Merge pull request #627 from 0xProject/feature/contracts/erc721SafeTransferFrom

On-Chain AssetData Decoding Lib + safeTransferFrom for ERC721 + Memcpy

27 files changed, 673 insertions, 140 deletions

diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
index 2c321e134..dd25bf41a 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
@@ -34,34 +34,30 @@ contract ERC20Proxy is
     uint8 constant PROXY_ID = 1;
 
     /// @dev Internal version of `transferFrom`.
-    /// @param assetMetadata Encoded byte array.
+    /// @param assetData Encoded byte array.
     /// @param from Address to transfer asset from.
     /// @param to Address to transfer asset to.
     /// @param amount Amount of asset to transfer.
     function transferFromInternal(
-        bytes memory assetMetadata,
+        bytes memory assetData,
         address from,
         address to,
         uint256 amount
     )
         internal
     {
-        // Data must be intended for this proxy.
-        uint256 length = assetMetadata.length;
+        // Decode asset data.
+        (
+            uint8 proxyId,
+            address token
+        ) = decodeERC20AssetData(assetData);
 
+        // Data must be intended for this proxy.
         require(
-            length == 21,
-            LENGTH_21_REQUIRED
-        );
-        // TODO: Is this too inflexible in the future?
-        require(
-            uint8(assetMetadata[length - 1]) == PROXY_ID,
+            proxyId == PROXY_ID,
             ASSET_PROXY_ID_MISMATCH
         );
 
-        // Decode metadata.
-        address token = readAddress(assetMetadata, 0);
-
         // Transfer tokens.
         bool success = IERC20Token(token).transferFrom(from, to, amount);
         require(
@@ -79,4 +75,30 @@ 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 07e01c774..25136133d 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
@@ -34,29 +34,30 @@ contract ERC721Proxy is
     uint8 constant PROXY_ID = 2;
 
     /// @dev Internal version of `transferFrom`.
-    /// @param assetMetadata Encoded byte array.
+    /// @param assetData Encoded byte array.
     /// @param from Address to transfer asset from.
     /// @param to Address to transfer asset to.
     /// @param amount Amount of asset to transfer.
     function transferFromInternal(
-        bytes memory assetMetadata,
+        bytes memory assetData,
         address from,
         address to,
         uint256 amount
     )
         internal
     {
-        // Data must be intended for this proxy.
-        uint256 length = assetMetadata.length;
+        // Decode asset data.
+        (
+            uint8 proxyId,
+            address token,
+            uint256 tokenId,
+            bytes memory receiverData
+        ) = decodeERC721AssetData(assetData);
 
-        require(
-            length == 53,
-            LENGTH_53_REQUIRED
-        );
 
-        // TODO: Is this too inflexible in the future?
+        // Data must be intended for this proxy.
         require(
-            uint8(assetMetadata[length - 1]) == PROXY_ID,
+            proxyId == PROXY_ID,
             ASSET_PROXY_ID_MISMATCH
         );
 
@@ -66,15 +67,13 @@ contract ERC721Proxy is
             INVALID_AMOUNT
         );
 
-        // Decode metadata
-        address token = readAddress(assetMetadata, 0);
-        uint256 tokenId = readUint256(assetMetadata, 20);
-
-        // Transfer token.
-        // Either succeeds or throws.
-        // @TODO: Call safeTransferFrom if there is additional
-        //        data stored in `assetMetadata`.
-        ERC721Token(token).transferFrom(from, to, tokenId);
+        // Transfer token. Saves gas by calling safeTransferFrom only
+        // when there is receiverData present. Either succeeds or throws.
+        if(receiverData.length > 0) {
+            ERC721Token(token).safeTransferFrom(from, to, tokenId, receiverData);
+        } else {
+            ERC721Token(token).transferFrom(from, to, tokenId);
+        }
     }
 
     /// @dev Gets the proxy id associated with the proxy address.
@@ -86,4 +85,44 @@ contract ERC721Proxy is
     {
         return PROXY_ID;
     }
+
+    /// @dev Decodes ERC721 Asset data.
+    /// @param assetData Encoded byte array.
+    /// @return proxyId Intended ERC721 proxy id.
+    /// @return token ERC721 token address.
+    /// @return tokenId ERC721 token id.
+    /// @return receiverData Additional data with no specific format, which
+    ///                      is passed to the receiving contract's onERC721Received.
+    function decodeERC721AssetData(bytes memory assetData)
+        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) {
+            receiverData = readBytes(assetData, 52);
+        }
+        proxyId = uint8(assetData[length - 1]);
+
+        return (
+            proxyId,
+            token,
+            tokenId,
+            receiverData
+        );
+    }
 }
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol
index 5fa33cbef..9032658e7 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol
@@ -28,12 +28,12 @@ contract MixinAssetProxy is
 {
 
     /// @dev Transfers assets. Either succeeds or throws.
-    /// @param assetMetadata Encoded byte array.
+    /// @param assetData Encoded byte array.
     /// @param from Address to transfer asset from.
     /// @param to Address to transfer asset to.
     /// @param amount Amount of asset to transfer.
     function transferFrom(
-        bytes assetMetadata,
+        bytes assetData,
         address from,
         address to,
         uint256 amount
@@ -42,7 +42,7 @@ contract MixinAssetProxy is
         onlyAuthorized
     {
         transferFromInternal(
-            assetMetadata,
+            assetData,
             from,
             to,
             amount
@@ -50,12 +50,12 @@ contract MixinAssetProxy is
     }
 
     /// @dev Makes multiple transfers of assets. Either succeeds or throws.
-    /// @param assetMetadata Array of byte arrays encoded for the respective asset proxy.
+    /// @param assetData Array of byte arrays encoded for the respective asset proxy.
     /// @param from Array of addresses to transfer assets from.
     /// @param to Array of addresses to transfer assets to.
     /// @param amounts Array of amounts of assets to transfer.
     function batchTransferFrom(
-        bytes[] memory assetMetadata,
+        bytes[] memory assetData,
         address[] memory from,
         address[] memory to,
         uint256[] memory amounts
@@ -63,9 +63,9 @@ contract MixinAssetProxy is
         public
         onlyAuthorized
     {
-        for (uint256 i = 0; i < assetMetadata.length; i++) {
+        for (uint256 i = 0; i < assetData.length; i++) {
             transferFromInternal(
-                assetMetadata[i],
+                assetData[i],
                 from[i],
                 to[i],
                 amounts[i]
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol
index 7e1848889..22f43b12f 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol
@@ -26,12 +26,12 @@ contract IAssetProxy is
 {
 
