将一个大整数编码为base62

Question

我需要创建独特的推荐代码。为了使每个引用代码都是唯一的，我尝试执行如下所示的操作。

const stringVal = `${currentTimestamp}${someVal}${someKey}`

这里，someVal本身就是BigInt mysql数据类型，someKey总是两位数。

为了编码，我使用base62包。

无论我超过99次通过someVal，我都会得到意想不到的结果。

function generateReferralCode(someVal) {
   const currentTimestamp = Date.now()
   let someKey = getSomeKey(someVal)
   const val = `${currentTimestamp}${someVal}${someKey}`
   console.log(`number to string : ${val}`)
   console.log(`longed value from string : ${Long.fromString(val)}`)
   const encodedVal = await base62.encode(Long.fromString(val))
   return encodedVal
}
function parseReferralCode(referralCode) {
    const decodedVal = base62.decode(referralCode)
    console.log(`decoded number : ${decodedVal}`)
    //extract someValue
    let  somevalue = parseInt(decodedVal / 100) % ( Math.pow(10, (decodedVal % 100)))
    return someValue
}

async function test() {
    const encoded = await generateReferralCode(100)
    console.log(`encoded val: ${encoded}`)
    const decoded = await parseReferralCode(encoded)
    console.log(`decoded val: ${decoded}`)
}
test()

Output:

number to  string : '158632196111710003'
longed value from string : 158632196111710003
encoded val: 'bIxiLMdWrm'
decoded number : 158632196111710000 //this should be as encoded string or longed val
decoded val: 1586321961117100 //this should be 100

以上对于someValue > 99的值不起作用。我知道这是因为javascript中的integer长度。

我也尝试过使用长，但它也不起作用。

我认为base62包也不支持大整数。

有人能帮我吗？base62怎么编码这么大的数字？

Answer 1

FWIW，下面是两个帮助函数，它们将BigInt转换为所需的基础，反之亦然.

​

var digits = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

function bigint2base( x, baseDigits ) {

  let base = BigInt( baseDigits.length );
  let result = '';
  
  while ( 0 < x ) {
    result = baseDigits.charAt( Number( x % base ) ) + result;
    x = x / base;
  }
    
  return result || '0';
  
}


function base2bigint( x, baseDigits ) {

  let base = BigInt( baseDigits.length ); 
  let result = 0n;
  
  for ( let i = 0; i < x.length; i++ ) {
    result = result * base + BigInt( baseDigits.indexOf( x.charAt( i ) ) );
  }
  
  return result;
}

console.log( `BigInt 158632196111710003n to base62 ( '${digits}' )...`);
base62val = bigint2base( 158632196111710003n, digits );
console.log( base62val );

console.log( `Converted back to BigInt is...` );
console.log( base2bigint( base62val, digits ).toString() );

console.log('');
console.log( `BigInt 31957108571341948394931814703184314387417471347093174n to base62 ( '${digits}' )...`);
base62val = bigint2base( 31957108571341948394931814703184314387417471347093174n, digits );
console.log( base62val );

console.log( `Converted back to BigInt is...` );
console.log( base2bigint( base62val, digits ).toString() );

​

希望这能帮上忙。