javascript - 使用指针将 C++ 转换为 JavaScript( Node )*

Question

我想将此 C++ 代码转换为 JavaScript( Node )并且它具有指针

这里是我如何转换的但是返回的结果不一样

我的 C++ 代码:

#include <stdio.h>
#include <stdlib.h>

unsigned int CRC_TAB[]={ /* CRC tab */
    0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
    0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
    0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
    0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
    0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
    0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
    0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
    0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
    0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
    0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
    0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
    0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
    0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
    0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
    0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
    0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
    0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
    0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
    0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
    0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
    0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
    0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
    0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
    0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
    0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
    0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
    0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
    0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
    0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
    0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
    0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
    0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0
    };

    unsigned short Pack_crc(unsigned char *ptr, unsigned char len)
    {
        unsigned int crc;
        unsigned char dat;
        crc=0;
        while(len--!=0)
        {
            dat=crc>>8; 
            crc<<=8; 
            crc^=CRC_TAB[dat^*ptr]; 
            ptr++;
        }

        return crc;
    }

    unsigned char mypacket[]=
    {
     0x10, 0x01, 0x0b, 0x01, 0x19, 0x00, 0x31, 0x01, 0x33, 0x07, 0x00, 0x00, 
     0x00, 0x04

    };

    int main(void)
    {
        unsigned short crcval= Pack_crc(mypacket,sizeof(mypacket));
        printf("Packet Size:%lu\r\n",sizeof(mypacket));
        printf("a crc value:%04X\r\n",crcval);
    }

这是我的代码的在线 C++ 编译器:https://www.onlinegdb.com/B1amfkDgV

输出是: 8B20

现在这是我的 javascript 代码:(没有 CRC_TAB)

function Pack_crc(ptr, len) {
  var crc;
  var dat;
  crc = 0;
  var i = 0;
  while (len-- != 0) {
    dat = crc >>> 8;
    crc <<= 8;
    crc ^= CRC_TAB[dat ^ ptr[i]];
    i++;
  }

  return crc;
}

const mypacket = Buffer.from([0x10, 0x01, 0x0b, 0x01, 0x19, 0x00, 0x31, 
0x01, 0x33, 0x07, 0x00, 0x00, 0x00, 0x04]);

var finish = Pack_crc(mypacket, mypacket.length);
console.log(finish);

Node 链接:https://repl.it/@aminjoharinia/OvalWelcomeCustomization

我想我不能正确地替换指针

我怎样才能得到相同的结果？

谢谢

Answer 1

你错过了两件事，都与类型有关:

• dat 是一个 unsigned char，所以 dat=crc>>8; 在 C++ 代码中隐式地将结果 chop 为8 位。等效的 JavaScript 代码是:

  dat = (crc >>> 8) & 0xff;
  

• Pack_crc 在 C++ 中被声明为返回一个 unsigned short，因此 return crc; 将结果隐式 chop 为 16 位。等效的 JavaScript 代码是:

  return crc & 0xffff;
  

通过这两项更改，我得到了 8b20 作为输出，与 C++ 版本相同。