x11-xserver-utils/sessreg/sessreg.c

/*
 * Copyright 1990, 1998  The Open Group
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that
 * copyright notice and this permission notice appear in supporting
 * documentation.
 * 
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 * 
 * Except as contained in this notice, the name of The Open Group shall
 * not be used in advertising or otherwise to promote the sale, use or
 * other dealings in this Software without prior written authorization
 * from The Open Group.
 *
 */

/* Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

/*
 * Author:  Keith Packard, MIT X Consortium
 * Lastlog support and dynamic utmp entry allocation
 *   by Andreas Stolcke <stolcke@icsi.berkeley.edu>
 */

/*
 * sessreg
 *
 * simple wtmp/utmp frobber
 *
 * usage: sessreg [ -w <wtmp-file> ] [ -u <utmp-file> ]
 *		  [ -l <line> ]
 *		  [ -L <lastlog-file> ]		      / #ifndef NO_LASTLOG
 *		  [ -h <host-name> ]				/ BSD only
 *		  [ -s <slot-number> ] [ -x Xservers-file ]	/ BSD only
 *		  [ -t <ttys-file> ]				/ BSD only
 *	          [ -a ] [ -d ] user-name
 *
 * one of -a or -d must be specified
 */

#include "sessreg.h"

# include	<X11/Xos.h>
# include	<X11/Xfuncs.h>
# include	<stdio.h>
# include	<stdlib.h>

#if defined(__SVR4) || defined(SVR4) || defined(linux) || defined(__GLIBC__)
# define SYSV
#endif

#include <time.h>
#define Time_t time_t

#ifdef USE_UTMP
static void set_utmp (struct utmp *u, char *line, char *user, char *host,
		      Time_t date, int addp);
#endif

#ifdef USE_UTMPX
static void set_utmpx (struct utmpx *u, const char *line, const char *user,
		       const char *host, Time_t date, int addp);
#endif

#ifdef SYSV
/* used for hashing ut_id */
typedef  unsigned long  int  ub4;   /* unsigned 4-byte quantities */
typedef  unsigned       char ub1;   /* unsigned 1-byte quantities */

#define hashsize(n) ((ub4)1<<(n))
#define hashmask(n) (hashsize(n)-1)

ub4 hash(register ub1 *k, register ub4 length, register ub4 initval);

#endif

static int wflag, uflag, lflag;
static char *wtmp_file, *utmp_file, *line;
#ifdef USE_UTMPX
#ifdef HAVE_UPDWTMPX
static char *wtmpx_file = NULL;
#endif
#ifdef HAVE_UTMPXNAME
static char *utmpx_file = NULL;
#endif
#endif
static int utmp_none, wtmp_none;
/*
 * BSD specific variables.  To make life much easier for Xstartup/Xreset
 * maintainers, these arguments are accepted but ignored for sysV
 */
static int hflag, sflag, xflag, tflag;
static char *host_name = NULL;
#ifdef USE_UTMP
static int slot_number;
#endif
static char *xservers_file, *ttys_file;
static char *user_name;
static int aflag, dflag;
#ifndef NO_LASTLOG
static char *llog_file;
static int llog_none, Lflag;
#endif

static char *program_name;

#ifndef SYSV
static int findslot (char *line_name, char *host_name, int addp, int slot);
static int Xslot (char *ttys_file, char *servers_file, char *tty_line,
		  char *host_name, int addp);
#endif

static int
usage (int x)
{
	if (x) {
		fprintf (stderr, "%s: usage %s {-a -d} [-w wtmp-file] [-u utmp-file]", program_name, program_name);
#ifndef NO_LASTLOG
		fprintf (stderr, " [-L lastlog-file]");
#endif
		fprintf (stderr, "\n");
		fprintf (stderr, "             [-t ttys-file] [-l line-name] [-h host-name]\n");
		fprintf (stderr, "             [-s slot-number] [-x servers-file] user-name\n");
		exit (1);
	}
	return x;
}

static char *
getstring (char ***avp, int *flagp)
{
	char	**a = *avp;

	usage ((*flagp)++);
	if (*++*a)
		return *a;
	++a;
	usage (!*a);
	*avp = a;
	return *a;
}

