You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
30 lines
939 B
30 lines
939 B
7 years ago
|
pragma solidity ^0.4.24;
|
||
|
|
|
||
|
|
|
||
|
|
/**
|
||
|
|
* @title AutoIncrementing
|
||
|
|
* @author Matt Condon (@shrugs)
|
||
|
|
* @dev Provides an auto-incrementing uint256 id acquired by the `Counter#nextId` getter.
|
||
|
|
* Use this for issuing ERC721Token ids or keeping track of request ids, anything you want, really.
|
||
|
|
*
|
||
|
|
* Include with `using AutoIncrementing for AutoIncrementing.Counter;`
|
||
|
|
* @notice Does not allow an Id of 0, which is popularly used to signify a null state in solidity.
|
||
|
|
* Does not protect from overflows, but if you have 2^256 ids, you have other problems.
|
||
|
|
* (But actually, it's generally impossible to increment a counter this many times, energy wise
|
||
|
|
* so it's not something you have to worry about.)
|
||
|
|
*/
|
||
|
|
library AutoIncrementing {
|
||
|
|
|
||
|
|
struct Counter {
|
||
|
|
uint256 prevId; // default: 0
|
||
|
|
}
|
||
|
|
|
||
|
|
function nextId(Counter storage _counter)
|
||
|
|
internal
|
||
|
|
returns (uint256)
|
||
|
|
{
|
||
|
|
_counter.prevId = _counter.prevId + 1;
|
||
|
|
return _counter.prevId;
|
||
|
|
}
|
||
|
|
}
|