/* 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/Ownable/Ownable.sol"; import "../../utils/LibBytes/LibBytes.sol"; import "./mixins/MAssetProxyDispatcher.sol"; import "../AssetProxy/interfaces/IAssetProxy.sol"; contract MixinAssetProxyDispatcher is Ownable, MAssetProxyDispatcher { using LibBytes for bytes; // Mapping from Asset Proxy Id's to their respective Asset Proxy mapping (bytes4 => IAssetProxy) public assetProxies; /// @dev Registers an asset proxy to an asset proxy id. /// An id can only be assigned to a single proxy at a given time. /// @param assetProxyId Id to register`newAssetProxy` under. /// @param newAssetProxy Address of new asset proxy to register, or 0x0 to unset assetProxyId. /// @param oldAssetProxy Existing asset proxy to overwrite, or 0x0 if assetProxyId is currently unused. function registerAssetProxy( bytes4 assetProxyId, address newAssetProxy, address oldAssetProxy ) external onlyOwner { // Ensure the existing asset proxy is not unintentionally overwritten address currentAssetProxy = assetProxies[assetProxyId]; require( oldAssetProxy == currentAssetProxy, "ASSET_PROXY_MISMATCH" ); IAssetProxy assetProxy = IAssetProxy(newAssetProxy); // Ensure that the id of newAssetProxy matches the passed in assetProxyId, unless it is being reset to 0. if (newAssetProxy != address(0)) { bytes4 newAssetProxyId = assetProxy.getProxyId(); require( newAssetProxyId == assetProxyId, "ASSET_PROXY_ID_MISMATCH" ); } // Add asset proxy and log registration. assetProxies[assetProxyId] = assetProxy; emit AssetProxySet( assetProxyId, newAssetProxy, oldAssetProxy ); } /// @dev Gets an asset proxy. /// @param assetProxyId Id of the asset proxy. /// @return The asset proxy registered to assetProxyId. Returns 0x0 if no proxy is registered. function getAssetProxy(bytes4 assetProxyId) external view returns (address) { return assetProxies[assetProxyId]; } /// @dev Forwards arguments to assetProxy and calls `transferFrom`. Either succeeds or throws. /// @param assetData Byte array encoded for the asset. /// @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, address from, address to, uint256 amount ) internal { // Do nothing if no amount should be transferred. if (amount > 0) { // Ensure assetData length is valid require( assetData.length > 3, "LENGTH_GREATER_THAN_3_REQUIRED" ); // Lookup assetProxy bytes4 assetProxyId; assembly { assetProxyId := and(mload( add(assetData, 32)), 0xFFFFFFFF00000000000000000000000000000000000000000000000000000000 ) } IAssetProxy assetProxy = assetProxies[assetProxyId]; // Ensure that assetProxy exists require( assetProxy != address(0), "ASSET_PROXY_DOES_NOT_EXIST" ); // We construct calldata for the `assetProxy.transferFrom` ABI. // The layout of this calldata is in the table below. // // | Area | Offset | Length | Contents | // | -------- |--------|---------|-------------------------------------------- | // | Header | 0 | 4 | function selector | // | Params | | 4 * 32 | function parameters: | // | | 4 | | 1. offset to assetData (*) | // | | 36 | | 2. from | // | | 68 | | 3. to | // | | 100 | | 4. amount | // | Data | | | assetData: | // | | 132 | 32 | assetData Length | // | | 164 | ** | assetData Contents | bool success; assembly { /////// Setup State /////// // `cdStart` is the start of the calldata for `assetProxy.transferFrom` (equal to free memory ptr). let cdStart := mload(64) // `dataAreaLength` is the total number of words needed to store `assetData` // As-per the ABI spec, this value is padded up to the nearest multiple of 32, // and includes 32-bytes for length. let dataAreaLength := and(add(mload(assetData), 63), 0xFFFFFFFFFFFE0) // `cdEnd` is the end of the calldata for `assetProxy.transferFrom`. let cdEnd := add(cdStart, add(132, dataAreaLength)) /////// Setup Header Area /////// // This area holds the 4-byte `transferFromSelector`. // bytes4(keccak256("transferFrom(bytes,address,address,uint256)")) = 0xa85e59e4 mstore(cdStart, 0xa85e59e400000000000000000000000000000000000000000000000000000000) /////// Setup Params Area /////// // Each parameter is padded to 32-bytes. The entire Params Area is 128 bytes. // Notes: // 1. The offset to `assetData` is the length of the Params Area (128 bytes). // 2. A 20-byte mask is applied to addresses to zero-out the unused bytes. mstore(add(cdStart, 4), 128) mstore(add(cdStart, 36), and(from, 0xffffffffffffffffffffffffffffffffffffffff)) mstore(add(cdStart, 68), and(to, 0xffffffffffffffffffffffffffffffffffffffff)) mstore(add(cdStart, 100), amount) /////// Setup Data Area /////// // This area holds `assetData`. let dataArea := add(cdStart, 132) for {} lt(dataArea, cdEnd) {} { mstore(dataArea, mload(assetData)) dataArea := add(dataArea, 32) assetData := add(assetData, 32) } /////// Call `assetProxy.transferFrom` using the constructed calldata /////// success := call( gas, // forward all gas assetProxy, // call address of asset proxy 0, // don't send any ETH cdStart, // pointer to start of input sub(cdEnd, cdStart), // length of input cdStart, // write output over input 512 // reserve 512 bytes for output ) if eq(success, 0) { revert(cdStart, returndatasize()) } } } } }