#ifndef SYSV
static int
syserr (int x, const char *s)
{
	if (x == -1) {
		perror (s);
		exit (1);
	}
	return x;
}
#endif

static int
sysnerr (int x, const char *s)
{
	if (x == 0) {
		perror (s);
		exit (1);
	}
	return x;
}

int
main (int argc, char **argv)
{
#if defined(USE_UTMP) && !defined(SYSV)
	int		utmp;
#endif
	char		*line_tmp;
#ifndef USE_UTMPX	
	int		wtmp;
#endif	
	Time_t		current_time;
#ifdef USE_UTMP
	struct utmp	utmp_entry;
#endif
#ifdef USE_UTMPX
	struct utmpx	utmpx_entry;
#endif

	program_name = argv[0];
	while (*++argv && **argv == '-') {
		switch (*++*argv) {
		case 'w':
			wtmp_file = getstring (&argv, &wflag);
			if (!strcmp (wtmp_file, "none"))
				wtmp_none = 1;
			break;
		case 'u':
			utmp_file = getstring (&argv, &uflag);
			if (!strcmp (utmp_file, "none"))
				utmp_none = 1;
			break;
#ifndef NO_LASTLOG
		case 'L':
			llog_file = getstring (&argv, &Lflag);
			if (!strcmp (llog_file, "none"))
				llog_none = 1;
			break;
#endif
		case 't':
			ttys_file = getstring (&argv, &tflag);
			break;
		case 'l':
			line = getstring (&argv, &lflag);
			break;
		case 'h':
			host_name = getstring (&argv, &hflag);
			break;
		case 's':
#ifdef USE_UTMP
			slot_number = atoi (getstring (&argv, &sflag));
#endif
			break;
		case 'x':
			xservers_file = getstring (&argv, &xflag);
			break;
		case 'a':
			aflag++;
			break;
		case 'd':
			dflag++;
			break;
		default:
			usage (1);
		}
	}
	usage (!(user_name = *argv++));
	usage (*argv != NULL);
	/*
	 * complain if neither aflag nor dflag are set,
	 * or if both are set.
	 */
	usage (!(aflag ^ dflag));
	usage (xflag && !lflag);
	/* set up default file names */
	if (!wflag) {
		wtmp_file = WTMP_FILE;
#if defined(USE_UTMPX) && defined(HAVE_UPDWTMPX)
		wtmpx_file = WTMPX_FILE;
#endif
	}
#ifndef NO_UTMP
	if (!uflag) {
		utmp_file = UTMP_FILE;
#if defined(USE_UTMPX) && defined(HAVE_UTMPXNAME)
		utmpx_file = UTMPX_FILE;
#endif
	}
#else
	utmp_none = 1;
#endif
#ifndef NO_LASTLOG
	if (!Lflag)
		llog_file = LLOG_FILE;
#endif
#if defined(USE_UTMP) && !defined(SYSV) && !defined(linux) && !defined(__QNX__)
	if (!tflag)
		ttys_file = TTYS_FILE;
	if (!sflag && !utmp_none) {
		if (xflag)
			sysnerr (slot_number = Xslot (ttys_file, xservers_file, line, host_name, aflag), "Xslot");
		else
			sysnerr (slot_number = ttyslot (), "ttyslot");
	}
#endif
	if (!lflag) {
		sysnerr ((line_tmp = ttyname (0)) != NULL, "ttyname");
		line = strrchr(line_tmp, '/');
		if (line)
			line = line + 1;
		else
			line = line_tmp;
	}
	time (&current_time);
#ifdef USE_UTMP
	set_utmp (&utmp_entry, line, user_name, host_name, current_time, aflag);
#endif

