Copyright (c) 1999-2001 by Open Source Telecom Corporation.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
Version 1.1 or any later version published by the Free Software
Foundation; with no Invariant Sections, no Front-Cover Texts and
no Back-Cover Texts.  A copy of the license is included in the
section entitled "GNU Free Documentation License".

PLEASE NOTE; This document is old and somewhat obsolete.  It is in the 
process of being rewritten and will soon be available in texinfo.

GNU Common C++ Overview Documentation; Draft 2

Introduction
------------
In writing this document I hope to better explain what the GNU Common C++
library is about and how it may be used in developing your own  C++
applications.  This document is intended as an overview and unifying
document to support the already detailed class-by-class function
descriptions found and browsable in the "doc" subdirectory of the Common
C++ distribution.

GNU Common C++ offers a set of "portable" classes that can be used to 
build highly portable applications in C++.  In particular, Common C++ 
offers classes that abstract threading, sockets, synchronization, serial 
I/O, "config" file parsing, class object persistence, shared object module
loading, daemon management, and optimized "block" and memory mapped file
I/O under a set of consistent classes that your application can then
be built from.  The goal is to write your application to use the portable
abstract services and classes of the GNU Common C++ libraries rather than
having to access low level system services directly.

There is a large diversity of views in how one should code a C++
framework.  Since a large number of older C++ compilers remain in everyday
use, I choose to use what I felt was an appropriate set of C++ language
features and practices to provide the greatest compiler compatibility and
to generate the most optimized code for GNU Common C++.  To further reduce 
the
overhead of writing GNU Common C++ applications, I have split the primary
library image itself into several different shared libraries.  This
allowed me to collect the more obscure and less likely to be used features
into separate libraries which need never be loaded.

Finally, in designing GNU Common C++, I assume that class extension
(inheritance) is the primary vehicle for application development. The 
GNU Common C++ framework, while offering many classes that are usable
directly, is designed for one to create applications by extending Common
C++ "base" classes into an application specific versions of said classes
as needed. 

GNU Common C++ Threading Concepts
---------------------------------
Threading was the first part of GNU Common C++ I wrote, back when it was 
still the APE library.  My goal for GNU Common C++ threading has been to 
make threading as natural and easy to use in C++ application development 
as threading is in Java.  With this said, one does not need to use 
threading at all to take advantage of GNU Common C++.  However, all 
GNU Common C++ classes are designed at least to be thread-aware/thread-safe 
as appropriate and necessary.

GNU Common C++ threading is currently built either from the Posix 
"pthread" library or using the win32 SDK.  In that the Posix "pthread" 
draft has gone through many revisions, and many system implementations are
only marginally compliant, and even then usually in different ways, I
wrote a large series of autoconf macros found in ost_pthread.m4 which
handle the task of identifying which pthread features and capabilities
your target platform supports.  In the process I learned much about what
autoconf can and cannot do for you..

Currently the GNU Portable Thread library (GNU pth) is not directly
supported in GNU Common C++.  While GNU "Pth" doesn't offer direct
native threading support or benefit from SMP hardware, many of the design
advantages of threading can be gained from it's use, and the  Pth pthread
"emulation" library should be usable with GNU Common C++.  In the future,
GNU Common C++ will directly support Pth, as well as OS/2 and BeOS native
threading API's.

GNU Common C++ itself defines a fairly "neutral" threading model that is
not tied to any specific API such as pthread, win32, etc.  This neutral
thread model is contained in a series of classes which handle threading
and synchronization and which may be used together to build reliable
threaded applications.

GNU Common C++ defines application specific threads as objects which are
derived from the GNU Common C++ "Thread" base class.  At minimum the "Run"
method must be implemented, and this method essentially is the "thread",
for it is executed within the execution context of the thread, and when
the Run method terminates the thread is assumed to have terminated.

GNU Common C++ allows one to specify the running priority of a newly 
created thread relative to the "parent" thread which is the thread that is
executing when the constructor is called.  Since most newer C++
implementations do not allow one to call virtual constructors or virtual
methods from constructors, the thread must be "started" after the
constructor returns.  This is done either by defining a "starting"
semaphore object that one or more newly created thread objects can wait
upon, or by invoking an explicit "Start" member function.

