php函数crc32存在的问题

中午突然获知AS客户端与服务端c协议通讯时，为了验证完整性和防外挂，服务端要求协议带上crc的验证信息，我做的php后台有Socket形式的GM命令也要求相同的协议。

但php和服务端计算出来的验证值是不同的，然后我试了下python写crc，python和服务端计算后的验证值是相同的。

经过一番搜索，通过文章1、文章2得知，在python2.x中 binascii.crc32(v) 求出了v的crc32值，是一个long型，经过 binascii.crc32(v) & 0xffffffff 计算后的验证值跟php一样的，可以说：

php的crc32 = python的 binascii.crc32(v) & 0xffffffff

此文验证结果没错，但原理性内容存在问题，待我学习crc算法，慎读。

查看PHP手册：

Warning 由于 PHP 的整数是带符号的，所以在 32 位系统上许多 crc32 校验码将返回负整数。 尽管在 64 位上所有crc32() 的结果将都是正整数。

尽管php环境也是64位的，估计为了统一性，猜测php底层在对crc算法计算后的值进行了暴力处理（不影响验证），这方面还需要查看php底层后再确认，但可以通过下面的方法得到原始验证值。

function crcKw($num){
    $crc = crc32($num);
    if($crc & 0x80000000){
        $crc ^= 0xffffffff;
        $crc += 1;
        $crc = -$crc;
    }
    return $crc;
}

我的php验证代码：

<?php
header("charset=utf-8;");
//字符串转二进制
function StrToBin($str){
    //1.列出每个字符
    $arr = preg_split('/(?<!^)(?!$)/u', $str);
    //2.unpack字符
    foreach($arr as &$v){
        $temp = unpack('H*', $v);
        $v = base_convert($temp[1], 16, 2);
        unset($temp);
    }
    return join('',$arr);
}
//二进制转字符串
function BinToStr($str){
    $arr = explode('', $str);
    foreach($arr as &$v){
        $v = pack("H".strlen(base_convert($v, 2, 16)), base_convert($v, 2, 16));
    }

    return join('', $arr);
}
//crc32函数改进版，32位转64位
function crcKw($num){
    $crc = crc32($num);
    if($crc & 0x80000000){
        $crc ^= 0xffffffff;
        $crc += 1;
        $crc = -$crc;
    }
    return $crc;
}

printf('%d',crc32('a'));
echo "\n";
printf('%d',crcKw('a'));
echo "\n";

我的python验证代码：

#!/usr/bin/env python
#-*- coding:utf-8 -*-

import binascii

print binascii.crc32("a")
print binascii.crc32("a") & 0xFFFFFFFF

追加

  • 关于客户端反映的中文需要转成二进制内容，否则出现问题，php在这方面测试没遇到。

  • as处理代码。

    package com.game.utils{
    import flash.utils.ByteArray;

