Add string and bytes support to the StorageSlots library
#4008
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| /** | ||
| * @dev Returns an `StringSlot` representation of the string storage pointer `store`. | ||
| */ | ||
| function getStringSlot(string storage store) internal pure returns (StringSlot storage r) { |
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I think we can make the assumption that a string will always have offset zero. But I would consider adding an assertion/require just to make sure. Do you know what I mean?
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Storage pointers have an .offset field in addition to the .slot field. The offset indicates where in the slot the value begins. It can be non-zero when multiple values are packed in a slot. What I'm saying is that for a string pointer we can probably assume offset 0 but it's something we need to be aware of.
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I was not able to create a storage string pointer with an offset.
contract Test {
struct MyStruct {
uint256 a;
bool b;
string c;
}
uint256 private constant KEY = uint256(keccak256("some.key.for.the.mapping"));
mapping(uint256 => MyStruct) private mymapping;
function getMyStruct() public view returns (uint256 slot, uint256 offset) {
MyStruct storage ptr = mymapping[KEY];
assembly {
slot := ptr.slot
offset := ptr.offset
}
}
function getMyStructString() public view returns (uint256 slot, uint256 offset) {
string storage ptr = mymapping[KEY].c;
assembly {
slot := ptr.slot
offset := ptr.offset
}
}
}Offset is 0 in both cases,
slot for getMyStructString is 2 more than getMyStruct
Co-authored-by: Francisco <frangio.1@gmail.com>
String manipulation usefull for an upcoming ShortString library.
See #3969
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