#ifdef USE_UTMPX
	/* need to set utmpxname() before calling set_utmpx() for
	   UtmpxIdOpen to work */
# ifdef HAVE_UTMPXNAME
	if (utmpx_file != NULL) {
	        utmpxname (utmpx_file);
	}
# endif
	set_utmpx (&utmpx_entry, line, user_name,
		   host_name, current_time, aflag);
#endif	

	if (!utmp_none) {
#ifdef USE_UTMPX
# ifdef HAVE_UTMPX_NAME
	    if (utmpx_file != NULL)
# endif
	    {
		setutxent ();
		(void) getutxid (&utmpx_entry);
		pututxline (&utmpx_entry);
		endutxent ();
	    }
#endif
#ifdef USE_UTMP
# ifdef SYSV
		utmpname (utmp_file);
		setutent ();
		(void) getutid (&utmp_entry);
		pututline (&utmp_entry);
		endutent ();
# else
		utmp = open (utmp_file, O_RDWR);
		if (utmp != -1) {
			syserr ((int) lseek (utmp, (long) slot_number * sizeof (struct utmp), 0), "lseek");
			sysnerr (write (utmp, (char *) &utmp_entry, sizeof (utmp_entry))
				        == sizeof (utmp_entry), "write utmp entry");
			close (utmp);
		}
# endif
#endif /* USE_UTMP */
	}
	if (!wtmp_none) {
#ifdef USE_UTMPX
# ifdef HAVE_UPDWTMPX
		if (wtmpx_file != NULL) {
			updwtmpx(wtmpx_file, &utmpx_entry);
		}
# endif
#else
		wtmp = open (wtmp_file, O_WRONLY|O_APPEND);
		if (wtmp != -1) {
			sysnerr (write (wtmp, (char *) &utmp_entry, sizeof (utmp_entry))
				        == sizeof (utmp_entry), "write wtmp entry");
			close (wtmp);
		}
#endif		
	}
#ifndef NO_LASTLOG
	if (aflag && !llog_none) {
	        int llog;
	        struct passwd *pwd = getpwnam(user_name);

	        sysnerr( pwd != NULL, "get user id");
	        llog = open (llog_file, O_RDWR);

		if (llog != -1) {
			struct lastlog ll;

			sysnerr (lseek(llog, (long) pwd->pw_uid*sizeof(ll), 0)
				        != -1, "seeking lastlog entry");
			bzero((char *)&ll, sizeof(ll));
			ll.ll_time = current_time;
			if (line)
			 (void) strncpy (ll.ll_line, line, sizeof (ll.ll_line));
			if (host_name)
			 (void) strncpy (ll.ll_host, host_name, sizeof (ll.ll_host));

			sysnerr (write (llog, (char *) &ll, sizeof (ll))
				        == sizeof (ll), "write lastlog entry");
			close (llog);
		}
	}
#endif
	return 0;
}

/*
 * fill in the appropriate records of the utmp entry
 */

#ifdef USE_UTMP
static void
set_utmp (struct utmp *u, char *line, char *user, char *host, Time_t date, int addp)
{
	bzero (u, sizeof (*u));
	if (line)
		(void) strncpy (u->ut_line, line, sizeof (u->ut_line));
	else
		bzero (u->ut_line, sizeof (u->ut_line));
	if (addp && user)
		(void) strncpy (u->ut_name, user, sizeof (u->ut_name));
	else
		bzero (u->ut_name, sizeof (u->ut_name));
#ifdef SYSV
	if (line) {
		/*
		 * The ut_id is 4 bytes long.  We make a hash of the line
		 * received, preceding it by ":" to prevent clashing with
		 * other ut_ids.
		 */
		ub4 h;
		u->ut_id[0]=':';
		h = hash(line, strlen(line),0x9e3779b9);
		h = (h & hashmask((sizeof(u->ut_id)-sizeof(char))*8));
		(void) strncpy (u->ut_id + 1,(char *) &h,  sizeof (u->ut_id)-sizeof(char));
	} else
		/*
		 * From utmp(5):
		 * Clearing ut_id may result in race conditions leading to corrupted
		 * utmp entries and and potential security holes.
		 */
		/* TODO: CHECK this  */
		bzero (u->ut_id, sizeof (u->ut_id));
	if (addp) {
		u->ut_pid = getppid ();
		u->ut_type = USER_PROCESS;
	} else {
		u->ut_pid = 0;
		u->ut_type = DEAD_PROCESS;
	}
#endif
#if (!defined(SYSV) && !defined(__QNX__)) || defined(linux)
	if (addp && host)
		(void) strncpy (u->ut_host, host, sizeof (u->ut_host));
	else
		bzero (u->ut_host, sizeof (u->ut_host));
#endif
	u->ut_time = date;
}
#endif /* USE_UTMP */

