<?php

namespace common\helpers;

use Yii;


/**
 * 十进制转64进制
 * @package common\helpers
 * @author qimall
 */
class Base64Helper
{
    private static $alphabet = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ+/';
    /**
     * 十进制转64进制
     * @Author bing
     * @DateTime 2021-11-29 16:06:52
     * @copyright: Copyright (c) 2020 广东七件事集团
     * @param [type] $dec_num
     * @return void
     */
    public static function dec2Base64($dec_num)
    {
        $base64_num = '';
        $base = strlen(self::$alphabet);
        if($dec_num == 0) $base64_num = self::$alphabet[0];
        while($dec_num > 0){
            $remainder = $dec_num % $base;
            $dec_num = ($dec_num-$remainder) / $base;
            if($remainder == 0){
                $base64_num = self::$alphabet[0] . $base64_num;
            }else{
                $base64_num = self::$alphabet[$remainder] . $base64_num;
            }
        }
        return $base64_num;
    }
    
     /**
     * 64进制转十进制
     * @Author bing
     * @DateTime 2021-11-29 16:06:52
     * @copyright: Copyright (c) 2020 广东七件事集团
     * @param [type] $dec_num
     * @return void
     */
     public static function Base642dec($base64_num){
         $digit = strlen($base64_num);
         $base = strlen(self::$alphabet);
         $dec_num = 0;
         for($i = 0; $i < $digit; $i++){
             //每一位分别读取
             $mult = 1;
             for($j = $digit - 1; $j > $i; $j--){
                 //构造当前位需要乘的数
                 if($i == ($digit - 1)){
                     $mult = 1;
                 }else{
                     $mult = $mult * $base;
                 }
             }
             //计算当前位数代表的十进制数，然后累加   
             $dec_num += strpos(self::$alphabet, $base64_num[$i]) * $mult;
         }
         return $dec_num;
     }
}