Java(tm) Binary Kernel Support for Linux v1.03
                 ----------------------------------------------
  
  Linux beats them ALL! While all other OS's are TALKING about direct
  support of Java Binaries in the OS, Linux is doing it!
  
  You can execute Java applications and Java Applets just like any
  other program after you have done the following:
  
  1) You MUST FIRST install the Java Developers Kit for Linux.
     The Java on Linux HOWTO gives the details on getting and
     installing this. This HOWTO can be found at:
  
  	ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/Java-HOWTO
  
     You should also set up a reasonable CLASSPATH environment
     variable to use Java applications that make use of any
     nonstandard classes (not included in the same directory
     as the application itself).
  
  2) You have to compile BINFMT_MISC either as a module or into
     the kernel (CONFIG_BINFMT_MISC) and set it up properly.
     If you choose to compile it as a module, you will have
     to insert it manually with modprobe/insmod, as kmod
     cannot easily be supported with binfmt_misc. 
     Read the file 'binfmt_misc.txt' in this directory to know
     more about the configuration process.
  
  3) Add the following configuration items to binfmt_misc
     (you should really have read binfmt_misc.txt now):
     support for Java applications:
       ':Java:M::\xca\xfe\xba\xbe::/usr/local/bin/javawrapper:'
     support for executable Jar files:
       ':ExecutableJAR:E::jar::/usr/local/bin/jarwrapper:'
     support for Java Applets:
       ':Applet:E::html::/usr/bin/appletviewer:'
     or the following, if you want to be more selective:
       ':Applet:M::<!--applet::/usr/bin/appletviewer:'
  
     Of course you have to fix the path names. The path/file names given in this
     document match the Debian 2.1 system. (i.e. jdk installed in /usr,
     custom wrappers from this document in /usr/local)
  
     Note, that for the more selective applet support you have to modify
     existing html-files to contain <!--applet--> in the first line
     ('<' has to be the first character!) to let this work!
  
     For the compiled Java programs you need a wrapper script like the
     following (this is because Java is broken in case of the filename
     handling), again fix the path names, both in the script and in the
     above given configuration string.
  
     You, too, need the little program after the script. Compile like
     gcc -O2 -o javaclassname javaclassname.c
     and stick it to /usr/local/bin.
  
     Both the javawrapper shellscript and the javaclassname program
     were supplied by Colin J. Watson <cjw44@cam.ac.uk>.
  
  ====================== Cut here ===================
  #!/bin/bash
  # /usr/local/bin/javawrapper - the wrapper for binfmt_misc/java
  
  if [ -z "$1" ]; then
  	exec 1>&2
  	echo Usage: $0 class-file
  	exit 1
  fi
  
  CLASS=$1
  FQCLASS=`/usr/local/bin/javaclassname $1`
  FQCLASSN=`echo $FQCLASS | sed -e 's/^.*\.\([^.]*\)$/\1/'`
  FQCLASSP=`echo $FQCLASS | sed -e 's-\.-/-g' -e 's-^[^/]*$--' -e 's-/[^/]*$--'`
  
  # for example:
  # CLASS=Test.class
  # FQCLASS=foo.bar.Test
  # FQCLASSN=Test
  # FQCLASSP=foo/bar
  
  unset CLASSBASE
  
  declare -i LINKLEVEL=0
  
  while :; do
  	if [ "`basename $CLASS .class`" == "$FQCLASSN" ]; then
  		# See if this directory works straight off
  		cd -L `dirname $CLASS`
  		CLASSDIR=$PWD
  		cd $OLDPWD
  		if echo $CLASSDIR | grep -q "$FQCLASSP$"; then
  			CLASSBASE=`echo $CLASSDIR | sed -e "s.$FQCLASSP$.."`
  			break;
  		fi
  		# Try dereferencing the directory name
  		cd -P `dirname $CLASS`
  		CLASSDIR=$PWD
  		cd $OLDPWD
  		if echo $CLASSDIR | grep -q "$FQCLASSP$"; then
  			CLASSBASE=`echo $CLASSDIR | sed -e "s.$FQCLASSP$.."`
  			break;
  		fi
  		# If no other possible filename exists
  		if [ ! -L $CLASS ]; then
  			exec 1>&2
  			echo $0:
  			echo "  $CLASS should be in a" \
  			     "directory tree called $FQCLASSP"
  			exit 1
  		fi
  	fi
  	if [ ! -L $CLASS ]; then break; fi
  	# Go down one more level of symbolic links
  	let LINKLEVEL+=1
  	if [ $LINKLEVEL -gt 5 ]; then
  		exec 1>&2
  		echo $0:
  		echo "  Too many symbolic links encountered"
  		exit 1
  	fi
  	CLASS=`ls --color=no -l $CLASS | sed -e 's/^.* \([^ ]*\)$/\1/'`
  done
  