Threads can be "suspended" and "resumed".  As this behavior is not defined
in the Posix "pthread" specification, it is often emulated through
signals.  Typically SIGUSR1 will be used for this purpose in GNU Common 
C++ applications, depending in the target platform.  On Linux, since 
threads are indeed processes, SIGSTP and SIGCONT can be used.  On solaris, 
the Solaris thread library supports suspend and resume directly.

Threads can be canceled.  Not all platforms support the concept of
externally cancelable threads.  On those platforms and API
implementations that do not, threads are typically canceled through the
action of a signal handler.

As noted earlier, threads are considered running until the "Run" method
returns, or until a cancellation request is made.  GNU Common C++ threads 
can control how they respond to cancellation, using setCancellation().
Cancellation requests can be ignored, set to occur only when a
cancellation "point" has been reached in the code, or occur immediately.
Threads can also exit by returning from Run() or by invoking the Exit()
method.

Generally it is a good practice to initialize any resources the thread may
require within the constructor of your derived thread class, and to purge
or restore any allocated resources in the destructor.  In most cases, the
destructor will be executed after the thread has terminated, and hence
will execute within the context of the thread that requested a join rather
than in the context of the thread that is being terminated.  Most
destructors in derived thread classes should first call Terminate() to
make sure the thread has stopped running before releasing resources.

A GNU Common C++ thread is normally canceled by deleting the thread 
object.  The process of deletion invokes the thread's destructor, and the
destructor will then perform a "join" against the thread using the
Terminate() function.  This behavior is not always desirable since the
thread may block itself from cancellation and block the current "delete"
operation from completing.  One can alternately invoke Terminate()
directly before deleting a thread object.

When a given GNU Common C++ thread exits on it's own through it's Run()
method, a "Final" method will be called.  This Final method will be called
while the thread is "detached".  If a thread object is constructed through
a "new" operator, it's final method can be used to "self delete" when
done, and allows an independent thread to construct and remove itself
autonomously.

A special global function, getThread(), is provided to identify the thread
object that represents the current execution context you are running
under.  This is sometimes needed to deliver signals to the correct thread.
Since all thread manipulation should be done through the GNU Common C++ 
(base) thread class itself, this provides the same functionality as 
things like "pthread_self" for GNU Common C++.

GNU Common C++ threads are often aggregated into other classes to provide
services that are "managed" from or operate within the context of a
thread, even within the GNU Common C++ framework itself.  A good example 
of this is the TCPSession class, which essentially is a combination of a 
TCP client connection and a separate thread the user can define by 
deriving a class with a Run() method to handle the connected service.  
This aggregation logically connects the successful allocation of a given
resource with the construction of a thread to manage and perform 
operations for said resource.

Threads are also used in "service pools".  In GNU Common C++, a service 
pool is one or more threads that are used to manage a set of resources.  
While GNU Common C++ does not provide a direct "pool" class, it does 
provide a model for their implementation, usually by constructing an array 
of thread "service" objects, each of which can then be assigned the next 
new instance of a given resource in turn or algorithmically.

Threads have signal handlers associated with them.  Several signal types
are "predefined" and have special meaning.  All signal handlers are
defined as virtual member functions of the Thread class which are called
when a specific signal is received for a given thread.  The "SIGPIPE"
event is defined as a "Disconnect" event since it's normally associated
with a socket disconnecting or broken fifo.  The Hangup() method is
associated with the SIGHUP signal.  All other signals are handled through
the more generic Signal().

Incidently, unlike Posix, the win32 API has no concept of signals, and
certainly no means to define or deliver signals on a per-thread basis.
For this reason, no signal handling is supported or emulated in the win32
implementation of GNU Common C++ at this time.

In addition to TCPStream, there is a TCPSession class which combines a
thread with a TCPStream object.  The assumption made by TCPSession is that
one will service each TCP connection with a separate thread, and this
makes sense for systems where extended connections may be maintained and
complex protocols are being used over TCP.

GNU Common C++ Synchronization
------------------------------
Synchronization objects are needed when a single object can be
potentially manipulated by more than one thread (execution) context
concurrently.  GNU Common C++ provides a number of specialized classes and
objects that can be used to synchronize threads.

One of the most basic GNU Common C++ synchronization object is the Mutex
class.  A Mutex only allows one thread to continue execution at a given
time over a specific section of code.  Mutex's have a enter and leave
method; only one thread can continue from the Enter until the Leave is
called.  The next thread waiting can then get through.  Mutex's are also
known as "CRITICAL SECTIONS" in win32-speak.

