Converting 8 bit CRC function written in C to PHP -

i trying convert c function php 8 bit crc calculation.

the original c code:

uint8_t crccalc (uint8_t* pointer, uint16_t len) {      uint8_t crc = 0x00;      uint16_t tmp;      while(len > 0) {          tmp = crc << 1;          tmp += *pointer;          crc = (tmp & 0xff) + (tmp >> 8);          pointer++;          --len;      }      return crc;  } 

the php code have come is:

function crc8_calc($hex_string) {     $bin_data = pack('h*',$hex_string);     $bin_length = strlen($bin_data);      $crc    =   0x00;     $pos    =   0;      while($bin_length>0)     {         //$pos = $crc << 1;          $crc = ($bin_data[$pos] & 0xff) + ($bin_data[$pos] >> 8);         $bin_length --;         $pos++ ;     }      return $crc; } 

there missing results php functions not correct. not familiar c, not sure if conversion correct. c function gives out correct crc

for example, if hex representation of string is: 280500000805151001240000000010017475260004041001372068828503000000000000

the crc should d4.

i have seen following links crc8 calculation, seem missing something

how generate 8bit crc in php crc8-check in php

i have taken bits of conversion code answer convert c php crc16 function

try this:

function crc8_calc($hex_string) {     $bin_data = pack('h*',$hex_string);     $bin_length = strlen($bin_data);      $crc = 0;     $tmp = 0;     $pos = 0;      while($bin_length>0)     {         $tmp = $crc << 1;         $tmp = $tmp + ord($bin_data[$pos]); //added ord          $crc = ($tmp + ($tmp >> 8)) & 0xff;         $bin_length --;         $pos++ ;     }     return $crc; }