str 2 hex

void str2hex(const char*p,unsigned int index)
{
      unsigned char i=0,j=0;
      for(;i < index;)
      {
          hexBuf[j]<<=4;
          if(*p >= '0' && '9' >= *p)
          {
              hexBuf[j]|=*p++ - '0';
          }
          else if(*p >='a' && 'f'>=*p)
          {
              hexBuf[j]|=*p++ - 87;
          }
          else if(*p >='A' && 'F'>=*p)
          {
              hexBuf[j]|=*p++ - 55;
          }
          else
          {
              return;             //invalid package received
          }
          i++;
          if(!(i%2))
          {
              j++;
          }
      }
}