The GNU Common C++ mutex is presumed to support recursive locking.  This 
was deemed essential because a mutex might be used to block individual 
file requests in say, a database, but the same mutex might be needed to 
block a whole series of database updates that compose a "transaction" for 
one thread to complete together without having to write alternate 
non-locking member functions to invoke for each part of a transaction.

Strangely enough, the original pthread draft standard does not directly
support recursive mutexes.  In fact this is the most common "NP" extension
for most pthread implementations.  GNU Common C++ emulates recursive mutex
behavior when the target platform does not directly support it.

In addition to the Mutex, GNU Common C++ supports a rwlock class.  This
implements the X/Open recommended "rwlock".  On systems which do not
support rwlock's, the behavior is emulated with a Mutex; however, the
advantage of a rwlock over a mutex is then entirely lost.  There has been
some suggested clever hacks for "emulating" the behavior of a rwlock with
a pair of mutexes and a semaphore, and one of these will be adapted for
GNU Common C++ in the future for platforms that do not support rwlock's
directly.

GNU Common C++ also supports "semaphores".  Semaphores are typically used 
as a counter for protecting or limiting concurrent access to a given
resource, such as to permitting at most "x" number of threads to use
resource "y", for example.  Semaphore's are also convenient to use as
synchronization objects to rondevous and signal activity and/or
post pending service requests between one thread thread and another.

In addition to Semaphore objects, GNU Common C++ supports "Event" objects.
Event objects are triggered "events" which are used to notify one thread
of some event it is waiting for from another thread.  These event objects
use a trigger/reset mechanism and are related to low level conditional
variables.

A special class, the ThreadKey, is used to hold state information that
must be unique for each thread of context.  Finally, GNU Common C++ 
supports a thread-safe "AtomicCounter" class.  This can often be used for 
reference counting without having to protect the counter with a separate 
Mutex counter.  This lends to lighter-weight code.

GNU Common C++ Sockets
----------------------
GNU Common C++ provides a set of classes that wrap and define the 
operation of network "sockets".  Much like with Java, there are also a 
related set of classes that are used to define and manipulate objects 
which act as "hostname" and "network addresses" for socket connections.

The network name and address objects are all derived from a common 
InetAddress base class. Specific classes, such as InetHostAddress,
InetMaskAddress, etc, are defined from InetAddress entirely so that the
manner a network address is being used can easily be documented and
understood from the code and to avoid common errors and accidental misuse 
of the wrong address object.  For example, a "connection" to something
that is declared as a "InetHostAddress" can be kept type-safe from a
"connection" accidently being made to something that was declared a 
"InetBroadcastAddress".

The socket is itself defined in a single base class named, quite
unremarkably, "Socket".  This base class is not directly used, but is
provided to offer properties common to other GNU Common C++ socket 
classes, including the socket exception model and the ability to set 
socket properties such as QoS, "sockopts" properties like Dont-Route
and Keep-Alive, etc.

The first usable socket class is the TCPStream.  Since a TCP connection
is always a "streamed" virtual circuit with flow control, the standard
stream operators ("<<" and ">>") may be used with TCPStream directly.
TCPStream itself can be formed either by connecting to a bound network
address of a TCP server, or can be created when "accepting" a
network connection from a TCP server.

An implicit and unique TCPSocket object exists in GNU Common C++ to 
represent a bound TCP socket acting as a "server" for receiving connection 
requests.  This class is not part of TCPStream because such objects 
normally perform no physical I/O (read or write operations) other than to 
specify a listen backlog queue and perform "accept" operations for pending 
connections.  The GNU Common C++ TCPSocket offers a Peek method to examine 
where the next pending connection is coming from, and a Reject method to 
flush the next request from the queue without having to create a session.

The TCPSocket also supports a "OnAccept" method which can be called when a
TCPStream related object is created from a TCPSocket.  By creating a
TCPStream from a TCPSocket, an accept operation automatically occurs, and
the TCPSocket can then still reject the client connection through the
return status of it's OnAccept method.

In addition to connected TCP sessions, GNU Common C++ supports UDP sockets 
and these also cover a range of functionality.  Like a TCPSocket, A 
UDPSocket can be created bound to a specific network interface and/or port 
address, although this is not required.  UDP sockets also are usually 
either  connected or otherwise "associated" with a specific "peer" UDP 
socket.  Since UDP sockets operate through discreet packets, there are no 
streaming operators used with UDP sockets.

