text: /* 
   * Licensed under the GPL
   */
  
  #ifndef __UM_SYSDEP_CHECKSUM_H
  #define __UM_SYSDEP_CHECKSUM_H
  
  #include "linux/string.h"
  
  /*
   * computes the checksum of a memory block at buff, length len,
   * and adds in "sum" (32-bit)
   *
   * returns a 32-bit number suitable for feeding into itself
   * or csum_tcpudp_magic
   *
   * this function must be called with even lengths, except
   * for the last fragment, which may be odd
   *
   * it's best to have buff aligned on a 32-bit boundary
   */
  unsigned int csum_partial(const unsigned char * buff, int len, 
  			  unsigned int sum);
  
  /*
   * the same as csum_partial, but copies from src while it
   * checksums, and handles user-space pointer exceptions correctly, when needed.
   *
   * here even more important to align src and dst on a 32-bit (or even
   * better 64-bit) boundary
   */
  
  unsigned int csum_partial_copy_to(const char *src, char *dst, int len, 
  				  int sum, int *err_ptr);
  unsigned int csum_partial_copy_from(const char *src, char *dst, int len, 
  				    int sum, int *err_ptr);
  
  /*
   *	Note: when you get a NULL pointer exception here this means someone
   *	passed in an incorrect kernel address to one of these functions.
   *
   *	If you use these functions directly please don't forget the
   *	verify_area().
   */
  
  static __inline__
  unsigned int csum_partial_copy_nocheck(const char *src, char *dst,
  				       int len, int sum)
  {
  	memcpy(dst, src, len);
  	return(csum_partial(dst, len, sum));
  }
  
  static __inline__
  unsigned int csum_partial_copy_from_user(const char *src, char *dst,
  					 int len, int sum, int *err_ptr)
  {
  	return csum_partial_copy_from(src, dst, len, sum, err_ptr);
  }
  
  /*
   * These are the old (and unsafe) way of doing checksums, a warning message 
   * will be printed if they are used and an exception occurs.
   *
   * these functions should go away after some time.
   */
  
  #define csum_partial_copy_fromuser csum_partial_copy_from_user
  unsigned int csum_partial_copy( const char *src, char *dst, int len, int sum);
  
  /*
   *	This is a version of ip_compute_csum() optimized for IP headers,
   *	which always checksum on 4 octet boundaries.
   *
   *	By Jorge Cwik <jorge@laser.satlink.net>, adapted for linux by
   *	Arnt Gulbrandsen.
   */
  static inline unsigned short ip_fast_csum(unsigned char * iph,
  					  unsigned int ihl)
  {
  	unsigned int sum;
  
  	__asm__ __volatile__(
  	    "movl (%1), %0	;\n"
  	    "subl $4, %2	;\n"
  	    "jbe 2f		;\n"
  	    "addl 4(%1), %0	;\n"
  	    "adcl 8(%1), %0	;\n"
  	    "adcl 12(%1), %0	;\n"
  "1:	    adcl 16(%1), %0	;\n"
  	    "lea 4(%1), %1	;\n"
  	    "decl %2		;\n"
  	    "jne 1b		;\n"
  	    "adcl $0, %0	;\n"
  	    "movl %0, %2	;\n"
  	    "shrl $16, %0	;\n"
  	    "addw %w2, %w0	;\n"
  	    "adcl $0, %0	;\n"
  	    "notl %0		;\n"
  "2:				;\n"
  	/* Since the input registers which are loaded with iph and ipl
  	   are modified, we must also specify them as outputs, or gcc
  	   will assume they contain their original values. */
  	: "=r" (sum), "=r" (iph), "=r" (ihl)
  	: "1" (iph), "2" (ihl));
  	return(sum);
  }
  
  /*
   *	Fold a partial checksum
   */
  
  static inline unsigned int csum_fold(unsigned int sum)
  {
  	__asm__(
  		"addl %1, %0		;\n"
  		"adcl $0xffff, %0	;\n"
  		: "=r" (sum)
  		: "r" (sum << 16), "0" (sum & 0xffff0000)
  	);
  	return (~sum) >> 16;
  }
  
  static inline unsigned long csum_tcpudp_nofold(unsigned long saddr,
  						   unsigned long daddr,
  						   unsigned short len,
  						   unsigned short proto,
  						   unsigned int sum)
  {
      __asm__(
  	"addl %1, %0	;\n"
  	"adcl %2, %0	;\n"
  	"adcl %3, %0	;\n"
  	"adcl $0, %0	;\n"
  	: "=r" (sum)
  	: "g" (daddr), "g"(saddr), "g"((ntohs(len)<<16)+proto*256), "0"(sum));
      return sum;
  }
  
  /*
   * computes the checksum of the TCP/UDP pseudo-header
   * returns a 16-bit checksum, already complemented
   */
  static inline unsigned short int csum_tcpudp_magic(unsigned long saddr,
  						   unsigned long daddr,
  						   unsigned short len,
  						   unsigned short proto,
  						   unsigned int sum)
  {
  	return csum_fold(csum_tcpudp_nofold(saddr,daddr,len,proto,sum));
  }
  
  /*
   * this routine is used for miscellaneous IP-like checksums, mainly
   * in icmp.c
   */
  
  static inline unsigned short ip_compute_csum(unsigned char * buff, int len)
  {
      return csum_fold (csum_partial(buff, len, 0));
  }
  
  #define _HAVE_ARCH_IPV6_CSUM
  static __inline__ unsigned short int csum_ipv6_magic(struct in6_addr *saddr,
  						     struct in6_addr *daddr,
  						     __u32 len,
  						     unsigned short proto,
  						     unsigned int sum)
  {
  	__asm__(
  		"addl 0(%1), %0		;\n"
  		"adcl 4(%1), %0		;\n"
  		"adcl 8(%1), %0		;\n"
  		"adcl 12(%1), %0	;\n"
  		"adcl 0(%2), %0		;\n"
  		"adcl 4(%2), %0		;\n"
  		"adcl 8(%2), %0		;\n"
  		"adcl 12(%2), %0	;\n"
  		"adcl %3, %0		;\n"
  		"adcl %4, %0		;\n"
  		"adcl $0, %0		;\n"
  		: "=&r" (sum)
  		: "r" (saddr), "r" (daddr),
  		  "r"(htonl(len)), "r"(htonl(proto)), "0"(sum));
  
  	return csum_fold(sum);
  }
  
  /*
   *	Copy and checksum to user
   */
  #define HAVE_CSUM_COPY_USER
  static __inline__ unsigned int csum_and_copy_to_user(const char *src, 
  						     char *dst, int len,
  						     int sum, int *err_ptr)
  {
  	if (access_ok(VERIFY_WRITE, dst, len))
  		return(csum_partial_copy_to(src, dst, len, sum, err_ptr));
  
  	if (len)
  		*err_ptr = -EFAULT;
  
  	return -1; /* invalid checksum */
  }
  
  #endif
  
  /*
   * Overrides for Emacs so that we follow Linus's tabbing style.
   * Emacs will notice this stuff at the end of the file and automatically
   * adjust the settings for this buffer only.  This must remain at the end
   * of the file.
   * ---------------------------------------------------------------------------
   * Local variables:
   * c-file-style: "linux"
   * End:
   */
  