#ifdef USE_UTMPX
static int
UtmpxIdOpen( char *utmpId )
{
	struct utmpx *u;	/* pointer to entry in utmp file           */
	int    status = 1;	/* return code                             */

	setutxent();
 
	while ( (u = getutxent()) != NULL ) {
		
		if ( (strncmp(u->ut_id, utmpId, 4) == 0 ) &&
		     u->ut_type != DEAD_PROCESS ) {
			
			status = 0;
			break;
		}
	}
 
	endutxent();
	return (status);
}

static void
set_utmpx (struct utmpx *u, const char *line, const char *user,
	   const char *host, Time_t date, int addp)
{
	static const char letters[] =
	       "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

        if (line)
	{
                if(strcmp(line, ":0") == 0)
                        (void) strcpy(u->ut_line, "console");
                else
                        (void) strncpy (u->ut_line, line, sizeof (u->ut_line));

		strncpy(u->ut_host, line, sizeof(u->ut_host));
#if HAVE_UTMPX_UT_SYSLEN
		u->ut_syslen = strlen(line); 
#endif
	}
        else
                bzero (u->ut_line, sizeof (u->ut_line));
        if (addp && user)
                (void) strncpy (u->ut_user, user, sizeof (u->ut_user));
        else
                bzero (u->ut_user, sizeof (u->ut_user));

        if (line) {
                int     i;
                /*
                 * this is a bit crufty, but
                 * follows the apparent conventions in
                 * the ttys file.  ut_id is only 4 bytes
                 * long, and the last 4 bytes of the line
                 * name are written into it, left justified.
                 */
                i = strlen (line);
                if (i >= sizeof (u->ut_id))
                        i -= sizeof (u->ut_id);
                else
                        i = 0;
                (void) strncpy (u->ut_id, line + i, sizeof (u->ut_id));

		/* make sure there is no entry using identical ut_id */
		if (!UtmpxIdOpen(u->ut_id) && addp) {
                        int limit = sizeof(letters) - 1;
                        int t = 0;

                        u->ut_id[1] = line[i];
                        u->ut_id[2] = line[i+1];
                        u->ut_id[3] = line[i+2];
                        do {
                                u->ut_id[0] = letters[t];
                                t++;
                        } while (!UtmpxIdOpen(u->ut_id) && (t < limit));
                }
                if (!addp && strstr(line, ":") != NULL) {
                        struct utmpx *tmpu;             

                        while ( (tmpu = getutxent()) != NULL ) {
                                if ( (strcmp(tmpu->ut_host, line) == 0 ) &&
                                        tmpu->ut_type != DEAD_PROCESS ) {
                                        strncpy(u->ut_id, tmpu->ut_id,
						sizeof(u->ut_id));
                                        break;
                                }
                        }
                        endutxent();
                }
        } else
                bzero (u->ut_id, sizeof (u->ut_id));
	
        if (addp) {
                u->ut_pid = getppid ();
                u->ut_type = USER_PROCESS;
        } else {
                u->ut_pid = 0;
                u->ut_type = DEAD_PROCESS;
        }
	u->ut_tv.tv_sec = date;
	u->ut_tv.tv_usec = 0;
}
#endif /* USE_UTMPX */

#if defined(USE_UTMP) && !defined(SYSV)
/*
 * compute the slot-number for an X display.  This is computed
 * by counting the lines in /etc/ttys and adding the line-number
 * that the display appears on in Xservers.  This is a poor
 * design, but is limited by the non-existant interface to utmp.
 * If host_name is non-NULL, assume it contains the display name,
 * otherwise use the tty_line argument (i.e., the tty name).
 */

static int
Xslot (char *ttys_file, char *servers_file, char *tty_line, char *host_name,
       int addp)
{
	FILE	*ttys, *servers;
	int	c;
	int	slot = 1;
	int	column0 = 1;
	char	servers_line[1024];
	char	disp_name[512];
	int	len;
	char	*pos;

