<?php

namespace ZX\Algorithm;
/*
 * 超大10进制数字转换成62进制
 * 为什么只支持62进制,主要原因就是url协议支持的字符是有限的
 * 大小写字母+数字,几个特殊字符比如"$-_.+!*'(),"
 * 方便互联网使用,如果你需要支持128进制,256进制,可以根据下列方法扩展
 */

class LargeDigitalConversion62
{

 protected static $dict = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
 protected static $codeLength = 62;

 public static function from10To62($num)
 {
 $to = self::$codeLength;
 $dict = self::$dict;
 $ret = '';
 do {
 $ret = $dict[bcmod($num, $to)] . $ret;
 $num = bcdiv($num, $to);
 } while ($num > 0);
 return $ret;
 }

 public static function from62To10($num)
 {
 $from = self::$codeLength;
 $num = strval($num);
 $dict = self::$dict;
 $len = strlen($num);
 $dec = 0;
 for ($i = 0; $i < $len; $i++) {
 $pos = strpos($dict, $num[$i]);
 $dec = bcadd(bcmul(bcpow($from, $len - $i - 1), $pos), $dec);
 }
 return $dec;
 }

}