt(i, lenFullWords) {i := add(i, 1)} {
-                let lhsWord := mload(add(lhs, mul(i, 0x20)))
-                let rhsWord := mload(add(rhs, mul(i, 0x20)))
-                equal := eq(lhsWord, rhsWord)
-                if eq(equal, 0) {
-                    // Break
-                    i := lenFullWords
-                }
-            }
-       }
-
-       return equal;
-    }
-
     /// @dev Reads an address from a position in a byte array.
     /// @param b Byte array containing an address.
     /// @param index Index in byte array of address.
@@ -346,4 +312,62 @@ contract LibBytes is
             input.length + 32               // +32 bytes to store <input> length
         );
     }
+
+    /// @dev Tests equality of two byte arrays.
+    /// @param lhs First byte array to compare.
+    /// @param rhs Second byte array to compare.
+    /// @return True if arrays are the same. False otherwise.
+    function areBytesEqual(
+        bytes memory lhs,
+        bytes memory rhs
+    )
+        internal
+        pure
+        returns (bool equal)
+    {
+        assembly {
+            // Get the number of words occupied by <lhs>
+            let lenFullWords := div(add(mload(lhs), 0x1F), 0x20)
+
+            // Add 1 to the number of words, to account for the length field
+            lenFullWords := add(lenFullWords, 0x1)
+
+            // Test equality word-by-word.
+            // Terminates early if there is a mismatch.
+            for {let i := 0} lt(i, lenFullWords) {i := add(i, 1)} {
+                let lhsWord := mload(add(lhs, mul(i, 0x20)))
+                let rhsWord := mload(add(rhs, mul(i, 0x20)))
+                equal := eq(lhsWord, rhsWord)
+                if eq(equal, 0) {
+                    // Break
+                    i := lenFullWords
+                }
+            }
+       }
+
+       return equal;
+    }
+
+    /// @dev Performs a deep copy of a byte array onto another byte array of greater than or equal length.
+    /// @param dest Byte array that will be overwritten with source bytes.
+    /// @param source Byte array to copy onto dest bytes.
+    function deepCopyBytes(
+        bytes memory dest,
+        bytes memory source
+    )
+        internal
+        pure
+    {
+        uint256 sourceLen = source.length;
+        // Dest length must be >= source length, or some bytes would not be copied.
+        require(
+            dest.length >= sourceLen,
+            GREATER_OR_EQUAL_TO_SOURCE_BYTES_LENGTH_REQUIRED
+        );
+        memCopy(
+            getMemAddress(dest) + 32,    // +32 to skip length of <dest>
+            getMemAddress(source) + 32,  // +32 to skip length of <source>
+            sourceLen
+        );
+    }
 }
diff --git a/packages/contracts/src/utils/constants.ts b/packages/contracts/src/utils/constants.ts
index af3f26d82..ec3c8fd36 100644
--- a/packages/contracts/src/utils/constants.ts
+++ b/packages/contracts/src/utils/constants.ts
@@ -24,10 +24,14 @@ export const constants = {
     LIB_BYTES_GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED: 'GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED',
     LIB_BYTES_GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED: 'GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED',
     LIB_BYTES_GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED: 'GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED',
+    LIB_BYTES_GREATER_OR_EQUAL_TO_SOURCE_BYTES_LENGTH_REQUIRED: 'GREATER_OR_EQUAL_TO_SOURCE_BYTES_LENGTH_REQUIRED',
     ERC20_INSUFFICIENT_BALANCE: 'Insufficient balance to complete transfer.',
     ERC20_INSUFFICIENT_ALLOWANCE: 'Insufficient allowance to complete transfer.',
     TESTRPC_NETWORK_ID: 50,
-    AWAIT_TRANSACTION_MINED_MS: 100,
+    // Note(albrow): In practice V8 and most other engines limit the minimum
+    // interval for setInterval to 10ms. We still set it to 0 here in order to
+    // ensure we always use the minimum interval.
+    AWAIT_TRANSACTION_MINED_MS: 0,
     MAX_ETHERTOKEN_WITHDRAW_GAS: 43000,
     MAX_TOKEN_TRANSFERFROM_GAS: 80000,
     MAX_TOKEN_APPROVE_GAS: 60000,
diff --git a/packages/contracts/src/utils/exchange_wrapper.ts b/packages/contracts/src/utils/exchange_wrapper.ts
index e74b91fe2..38dcb891a 100644
--- a/packages/contracts/src/utils/exchange_wrapper.ts
+++ b/packages/contracts/src/utils/exchange_wrapper.ts
@@ -165,14 +165,14 @@ export class ExchangeWrapper {
     public async marketBuyOrdersNoThrowAsync(
         orders: SignedOrder[],
         from: string,
-        opts: { makerAssetFillAmount: BigNumber },
+        opts: { makerAssetFillAmount: BigNumber; gas?: number },
     ): Promise<TransactionReceiptWithDecodedLogs> {
         const params = formatters.createMarketBuyOrders(orders, opts.makerAssetFillAmount);
         const txHash = await this._exchange.marketBuyOrdersNoThrow.sendTransactionAsync(
             params.orders,
             params.makerAssetFillAmount,
             params.signatures,
-            { from },
+            { from, gas: opts.gas },
         );
         const tx = await this._logDecoder.getTxWithDecodedLogsAsync(txHash);
         return tx;
diff --git a/packages/contracts/src/utils/formatters.ts b/packages/contracts/src/utils/formatters.ts
index 1035f2d7c..32e4787d6 100644
--- a/packages/contracts/src/utils/formatters.ts
+++ b/packages/contracts/src/utils/formatters.ts
@@ -2,6 +2,7 @@ import { SignedOrder } from '@0xproject/types';
 import { BigNumber } from '@0xproject/utils';
 import * as _ from 'lodash';
 