	/* remove screen number from the display name */
	memset(disp_name, 0, sizeof(disp_name));
	strncpy(disp_name, host_name ? host_name : tty_line, sizeof(disp_name)-1);
	pos = strrchr(disp_name, ':');
	if (pos) {
	    pos = strchr(pos, '.');
	    if (pos)
		*pos = '\0';
	}
	sysnerr ((int)(long)(ttys = fopen (ttys_file, "r")), ttys_file);
	while ((c = getc (ttys)) != EOF)
		if (c == '\n') {
			++slot;
			column0 = 1;
		} else
			column0 = 0;
	if (!column0)
		++slot;
	(void) fclose (ttys);
	sysnerr ((int)(long)(servers = fopen (servers_file, "r")), servers_file);

	len = strlen (disp_name);
	column0 = 1;
	while (fgets (servers_line, sizeof (servers_line), servers)) {
		if (column0 && *servers_line != '#') {
			if (!strncmp (disp_name, servers_line, len) &&
			    (servers_line[len] == ' ' ||
			     servers_line[len] == '\t'))
				return slot;
			++slot;
		}
		if (servers_line[strlen(servers_line)-1] != '\n')
			column0 = 0;
		else
			column0 = 1;
	}
	/*
	 * display not found in Xservers file - allocate utmp entry dinamically
	 */
	return findslot (tty_line, host_name, addp, slot);
}

/*
 * find a free utmp slot for the X display.  This allocates a new entry
 * past the regular tty entries if necessary, reusing existing entries
 * (identified by (line,hostname)) if possible.
 */
static int
findslot (char *line_name, char *host_name, int addp, int slot)
{
	int	utmp;
	struct	utmp entry;
	int	found = 0;
	int	freeslot = -1;

	syserr(utmp = open (utmp_file, O_RDONLY), "open utmp");

	/*
	 * first, try to locate a previous entry for this display
	 * also record location of a free slots in case we need a new one
	 */
	syserr ((int) lseek (utmp, (long) slot * sizeof (struct utmp), 0), "lseek");

	if (!host_name)
		host_name = "";

	while (read (utmp, (char *) &entry, sizeof (entry)) == sizeof (entry)) {
		if (strncmp(entry.ut_line, line_name,
			sizeof(entry.ut_line)) == 0 
#ifndef __QNX__
                    &&
		    strncmp(entry.ut_host, host_name,
			sizeof(entry.ut_host)) == 0
#endif
                   ) {
			found = 1;
			break;
		}
		if (freeslot < 0 && *entry.ut_name == '\0')
			freeslot = slot;
		++slot;
	}

	close (utmp);

	if (found)
		return slot;
	else if (!addp)
		return 0;	/* trying to delete a non-existing entry */
	else if (freeslot < 0)
		return slot;	/* first slot past current entries */
	else
		return freeslot;
}
#endif

#ifdef SYSV
/*
--------------------------------------------------------------------
mix -- mix 3 32-bit values reversibly.
For every delta with one or two bits set, and the deltas of all three
  high bits or all three low bits, whether the original value of a,b,c
  is almost all zero or is uniformly distributed,
* If mix() is run forward or backward, at least 32 bits in a,b,c
  have at least 1/4 probability of changing.
* If mix() is run forward, every bit of c will change between 1/3 and
  2/3 of the time.  (Well, 22/100 and 78/100 for some 2-bit deltas.)
mix() was built out of 36 single-cycle latency instructions in a
  structure that could supported 2x parallelism, like so:
      a -= b;
      a -= c; x = (c>>13);
      b -= c; a ^= x;
      b -= a; x = (a<<8);
      c -= a; b ^= x;
      c -= b; x = (b>>13);
      ...
  Unfortunately, superscalar Pentiums and Sparcs can't take advantage
  of that parallelism.  They've also turned some of those single-cycle
  latency instructions into multi-cycle latency instructions.  Still,
  this is the fastest good hash I could find.  There were about 2^^68
  to choose from.  I only looked at a billion or so.
--------------------------------------------------------------------
*/
#define mix(a,b,c) \
{ \
  a -= b; a -= c; a ^= (c>>13); \
  b -= c; b -= a; b ^= (a<<8); \
  c -= a; c -= b; c ^= (b>>13); \
  a -= b; a -= c; a ^= (c>>12);  \
  b -= c; b -= a; b ^= (a<<16); \
  c -= a; c -= b; c ^= (b>>5); \
  a -= b; a -= c; a ^= (c>>3);  \
  b -= c; b -= a; b ^= (a<<10); \
  c -= a; c -= b; c ^= (b>>15); \
}

