In one of my use case, I have a mapping that maps a string to an array of bytes. The reason for using bytes instead of bytes32 is because this bytes value is obtained by using abi.encode for multiple values. I am not using abi.encodePacked because there's no native way of decoding a packed data in solidity.
Now EnumerableSet doesn't have a set for bytes.
To make it work with my use case, I copied the code related to bytes32 and changed it bytes.
The code:
pragma solidity ^0.8.20;
library EnumerableSet {
struct Set {
// Storage of set values
bytes [] _values;
// Position is the index of the value in the `values` array plus 1.
// Position 0 is used to mean a value is not in the set.
mapping(bytes value => uint256) _positions;
}
/**
* @dev Add a value to a set. O(1).
*
* Returns true if the value was added to the set, that is if it was not
* already present.
*/
function _add(Set storage set, bytes memory value) private returns (bool) {
if (!_contains(set, value)) {
set._values.push(value);
// The value is stored at length-1, but we add 1 to all indexes
// and use 0 as a sentinel value
set._positions[value] = set._values.length;
return true;
} else {
return false;
}
}
/**
* @dev Removes a value from a set. O(1).
*
* Returns true if the value was removed from the set, that is if it was
* present.
*/
function _remove(Set storage set, bytes memory value) private returns (bool) {
// We cache the value's position to prevent multiple reads from the same storage slot
uint256 position = set._positions[value];
if (position != 0) {
// Equivalent to contains(set, value)
// To delete an element from the _values array in O(1), we swap the element to delete with the last one in
// the array, and then remove the last element (sometimes called as 'swap and pop').
// This modifies the order of the array, as noted in {at}.
uint256 valueIndex = position - 1;
uint256 lastIndex = set._values.length - 1;
if (valueIndex != lastIndex) {
bytes memory lastValue = set._values[lastIndex];
// Move the lastValue to the index where the value to delete is
set._values[valueIndex] = lastValue;
// Update the tracked position of the lastValue (that was just moved)
set._positions[lastValue] = position;
}
// Delete the slot where the moved value was stored
set._values.pop();
// Delete the tracked position for the deleted slot
delete set._positions[value];
return true;
} else {
return false;
}
}
/**
* @dev Returns true if the value is in the set. O(1).
*/
function _contains(Set storage set, bytes memory value) private view returns (bool) {
return set._positions[value] != 0;
}
/**
* @dev Returns the number of values on the set. O(1).
*/
function _length(Set storage set) private view returns (uint256) {
return set._values.length;
}
/**
* @dev Returns the value stored at position `index` in the set. O(1).
*
* Note that there are no guarantees on the ordering of values inside the
* array, and it may change when more values are added or removed.
*
* Requirements:
*
* - `index` must be strictly less than {length}.
*/
function _at(Set storage set, uint256 index) private view returns (bytes memory ) {
return set._values[index];
}
/**
* @dev Return the entire set in an array
*
* WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
* to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
* this function has an unbounded cost, and using it as part of a state-changing function may render the function
* uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
*/
function _values(Set storage set) private view returns (bytes [] memory) {
return set._values;
}
// bytes Set
struct bytesSet {
Set _inner;
}
/**
* @dev Add a value to a set. O(1).
*
* Returns true if the value was added to the set, that is if it was not
* already present.
*/
function add(bytesSet storage set, bytes memory value) internal returns (bool) {
return _add(set._inner, value);
}
/**
* @dev Removes a value from a set. O(1).
*
* Returns true if the value was removed from the set, that is if it was
* present.
*/
function remove(bytesSet storage set, bytes memory value) internal returns (bool) {
return _remove(set._inner, value);
}
/**
* @dev Returns true if the value is in the set. O(1).
*/
function contains(bytesSet storage set, bytes memory value) internal view returns (bool) {
return _contains(set._inner, value);
}
/**
* @dev Returns the number of values in the set. O(1).
*/
function length(bytesSet storage set) internal view returns (uint256) {
return _length(set._inner);
}
/**
* @dev Returns the value stored at position `index` in the set. O(1).
*
* Note that there are no guarantees on the ordering of values inside the
* array, and it may change when more values are added or removed.
*
* Requirements:
*
* - `index` must be strictly less than {length}.
*/
function at(bytesSet storage set, uint256 index) internal view returns (bytes memory ) {
return _at(set._inner, index);
}
/**
* @dev Return the entire set in an array
*
* WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
* to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
* this function has an unbounded cost, and using it as part of a state-changing function may render the function
* uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
*/
function values(bytesSet storage set) internal view returns (bytes [] memory) {
bytes [] memory store = _values(set._inner);
bytes [] memory result;
/// @solidity memory-safe-assembly
assembly {
result := store
}
return result;
}
}
This is exactly same as OZ EnumerableSet just the bytes32 has been changed to bytes.
It also seems to working fine at a high level glance.
But I want to know if this is security wise safe to use, if yes then why this bytes set is not included in OZ EnumerableSet librar?
Appreciate any insights on this approach.