+import { constants } from './constants';
 import { orderUtils } from './order_utils';
 import { BatchCancelOrders, BatchFillOrders, MarketBuyOrders, MarketSellOrders } from './types';
 
@@ -28,8 +29,11 @@ export const formatters = {
             signatures: [],
             takerAssetFillAmount,
         };
-        _.forEach(signedOrders, signedOrder => {
+        _.forEach(signedOrders, (signedOrder, i) => {
             const orderWithoutExchangeAddress = orderUtils.getOrderWithoutExchangeAddress(signedOrder);
+            if (i !== 0) {
+                orderWithoutExchangeAddress.takerAssetData = constants.NULL_BYTES;
+            }
             marketSellOrders.orders.push(orderWithoutExchangeAddress);
             marketSellOrders.signatures.push(signedOrder.signature);
         });
@@ -41,8 +45,11 @@ export const formatters = {
             signatures: [],
             makerAssetFillAmount,
         };
-        _.forEach(signedOrders, signedOrder => {
+        _.forEach(signedOrders, (signedOrder, i) => {
             const orderWithoutExchangeAddress = orderUtils.getOrderWithoutExchangeAddress(signedOrder);
+            if (i !== 0) {
+                orderWithoutExchangeAddress.makerAssetData = constants.NULL_BYTES;
+            }
             marketBuyOrders.orders.push(orderWithoutExchangeAddress);
             marketBuyOrders.signatures.push(signedOrder.signature);
         });
diff --git a/packages/contracts/src/utils/order_utils.ts b/packages/contracts/src/utils/order_utils.ts
index 40643fa75..019f6e74b 100644
--- a/packages/contracts/src/utils/order_utils.ts
+++ b/packages/contracts/src/utils/order_utils.ts
@@ -1,6 +1,7 @@
 import { OrderWithoutExchangeAddress, SignedOrder } from '@0xproject/types';
 import { BigNumber } from '@0xproject/utils';
 
+import { constants } from './constants';
 import { CancelOrder, MatchOrder } from './types';
 
 export const orderUtils = {
@@ -50,6 +51,8 @@ export const orderUtils = {
             leftSignature: signedOrderLeft.signature,
             rightSignature: signedOrderRight.signature,
         };
+        fill.right.makerAssetData = constants.NULL_BYTES;
+        fill.right.takerAssetData = constants.NULL_BYTES;
         return fill;
     },
 };