     public class Crc32{
     public function Crc32(){
         
     }

     private static var CRC32_TAB:Array = new Array( 
         0x00000000,0x77073096,0xEE0E612C,0x990951BA,0x076DC419,0x706AF48F,0xE963A535,0x9E6495A3,
         0x0EDB8832,0x79DCB8A4,0xE0D5E91E,0x97D2D988,0x09B64C2B,0x7EB17CBD,0xE7B82D07,0x90BF1D91,
         0x1DB71064,0x6AB020F2,0xF3B97148,0x84BE41DE,0x1ADAD47D,0x6DDDE4EB,0xF4D4B551,0x83D385C7,
         0x136C9856,0x646BA8C0,0xFD62F97A,0x8A65C9EC,0x14015C4F,0x63066CD9,0xFA0F3D63,0x8D080DF5,
         0x3B6E20C8,0x4C69105E,0xD56041E4,0xA2677172,0x3C03E4D1,0x4B04D447,0xD20D85FD,0xA50AB56B,
         0x35B5A8FA,0x42B2986C,0xDBBBC9D6,0xACBCF940,0x32D86CE3,0x45DF5C75,0xDCD60DCF,0xABD13D59,
         0x26D930AC,0x51DE003A,0xC8D75180,0xBFD06116,0x21B4F4B5,0x56B3C423,0xCFBA9599,0xB8BDA50F,
         0x2802B89E,0x5F058808,0xC60CD9B2,0xB10BE924,0x2F6F7C87,0x58684C11,0xC1611DAB,0xB6662D3D,
         0x76DC4190,0x01DB7106,0x98D220BC,0xEFD5102A,0x71B18589,0x06B6B51F,0x9FBFE4A5,0xE8B8D433,
         0x7807C9A2,0x0F00F934,0x9609A88E,0xE10E9818,0x7F6A0DBB,0x086D3D2D,0x91646C97,0xE6635C01,
         0x6B6B51F4,0x1C6C6162,0x856530D8,0xF262004E,0x6C0695ED,0x1B01A57B,0x8208F4C1,0xF50FC457,
         0x65B0D9C6,0x12B7E950,0x8BBEB8EA,0xFCB9887C,0x62DD1DDF,0x15DA2D49,0x8CD37CF3,0xFBD44C65,
         0x4DB26158,0x3AB551CE,0xA3BC0074,0xD4BB30E2,0x4ADFA541,0x3DD895D7,0xA4D1C46D,0xD3D6F4FB,
         0x4369E96A,0x346ED9FC,0xAD678846,0xDA60B8D0,0x44042D73,0x33031DE5,0xAA0A4C5F,0xDD0D7CC9,
         0x5005713C,0x270241AA,0xBE0B1010,0xC90C2086,0x5768B525,0x206F85B3,0xB966D409,0xCE61E49F,
         0x5EDEF90E,0x29D9C998,0xB0D09822,0xC7D7A8B4,0x59B33D17,0x2EB40D81,0xB7BD5C3B,0xC0BA6CAD,
         0xEDB88320,0x9ABFB3B6,0x03B6E20C,0x74B1D29A,0xEAD54739,0x9DD277AF,0x04DB2615,0x73DC1683,
         0xE3630B12,0x94643B84,0x0D6D6A3E,0x7A6A5AA8,0xE40ECF0B,0x9309FF9D,0x0A00AE27,0x7D079EB1,
         0xF00F9344,0x8708A3D2,0x1E01F268,0x6906C2FE,0xF762575D,0x806567CB,0x196C3671,0x6E6B06E7,
         0xFED41B76,0x89D32BE0,0x10DA7A5A,0x67DD4ACC,0xF9B9DF6F,0x8EBEEFF9,0x17B7BE43,0x60B08ED5,
         0xD6D6A3E8,0xA1D1937E,0x38D8C2C4,0x4FDFF252,0xD1BB67F1,0xA6BC5767,0x3FB506DD,0x48B2364B,
         0xD80D2BDA,0xAF0A1B4C,0x36034AF6,0x41047A60,0xDF60EFC3,0xA867DF55,0x316E8EEF,0x4669BE79,
         0xCB61B38C,0xBC66831A,0x256FD2A0,0x5268E236,0xCC0C7795,0xBB0B4703,0x220216B9,0x5505262F,
         0xC5BA3BBE,0xB2BD0B28,0x2BB45A92,0x5CB36A04,0xC2D7FFA7,0xB5D0CF31,0x2CD99E8B,0x5BDEAE1D,
         0x9B64C2B0,0xEC63F226,0x756AA39C,0x026D930A,0x9C0906A9,0xEB0E363F,0x72076785,0x05005713,
         0x95BF4A82,0xE2B87A14,0x7BB12BAE,0x0CB61B38,0x92D28E9B,0xE5D5BE0D,0x7CDCEFB7,0x0BDBDF21,
         0x86D3D2D4,0xF1D4E242,0x68DDB3F8,0x1FDA836E,0x81BE16CD,0xF6B9265B,0x6FB077E1,0x18B74777,
         0x88085AE6,0xFF0F6A70,0x66063BCA,0x11010B5C,0x8F659EFF,0xF862AE69,0x616BFFD3,0x166CCF45,
         0xA00AE278,0xD70DD2EE,0x4E048354,0x3903B3C2,0xA7672661,0xD06016F7,0x4969474D,0x3E6E77DB,
         0xAED16A4A,0xD9D65ADC,0x40DF0B66,0x37D83BF0,0xA9BCAE53,0xDEBB9EC5,0x47B2CF7F,0x30B5FFE9,
         0xBDBDF21C,0xCABAC28A,0x53B39330,0x24B4A3A6,0xBAD03605,0xCDD70693,0x54DE5729,0x23D967BF,
         0xB3667A2E,0xC4614AB8,0x5D681B02,0x2A6F2B94,0xB40BBE37,0xC30C8EA1,0x5A05DF1B,0x2D02EF8D
     );
     

        public static function encode(ba:ByteArray):int{
            /*var ba:ByteArray = new ByteArray();
            ba.writeUTFBytes(str);
            ba.position = 0;*/
            
            var i:int,len:int,crc:int;
            len = ba.length;
            crc = 0xFFFFFFFF;
            
            for(i = 0; i < len; i++){
                crc = crc32Add(crc, ba.readUnsignedByte());
            }
            
            return crc^0xFFFFFFFF;
        }
        
        
        private static function crc32Add(crc:int,c:int):int{
            return CRC32_TAB[(crc^c)&0xFF]^((crc>>8)&0xFFFFFF);
        };
    }
}

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