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ERC20 manual memory layout

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This commit is contained in:
Remco Bloemen
2018-06-25 21:40:10 +02:00
committed by Amir Bandeali
parent 3b46e82625
commit b79588c4a0
1 changed files with 6 additions and 11 deletions
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17
packages/contracts/src/contracts/current/protocol/AssetProxy/MixinERC20Transfer.sol
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@@ -99,29 +99,25 @@ contract MixinERC20Transfer is
// So we read location 4 and add 32 + 4 + 4 to it.
let token := calldataload(add(calldataload(4), 40))
/////// Setup State ///////
// `cdStart` is the start of the calldata for `token.transferFrom` (equal to free memory ptr).
let cdStart := mload(64)
/////// Setup Header Area ///////
// This area holds the 4-byte `transferFrom` selector.
// Any trailing data in transferFromSelector will be
// overwritten in the next `mstore` call.
mstore(cdStart, 0x23b872dd00000000000000000000000000000000000000000000000000000000)
mstore(0, 0x23b872dd00000000000000000000000000000000000000000000000000000000)
/////// Setup Params Area ///////
// We copy the fields `from`, `to` and `amount` in bulk
// from our own calldata to the new calldata.
calldatacopy(add(cdStart, 4), 36, 96)
calldatacopy(4, 36, 96)
/////// Call `token.transferFrom` using the calldata ///////
let success := call(
gas, // forward all gas
token, // call address of token contract
0, // don't send any ETH
cdStart, // pointer to start of input
0, // pointer to start of input
100, // length of input
cdStart, // write output over input
0, // write output over input
32 // output size should be 32 bytes
)
@@ -137,7 +133,7 @@ contract MixinERC20Transfer is
iszero(returndatasize),
and(
eq(returndatasize, 32),
gt(mload(cdStart), 0)
gt(mload(0), 0)
)
))
if success {
@@ -152,8 +148,7 @@ contract MixinERC20Transfer is
revert(0, 100)
}
}
/// @dev Internal version of `transferFrom`.
/// @param assetData Encoded byte array.
/// @param from Address to transfer asset from.