     /// @dev Transfers assets. Either succeeds or throws.
-    /// @param assetMetadata Byte array encoded for the respective asset proxy.
+    /// @param assetData Byte array encoded for the respective asset proxy.
     /// @param from Address to transfer asset from.
     /// @param to Address to transfer asset to.
     /// @param amount Amount of asset to transfer.
     function transferFrom(
-        bytes assetMetadata,
+        bytes assetData,
         address from,
         address to,
         uint256 amount
@@ -39,12 +39,12 @@ contract IAssetProxy is
         external;
     
     /// @dev Makes multiple transfers of assets. Either succeeds or throws.
-    /// @param assetMetadata Array of byte arrays encoded for the respective asset proxy.
+    /// @param assetData Array of byte arrays encoded for the respective asset proxy.
     /// @param from Array of addresses to transfer assets from.
     /// @param to Array of addresses to transfer assets to.
     /// @param amounts Array of amounts of assets to transfer.
     function batchTransferFrom(
-        bytes[] memory assetMetadata,
+        bytes[] memory assetData,
         address[] memory from,
         address[] memory to,
         uint256[] memory amounts
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 e0c7fc796..80180a0d9 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/libs/LibAssetProxyErrors.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/libs/LibAssetProxyErrors.sol
@@ -29,9 +29,9 @@ contract LibAssetProxyErrors {
     /// 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. 
+    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_53_REQUIRED = "LENGTH_53_REQUIRED";                    // Byte array must have a length of 53.
+    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/AssetProxy/mixins/MAssetProxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol
index de9d65a53..a52cb56f9 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol
@@ -26,12 +26,12 @@ contract MAssetProxy is
 {
 
     /// @dev Internal version of `transferFrom`.
-    /// @param assetMetadata Encoded byte array.
+    /// @param assetData Encoded byte array.
     /// @param from Address to transfer asset from.
     /// @param to Address to transfer asset to.
     /// @param amount Amount of asset to transfer.
     function transferFromInternal(
-        bytes memory assetMetadata,
+        bytes memory assetData,
         address from,
         address to,
         uint256 amount
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/Exchange.sol b/packages/contracts/src/contracts/current/protocol/Exchange/Exchange.sol
index b7b308069..51f99bafa 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/Exchange.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/Exchange.sol
@@ -40,11 +40,11 @@ contract Exchange is
     string constant public VERSION = "2.0.1-alpha";
 
     // Mixins are instantiated in the order they are inherited
-    constructor (bytes memory _zrxProxyData)
+    constructor (bytes memory _zrxAssetData)
         public
         MixinExchangeCore()
         MixinMatchOrders()
-        MixinSettlement(_zrxProxyData)
+        MixinSettlement(_zrxAssetData)
         MixinSignatureValidator()
         MixinTransactions()
         MixinAssetProxyDispatcher()
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
index 8f9342739..e77d81c06 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
@@ -80,12 +80,12 @@ contract MixinAssetProxyDispatcher is
     }
 
     /// @dev Forwards arguments to assetProxy and calls `transferFrom`. Either succeeds or throws.
-    /// @param assetMetadata Byte array encoded for the respective asset proxy.
+    /// @param assetData Byte array encoded for the respective asset proxy.
     /// @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 assetMetadata,
+        bytes memory assetData,
         address from,
         address to,
         uint256 amount
@@ -96,16 +96,16 @@ contract MixinAssetProxyDispatcher is
         if (amount > 0) {
 
             // Lookup asset proxy
-            uint256 length = assetMetadata.length;
+            uint256 length = assetData.length;
             require(
                 length > 0,
                 LENGTH_GREATER_THAN_0_REQUIRED
             );
-            uint8 assetProxyId = uint8(assetMetadata[length - 1]);
+            uint8 assetProxyId = uint8(assetData[length - 1]);
             IAssetProxy assetProxy = assetProxies[assetProxyId];
 
             // transferFrom will either succeed or throw.
-            assetProxy.transferFrom(assetMetadata, from, to, amount);
+            assetProxy.transferFrom(assetData, from, to, amount);
         }
     }
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol
index 646d3ed58..83e9dfdf4 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol
@@ -40,7 +40,7 @@ contract MixinSettlement is
     bytes internal ZRX_PROXY_DATA;
 
     /// @dev Gets the ZRX metadata used for fee transfers.
-    function zrxProxyData()
+    function zrxAssetData()
         external
         view
         returns (bytes memory)
@@ -48,13 +48,13 @@ contract MixinSettlement is
         return ZRX_PROXY_DATA;
     }
 
-    /// TODO: _zrxProxyData should be a constant in production.
+    /// TODO: _zrxAssetData should be a constant in production.
     /// @dev Constructor sets the metadata that will be used for paying ZRX fees.
-    /// @param _zrxProxyData Byte array containing ERC20 proxy id concatenated with address of ZRX.
-    constructor (bytes memory _zrxProxyData)
+    /// @param _zrxAssetData Byte array containing ERC20 proxy id concatenated with address of ZRX.
+    constructor (bytes memory _zrxAssetData)
         public
     {
-        ZRX_PROXY_DATA = _zrxProxyData;
+        ZRX_PROXY_DATA = _zrxAssetData;
     }
 
     /// @dev Settles an order by transferring assets between counterparties.
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol
index 0ad0710ce..e09f80bcc 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol
@@ -40,7 +40,8 @@ contract MixinWrapperFunctions is
     function fillOrKillOrder(
         LibOrder.Order memory order,
         uint256 takerAssetFillAmount,
-        bytes memory signature)
+        bytes memory signature
+    )
         public
         returns (FillResults memory fillResults)
     {
@@ -65,7 +66,8 @@ contract MixinWrapperFunctions is
     function fillOrderNoThrow(
         LibOrder.Order memory order,
         uint256 takerAssetFillAmount,
-        bytes memory signature)
+        bytes memory signature
+    )
         public
         returns (FillResults memory fillResults)
     {
@@ -91,12 +93,12 @@ contract MixinWrapperFunctions is
         // |          | 0x0E0  |         |   8.  takerFeeAmount                        |
         // |          | 0x100  |         |   9.  expirationTimeSeconds                 |
         // |          | 0x120  |         |   10. salt                                  |
-        // |          | 0x140  |         |   11. Offset to makerAssetProxyMetadata (*) |
-        // |          | 0x160  |         |   12. Offset to takerAssetProxyMetadata (*) |
-        // |          | 0x180  | 32      | makerAssetProxyMetadata Length              |
-        // |          | 0x1A0  | **      | makerAssetProxyMetadata Contents            |
-        // |          | 0x1C0  | 32      | takerAssetProxyMetadata Length              |
-        // |          | 0x1E0  | **      | takerAssetProxyMetadata Contents            |
+        // |          | 0x140  |         |   11. Offset to makerAssetData (*)          |
+        // |          | 0x160  |         |   12. Offset to takerAssetData (*)          |
+        // |          | 0x180  | 32      | makerAssetData Length                       |
+        // |          | 0x1A0  | **      | makerAssetData Contents                     |
+        // |          | 0x1C0  | 32      | takerAssetData Length                       |
+        // |          | 0x1E0  | **      | takerAssetData Contents                     |
         // |          | 0x200  | 32      | signature Length                            |
         // |          | 0x220  | **      | signature Contents                          |
 