In addition to the UDP "socket" class, there is a "UDPBroadcast" class.
The UDPBroadcast is a socket that is set to send messages to a subnet as a
whole rather than to an individual peer socket that it may be associated
with.

UDP sockets are often used for building "realtime" media  streaming
protocols and full duplex messaging services.  When used in this manner,
typically a pair of UDP sockets are used together; one socket is used to
send and the other to receive data with an associated pair of UDP sockets
on a "peer" host.  This concept is represented through the GNU Common C++
UDPDuplex object, which is a pair of sockets that communicate with another
UDPDuplex pair.

Finally, a special set of classes, "SocketPort" and "SocketService", exist
for building realtime streaming media servers on top of UDP and TCP
protocols.  The "SocketPort" is used to hold a connected or associated TCP
or UDP socket which is being "streamed" and which offers callback methods
that are invoked from a "SocketService" thread.  SocketService's can be
pooled into logical thread pools that can service a group of SocketPorts.
A millisecond accurate "timer" is associated with each SocketPort and can
be used to time synchronize SocketPort I/O operations.

GNU Common C++ Serial I/O
-------------------------
GNU Common C++ serial I/O classes are used to manage serial devices and
implement serial device protocols.  From the point of view of GNU Common 
C++, serial devices are supported by the underlying Posix specified 
"termios" call interface.

The serial I/O base class is used to hold a descriptor to a serial device
and to provide an exception handling interface for all serial I/O classes.
The base class is also used to specify serial I/O properties such as
communication speed, flow control, data size, and parity.  The "Serial"
base class is not itself directly used in application development,
however.

GNU Common C++ Serial I/O is itself divided into two conceptual modes; 
frame oriented and line oriented I/O.  Both frame and line oriented I/O 
makes use of the ability of the underlying tty driver to buffer data and 
return "ready" status from when select either a specified number of bytes 
or newline record has been reached by manipulating termios c_cc fields
appropriately.  This provides some advantage in that a given thread
servicing a serial port can block and wait rather than have to continually
poll or read each and every byte as soon as it appears at the serial port.

The first application relevant serial I/O class is the TTYStream class.
TTYStream offers a linearly buffered "streaming" I/O session with the
serial device.  Furthermore, traditional C++ "stream" operators (<< and
>>) may be used with the serial device.  A more "true" to ANSI C++ library
format "ttystream" is also available, and this supports an "open" method
in which one can pass initial serial device parameters immediately
following the device name in a single string, as in
"/dev/tty3a:9600,7,e,1", as an example.

The TTYSession aggragates a TTYStream and a GNU Common C++ Thread which is
assumed to be the execution context that will be used to perform actual
I/O operations.  This class is very anagolous to TCPSession.

The TTYPort and TTYService classes are used to form thread-pool serviced
serial I/O protocol sets.  These can be used when one has a large number
of serial devices to manage, and a single (or limited number of) thread(s)
can then be used to service the tty port objects present.  Each tty port
supports a timer control and several virtual methods that the service
thread can call when events occur.  This model provides for "callback"
event management, whereby the service thread performs a "callback" into
the port object when events occur.  Specific events supported include the
expiration of a TTYPort timer, pending input data waiting to be read, and
"sighup" connection breaks.   

GNU Common C++ Block I/O
------------------------
GNU Common C++ block I/O classes are meant to provide more convenient file
control for paged or random access files portably, and to answer many
issues that ANSI C++ leaves untouched in this area.  A common base class,
RandomFile, is provided for setting descriptor attributes and handling
exceptions.  From this, three kinds of random file access are supported.

ThreadFile is meant for use by a threaded database server where multiple
threads may each perform semi-independent operations on a given database
table stored on disk.  A special "fcb" structure is used to hold file
"state", and pread/pwrite is used whenever possible for optimized I/O.  On
systems that do not offer pwread/pwrite, a Mutex lock is used to protect
concurrent lseek and read/write operations.  ThreadFile managed databases
are assumed to be used only by the local server and through a single file
descriptor.

SharedFile is used when a database may be shared between multiple
processes.  SharedFile automatically applies low level byte-range "file
locks", and provides an interface to fetch and release byte-range locked
portions of a file.

The MappedFile class provides a portable interface to memory mapped file
access.  One can map and unmap portions of a file on demand, and update
changed memory pages mapped from files immediately through sync().

