calculation of 32 bit CRC(Cyclic Redundancy Code)in C

[khatavkar]

please help me!!
i have written a program to calculate 32 bit CRC(used for ETHERNET)..but its not working and giving correct output..
please let me know my mistakes..

output should be :E7 B0 51 93

/**************  program starts here *************************/
typedef unsigned long ul;
typedef unsigned char uchar;
 
uchar buffer_bytes[64] = {0x00,0x14,0x85,0x31,0x24,0x10,0x00,0x15,0x00,0x15,0x9f,0x07,0x08,0x06,0x00,0x01,0x08,0x00,0x06,0x04,0x00,0x02,0x00,0x15,0x00,0x15,0x9f,0x07,0xc0,0xa8,0x00,0x02,0x00,0x14,0x85,0x31,0x24,0x10,0xc0,0xa8,0x00,0x01,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00};
ul     remainder ,temp;        //to get 32 bit number
unsigned short weld,joint;
 
unsigned char i,count = 0 ,str_length =64,  *ptr,j;
 
 
#define MSB 0x80000000;
#define POLY 0x04C11DB7    
#define printf printf_fast_f
 
void init_uart(void)
{
    ES = 0 ;                    //Disable serial interrupt.
    SCON = 0x50 ;                //mode 0,REN enabled
    BDRCON = 0x0E ;                //
 
    PCON &= 0x7F ;
    BRL = 224 ;
    BDRCON |= 0x10 ;    
}
 
void putchar(uchar send_this)
{
    uart_send_char(send_this);
}
 
void main(void)
{
    init_uart();
 
    ptr = &buffer_bytes[0];
 
    //----------------------------------------------------------------------------------------------------------/
    //            get 32 bit number out of the whole string                                                         /
    //----------------------------------------------------------------------------------------------------------/
    weld = (unsigned short)*ptr;                                                                                                   
    ptr++;                                                                                                                              
    weld = ((weld << 8) & 0xff00) +  (unsigned short)*ptr;        //16 bit number higher                                            
    ptr++;
    joint =  (unsigned short)*ptr;
    ptr ++;
 
    joint = ((joint << 8) &0xff00) + (unsigned short) *ptr    ;    //16 bit number lower
    ptr ++;                                                        //pointer points the next byte after 4th byte
    remainder =  weld;
    remainder = (remainder << 16) & 0xffff0000  ;        
    remainder = remainder + joint;                                    //32 bit number
 
 
    //remainder = remainder ^ (ul) 0xFFFFFFFF;
//----------------------------------------------------------------------------------------------------
 
    //str_length = str_length  - 4;
 
    for(j = str_length; j>0 ; j--)                    //str_length = no. of bytes in string
    {
        if((remainder & (ul)0xFF000000)==0x00000000)
        {
            remainder = remainder << 8;
            remainder = (remainder & (ul)0xFFFFFF00) | (ul)*ptr;
        }
        else
        {
            for(i=0; i<8 ; i++)
            {
            printf(" %lx\r\n",remainder);
                if((remainder & (ul)0x80000000) == (ul)0x80000000)        //if MSB is high then shift left by 1, get next bit 0
                {                                                        
                    remainder = remainder << 1;
 
                    if((*ptr & 0x80) == 0x80)
                    {
                        remainder |= (ul)0x00000001;
                    }
                    else 
                    {
                        remainder |= (ul)0x00000000;
                    }
                    *ptr = *ptr << 1;                            //XOR remainder with POLY
                    printf("msg %lx\r\n",remainder);
 
                    remainder = remainder ^ (ul)0x04C11DB7;
                    printf("XOR abov msg wiD POLY\r\n");
                }
                else
                {
 
                //    while((remainder & (ul)0x80000000) == (ul)0x00000000)
                //    {
                        remainder = remainder << 1;
                        if((*ptr & 0x80) == 0x80)
                        {
                            remainder |= (ul)0x00000001;
                        }
                        else
                        { 
                            remainder |= (ul)0x00000000;
                        }
                        *ptr = *ptr << 1;
                //        i++;
                //        if (i >= 8)break;
                    //}
 
                }
            }
            ptr ++;
            //printf("ptr = %2x\r\n",*ptr);
        }
    }