@@ -163,43 +165,43 @@ contract MixinWrapperFunctions is
             mstore(add(dataAreaEnd, 0xE0), mload(add(sourceOffset, 0xE0)))      // takerFeeAmount
             mstore(add(dataAreaEnd, 0x100), mload(add(sourceOffset, 0x100)))    // expirationTimeSeconds
             mstore(add(dataAreaEnd, 0x120), mload(add(sourceOffset, 0x120)))    // salt
-            mstore(add(dataAreaEnd, 0x140), mload(add(sourceOffset, 0x140)))    // Offset to makerAssetProxyMetadata
-            mstore(add(dataAreaEnd, 0x160), mload(add(sourceOffset, 0x160)))    // Offset to takerAssetProxyMetadata
+            mstore(add(dataAreaEnd, 0x140), mload(add(sourceOffset, 0x140)))    // Offset to makerAssetData
+            mstore(add(dataAreaEnd, 0x160), mload(add(sourceOffset, 0x160)))    // Offset to takerAssetData
             dataAreaEnd := add(dataAreaEnd, 0x180)
             sourceOffset := add(sourceOffset, 0x180)
 
-            // Write offset to <order.makerAssetProxyMetadata>
+            // Write offset to <order.makerAssetData>
             mstore(add(dataAreaStart, mul(10, 0x20)), sub(dataAreaEnd, dataAreaStart))
 
-            // Calculate length of <order.makerAssetProxyMetadata>
+            // Calculate length of <order.makerAssetData>
             arrayLenBytes := mload(sourceOffset)
             sourceOffset := add(sourceOffset, 0x20)
             arrayLenWords := div(add(arrayLenBytes, 0x1F), 0x20)
 
-            // Write length of <order.makerAssetProxyMetadata>
+            // Write length of <order.makerAssetData>
             mstore(dataAreaEnd, arrayLenBytes)
             dataAreaEnd := add(dataAreaEnd, 0x20)
 
-            // Write contents of <order.makerAssetProxyMetadata>
+            // Write contents of <order.makerAssetData>
             for {let i := 0} lt(i, arrayLenWords) {i := add(i, 1)} {
                 mstore(dataAreaEnd, mload(sourceOffset))
                 dataAreaEnd := add(dataAreaEnd, 0x20)
                 sourceOffset := add(sourceOffset, 0x20)
             }
 
-            // Write offset to <order.takerAssetProxyMetadata>
+            // Write offset to <order.takerAssetData>
             mstore(add(dataAreaStart, mul(11, 0x20)), sub(dataAreaEnd, dataAreaStart))
 
-            // Calculate length of <order.takerAssetProxyMetadata>
+            // Calculate length of <order.takerAssetData>
             arrayLenBytes := mload(sourceOffset)
             sourceOffset := add(sourceOffset, 0x20)
             arrayLenWords := div(add(arrayLenBytes, 0x1F), 0x20)
 
-            // Write length of <order.takerAssetProxyMetadata>
+            // Write length of <order.takerAssetData>
             mstore(dataAreaEnd, arrayLenBytes)
             dataAreaEnd := add(dataAreaEnd, 0x20)
 
-            // Write contents of  <order.takerAssetProxyMetadata>
+            // Write contents of  <order.takerAssetData>
             for {let i := 0} lt(i, arrayLenWords) {i := add(i, 1)} {
                 mstore(dataAreaEnd, mload(sourceOffset))
                 dataAreaEnd := add(dataAreaEnd, 0x20)
@@ -264,7 +266,8 @@ contract MixinWrapperFunctions is
     function batchFillOrders(
         LibOrder.Order[] memory orders,
         uint256[] memory takerAssetFillAmounts,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public
     {
         for (uint256 i = 0; i < orders.length; i++) {
@@ -283,7 +286,8 @@ contract MixinWrapperFunctions is
     function batchFillOrKillOrders(
         LibOrder.Order[] memory orders,
         uint256[] memory takerAssetFillAmounts,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public
     {
         for (uint256 i = 0; i < orders.length; i++) {
@@ -303,7 +307,8 @@ contract MixinWrapperFunctions is
     function batchFillOrdersNoThrow(
         LibOrder.Order[] memory orders,
         uint256[] memory takerAssetFillAmounts,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public
     {
         for (uint256 i = 0; i < orders.length; i++) {
@@ -323,7 +328,8 @@ contract MixinWrapperFunctions is
     function marketSellOrders(
         LibOrder.Order[] memory orders,
         uint256 takerAssetFillAmount,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public
         returns (FillResults memory totalFillResults)
     {
@@ -366,7 +372,8 @@ contract MixinWrapperFunctions is
     function marketSellOrdersNoThrow(
         LibOrder.Order[] memory orders,
         uint256 takerAssetFillAmount,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public
         returns (FillResults memory totalFillResults)
     {
@@ -408,7 +415,8 @@ contract MixinWrapperFunctions is
     function marketBuyOrders(
         LibOrder.Order[] memory orders,
         uint256 makerAssetFillAmount,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public
         returns (FillResults memory totalFillResults)
     {
@@ -459,7 +467,8 @@ contract MixinWrapperFunctions is
     function marketBuyOrdersNoThrow(
         LibOrder.Order[] memory orders,
         uint256 makerAssetFillAmount,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public
         returns (FillResults memory totalFillResults)
     {
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IAssetProxyDispatcher.sol
index 3ce5ef157..2c331dc34 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IAssetProxyDispatcher.sol
@@ -28,7 +28,8 @@ contract IAssetProxyDispatcher {
     function registerAssetProxy(
         uint8 assetProxyId,
         address newAssetProxy,
-        address oldAssetProxy)
+        address oldAssetProxy
+    )
         external;
 
