1 files changed, 103 insertions, 0 deletions
diff --git a/contracts/extensions/contracts/BalanceThresholdFilter/MixinExchangeCalldata.sol b/contracts/extensions/contracts/BalanceThresholdFilter/MixinExchangeCalldata.sol
new file mode 100644
index 000000000..bd26a468f
--- /dev/null
+++ b/contracts/extensions/contracts/BalanceThresholdFilter/MixinExchangeCalldata.sol
@@ -0,0 +1,103 @@
+    
+    /*
+
+  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/LICENSE2.0
+
+  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 "./mixins/MExchangeCalldata.sol";
+import "@0x/contracts-libs/contracts/libs/LibAddressArray.sol";
+
+
+contract MixinExchangeCalldata is 
+    MExchangeCalldata
+{
+
+    using LibAddressArray for address[];
+
+    /// @dev Emulates the `calldataload` opcode on the embedded Exchange calldata,
+    ///      which is accessed through `signedExchangeTransaction`.
+    /// @param offset  Offset into the Exchange calldata.
+    /// @return value  Corresponding 32 byte value stored at `offset`.
+    function exchangeCalldataload(uint256 offset)
+        internal pure
+        returns (bytes32 value)
+    {
+        assembly {
+            // Pointer to exchange transaction
+            // 0x04 for calldata selector
+            // 0x40 to access `signedExchangeTransaction`, which is the third parameter
+            let exchangeTxPtr := calldataload(0x44)
+
+            // Offset into Exchange calldata
+            // We compute this by adding 0x24 to the `exchangeTxPtr` computed above.
+            // 0x04 for calldata selector
+            // 0x20 for length field of `signedExchangeTransaction`
+            let exchangeCalldataOffset := add(exchangeTxPtr, add(0x24, offset))
+            value := calldataload(exchangeCalldataOffset)
+        }
+        return value;
+    }
+
+    /// @dev Convenience function that skips the 4 byte selector when loading
+    ///      from the embedded Exchange calldata.
+    /// @param offset  Offset into the Exchange calldata (minus the 4 byte selector)
+    /// @return value  Corresponding 32 byte value stored at `offset` + 4.
+    function loadExchangeData(uint256 offset)
+        internal pure
+        returns (bytes32 value)
+    {
+        value = exchangeCalldataload(offset + 4);
+        return value;
+    }
+
+    /// @dev Extracts the maker address from an order stored in the Exchange calldata
+    ///      (which is embedded in `signedExchangeTransaction`).
+    /// @param orderParamIndex  Index of the order in the Exchange function's signature.
+    /// @return makerAddress The extracted maker address.
+    function loadMakerAddressFromOrder(uint256 orderParamIndex)
+        internal pure
+        returns (address makerAddress)
+    {
+        uint256 orderOffsetInBytes = orderParamIndex * 32;
+        uint256 orderPtr = uint256(loadExchangeData(orderOffsetInBytes));
+        makerAddress = address(loadExchangeData(orderPtr));
+        return makerAddress;
+    }
+
+    /// @dev Extracts the maker addresses from an array of orders stored in the Exchange calldata
+    ///      (which is embedded in `signedExchangeTransaction`).
+    /// @param orderArrayParamIndex  Index of the order array in the Exchange function's signature
+    /// @return makerAddresses The extracted maker addresses.
+    function loadMakerAddressesFromOrderArray(uint256 orderArrayParamIndex)
+        internal pure
+        returns (address[] makerAddresses)
+    {
+        uint256 orderArrayOffsetInBytes = orderArrayParamIndex * 32;
+        uint256 orderArrayPtr = uint256(loadExchangeData(orderArrayOffsetInBytes));
+        uint256 orderArrayLength = uint256(loadExchangeData(orderArrayPtr));
+        uint256 orderArrayLengthInBytes = orderArrayLength * 32;
+        uint256 orderArrayElementPtr = orderArrayPtr + 32;
+        uint256 orderArrayElementEndPtr = orderArrayElementPtr + orderArrayLengthInBytes;
+        for (uint orderPtrOffset = orderArrayElementPtr; orderPtrOffset < orderArrayElementEndPtr; orderPtrOffset += 32) {
+            uint256 orderPtr = uint256(loadExchangeData(orderPtrOffset));
+            address makerAddress = address(loadExchangeData(orderPtr + orderArrayElementPtr));
+            makerAddresses = makerAddresses.append(makerAddress);
+        }
+        return makerAddresses;
+    }
+}