  if [ -z "$CLASSBASE" ]; then
  	if [ -z "$FQCLASSP" ]; then
  		GOODNAME=$FQCLASSN.class
  	else
  		GOODNAME=$FQCLASSP/$FQCLASSN.class
  	fi
  	exec 1>&2
  	echo $0:
  	echo "  $FQCLASS should be in a file called $GOODNAME"
  	exit 1
  fi
  
  if ! echo $CLASSPATH | grep -q "^\(.*:\)*$CLASSBASE\(:.*\)*"; then
  	# class is not in CLASSPATH, so prepend dir of class to CLASSPATH
  	if [ -z "${CLASSPATH}" ] ; then
  		export CLASSPATH=$CLASSBASE
  	else
  		export CLASSPATH=$CLASSBASE:$CLASSPATH
  	fi
  fi
  
  shift
  /usr/bin/java $FQCLASS "$@"
  ====================== Cut here ===================
  
  
  ====================== Cut here ===================
  /* javaclassname.c
   *
   * Extracts the class name from a Java class file; intended for use in a Java
   * wrapper of the type supported by the binfmt_misc option in the Linux kernel.
   *
   * Copyright (C) 1999 Colin J. Watson <cjw44@cam.ac.uk>.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #include <stdlib.h>
  #include <stdio.h>
  #include <stdarg.h>
  #include <sys/types.h>
  
  /* From Sun's Java VM Specification, as tag entries in the constant pool. */
  
  #define CP_UTF8 1
  #define CP_INTEGER 3
  #define CP_FLOAT 4
  #define CP_LONG 5
  #define CP_DOUBLE 6
  #define CP_CLASS 7
  #define CP_STRING 8
  #define CP_FIELDREF 9
  #define CP_METHODREF 10
  #define CP_INTERFACEMETHODREF 11
  #define CP_NAMEANDTYPE 12
  
  /* Define some commonly used error messages */
  
  #define seek_error() error("%s: Cannot seek
  ", program)
  #define corrupt_error() error("%s: Class file corrupt
  ", program)
  #define eof_error() error("%s: Unexpected end of file
  ", program)
  #define utf8_error() error("%s: Only ASCII 1-255 supported
  ", program);
  
  char *program;
  
  long *pool;
  
  u_int8_t read_8(FILE *classfile);
  u_int16_t read_16(FILE *classfile);
  void skip_constant(FILE *classfile, u_int16_t *cur);
  void error(const char *format, ...);
  int main(int argc, char **argv);
  
  /* Reads in an unsigned 8-bit integer. */
  u_int8_t read_8(FILE *classfile)
  {
  	int b = fgetc(classfile);
  	if(b == EOF)
  		eof_error();
  	return (u_int8_t)b;
  }
  
  /* Reads in an unsigned 16-bit integer. */
  u_int16_t read_16(FILE *classfile)
  {
  	int b1, b2;
  	b1 = fgetc(classfile);
  	if(b1 == EOF)
  		eof_error();
  	b2 = fgetc(classfile);
  	if(b2 == EOF)
  		eof_error();
  	return (u_int16_t)((b1 << 8) | b2);
  }
  
  /* Reads in a value from the constant pool. */
  void skip_constant(FILE *classfile, u_int16_t *cur)
  {
  	u_int16_t len;
  	int seekerr = 1;
  	pool[*cur] = ftell(classfile);
  	switch(read_8(classfile))
  	{
  	case CP_UTF8:
  		len = read_16(classfile);
  		seekerr = fseek(classfile, len, SEEK_CUR);
  		break;
  	case CP_CLASS:
  	case CP_STRING:
  		seekerr = fseek(classfile, 2, SEEK_CUR);
  		break;
  	case CP_INTEGER:
  	case CP_FLOAT:
  	case CP_FIELDREF:
  	case CP_METHODREF:
  	case CP_INTERFACEMETHODREF:
  	case CP_NAMEANDTYPE:
  		seekerr = fseek(classfile, 4, SEEK_CUR);
  		break;
  	case CP_LONG:
  	case CP_DOUBLE:
  		seekerr = fseek(classfile, 8, SEEK_CUR);
  		++(*cur);
  		break;
  	default:
  		corrupt_error();
  	}
  	if(seekerr)
  		seek_error();
  }
  
