Dart/Flutter: FNV-1a 64-bit hash function (Web compatible)

fnv1a.dart

import 'dart:convert';

final fnv1A64Init = BigInt.parse("0xcbf29ce484222325");
final fnv1A64Prime = BigInt.from(0x100000001b3);
final uint64Mask = BigInt.parse("0xffffffffffffffff");

// FNV-1a 64-bit hash function (JavaScript compatible)
// This function is for you if you have seen errors like "Error: The integer literal 0xcbf29ce484222325 can't be represented exactly in JavaScript."
String fnv1A64(String string) {
  var hash = fnv1A64Init;
  final bytes = utf8.encode(string);
  for (final b in bytes) {
    hash ^= BigInt.from(b);
    hash *= fnv1A64Prime;
  }
  hash &= uint64Mask;
  return hash.toRadixString(16).padLeft(16, '0');
}

Examples:

fnv1A64('throne') == '265610cb61f74d53'
fnv1A64('crown') == '0c29519f09f0f250'