GNU Common C++ Daemon Support
-----------------------------
Daemon support consists of two GNU Common C++ features.  The first is the
"pdetach" function.  This function provides a simple and portable means to
fork/detach a process into a daemon.  In addition, the "slog" object is
provided.

"slog" is an object which behaves very similar to the Standard C++ "clog".
The key difference is that the "slog" object sends it's output to the
system logging daemon (typically syslogd) rather than through stderr.
"slog" can be streamed with the << operator just like "clog".  "slog" can
also accept arguments to specify logging severity level, etc.

GNU Common C++ Persistence
--------------------------
The GNU Common C++ Persistence library was designed with one thought
foremost - namely that large interlinked structures should be
easily serializable. The current implementation is _NOT_ endian
safe, and so, whilst it should in theory be placed in the "Extras"
section, the codebase itself is considered stable enough to be
part of the main distribution.

The Persistence library classes are designed to provide a quick and
easy way to make your data structures serializable. The only way of
doing this safely is to inherit your classes from the provided class
Persistence::BaseObject. The macros "IMPLEMENT_PERSISTENCE" and
"DECLARE_PERSISTENCE" provide all the function prototypes and 
implementation details you may require to get your code off the ground.

GNU Common C++ Config & Misc
----------------------------
There are a number of odd and specialized utility classes found in Common
C++.  The most common of these is the "MemPager" class.  This is basically
a class to enable page-grouped "cumulative" memory allocation; all
accumulated allocations are dropped during the destructor.  This class has
found it's way in a lot of other utility classes in GNU Common C++.

The most useful of the misc. classes is the Keydata class.  This class is
used to load and then hold "keyword = value" pairs parsed from a text
based "config" file that has been divided into "[sections]".  Keydata can
also load a table of "initialization" values for keyword pairs that were
not found in the external file.

One typically derives an application specific keydata class to load a
specific portion of a known config file and initialize it's values.  One
can then declare a global instance of these objects and have
configuration data initialized automatically as the executable is loaded.

Hence, if I have a "[paths]" section in a "/etc/server.conf" file, I might
define something like:

class KeyPaths : public Keydata
{
public:
	KeyPaths() : Keydata("/server/paths")
	{
		static KEYDEF *defvalues = {
		{"datafiles", "/var/server"},
		{NULL, NULL}};

		// override with [paths] from "~/.serverrc" if avail.

		Load("~server/paths");
		Load(defvalues);
	}
};

KeyPaths keypaths;

GNU Common C++ Automake Services
--------------------------------
GNU Common C++ does a few things special with automake and autoconf.  When 
the Common C++ library is built, it saves a number of compiler options in 
a "config.def" file that can be retrieved by an application being 
configured to use GNU Common C++.  This is done to assure the same 
compiler options are used to build your application that were in effect 
when GNU Common C++ itself was built.  Since linkage information is also 
saved in this manner, this means your application's "configure" script 
does not have to go through the entire process of testing for libraries or 
GNU Common C++ related compiler options all over again.  Finally, GNU 
Common C++ saves it's own generated "config.h" file in cc++/config.h.

If you are using automake, you can add the ost_commoncxx.m4 macros to your
projects autoconf "m4" directory and use several CCXX_ macros for your
convenience.  A "minimal" configure.in can be constructed as:

AC_INIT(something...)
AC_PROG_CXX
AC_PROG_CXXCPP
AM_PROG_LIBTOOL
AM_INIT_AUTOMAKE(....)
AM_CONFIG_HEADER(my-local-config.h)
OST_CCXX_COMMON


In addition, if you plan to use classes found in -lccio, you can use
OST_CCXX_FILE, and if you plan to use anything from the "common"
directory, you can define OST_CCXX_STD.  OST_CCXX_HOARD will test for and,
if found, add the SMP optimized Hoard memory allocator to your
application link LIBS.

GNU Common C++ "Extras"
-----------------------
At the time of the release of GNU Common C++ 1.0, it was deemed that
several class libraries either were incomplete or still experimental, and
the 1.0 designation seemed very inappropriate for these libraries.  I
also wanted to have a mechanism to later add new GNU Common C++ class
libraries without having to disrupt or add experimental code into the
main GNU Common C++ release.