     /// @dev Gets an asset proxy.
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ITransactions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ITransactions.sol
index d973bf001..2f9a5bc7c 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ITransactions.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/ITransactions.sol
@@ -28,6 +28,7 @@ contract ITransactions {
         uint256 salt,
         address signer,
         bytes data,
-        bytes signature)
+        bytes signature
+    )
         external;
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWrapperFunctions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWrapperFunctions.sol
index 8682b394a..acd4f359c 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWrapperFunctions.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IWrapperFunctions.sol
@@ -33,7 +33,8 @@ contract IWrapperFunctions is
     function fillOrKillOrder(
         LibOrder.Order memory order,
         uint256 takerAssetFillAmount,
-        bytes memory signature)
+        bytes memory signature
+    )
         public
         returns (LibFillResults.FillResults memory fillResults);
 
@@ -46,7 +47,8 @@ contract IWrapperFunctions is
     function fillOrderNoThrow(
         LibOrder.Order memory order,
         uint256 takerAssetFillAmount,
-        bytes memory signature)
+        bytes memory signature
+    )
         public
         returns (LibFillResults.FillResults memory fillResults);
 
@@ -57,7 +59,8 @@ contract IWrapperFunctions is
     function batchFillOrders(
         LibOrder.Order[] memory orders,
         uint256[] memory takerAssetFillAmounts,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public;
 
     /// @dev Synchronously executes multiple calls of fillOrKill.
@@ -67,7 +70,8 @@ contract IWrapperFunctions is
     function batchFillOrKillOrders(
         LibOrder.Order[] memory orders,
         uint256[] memory takerAssetFillAmounts,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public;
 
     /// @dev Fills an order with specified parameters and ECDSA signature.
@@ -78,7 +82,8 @@ contract IWrapperFunctions is
     function batchFillOrdersNoThrow(
         LibOrder.Order[] memory orders,
         uint256[] memory takerAssetFillAmounts,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public;
 
     /// @dev Synchronously executes multiple calls of fillOrder until total amount of takerAsset is sold by taker.
@@ -89,7 +94,8 @@ contract IWrapperFunctions is
     function marketSellOrders(
         LibOrder.Order[] memory orders,
         uint256 takerAssetFillAmount,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public
         returns (LibFillResults.FillResults memory totalFillResults);
 
@@ -102,7 +108,8 @@ contract IWrapperFunctions is
     function marketSellOrdersNoThrow(
         LibOrder.Order[] memory orders,
         uint256 takerAssetFillAmount,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public
         returns (LibFillResults.FillResults memory totalFillResults);
 
@@ -114,7 +121,8 @@ contract IWrapperFunctions is
     function marketBuyOrders(
         LibOrder.Order[] memory orders,
         uint256 makerAssetFillAmount,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public
         returns (LibFillResults.FillResults memory totalFillResults);
 
@@ -127,7 +135,8 @@ contract IWrapperFunctions is
     function marketBuyOrdersNoThrow(
         LibOrder.Order[] memory orders,
         uint256 makerAssetFillAmount,
-        bytes[] memory signatures)
+        bytes[] memory signatures
+    )
         public
         returns (LibFillResults.FillResults memory totalFillResults);
 
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 87c5f6361..82eafb529 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
@@ -33,12 +33,12 @@ contract MAssetProxyDispatcher is
     );
 
     /// @dev Forwards arguments to assetProxy and calls `transferFrom`. Either succeeds or throws.
-    /// @param assetMetadata Byte array encoded for the respective asset proxy.
+    /// @param assetData Byte array encoded for the respective asset proxy.
     /// @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 assetMetadata,
+        bytes memory assetData,
         address from,
         address to,
         uint256 amount
diff --git a/packages/contracts/src/contracts/current/test/DummyERC20Token/DummyERC20Token.sol b/packages/contracts/src/contracts/current/test/DummyERC20Token/DummyERC20Token.sol
index 0c7b18c0c..b2fe2df06 100644
--- a/packages/contracts/src/contracts/current/test/DummyERC20Token/DummyERC20Token.sol
+++ b/packages/contracts/src/contracts/current/test/DummyERC20Token/DummyERC20Token.sol
@@ -31,7 +31,8 @@ contract DummyERC20Token is Mintable, Ownable {
         string _name,
         string _symbol,
         uint256 _decimals,
-        uint256 _totalSupply)
+        uint256 _totalSupply
+    )
         public
     {
         name = _name;
diff --git a/packages/contracts/src/contracts/current/test/DummyERC721Receiver/DummyERC721Receiver.sol b/packages/contracts/src/contracts/current/test/DummyERC721Receiver/DummyERC721Receiver.sol
new file mode 100644
index 000000000..c584d0b54
--- /dev/null
+++ b/packages/contracts/src/contracts/current/test/DummyERC721Receiver/DummyERC721Receiver.sol
@@ -0,0 +1,63 @@
+/*
+The MIT License (MIT)
+
+Copyright (c) 2016 Smart Contract Solutions, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+pragma solidity ^0.4.24;
+
+import "../../tokens/ERC721Token/IERC721Receiver.sol";
+
+contract DummyERC721Receiver is
+    IERC721Receiver
+{
+
+    event TokenReceived(
+        address from,
+        uint256 tokenId,
+        bytes data
+    );
+
+    /**
+    * @notice Handle the receipt of an NFT
+    * @dev The ERC721 smart contract calls this function on the recipient
+    *  after a `safetransfer`. This function MAY throw to revert and reject the
+    *  transfer. This function MUST use 50,000 gas or less. Return of other
+    *  than the magic value MUST result in the transaction being reverted.
+    *  Note: the contract address is always the message sender.
+    * @param _from The sending address
+    * @param _tokenId The NFT identifier which is being transfered
+    * @param _data Additional data with no specified format
+    * @return `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`
+    */
+    function onERC721Received(
+        address _from,
+        uint256 _tokenId,
+        bytes _data
+    )
+        public
+        returns (bytes4)
+    {
+        emit TokenReceived(_from, _tokenId, _data);
+        return ERC721_RECEIVED;
+    }
+}
diff --git a/packages/contracts/src/contracts/current/test/DummyERC721Token/DummyERC721Token.sol b/packages/contracts/src/contracts/current/test/DummyERC721Token/DummyERC721Token.sol
index 369a2950d..5503eb2f2 100644
--- a/packages/contracts/src/contracts/current/test/DummyERC721Token/DummyERC721Token.sol
+++ b/packages/contracts/src/contracts/current/test/DummyERC721Token/DummyERC721Token.sol
@@ -34,7 +34,8 @@ contract DummyERC721Token is
     */
     constructor (
         string name,
-        string symbol)
+        string symbol
+    )
         public
         ERC721Token(name, symbol)
     {}
diff --git a/packages/contracts/src/contracts/current/test/TestAssetDataDecoders/TestAssetDataDecoders.sol b/packages/contracts/src/contracts/current/test/TestAssetDataDecoders/TestAssetDataDecoders.sol
new file mode 100644
index 000000000..2c6a8fdb0
--- /dev/null
+++ b/packages/contracts/src/contracts/current/test/TestAssetDataDecoders/TestAssetDataDecoders.sol
@@ -0,0 +1,77 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.24;
+pragma experimental ABIEncoderV2;
+
+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.
+    /// @return token ERC721 token address.
+    /// @return tokenId ERC721 token id.
+    /// @return receiverData Additional data with no specific format, which
+    ///                      is passed to the receiving contract's onERC721Received.
+    function publicDecodeERC721Data(bytes memory assetData)
+        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 11ca0617d..2ae69e0ef 100644
--- a/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol
@@ -23,12 +23,12 @@ import "../../protocol/Exchange/MixinAssetProxyDispatcher.sol";
 
