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authorAmir Bandeali <abandeali1@gmail.com>2018-06-26 05:13:31 +0800
committerAmir Bandeali <abandeali1@gmail.com>2018-06-26 07:19:08 +0800
commit0163984ea4f9d7623613d2d7cd8e2e946acecdf5 (patch)
tree5b9cf08a11bc658e02da33583b69a19852d15094 /packages/contracts/src
parentdb3ce08cab7e8c273121996867f491abed1179af (diff)
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Add comments to dispatchTransferFrom
Diffstat (limited to 'packages/contracts/src')
-rw-r--r--packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol86
1 files changed, 56 insertions, 30 deletions
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
index 96763970c..3203322aa 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
@@ -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(