/*
--------------------------------------------------------------------
hash() -- hash a variable-length key into a 32-bit value
  k       : the key (the unaligned variable-length array of bytes)
  len     : the length of the key, counting by bytes
  initval : can be any 4-byte value
Returns a 32-bit value.  Every bit of the key affects every bit of
the return value.  Every 1-bit and 2-bit delta achieves avalanche.
About 6*len+35 instructions.

The best hash table sizes are powers of 2.  There is no need to do
mod a prime (mod is sooo slow!).  If you need less than 32 bits,
use a bitmask.  For example, if you need only 10 bits, do
  h = (h & hashmask(10));
In which case, the hash table should have hashsize(10) elements.

If you are hashing n strings (ub1 **)k, do it like this:
  for (i=0, h=0; i<n; ++i) h = hash( k[i], len[i], h);

By Bob Jenkins, 1996.  bob_jenkins@burtleburtle.net.  You may use this
code any way you wish, private, educational, or commercial.  It's free.

[On 27 May 2004, Bob Jenkins further clarified the above statement.

  From: Bob Jenkins <bob_jenkins@burtleburtle.net>
  Date: Thu, 27 May 2004 22:33:06 -0700
  To: Margarita Manterola <marga@marga.com.ar>
  Subject: Re: Hash function

  The algorithm is public domain.  I ask that I be referenced as the
  source of the algorithm, but I can't enforce that, since being public
  domain means I've reserved no rights at all.

-- Branden Robinson, 2004-06-06]

See http://burtleburtle.net/bob/hash/evahash.html
Use for hash table lookup, or anything where one collision in 2^^32 is
acceptable.  Do NOT use for cryptographic purposes.
--------------------------------------------------------------------
*/

ub4
hash(register ub1 *k, register ub4 length, register ub4 initval)
{
   register ub4 a,b,c,len;

   /* Set up the internal state */
   len = length;
   a = b = 0x9e3779b9;  /* the golden ratio; an arbitrary value */
   c = initval;         /* the previous hash value */

   /*---------------------------------------- handle most of the key */
   while (len >= 12)
   {
      a += (k[0] +((ub4)k[1]<<8) +((ub4)k[2]<<16) +((ub4)k[3]<<24));
      b += (k[4] +((ub4)k[5]<<8) +((ub4)k[6]<<16) +((ub4)k[7]<<24));
      c += (k[8] +((ub4)k[9]<<8) +((ub4)k[10]<<16)+((ub4)k[11]<<24));
      mix(a,b,c);
      k += 12; len -= 12;
   }

   /*------------------------------------- handle the last 11 bytes */
   c += length;
   switch(len)              /* all the case statements fall through */
   {
   case 11: c+=((ub4)k[10]<<24);
   case 10: c+=((ub4)k[9]<<16);
   case 9 : c+=((ub4)k[8]<<8);
      /* the first byte of c is reserved for the length */
   case 8 : b+=((ub4)k[7]<<24);
   case 7 : b+=((ub4)k[6]<<16);
   case 6 : b+=((ub4)k[5]<<8);
   case 5 : b+=k[4];
   case 4 : a+=((ub4)k[3]<<24);
   case 3 : a+=((ub4)k[2]<<16);
   case 2 : a+=((ub4)k[1]<<8);
   case 1 : a+=k[0];
     /* case 0: nothing left to add */
   }
   mix(a,b,c);
   /*-------------------------------------------- report the result */
   return c;
}

#endif