 contract TestAssetProxyDispatcher is MixinAssetProxyDispatcher {
     function publicDispatchTransferFrom(
-        bytes memory assetMetadata,
+        bytes memory assetData,
         address from,
         address to,
         uint256 amount)
         public
     {
-        dispatchTransferFrom(assetMetadata, from, to, amount);
+        dispatchTransferFrom(assetData, 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 69554605d..22c84504c 100644
--- a/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol
+++ b/packages/contracts/src/contracts/current/test/TestLibBytes/TestLibBytes.sol
@@ -68,7 +68,8 @@ contract TestLibBytes is
     /// @return address from byte array.
     function publicReadAddress(
         bytes memory b,
-        uint256 index)
+        uint256 index
+    )
         public
         pure
         returns (address result)
@@ -84,7 +85,8 @@ contract TestLibBytes is
     function publicWriteAddress(
         bytes memory b,
         uint256 index,
-        address input)
+        address input
+    )
         public
         pure
         returns (bytes memory)
@@ -99,7 +101,8 @@ contract TestLibBytes is
     /// @return bytes32 value from byte array.
     function publicReadBytes32(
         bytes memory b,
-        uint256 index)
+        uint256 index
+    )
         public
         pure
         returns (bytes32 result)
@@ -115,7 +118,8 @@ contract TestLibBytes is
     function publicWriteBytes32(
         bytes memory b,
         uint256 index,
-        bytes32 input)
+        bytes32 input
+    )
         public
         pure
         returns (bytes memory)
@@ -130,7 +134,8 @@ contract TestLibBytes is
     /// @return uint256 value from byte array.
     function publicReadUint256(
         bytes memory b,
-        uint256 index)
+        uint256 index
+    )
         public
         pure
         returns (uint256 result)
@@ -146,7 +151,8 @@ contract TestLibBytes is
     function publicWriteUint256(
         bytes memory b,
         uint256 index,
-        uint256 input)
+        uint256 input
+    )
         public
         pure
         returns (bytes memory)
@@ -166,4 +172,38 @@ contract TestLibBytes is
         result = readFirst4(b);
         return result;
     }
+
+    /// @dev Reads nested bytes from a specific position.
+    /// @param b Byte array containing nested bytes.
+    /// @param index Index of nested bytes.
+    /// @return result Nested bytes.
+    function publicReadBytes(
+        bytes memory b,
+        uint256 index
+    )
+        public
+        pure
+        returns (bytes memory result)
+    {
+        result = readBytes(b, index);
+        return result;
+    }
+
+    /// @dev Inserts bytes at a specific position in a byte array.
+    /// @param b Byte array to insert <input> into.
+    /// @param index Index in byte array of <input>.
+    /// @param input bytes to insert.
+    /// @return b Updated input byte array
+    function publicWriteBytes(
+        bytes memory b,
+        uint256 index,
+        bytes memory input
+    )
+        public
+        pure
+        returns (bytes memory)
+    {
+        writeBytes(b, index, input);
+        return b;
+    }
 }
diff --git a/packages/contracts/src/contracts/current/test/TestLibMem/TestLibMem.sol b/packages/contracts/src/contracts/current/test/TestLibMem/TestLibMem.sol
new file mode 100644
index 000000000..b7e2e06b8
--- /dev/null
+++ b/packages/contracts/src/contracts/current/test/TestLibMem/TestLibMem.sol
@@ -0,0 +1,56 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.24;
+
+import "../../utils/LibMem/LibMem.sol";
+
+contract TestLibMem is
+    LibMem
+{
+
+    /// @dev Copies a block of memory from one location to another.
+    /// @param mem Memory contents we want to apply memCopy to
+    /// @param dest Destination offset into <mem>.
+    /// @param source Source offset into <mem>.
+    /// @param length Length of bytes to copy from <source> to <dest>
+    /// @return mem Memory contents after calling memCopy.
+    function testMemcpy(
+        bytes mem,
+        uint256 dest,
+        uint256 source,
+        uint256 length
+    )
+        public // not external, we need input in memory
+        pure
+        returns (bytes)
+    {
+        // Sanity check. Overflows are not checked.
+        require(source + length <= mem.length);
+        require(dest + length <= mem.length);
+
+        // Get pointer to memory contents
+        uint256 offset = getMemAddress(mem) + 32;
+
+        // Execute memCopy adjusted for memory array location
+        memCopy(offset + dest, offset + source, length);
+
+        // Return modified memory contents
+        return mem;
+    }
+}
diff --git a/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol b/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
index df2221c93..d1d10476f 100644
--- a/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
+++ b/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
@@ -18,14 +18,18 @@
 
 pragma solidity ^0.4.24;
 
-contract LibBytes {
+import "../LibMem/LibMem.sol";
+
+contract LibBytes is
+    LibMem
+{
 