To resolve this issue, a second package has been created, and is named
GNU "GNU Common C++ Extras".  The extras package simply holds class 
frameworks that are still not considered "mature" or "recommended".  This 
package can be downloaded, compiled, and installed, after GNU Common C++ 
itself.  Many of the class libraries appearing in the extras package are 
likely to appear in GNU Common C++ proper at some future date, and should 
be considered usable in their current form.  They are made available both 
to support continued development of GNU Common C++ proper and because, 
while not yet mature, they are considered "useful" in some manner.

The initial GNU Common C++ "extras" package consisted of two libraries; 
Common C++ "scripting" and "math".  The scripting library (-lccscript) is 
the GNU Bayonne scripting engine which is used as a near-realtime event 
driven embedded scripting engine for "callback" driven state-event server
applications.  The Bayonne scripting engine directly uses C++ inheritance
to extend the Bayonne dialect for application specific features and is
used as a core technology in the GNU Bayonne, DBS, and Meridian telephony
servers and as part of the a free home automation project.  There has been
some discussion about folding the GNU Bayonne scripting concepts around a 
more conventional scripting language, and so this package currently 
remains in "extras" rather than part of GNU Common C++ itself.

The other package found in the initial "extras" distribution is the Common
C++ math libraries.  These are still at a VERY early stage of development,
and may well be depreciated if another suitable free C++ math/numerical
analysis package comes along.

GNU Common C++ "serverlets"
---------------------------
Serverlets are a concept popularized with Java and web servers.  There is
a broad abstract architectural concept of serverlets or plugins that one
also finds in my GNU Common C++ projects, though they are not directly
defined as part of GNU Common C++ itself.

A GNU Common C++ "serverlet" comes about in a Common C++ server project, 
such as the Bayonne telephony server, where one wishes to define 
functionality for alternate hardware or API's in alternated shared object 
files that are selected at runtime, or to add "plugins" to enhance 
functionality.  A serverlet is defined in this sense as a "DSO" loaded 
"-module" object file which is linked at runtime against a server process 
that exports it's base classes using "-export-dynamic".  The "server" 
image then acts as a carrier for the runtime module's base functionality.

Modules, or "serverlets", defined in this way do not need to be compiled
with position independent code.  The module is only used with a
specific server image and so the runtime address is only resolved once
rather than at different load addresses for different arbitrary processes.

I recommend that GNU Common C++ based "servers" which publish and export 
base classes in this manner for plugins should also have a server
specific "include" file which can be installed in the cc++ include
directory.

GNU Free Documentation License
------------------------------

Version 1.1, March 2000

Copyright (C) 2000  Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.

0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other 
written document "free" in the sense of freedom: to assure everyone the 
effective freedom to copy and redistribute it, with or without modifying 
it, either commercially or noncommercially. Secondarily, this License 
preserves for the author and publisher a way to get credit for their work, 
while not being considered responsible for modifications made by others.

This License is a kind of "copyleft", which means that derivative works of 
the document must themselves be free in the same sense. It complements the 
GNU General Public License, which is a copyleft license designed for free 
software.

We have designed this License in order to use it for manuals for free 
software, because free software needs free documentation: a free program 
should come with manuals providing the same freedoms that the software 
does. But this License is not limited to software manuals; it can be used 
for any textual work, regardless of subject matter or whether it is 
published as a printed book. We recommend this License principally for 
works whose purpose is instruction or reference.

1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work that contains a notice 
placed by the copyright holder saying it can be distributed under the 
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A "Modified Version" of the Document means any work containing the 
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The "Invariant Sections" are certain Secondary Sections whose titles are 
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formatters. A copy made in an otherwise Transparent file format whose 
markup has been designed to thwart or discourage subsequent modification 
by readers is not Transparent. A copy that is not "Transparent" is called 
"Opaque".

Examples of suitable formats for Transparent copies include plain ASCII 
without markup, Texinfo input format, LaTeX input format, SGML or XML 
using a publicly available DTD, and standard-conforming simple HTML 
designed for human modification. Opaque formats include PostScript, PDF, 
proprietary formats that can be read and edited only by proprietary word 
processors, SGML or XML for which the DTD and/or processing tools are not 
generally available, and the machine-generated HTML produced by some word 
processors for output purposes only.

The "Title Page" means, for a printed book, the title page itself, plus 
such following pages as are needed to hold, legibly, the material this 
License requires to appear in the title page. For works in formats which 
do not have any title page as such, "Title Page" means the text near the 
most prominent appearance of the work's title, preceding the beginning of 
the body of the text.

