80 lines
2.6 KiB
Solidity
80 lines
2.6 KiB
Solidity
// SPDX-License-Identifier: MIT
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pragma solidity ^0.8.19;
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import { IReputation } from "./lib/interfaces/IReputation.sol";
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contract Reputation is IReputation {
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/// @dev Asymptote numerator constant value for the `limiter` fx.
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uint256 public constant maxLimit = 1e6;
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/// @dev Denominator's constant operand for the `limiter` fx.
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uint256 public constant magicValue = 2.5e11;
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// prettier-ignore
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// solhint-disable no-inline-assembly
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// solhint-disable-next-line no-empty-blocks
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constructor(/* */) payable {/* */}
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function limiter(
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uint256 _userCredit
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)
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external
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pure
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override(IReputation)
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returns (uint256 _spendLimit)
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{
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_spendLimit = (1 +
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((maxLimit * _userCredit) /
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sqrt(
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magicValue + (_userCredit * _userCredit)
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)));
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}
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/// @notice Taken from Solmate's FixedPointMathLib.
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/// (https://github.com/transmissions11/solmate/blob/main/src/utils/FixedPointMathLib.sol)
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function sqrt(
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uint256 x
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) internal pure returns (uint256 z) {
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/// @solidity memory-safe-assembly
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assembly {
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let y := x // We start y at x, which will help us make our initial estimate.
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z := 181 // The "correct" value is 1, but this saves a multiplication later.
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// We check y >= 2^(k + 8) but shift right by k bits
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// each branch to ensure that if x >= 256, then y >= 256.
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if iszero(
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lt(y, 0x10000000000000000000000000000000000)
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) {
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y := shr(128, y)
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z := shl(64, z)
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}
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if iszero(lt(y, 0x1000000000000000000)) {
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y := shr(64, y)
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z := shl(32, z)
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}
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if iszero(lt(y, 0x10000000000)) {
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y := shr(32, y)
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z := shl(16, z)
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}
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if iszero(lt(y, 0x1000000)) {
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y := shr(16, y)
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z := shl(8, z)
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}
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// There is no overflow risk here since y < 2^136 after the first branch above.
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z := shr(18, mul(z, add(y, 65536))) // A mul() is saved from starting z at 181.
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// Given the worst case multiplicative error of 2.84 above, 7 iterations should be enough.
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z := shr(1, add(z, div(x, z)))
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z := shr(1, add(z, div(x, z)))
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z := shr(1, add(z, div(x, z)))
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z := shr(1, add(z, div(x, z)))
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z := shr(1, add(z, div(x, z)))
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z := shr(1, add(z, div(x, z)))
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z := shr(1, add(z, div(x, z)))
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z := sub(z, lt(div(x, z), z))
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}
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}
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}
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