     // Revert reasons
-    string constant GT_ZERO_LENGTH_REQUIRED = "Length must be greater than 0.";
-    string constant GTE_4_LENGTH_REQUIRED = "Length must be greater than or equal to 4.";
-    string constant GTE_20_LENGTH_REQUIRED = "Length must be greater than or equal to 20.";
-    string constant GTE_32_LENGTH_REQUIRED = "Length must be greater than or equal to 32.";
-    string constant INDEX_OUT_OF_BOUNDS = "Specified array index is out of bounds.";
+    string constant GREATER_THAN_ZERO_LENGTH_REQUIRED = "GREATER_THAN_ZERO_LENGTH_REQUIRED";
+    string constant GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED = "GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED";
+    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";
 
     /// @dev Pops the last byte off of a byte array by modifying its length.
     /// @param b Byte array that will be modified.
@@ -37,12 +41,12 @@ contract LibBytes {
     {
         require(
             b.length > 0,
-            GT_ZERO_LENGTH_REQUIRED
+            GREATER_THAN_ZERO_LENGTH_REQUIRED
         );
 
         // Store last byte.
         result = b[b.length - 1];
-        
+
         assembly {
             // Decrement length of byte array.
             let newLen := sub(mload(b), 1)
@@ -61,7 +65,7 @@ contract LibBytes {
     {
         require(
             b.length >= 20,
-            GTE_20_LENGTH_REQUIRED
+            GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED
         );
 
         // Store last 20 bytes.
@@ -124,8 +128,8 @@ contract LibBytes {
     {
         require(
             b.length >= index + 20,  // 20 is length of address
-            GTE_20_LENGTH_REQUIRED
-        ); 
+            GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED
+        );
 
         // Add offset to index:
         // 1. Arrays are prefixed by 32-byte length parameter (add 32 to index)
@@ -156,8 +160,8 @@ contract LibBytes {
     {
         require(
             b.length >= index + 20,  // 20 is length of address
-            GTE_20_LENGTH_REQUIRED
-        ); 
+            GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED
+        );
 
         // Add offset to index:
         // 1. Arrays are prefixed by 32-byte length parameter (add 32 to index)
@@ -195,7 +199,7 @@ contract LibBytes {
     {
         require(
             b.length >= index + 32,
-            GTE_32_LENGTH_REQUIRED
+            GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED
         );
 
         // Arrays are prefixed by a 256 bit length parameter
@@ -222,7 +226,7 @@ contract LibBytes {
     {
         require(
             b.length >= index + 32,
-            GTE_32_LENGTH_REQUIRED
+            GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED
         );
 
         // Arrays are prefixed by a 256 bit length parameter
@@ -274,11 +278,72 @@ contract LibBytes {
     {
         require(
             b.length >= 4,
-            GTE_4_LENGTH_REQUIRED
+            GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED
         );
         assembly {
             result := mload(add(b, 32))
         }
         return result;
     }
+
+    /// @dev Reads nested bytes from a specific position.
+    /// @param b Byte array containing nested bytes.
+    /// @param index Index of nested bytes.
+    /// @return result Nested bytes.
+    function readBytes(
+        bytes memory b,
+        uint256 index
+    )
+        internal
+        pure
+        returns (bytes memory result)
+    {
+        // Read length of nested bytes
+        uint256 nestedBytesLength = readUint256(b, index);
+        index += 32;
+
+        // Assert length of <b> is valid, given
+        // length of nested bytes
+        require(
+            b.length >= index + nestedBytesLength,
+            GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED
+        );
+
+        // Allocate memory and copy value to result
+        result = new bytes(nestedBytesLength);
+        memCopy(
+            getMemAddress(result) + 32, // +32 skips array length
+            getMemAddress(b) + index + 32,
+            nestedBytesLength
+        );
+
+        return result;
+    }
+
+    /// @dev Inserts bytes at a specific position in a byte array.
+    /// @param b Byte array to insert <input> into.
+    /// @param index Index in byte array of <input>.
+    /// @param input bytes to insert.
+    function writeBytes(
+        bytes memory b,
+        uint256 index,
+        bytes memory input
+    )
+        internal
+        pure
+    {
+        // Assert length of <b> is valid, given
+        // length of input
+        require(
+            b.length >= index + 32 /* 32 bytes to store length */ + input.length,
+            GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED
+        );
+
+        // Copy <input> into <b>
+        memCopy(
+            getMemAddress(b) + 32 + index,  // +32 to skip length of <b>
+            getMemAddress(input),           // includes length of <input>
+            input.length + 32               // +32 bytes to store <input> length
+        );
+    }
 }
diff --git a/packages/contracts/src/contracts/current/utils/LibMem/LibMem.sol b/packages/contracts/src/contracts/current/utils/LibMem/LibMem.sol
new file mode 100644
index 000000000..6afb9973a
--- /dev/null
+++ b/packages/contracts/src/contracts/current/utils/LibMem/LibMem.sol
@@ -0,0 +1,140 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.4.24;
+
+contract LibMem
+{
+
+    /// @dev Gets the memory address for a byte array.
+    /// @param input Byte array to lookup.
+    /// @return memoryAddress Memory address of byte array.
+    function getMemAddress(bytes memory input)
+        internal
+        pure
+        returns (uint256 memoryAddress)
+    {
+        assembly {
+            memoryAddress := input
+        }
+        return memoryAddress;
+    }
+
+    /// @dev Copies `length` bytes from memory location `source` to `dest`.
+    /// @param dest memory address to copy bytes to.
+    /// @param source memory address to copy bytes from.
+    /// @param length number of bytes to copy.
+    function memCopy(
+        uint256 dest,
+        uint256 source,
+        uint256 length
+    )
+        internal
+        pure
+    {
+        if (length < 32) {
+            // Handle a partial word by reading destination and masking
+            // off the bits we are interested in.
+            // This correctly handles overlap, zero lengths and source == dest
+            assembly {
+                let mask := sub(exp(256, sub(32, length)), 1)
+                let s := and(mload(source), not(mask))
+                let d := and(mload(dest), mask)
+                mstore(dest, or(s, d))
+            }
+        } else {
+            // Skip the O(length) loop when source == dest.
+            if (source == dest) {
+                return;
+            }
+
+            // For large copies we copy whole words at a time. The final
+            // word is aligned to the end of the range (instead of after the
+            // previous) to handle partial words. So a copy will look like this:
+            //
+            //  ####
+            //      ####
+            //          ####
+            //            ####
+            //
+            // We handle overlap in the source and destination range by
+            // changing the copying direction. This prevents us from
+            // overwriting parts of source that we still need to copy.
+            //
+            // This correctly handles source == dest
+            //
+            if (source > dest) {
+                assembly {
+                    // Record the total number of full words to copy
+                    let nWords := div(length, 32)
+
+                    // We subtract 32 from `sEnd` and `dEnd` because it
+                    // is easier to compare with in the loop, and these
+                    // are also the addresses we need for copying the
+                    // last bytes.
+                    length := sub(length, 32)
+                    let sEnd := add(source, length)
+                    let dEnd := add(dest, length)
+
+                    // Remember the last 32 bytes of source
+                    // This needs to be done here and not after the loop
+                    // because we may have overwritten the last bytes in
+                    // source already due to overlap.
+                    let last := mload(sEnd)
+
+                    // Copy whole words front to back
+                    for {let i := 0} lt(i, nWords) {i := add(i, 1)} {
+                        mstore(dest, mload(source))
+                        source := add(source, 32)
+                        dest := add(dest, 32)
+                    }
+
+                    // Write the last 32 bytes
+                    mstore(dEnd, last)
+                }
+            } else {
+                assembly {
+                    // Record the total number of full words to copy
+                    let nWords := div(length, 32)
+
+                    // We subtract 32 from `sEnd` and `dEnd` because those
+                    // are the starting points when copying a word at the end.
+                    length := sub(length, 32)
+                    let sEnd := add(source, length)
+                    let dEnd := add(dest, length)
+
+                    // Remember the first 32 bytes of source
+                    // This needs to be done here and not after the loop
+                    // because we may have overwritten the first bytes in
+                    // source already due to overlap.
+                    let first := mload(source)
+
+                    // Copy whole words back to front
+                    for {let i := 0} lt(i, nWords) {i := add(i, 1)} {
+                        mstore(dEnd, mload(sEnd))
+                        sEnd := sub(sEnd, 32)
+                        dEnd := sub(dEnd, 32)
+                    }
+
+                    // Write the first 32 bytes
+                    mstore(dest, first)
+                }
+            }
+        }
+    }
+}
diff --git a/packages/contracts/src/utils/artifacts.ts b/packages/contracts/src/utils/artifacts.ts
index 357c66a0a..bf7221d6d 100644
--- a/packages/contracts/src/utils/artifacts.ts
+++ b/packages/contracts/src/utils/artifacts.ts
@@ -2,6 +2,7 @@ import { ContractArtifact } from '@0xproject/sol-compiler';
 