2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either 
commercially or noncommercially, provided that this License, the copyright 
notices, and the license notice saying this License applies to the 
Document are reproduced in all copies, and that you add no other 
conditions whatsoever to those of this License. You may not use technical 
measures to obstruct or control the reading or further copying of the 
copies you make or distribute. However, you may accept compensation in 
exchange for copies. If you distribute a large enough number of copies you 
must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and you 
may publicly display copies.

3. COPYING IN QUANTITY

If you publish printed copies of the Document numbering more than 100, and 
the Document's license notice requires Cover Texts, you must enclose the 
copies in covers that carry, clearly and legibly, all these Cover Texts: 
Front-Cover Texts on the front cover, and Back-Cover Texts on the back 
cover. Both covers must also clearly and legibly identify you as the 
publisher of these copies. The front cover must present the full title 
with all words of the title equally prominent and visible. You may add 
other material on the covers in addition. Copying with changes limited to 
the covers, as long as they preserve the title of the Document and satisfy 
these conditions, can be treated as verbatim copying in other respects.

If the required texts for either cover are too voluminous to fit legibly, 
you should put the first ones listed (as many as fit reasonably) on the 
actual cover, and continue the rest onto adjacent pages.

If you publish or distribute Opaque copies of the Document numbering more 
than 100, you must either include a machine-readable Transparent copy 
along with each Opaque copy, or state in or with each Opaque copy a 
publicly-accessible computer-network location containing a complete 
Transparent copy of the Document, free of added material, which the 
general network-using public has access to download anonymously at no 
charge using public-standard network protocols. If you use the latter 
option, you must take reasonably prudent steps, when you begin 
distribution of Opaque copies in quantity, to ensure that this Transparent 
copy will remain thus accessible at the stated location until at least one 
year after the last time you distribute an Opaque copy (directly or 
through your agents or retailers) of that edition to the public.

It is requested, but not required, that you contact the authors of the 
Document well before redistributing any large number of copies, to give 
them a chance to provide you with an updated version of the Document.

4. MODIFICATIONS

You may copy and distribute a Modified Version of the Document under the 
conditions of sections 2 and 3 above, provided that you release the 
Modified Version under precisely this License, with the Modified Version 
filling the role of the Document, thus licensing distribution and 
modification of the Modified Version to whoever possesses a copy of it. In 
addition, you must do these things in the Modified Version:

    * A. Use in the Title Page (and on the covers, if any) a title 
distinct from that of the Document, and from those of previous versions 
(which should, if there were any, be listed in the History section of the 
Document). You may use the same title as a previous version if the 
original publisher of that version gives permission.
    * B. List on the Title Page, as authors, one or more persons or 
entities responsible for authorship of the modifications in the Modified 
Version, together with at least five of the principal authors of the 
Document (all of its principal authors, if it has less than five).
    * C. State on the Title page the name of the publisher of the Modified 
Version, as the publisher.
    * D. Preserve all the copyright notices of the Document.
    * E. Add an appropriate copyright notice for your modifications 
adjacent to the other copyright notices.
    * F. Include, immediately after the copyright notices, a license 
notice giving the public permission to use the Modified Version under the 
terms of this License, in the form shown in the Addendum below.
    * G. Preserve in that license notice the full lists of Invariant 
Sections and required Cover Texts given in the Document's license notice.
    * H. Include an unaltered copy of this License.
    * I. Preserve the section entitled "History", and its title, and add 
to it an item stating at least the title, year, new authors, and publisher 
of the Modified Version as given on the Title Page. If there is no section 
entitled "History" in the Document, create one stating the title, year, 
authors, and publisher of the Document as given on its Title Page, then 
add an item describing the Modified Version as stated in the previous 
sentence.
    * J. Preserve the network location, if any, given in the Document for 
public access to a Transparent copy of the Document, and likewise the 
network locations given in the Document for previous versions it was based 
on. These may be placed in the "History" section. You may omit a network 
location for a work that was published at least four years before the 
Document itself, or if the original publisher of the version it refers to 
gives permission.
    * K. In any section entitled "Acknowledgements" or "Dedications", 
preserve the section's title, and preserve in the section all the 
substance and tone of each of the contributor acknowledgements and/or 
dedications given therein.
    * L. Preserve all the Invariant Sections of the Document, unaltered in 
their text and in their titles. Section numbers or the equivalent are not 
considered part of the section titles.
    * M. Delete any section entitled "Endorsements". Such a section may 
not be included in the Modified Version.
    * N. Do not retitle any existing section as "Endorsements" or to 
conflict in title with any Invariant Section.

