text: /*
   * arch/sh/lib/csum_parial.c
   *
   * This file contains network checksum routines that are better done
   * in an architecture-specific manner due to speed..
   */
  
  #undef DEBUG
  
  #include <linux/config.h>
  #include <linux/string.h>
  #include <linux/errno.h>
  #include <linux/kernel.h>
  #include <asm/byteorder.h>
  #include <asm/uaccess.h>
  
  static inline unsigned short from64to16(unsigned long long x)
  {
  	/* add up 32-bit words for 33 bits */
  	x = (x & 0xffffffff) + (x >> 32);
  	/* add up 16-bit and 17-bit words for 17+c bits */
  	x = (x & 0xffff) + (x >> 16);
  	/* add up 16-bit and 2-bit for 16+c bit */
  	x = (x & 0xffff) + (x >> 16);
  	/* add up carry.. */
  	x = (x & 0xffff) + (x >> 16);
  	return x;
  }
  
  static inline unsigned short foldto16(unsigned long x)
  {
  	/* add up 16-bit for 17 bits */
  	x = (x & 0xffff) + (x >> 16);
  	/* add up carry.. */
  	x = (x & 0xffff) + (x >> 16);
  	return x;
  }
  
  static inline unsigned short myfoldto16(unsigned long long x)
  {
  	/* Fold down to 32-bits so we don't loose in the typedef-less
  	   network stack.  */
  	/* 64 to 33 */
  	x = (x & 0xffffffff) + (x >> 32);
  	/* 33 to 32 */
  	x = (x & 0xffffffff) + (x >> 32);
  
  	/* add up 16-bit for 17 bits */
  	x = (x & 0xffff) + (x >> 16);
  	/* add up carry.. */
  	x = (x & 0xffff) + (x >> 16);
  	return x;
  }
  
  #define odd(x) ((x)&1)
  #define U16(x) ntohs(x)
  
  static unsigned long do_csum(const unsigned char *buff, int len)
  {
  	int odd, count;
  	unsigned long result = 0;
  
  	pr_debug("do_csum buff %p, len %d (0x%x)\n", buff, len, len);
  #ifdef DEBUG
  	for (i = 0; i < len; i++) {
  		if ((i % 26) == 0)
  			printk("\n");
  		printk("%02X ", buff[i]);
  	}
  #endif
  
  	if (len <= 0)
  		goto out;
  
  	odd = 1 & (unsigned long) buff;
  	if (odd) {
  		result = *buff << 8;
  		len--;
  		buff++;
  	}
  	count = len >> 1;	/* nr of 16-bit words.. */
  	if (count) {
  		if (2 & (unsigned long) buff) {
  			result += *(unsigned short *) buff;
  			count--;
  			len -= 2;
  			buff += 2;
  		}
  		count >>= 1;	/* nr of 32-bit words.. */
  		if (count) {
  			unsigned long carry = 0;
  			do {
  				unsigned long w = *(unsigned long *) buff;
  				buff += 4;
  				count--;
  				result += carry;
  				result += w;
  				carry = (w > result);
  			} while (count);
  			result += carry;
  			result = (result & 0xffff) + (result >> 16);
  		}
  		if (len & 2) {
  			result += *(unsigned short *) buff;
  			buff += 2;
  		}
  	}
  	if (len & 1)
  		result += *buff;
  	result = foldto16(result);
  	if (odd)
  		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
  
  	pr_debug("\nCHECKSUM is 0x%x\n", result);
  
        out:
  	return result;
  }
  
  /* computes the checksum of a memory block at buff, length len,
     and adds in "sum" (32-bit)  */
  unsigned int csum_partial(const unsigned char *buff, int len, unsigned int sum)
  {
  	unsigned long long result = do_csum(buff, len);
  
  	/* add in old sum, and carry.. */
  	result += sum;
  	/* 32+c bits -> 32 bits */
  	result = (result & 0xffffffff) + (result >> 32);
  
  	pr_debug("csum_partial, buff %p len %d sum 0x%x result=0x%016Lx\n",
  		buff, len, sum, result);
  
  	return result;
  }
  
  /* Copy while checksumming, otherwise like csum_partial.  */
  unsigned int
  csum_partial_copy(const unsigned char *src, unsigned char *dst, int len, unsigned int sum)
  {
  	sum = csum_partial(src, len, sum);
  	memcpy(dst, src, len);
  
  	return sum;
  }
  
  /* Copy from userspace and compute checksum.  If we catch an exception
     then zero the rest of the buffer.  */
  unsigned int
  csum_partial_copy_from_user(const unsigned char *src, unsigned char *dst, int len,
  			    unsigned int sum, int *err_ptr)
  {
  	int missing;
  
  	pr_debug
  	    ("csum_partial_copy_from_user src %p, dest %p, len %d, sum %08x, err_ptr %p\n",
  	     src, dst, len, sum, err_ptr);
  	missing = copy_from_user(dst, src, len);
  	pr_debug("  access_ok %d\n", __access_ok((unsigned long) src, len));
  	pr_debug("  missing %d\n", missing);
  	if (missing) {
  		memset(dst + len - missing, 0, missing);
  		*err_ptr = -EFAULT;
  	}
  
  	return csum_partial(dst, len, sum);
  }
  
  /* Copy to userspace and compute checksum.  */
  unsigned int
  csum_partial_copy_to_user(const unsigned char *src, unsigned char *dst, int len,
  			  unsigned int sum, int *err_ptr)
  {
  	sum = csum_partial(src, len, sum);
  
  	if (copy_to_user(dst, src, len))
  		*err_ptr = -EFAULT;
  
  	return sum;
  }
  
  /*
   *	This is a version of ip_compute_csum() optimized for IP headers,
   *	which always checksum on 4 octet boundaries.
   */
  unsigned short ip_fast_csum(unsigned char *iph, unsigned int ihl)
  {
  	pr_debug("ip_fast_csum %p,%d\n", iph, ihl);
  
  	return ~do_csum(iph, ihl * 4);
  }
  
  unsigned int csum_tcpudp_nofold(unsigned long saddr,
  				unsigned long daddr,
  				unsigned short len,
  				unsigned short proto, unsigned int sum)
  {
  	unsigned long long result;
  
  	pr_debug("ntohs(0x%x)=0x%x\n", 0xdead, ntohs(0xdead));
  	pr_debug("htons(0x%x)=0x%x\n", 0xdead, htons(0xdead));
  
  	result = ((unsigned long long) saddr +
  		  (unsigned long long) daddr +
  		  (unsigned long long) sum +
  		  ((unsigned long long) ntohs(len) << 16) +
  		  ((unsigned long long) proto << 8));
  
  	/* Fold down to 32-bits so we don't loose in the typedef-less
  	   network stack.  */
  	/* 64 to 33 */
  	result = (result & 0xffffffff) + (result >> 32);
  	/* 33 to 32 */
  	result = (result & 0xffffffff) + (result >> 32);
  
  	pr_debug("%s saddr %x daddr %x len %x proto %x sum %x result %08Lx\n",
  		__FUNCTION__, saddr, daddr, len, proto, sum, result);
  
  	return result;
  }
  
  // Post SIM:
  unsigned int
  csum_partial_copy_nocheck(const unsigned char *src, unsigned char *dst, int len, unsigned int sum)
  {
  	//  unsigned dummy;
  	pr_debug("csum_partial_copy_nocheck src %p dst %p len %d\n", src, dst,
  		len);
  
  	return csum_partial_copy(src, dst, len, sum);
  }
  