  void error(const char *format, ...)
  {
  	va_list ap;
  	va_start(ap, format);
  	vfprintf(stderr, format, ap);
  	va_end(ap);
  	exit(1);
  }
  
  int main(int argc, char **argv)
  {
  	FILE *classfile;
  	u_int16_t cp_count, i, this_class, classinfo_ptr;
  	u_int8_t length;
  
  	program = argv[0];
  
  	if(!argv[1])
  		error("%s: Missing input file
  ", program);
  	classfile = fopen(argv[1], "rb");
  	if(!classfile)
  		error("%s: Error opening %s
  ", program, argv[1]);
  
  	if(fseek(classfile, 8, SEEK_SET))  /* skip magic and version numbers */
  		seek_error();
  	cp_count = read_16(classfile);
  	pool = calloc(cp_count, sizeof(long));
  	if(!pool)
  		error("%s: Out of memory for constant pool
  ", program);
  
  	for(i = 1; i < cp_count; ++i)
  		skip_constant(classfile, &i);
  	if(fseek(classfile, 2, SEEK_CUR))	/* skip access flags */
  		seek_error();
  
  	this_class = read_16(classfile);
  	if(this_class < 1 || this_class >= cp_count)
  		corrupt_error();
  	if(!pool[this_class] || pool[this_class] == -1)
  		corrupt_error();
  	if(fseek(classfile, pool[this_class] + 1, SEEK_SET))
  		seek_error();
  
  	classinfo_ptr = read_16(classfile);
  	if(classinfo_ptr < 1 || classinfo_ptr >= cp_count)
  		corrupt_error();
  	if(!pool[classinfo_ptr] || pool[classinfo_ptr] == -1)
  		corrupt_error();
  	if(fseek(classfile, pool[classinfo_ptr] + 1, SEEK_SET))
  		seek_error();
  
  	length = read_16(classfile);
  	for(i = 0; i < length; ++i)
  	{
  		u_int8_t x = read_8(classfile);
  		if((x & 0x80) || !x)
  		{
  			if((x & 0xE0) == 0xC0)
  			{
  				u_int8_t y = read_8(classfile);
  				if((y & 0xC0) == 0x80)
  				{
  					int c = ((x & 0x1f) << 6) + (y & 0x3f);
  					if(c) putchar(c);
  					else utf8_error();
  				}
  				else utf8_error();
  			}
  			else utf8_error();
  		}
  		else if(x == '/') putchar('.');
  		else putchar(x);
  	}
  	putchar('
  ');
  	free(pool);
  	fclose(classfile);
  	return 0;
  }
  ====================== Cut here ===================
  
  
  ====================== Cut here ===================
  #!/bin/bash
  # /usr/local/java/bin/jarwrapper - the wrapper for binfmt_misc/jar
  
  java -jar $1
  ====================== Cut here ===================
  
  
  Now simply chmod +x the .class, .jar and/or .html files you want to execute.
  To add a Java program to your path best put a symbolic link to the main
  .class file into /usr/bin (or another place you like) omitting the .class
  extension. The directory containing the original .class file will be
  added to your CLASSPATH during execution.
  
  
  To test your new setup, enter in the following simple Java app, and name
  it "HelloWorld.java":
  
  	class HelloWorld {
  		public static void main(String args[]) {
  			System.out.println("Hello World!");
  		}
  	}
  
  Now compile the application with:
  	javac HelloWorld.java
  
  Set the executable permissions of the binary file, with:
  	chmod 755 HelloWorld.class
  
  And then execute it:
  	./HelloWorld.class
  
  
  To execute Java Jar files, simple chmod the *.jar files to include
  the execution bit, then just do
         ./Application.jar
  
  
  To execute Java Applets, simple chmod the *.html files to include
  the execution bit, then just do
  	./Applet.html
  
  
  originally by Brian A. Lantz, brian@lantz.com
  heavily edited for binfmt_misc by Richard Günther
  new scripts by Colin J. Watson <cjw44@cam.ac.uk>
  added executable Jar file support by Kurt Huwig <kurt@iku-netz.de>