If the Modified Version includes new front-matter sections or appendices 
that qualify as Secondary Sections and contain no material copied from the 
Document, you may at your option designate some or all of these sections 
as invariant. To do this, add their titles to the list of Invariant 
Sections in the Modified Version's license notice. These titles must be 
distinct from any other section titles.

You may add a section entitled "Endorsements", provided it contains 
nothing but endorsements of your Modified Version by various parties--for 
example, statements of peer review or that the text has been approved by 
an organization as the authoritative definition of a standard.

You may add a passage of up to five words as a Front-Cover Text, and a 
passage of up to 25 words as a Back-Cover Text, to the end of the list of 
Cover Texts in the Modified Version. Only one passage of Front-Cover Text 
and one of Back-Cover Text may be added by (or through arrangements made 
by) any one entity. If the Document already includes a cover text for the 
same cover, previously added by you or by arrangement made by the same 
entity you are acting on behalf of, you may not add another; but you may 
replace the old one, on explicit permission from the previous publisher 
that added the old one.

The author(s) and publisher(s) of the Document do not by this License give 
permission to use their names for publicity for or to assert or imply 
endorsement of any Modified Version.

5. COMBINING DOCUMENTS

You may combine the Document with other documents released under this 
License, under the terms defined in section 4 above for modified versions, 
provided that you include in the combination all of the Invariant Sections 
of all of the original documents, unmodified, and list them all as 
Invariant Sections of your combined work in its license notice.

The combined work need only contain one copy of this License, and multiple 
identical Invariant Sections may be replaced with a single copy. If there 
are multiple Invariant Sections with the same name but different contents, 
make the title of each such section unique by adding at the end of it, in 
parentheses, the name of the original author or publisher of that section 
if known, or else a unique number. Make the same adjustment to the section 
titles in the list of Invariant Sections in the license notice of the 
combined work.

In the combination, you must combine any sections entitled "History" in 
the various original documents, forming one section entitled "History"; 
likewise combine any sections entitled "Acknowledgements", and any 
sections entitled "Dedications". You must delete all sections entitled 
"Endorsements."

6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents 
released under this License, and replace the individual copies of this 
License in the various documents with a single copy that is included in 
the collection, provided that you follow the rules of this License for 
verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute 
it individually under this License, provided you insert a copy of this 
License into the extracted document, and follow this License in all other 
respects regarding verbatim copying of that document.

7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate and 
independent documents or works, in or on a volume of a storage or 
distribution medium, does not as a whole count as a Modified Version of 
the Document, provided no compilation copyright is claimed for the 
compilation. Such a compilation is called an "aggregate", and this License 
does not apply to the other self-contained works thus compiled with the 
Document, on account of their being thus compiled, if they are not 
themselves derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these copies 
of the Document, then if the Document is less than one quarter of the 
entire aggregate, the Document's Cover Texts may be placed on covers that 
surround only the Document within the aggregate. Otherwise they must 
appear on covers around the whole aggregate.

8. TRANSLATION

Translation is considered a kind of modification, so you may distribute 
translations of the Document under the terms of section 4. Replacing 
Invariant Sections with translations requires special permission from 
their copyright holders, but you may include translations of some or all 
Invariant Sections in addition to the original versions of these Invariant 
Sections. You may include a translation of this License provided that you 
also include the original English version of this License. In case of a 
disagreement between the translation and the original English version of 
this License, the original English version will prevail.

9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document except as 
expressly provided for under this License. Any other attempt to copy, 
modify, sublicense or distribute the Document is void, and will 
automatically terminate your rights under this License. However, parties 
who have received copies, or rights, from you under this License will not 
have their licenses terminated so long as such parties remain in full 
compliance.

10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the GNU 
Free Documentation License from time to time. Such new versions will be 
similar in spirit to the present version, but may differ in detail to 
address new problems or concerns. See http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number. If 
the Document specifies that a particular numbered version of this License 
"or any later version" applies to it, you have the option of following the 
terms and conditions either of that specified version or of any later 
version that has been published (not as a draft) by the Free Software 
Foundation. If the Document does not specify a version number of this 
License, you may choose any version ever published (not as a draft) by the 
Free Software Foundation.