 import * as AssetProxyOwner from '../artifacts/AssetProxyOwner.json';
 import * as DummyERC20Token from '../artifacts/DummyERC20Token.json';
+import * as DummyERC721Receiver from '../artifacts/DummyERC721Receiver.json';
 import * as DummyERC721Token from '../artifacts/DummyERC721Token.json';
 import * as ERC20Proxy from '../artifacts/ERC20Proxy.json';
 import * as ERC721Proxy from '../artifacts/ERC721Proxy.json';
@@ -9,8 +10,10 @@ import * as Exchange from '../artifacts/Exchange.json';
 import * as MixinAuthorizable from '../artifacts/MixinAuthorizable.json';
 import * as MultiSigWallet from '../artifacts/MultiSigWallet.json';
 import * as MultiSigWalletWithTimeLock from '../artifacts/MultiSigWalletWithTimeLock.json';
+import * as TestAssetDataDecoders from '../artifacts/TestAssetDataDecoders.json';
 import * as TestAssetProxyDispatcher from '../artifacts/TestAssetProxyDispatcher.json';
 import * as TestLibBytes from '../artifacts/TestLibBytes.json';
+import * as TestLibMem from '../artifacts/TestLibMem.json';
 import * as TestLibs from '../artifacts/TestLibs.json';
 import * as TestSignatureValidator from '../artifacts/TestSignatureValidator.json';
 import * as TokenRegistry from '../artifacts/TokenRegistry.json';
@@ -21,6 +24,7 @@ import * as ZRX from '../artifacts/ZRXToken.json';
 export const artifacts = {
     AssetProxyOwner: (AssetProxyOwner as any) as ContractArtifact,
     DummyERC20Token: (DummyERC20Token as any) as ContractArtifact,
+    DummyERC721Receiver: (DummyERC721Receiver as any) as ContractArtifact,
     DummyERC721Token: (DummyERC721Token as any) as ContractArtifact,
     ERC20Proxy: (ERC20Proxy as any) as ContractArtifact,
     ERC721Proxy: (ERC721Proxy as any) as ContractArtifact,
@@ -30,7 +34,9 @@ export const artifacts = {
     MultiSigWallet: (MultiSigWallet as any) as ContractArtifact,
     MultiSigWalletWithTimeLock: (MultiSigWalletWithTimeLock as any) as ContractArtifact,
     TestAssetProxyDispatcher: (TestAssetProxyDispatcher as any) as ContractArtifact,
+    TestAssetDataDecoders: (TestAssetDataDecoders as any) as ContractArtifact,
     TestLibBytes: (TestLibBytes as any) as ContractArtifact,
+    TestLibMem: (TestLibMem as any) as ContractArtifact,
     TestLibs: (TestLibs as any) as ContractArtifact,
     TestSignatureValidator: (TestSignatureValidator as any) as ContractArtifact,
     TokenRegistry: (TokenRegistry as any) as ContractArtifact,
diff --git a/packages/contracts/src/utils/constants.ts b/packages/contracts/src/utils/constants.ts
index fa2a4af3c..af3f26d82 100644
--- a/packages/contracts/src/utils/constants.ts
+++ b/packages/contracts/src/utils/constants.ts
@@ -19,11 +19,11 @@ const TESTRPC_PRIVATE_KEYS_STRINGS = [
 export const constants = {
     INVALID_OPCODE: 'invalid opcode',
     REVERT: 'revert',
-    LIB_BYTES_GT_ZERO_LENGTH_REQUIRED: 'Length must be greater than 0.',
-    LIB_BYTES_GTE_4_LENGTH_REQUIRED: 'Length must be greater than or equal to 4.',
-    LIB_BYTES_GTE_20_LENGTH_REQUIRED: 'Length must be greater than or equal to 20.',
-    LIB_BYTES_GTE_32_LENGTH_REQUIRED: 'Length must be greater than or equal to 32.',
-    LIB_BYTES_INDEX_OUT_OF_BOUNDS: 'Specified array index is out of bounds.',
+    LIB_BYTES_GREATER_THAN_ZERO_LENGTH_REQUIRED: 'GREATER_THAN_ZERO_LENGTH_REQUIRED',
+    LIB_BYTES_GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED: 'GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED',
+    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',
     ERC20_INSUFFICIENT_BALANCE: 'Insufficient balance to complete transfer.',
     ERC20_INSUFFICIENT_ALLOWANCE: 'Insufficient allowance to complete transfer.',
     TESTRPC_NETWORK_ID: 50,
diff --git a/packages/contracts/src/utils/match_order_tester.ts b/packages/contracts/src/utils/match_order_tester.ts
index f4f7f965b..fbb1b99db 100644
--- a/packages/contracts/src/utils/match_order_tester.ts
+++ b/packages/contracts/src/utils/match_order_tester.ts
@@ -237,11 +237,11 @@ export class MatchOrderTester {
         const expectedNewERC20BalancesByOwner = _.cloneDeep(erc20BalancesByOwner);
         const expectedNewERC721TokenIdsByOwner = _.cloneDeep(erc721TokenIdsByOwner);
         // Left Maker Asset (Right Taker Asset)
-        const makerAssetProxyIdLeft = assetProxyUtils.decodeProxyDataId(signedOrderLeft.makerAssetData);
