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run one final comment pass over the token transferrer #505

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Merged
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Jun 11, 2022
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run one final comment pass over the token transferrer #505

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29 changes: 24 additions & 5 deletions contracts/lib/TokenTransferrer.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,18 @@ import {

import { ConduitBatch1155Transfer } from "../conduit/lib/ConduitStructs.sol";

/**
* @title TokenTransferrer
* @author 0age
* @custom:coauthor d1ll0n
* @custom:coauthor transmissions11
* @notice TokenTransferrer is a library for performing optimized ERC20, ERC721,
* ERC1155, and batch ERC1155 transfers, used by both Seaport as well as
* by conduits deployed by the ConduitController. Use great caution when
* considering these functions for use in other codebases, as there are
* significant side effects and edge cases that need to be thoroughly
* understood and carefully addressed.
*/
contract TokenTransferrer is TokenTransferrerErrors {
/**
* @dev Internal function to transfer ERC20 tokens from a given originator
Expand Down Expand Up @@ -40,6 +52,11 @@ contract TokenTransferrer is TokenTransferrerErrors {
mstore(ERC20_transferFrom_amount_ptr, amount)

// Make call & copy up to 32 bytes of return data to scratch space.
// Scratch space does not need to be cleared ahead of time, as the
// subsequent check will ensure that either at least a full word of
// return data is received (in which case it will be overwritten) or
// that no data is received (in which case scratch space will be
// ignored) on a successful call to the given token.
let callStatus := call(
gas(),
token,
Expand All @@ -62,8 +79,8 @@ contract TokenTransferrer is TokenTransferrerErrors {
callStatus
)

// If the transfer failed or it returned nothing:
// Group these because they should be uncommon.
// Handle cases where either the transfer failed or no data was
// returned. Group these, as most transfers will succeed with data.
// Equivalent to `or(iszero(success), iszero(returndatasize()))`
// but after it's inverted for JUMPI this expression is cheaper.
if iszero(and(success, iszero(iszero(returndatasize())))) {
Expand Down Expand Up @@ -190,14 +207,14 @@ contract TokenTransferrer is TokenTransferrerErrors {
)
}

// Otherwise revert with error about token not having code:
// Otherwise, revert with error about token not having code:
mstore(NoContract_error_sig_ptr, NoContract_error_signature)
mstore(NoContract_error_token_ptr, token)
revert(NoContract_error_sig_ptr, NoContract_error_length)
}

// Otherwise the token just returned nothing but otherwise
// succeeded; no need to optimize for this as it's not
// Otherwise, the token just returned no data despite the call
// having succeeded; no need to optimize for this as it's not
// technically ERC20 compliant.
}

Expand Down Expand Up @@ -747,6 +764,8 @@ contract TokenTransferrer is TokenTransferrerErrors {

// Reset the free memory pointer to the default value; memory must
// be assumed to be dirtied and not reused from this point forward.
// Also note that the zero slot is not reset to zero, meaning empty
// arrays cannot be safely created or utilized until it is restored.
mstore(FreeMemoryPointerSlot, DefaultFreeMemoryPointer)
}
}
Expand Down