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Add comments to dispatchTransferFrom

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This commit is contained in:
Amir Bandeali
2018-06-25 14:13:31 -07:00
parent db3ce08cab
commit 0163984ea4
1 changed files with 56 additions and 30 deletions
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86
packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
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@@ -20,13 +20,11 @@ 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,
LibExchangeErrors,
MAssetProxyDispatcher
{
using LibBytes for bytes;
@@ -51,7 +49,7 @@ contract MixinAssetProxyDispatcher is
address currentAssetProxy = assetProxies[assetProxyId];
require(
oldAssetProxy == currentAssetProxy,
ASSET_PROXY_MISMATCH
"ASSET_PROXY_MISMATCH"
);
IAssetProxy assetProxy = IAssetProxy(newAssetProxy);
@@ -61,7 +59,7 @@ contract MixinAssetProxyDispatcher is
bytes4 newAssetProxyId = assetProxy.getProxyId();
require(
newAssetProxyId == assetProxyId,
ASSET_PROXY_ID_MISMATCH
"ASSET_PROXY_ID_MISMATCH"
);
}
@@ -100,61 +98,89 @@ contract MixinAssetProxyDispatcher is
{
// Do nothing if no amount should be transferred.
if (amount > 0) {
require(assetData.length >= 4, "ASSET_DATA_LENGTH");
// 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
assetProxyId := and(mload(
add(assetData, 32)),
0xFFFFFFFF00000000000000000000000000000000000000000000000000000000
)
}
IAssetProxy assetProxy = assetProxies[assetProxyId];
// Ensure that assetProxy exists
require(
assetProxy != address(0),
ASSET_PROXY_DOES_NOT_EXIST
"ASSET_PROXY_DOES_NOT_EXIST"
);
/*
assetProxy.transferFrom(
assetData,
from,
to,
amount
);
return;
*/
// 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 |
bytes4 transferFromSelector = IAssetProxy(assetProxy).transferFrom.selector;
bool success;
bool success;
assembly {
let cdStart := mload(0x40)
let dataAreaLength := mul(div(add(mload(assetData), 63), 32), 32)
/////// 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`.
mstore(cdStart, transferFromSelector)
/////// 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,
assetProxy,
0,
cdStart,
sub(cdEnd, cdStart),
cdStart,
0
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
0 // output size is 0 bytes
)
}
require(