+        const makerAssetProxyIdLeft = assetProxyUtils.decodeAssetDataId(signedOrderLeft.makerAssetData);
         if (makerAssetProxyIdLeft === AssetProxyId.ERC20) {
             // Decode asset data
-            const erc20ProxyData = assetProxyUtils.decodeERC20ProxyData(signedOrderLeft.makerAssetData);
-            const makerAssetAddressLeft = erc20ProxyData.tokenAddress;
+            const erc20AssetData = assetProxyUtils.decodeERC20AssetData(signedOrderLeft.makerAssetData);
+            const makerAssetAddressLeft = erc20AssetData.tokenAddress;
             const takerAssetAddressRight = makerAssetAddressLeft;
             // Left Maker
             expectedNewERC20BalancesByOwner[makerAddressLeft][makerAssetAddressLeft] = expectedNewERC20BalancesByOwner[
@@ -259,9 +259,9 @@ export class MatchOrderTester {
             ][makerAssetAddressLeft].add(expectedTransferAmounts.amountReceivedByTaker);
         } else if (makerAssetProxyIdLeft === AssetProxyId.ERC721) {
             // Decode asset data
-            const erc721ProxyData = assetProxyUtils.decodeERC721ProxyData(signedOrderLeft.makerAssetData);
-            const makerAssetAddressLeft = erc721ProxyData.tokenAddress;
-            const makerAssetIdLeft = erc721ProxyData.tokenId;
+            const erc721AssetData = assetProxyUtils.decodeERC721AssetData(signedOrderLeft.makerAssetData);
+            const makerAssetAddressLeft = erc721AssetData.tokenAddress;
+            const makerAssetIdLeft = erc721AssetData.tokenId;
             const takerAssetAddressRight = makerAssetAddressLeft;
             const takerAssetIdRight = makerAssetIdLeft;
             // Left Maker
@@ -272,11 +272,11 @@ export class MatchOrderTester {
         }
         // Left Taker Asset (Right Maker Asset)
         // Note: This exchange is only between the order makers: the Taker does not receive any of the left taker asset.
-        const takerAssetProxyIdLeft = assetProxyUtils.decodeProxyDataId(signedOrderLeft.takerAssetData);
+        const takerAssetProxyIdLeft = assetProxyUtils.decodeAssetDataId(signedOrderLeft.takerAssetData);
         if (takerAssetProxyIdLeft === AssetProxyId.ERC20) {
             // Decode asset data
-            const erc20ProxyData = assetProxyUtils.decodeERC20ProxyData(signedOrderLeft.takerAssetData);
-            const takerAssetAddressLeft = erc20ProxyData.tokenAddress;
+            const erc20AssetData = assetProxyUtils.decodeERC20AssetData(signedOrderLeft.takerAssetData);
+            const takerAssetAddressLeft = erc20AssetData.tokenAddress;
             const makerAssetAddressRight = takerAssetAddressLeft;
             // Left Maker
             expectedNewERC20BalancesByOwner[makerAddressLeft][takerAssetAddressLeft] = expectedNewERC20BalancesByOwner[
@@ -290,9 +290,9 @@ export class MatchOrderTester {
             );
         } else if (takerAssetProxyIdLeft === AssetProxyId.ERC721) {
             // Decode asset data
-            const erc721ProxyData = assetProxyUtils.decodeERC721ProxyData(signedOrderRight.makerAssetData);
-            const makerAssetAddressRight = erc721ProxyData.tokenAddress;
-            const makerAssetIdRight = erc721ProxyData.tokenId;
+            const erc721AssetData = assetProxyUtils.decodeERC721AssetData(signedOrderRight.makerAssetData);
+            const makerAssetAddressRight = erc721AssetData.tokenAddress;
+            const makerAssetIdRight = erc721AssetData.tokenId;
             const takerAssetAddressLeft = makerAssetAddressRight;
             const takerAssetIdLeft = makerAssetIdRight;
             // Right Maker
diff --git a/packages/contracts/src/utils/types.ts b/packages/contracts/src/utils/types.ts
index 491890fa1..bb8c12088 100644
--- a/packages/contracts/src/utils/types.ts
+++ b/packages/contracts/src/utils/types.ts
@@ -90,11 +90,14 @@ export enum ContractName {
     AccountLevels = 'AccountLevels',
     EtherDelta = 'EtherDelta',
     Arbitrage = 'Arbitrage',
+    TestAssetDataDecoders = 'TestAssetDataDecoders',
     TestAssetProxyDispatcher = 'TestAssetProxyDispatcher',
+    TestLibMem = 'TestLibMem',
     TestLibs = 'TestLibs',
     TestSignatureValidator = 'TestSignatureValidator',
     ERC20Proxy = 'ERC20Proxy',
     ERC721Proxy = 'ERC721Proxy',
+    DummyERC721Receiver = 'DummyERC721Receiver',
     DummyERC721Token = 'DummyERC721Token',
     TestLibBytes = 'TestLibBytes',
     Authorizable = 'Authorizable',