173 lines
7.3 KiB
Solidity
173 lines
7.3 KiB
Solidity
/*
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Copyright 2019 ZeroEx Intl.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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pragma solidity ^0.5.9;
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import "../archive/Ownable.sol";
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import "../src/interfaces/IAssetProxy.sol";
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import "../src/interfaces/IAssetProxyDispatcher.sol";
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contract MixinAssetProxyDispatcher is
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Ownable,
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IAssetProxyDispatcher
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{
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// Mapping from Asset Proxy Id's to their respective Asset Proxy
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mapping (bytes4 => address) public assetProxies;
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/// @dev Registers an asset proxy to its asset proxy id.
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/// Once an asset proxy is registered, it cannot be unregistered.
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/// @param assetProxy Address of new asset proxy to register.
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function registerAssetProxy(address assetProxy)
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external
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onlyOwner
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{
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// Ensure that no asset proxy exists with current id.
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bytes4 assetProxyId = IAssetProxy(assetProxy).getProxyId();
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address currentAssetProxy = assetProxies[assetProxyId];
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require(
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currentAssetProxy == address(0),
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"ASSET_PROXY_ALREADY_EXISTS"
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);
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// Add asset proxy and log registration.
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assetProxies[assetProxyId] = assetProxy;
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emit AssetProxyRegistered(
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assetProxyId,
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assetProxy
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);
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}
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/// @dev Gets an asset proxy.
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/// @param assetProxyId Id of the asset proxy.
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/// @return The asset proxy registered to assetProxyId. Returns 0x0 if no proxy is registered.
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function getAssetProxy(bytes4 assetProxyId)
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external
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view
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returns (address)
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{
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return assetProxies[assetProxyId];
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}
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/// @dev Forwards arguments to assetProxy and calls `transferFrom`. Either succeeds or throws.
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/// @param assetData Byte array encoded for the asset.
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/// @param from Address to transfer token from.
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/// @param to Address to transfer token to.
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/// @param amount Amount of token to transfer.
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function _dispatchTransferFrom(
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bytes memory assetData,
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address from,
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address to,
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uint256 amount
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)
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internal
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{
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// Do nothing if no amount should be transferred.
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if (amount > 0 && from != to) {
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// Ensure assetData length is valid
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require(
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assetData.length > 3,
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"LENGTH_GREATER_THAN_3_REQUIRED"
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);
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// Lookup assetProxy. We do not use `LibBytes.readBytes4` for gas efficiency reasons.
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bytes4 assetProxyId;
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assembly {
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assetProxyId := and(mload(
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add(assetData, 32)),
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0xFFFFFFFF00000000000000000000000000000000000000000000000000000000
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)
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}
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address assetProxy = assetProxies[assetProxyId];
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// Ensure that assetProxy exists
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require(
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assetProxy != address(0),
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"ASSET_PROXY_DOES_NOT_EXIST"
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);
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// We construct calldata for the `assetProxy.transferFrom` ABI.
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// The layout of this calldata is in the table below.
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//
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// | Area | Offset | Length | Contents |
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// | -------- |--------|---------|-------------------------------------------- |
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// | Header | 0 | 4 | function selector |
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// | Params | | 4 * 32 | function parameters: |
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// | | 4 | | 1. offset to assetData (*) |
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// | | 36 | | 2. from |
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// | | 68 | | 3. to |
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// | | 100 | | 4. amount |
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// | Data | | | assetData: |
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// | | 132 | 32 | assetData Length |
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// | | 164 | ** | assetData Contents |
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assembly {
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/////// Setup State ///////
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// `cdStart` is the start of the calldata for `assetProxy.transferFrom` (equal to free memory ptr).
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let cdStart := mload(64)
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// `dataAreaLength` is the total number of words needed to store `assetData`
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// As-per the ABI spec, this value is padded up to the nearest multiple of 32,
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// and includes 32-bytes for length.
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let dataAreaLength := and(add(mload(assetData), 63), 0xFFFFFFFFFFFE0)
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// `cdEnd` is the end of the calldata for `assetProxy.transferFrom`.
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let cdEnd := add(cdStart, add(132, dataAreaLength))
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/////// Setup Header Area ///////
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// This area holds the 4-byte `transferFromSelector`.
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// bytes4(keccak256("transferFrom(bytes,address,address,uint256)")) = 0xa85e59e4
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mstore(cdStart, 0xa85e59e400000000000000000000000000000000000000000000000000000000)
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/////// Setup Params Area ///////
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// Each parameter is padded to 32-bytes. The entire Params Area is 128 bytes.
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// Notes:
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// 1. The offset to `assetData` is the length of the Params Area (128 bytes).
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// 2. A 20-byte mask is applied to addresses to zero-out the unused bytes.
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mstore(add(cdStart, 4), 128)
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mstore(add(cdStart, 36), and(from, 0xffffffffffffffffffffffffffffffffffffffff))
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mstore(add(cdStart, 68), and(to, 0xffffffffffffffffffffffffffffffffffffffff))
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mstore(add(cdStart, 100), amount)
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/////// Setup Data Area ///////
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// This area holds `assetData`.
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let dataArea := add(cdStart, 132)
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// solhint-disable-next-line no-empty-blocks
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for {} lt(dataArea, cdEnd) {} {
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mstore(dataArea, mload(assetData))
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dataArea := add(dataArea, 32)
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assetData := add(assetData, 32)
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}
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/////// Call `assetProxy.transferFrom` using the constructed calldata ///////
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let success := call(
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gas, // forward all gas
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assetProxy, // call address of asset proxy
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0, // don't send any ETH
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cdStart, // pointer to start of input
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sub(cdEnd, cdStart), // length of input
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cdStart, // write output over input
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512 // reserve 512 bytes for output
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)
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if iszero(success) {
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revert(cdStart, returndatasize())
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}
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}
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}
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}
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}
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