punycode.sol

Solidity Punycode without IDNA.

• Library: Punycode.sol
  • ASCII strings: ~500 gas (fastpath)
  • Unicode strings:
    • Decode ~1300 gas/codepoint
    • Encode ~2500 gas/codepoint
• Available on NPM: import {Punycode} from "@adraffy/punycode-contracts/src/Punycode.sol";
• Foundry: forge install adraffy/punycode.sol
  • Suggested remapping: @adraffy/punycode-contracts/=lib/Punycode.sol/
• Reference Implementation: adraffy/punycode.js
• Demo ⭐
  • Deployment: base:0xBEfeca057ea022e7aB419670a659d32f125973C1

string memory unicode = Punycode.decode("xn--ls8h"); // "💩"
string memory punycode = Punycode.encode(unicode"💩"); // "xn--ls8h"

// reverts on failure
// let me know if a tryDecode() is needed
function decode(string memory s) pure returns (string memory);

// never fails
function encode(string memory s) pure returns (string memory);

Lower-level functions:

// src == dst if no encoding required
// otherwise, (dst-32) is effectively `bytes`
function decode(uint256 src, uint256 src_len) pure returns (uint256 dst, uint256 dst_len);
function encode(uint256 src, uint256 src_len) pure returns (uint256 dst, uint256 dst_len);

// example
string memory s = "abc.xn--ls8h.com";
uint256 src;
assembly { src := add(s, 32) }
(uint256 dst, uint256 len) = Punycode.decode(src + 4, 8); // "xn--ls8h"
console2.log(len); // 4 bytes
assembly { s := sub(dst, 32) }
console2.log(s); // "💩"
bytes32 h;
assembly { h := keccak256(dst, len) }
console2.logBytes32(h); // 0xba967c160905ade030f84952644a963994eeaed3881a6b8a4e9c8cbe452ad7a2

Test

1. (optional) git submodule update --remote
2. foundryup
3. npm i
4. npm run test — forge tests + random validation
5. (optional) npm run validate-all — complete validation
6. (optional) npm run fuzz — random inputs until cancelled

Gas Analysis

• npm run gas — estimate gas
• forge script GasEncode — estimate gas for encode()
• forge script GasDecode — estimate gas for decode()