/******************************************************************************
;   Code for application report slaa221 - "CRC Implementation with MSP430"
;
;   E.Lenchak
;   Texas Instruments, Inc
;   March 2004
;   Built with IAR Embedded Workbench Version: 3.20A
;******************************************************************************
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/**********************************************************************************
FUNCTIONS: 16/32-bit CRC Algorithms, bitwsie and table methods
ARGUMENTS: "bitwise algorithm function signature"
   return: CRC
   arg1: CRC init value
   arg2: CRC generator polynomial
   arg3: pointer to the message
   arg4: size of message in bytes

  "table-based algorithm function signature"
   return: CRC
   arg1: CRC init value
   arg2: pointer to CRC table (specific to generator polynomial)
   arg3: pointer to the message
   arg4: size of message in bytes
***********************************************************************************/

#ifdef __ICC430__
#include  "msp430x16x.h"
#endif

#include "..\inc\crc.h"

/**************************************
 CRC MEMBERS (FUNCTIONS)
**************************************/

// this is an equivalent C implementation to the assembly implementation
unsigned short crc16MakeBitwise(unsigned short crc, unsigned short poly, 
      unsigned char *pmsg, unsigned int msg_size)
{
    unsigned int i, j, carry;
    unsigned char msg;
    unsigned short temp;

 temp = *pmsg++ << 8;
 temp |= *pmsg++;
 crc ^= temp;
    
    for(i = 0 ; i < msg_size-2 ; i ++)
    {
        msg = *pmsg++;
        
  for(j = 0 ; j < 8 ; j++)
        {
   carry = crc & 0x8000;
   crc = (crc << 1) | (msg >> 7);
   if(carry) crc ^= poly;
   msg <<= 1;
        }
    }

    for(i = 0 ; i < 2 ; i ++)
    {   
  for(j = 0 ; j < 8 ; j++)
        {
   carry = crc & 0x8000;
   crc <<= 1;
   if(carry) crc ^= poly;
        } 
    }
    return(crc ^ CRC16_FINAL_XOR);
}

// this is a C-optimized implementation
unsigned short crc16MakeBitwise2(unsigned short crc, unsigned short poly,
      unsigned char *pmsg, unsigned int msg_size)
{
    unsigned int i, j;
    unsigned short msg;
    
    for(i = 0 ; i < msg_size ; i ++)
    {
        msg = (*pmsg++ << 8);
        
  for(j = 0 ; j < 8 ; j++)
        {
            if((msg ^ crc) >> 15) crc = (crc << 1) ^ poly;
   else crc <<= 1; 
   msg <<= 1;
        }
    }
   
    return(crc ^ CRC16_FINAL_XOR);
}

// this is an equivalent C implementation to the assembly implementation
unsigned long crc32MakeBitwise(unsigned long crc, unsigned long poly, 
      unsigned char *pmsg, unsigned int msg_size)
{
    unsigned int i, j, carry;
    unsigned char msg;
    unsigned long temp;

 temp = (unsigned long)(*pmsg++) << 24;
 temp |= (unsigned long)(*pmsg++) << 16;
 temp |= (unsigned long)(*pmsg++) << 8;
 temp |= (unsigned long)(*pmsg++);
 crc ^= temp;

    for(i = 0 ; i < msg_size-4 ; i ++)
    {
        msg = *pmsg++;

  for(j = 0 ; j < 8 ; j++)
        {
   carry = crc >> 31;
   crc = (crc << 1) | (msg >> 7);
   if(carry) crc ^= poly;
   msg <<= 1;
        }
    }
    
    for(i = 0 ; i < 4 ; i ++)
    {   
  for(j = 0 ; j < 8 ; j++)
        {
   carry = crc >> 31;
   crc <<= 1;
   if(carry) crc ^= poly;
        } 
    }
 
    return(crc ^ CRC32_FINAL_XOR);
}

// this is a C-optimized implementation
unsigned long crc32MakeBitwise2(unsigned long crc, unsigned long poly, 
        unsigned char *pmsg, unsigned int msg_size)
{
    unsigned int i, j;
    unsigned long msg;
            
    for(i = 0 ; i < msg_size ; i++)
    {
        msg = *pmsg++;
        msg <<= 24;
        
        for(j = 0 ; j < 8 ; j++)
        {
            if((msg ^ crc) >> 31) crc = (crc << 1) ^ poly;
   else crc <<= 1;
   msg <<= 1;
        }
    }
    
    return(crc ^ CRC32_FINAL_XOR);
}

unsigned short crc16MakeTableMethod(unsigned short crc, TBL_MEM unsigned short *table,
         unsigned char *pbuffer, unsigned int length)
{
    while(length--) 
        crc = table[((crc >> 8) ^ *pbuffer++)] ^ (crc << 8); // normal

    return(crc ^ CRC16_FINAL_XOR);
}

unsigned short crc16rMakeTableMethod(unsigned short crc, TBL_MEM unsigned short *table,
         unsigned char *pbuffer, unsigned int length)
{
    while(length--) 
        crc = table[(crc & 0xFF) ^ *pbuffer++] ^ (crc >> 8); // reflected

    return(crc ^ CRC16R_FINAL_XOR);
}

unsigned long crc32MakeTableMethod(unsigned long crc, TBL_MEM unsigned long *table, 
           unsigned char *pbuffer, unsigned int length)
{
    while(length--) 
        crc = table[((crc >> 24) ^ *pbuffer++)] ^ (crc << 8); // normal

    return(crc ^ CRC32_FINAL_XOR);
}

unsigned long crc32rMakeTableMethod(unsigned long crc, TBL_MEM unsigned long *table, 
           unsigned char *pbuffer, unsigned int length)
{
    while(length--) 
        crc = table[(crc ^ *pbuffer++) & 0xFFL] ^ (crc >> 8); // reflected

    return(crc ^ CRC32R_FINAL_XOR);
}

/************************************
 CRC UTILITIES
************************************/

void crc16BuildTable(unsigned short *ptable, unsigned short poly)
{
 unsigned int i, j;

    for(i = 0; i <= 255; i++)
    {
        ptable[i] = i << 8;
        for(j = 0; j < 8; j++)
            ptable[i] = (ptable[i] << 1) ^ (ptable[i] & 0x8000 ? poly : 0);
    }
}

void crc32BuildTable(unsigned long *ptable, unsigned long poly)
{
 unsigned int i, j;

    for(i = 0; i <= 255; i++)
    {
        ptable[i] = (long)i << 24;        
        for(j = 0; j < 8; j++)
            ptable[i] = (ptable[i] << 1) ^ (ptable[i] & 0x80000000 ? poly : 0);
    }
}

unsigned long bitReflect(unsigned long data, unsigned int width)
{
    unsigned long result = 0;
 unsigned int i;

    for (i = 1; i < (width + 1); i++)
    {
        if(data & 1) result |= 0x1L << (width - i);
        data >>= 1;
    }  

    return result;
}

/************************************ END ***************************************/