xref: /haiku/docs/user/book.dox (revision 610f99c838cb661ff85377789ffd3ad4ff672a08)
1/*!
2	\mainpage Welcome to the Haiku Book
3
4	Below you will find documentation on the Application Programming
5	Interface (API) of the Haiku operating system. This API describes
6	the internals of the operating system allowing developers to write
7	native C++ applications and device drivers. See the
8	<a href="https://api.haiku-os.org">online version</a> for the most
9	updated version of this document. If you would like to help contribute
10	contact the <a href="https://www.freelists.org/list/haiku-doc">documentation
11	mailing list</a>. For guidelines on how to help document the API see
12	the \link apidoc Documenting the API\endlink page. A list of
13	contributors can be found \ref credits page. Documenting the API is
14	an ongoing process so contributions are greatly appreciated.
15
16	The Haiku API is based on the BeOS R5 API but changes and additions have
17	been included where appropriate. Important compatibility differences are
18	detailed on the \ref compatibility page. New classes and methods
19	and incompatible API changes to the BeOS R5 API are noted in the
20	appropriate sections.
21
22	A complete reference to the BeOS R5 API is available on the web in
23	<a href="https://haiku-os.org/legacy-docs/bebook/">The Be Book</a>.
24	The Be Book is used with permission from
25	<a href="https://www.access-company.com/">Access Co.</a>, the current
26	owners of Be's intellectual property.
27
28	\section book_kits Kits and Servers
29
30	The API is split into several kits and servers each detailing a different
31	aspect of the operating system.
32		- The \ref app is the starting point for developing applications
33			and includes classes for messaging and for interacting with
34			the rest of the system.
35		- The \ref game provides classes for producing game sounds and
36			working with full screen apps.
37		- The \ref interface is used to create responsive and attractive
38			graphical user interfaces building on the messaging facilities
39			provided by the Application Kit.
40			- A \link interface_intro general introduction \endlink to the
41				Interface Kit.
42			- The \link layout_intro Layout API \endlink is a new addition
43				to the Interface Kit in Haiku which provides resources to
44				layout your application flexibly and easily.
45		- The \ref locale includes classes to localize your application to
46			different languages, timezones, number formatting conventions and
47			much more.
48		- The \ref mail includes classes to work with e-mail files, folders,
49			protocols, and filters, as part of Haiku's unique mail handling system.
50		- The \ref media provides a unified and consistent interface for media
51			streams and applications to intercommunicate.
52		- The \ref midi2 describes an interface to generating, processing,
53			and playing music in MIDI format. For reference documentation on the
54			\ref midi1 is also included.
55		- The \ref network handles everything network related, from interface
56			IP address settings to HTTP connections.
57		- The \ref storage is a collection of classes that deal with storing and
58			retrieving information from disk.
59		- The \ref support contains support classes to use in your application
60			including resources for thread safety, IO, and serialization.
61		- The \ref translation provides a framework for converting data streams
62			between media formats.
63
64	\section book_special_topics Special Topics
65
66	- \ref libroot
67	- \ref drivers
68	- \ref keyboard
69	- \ref json
70	- \ref netservices
71*/
72
73///// Define main kits /////
74
75/*!
76	\defgroup app Application Kit
77	\brief The Application Kit is the starting point for writing native Haiku
78		GUI applications.
79
80	The application kit is exactly what its name suggests &mdash; it is the
81	basis of Haiku applications. You should first read through this document
82	and the references here before moving on to the other parts of the API.
83
84	The Application Kit classes can be divided into two groups: the messaging
85	classes and the system interaction classes. The larger of the two groups is
86	the messaging classes. Since the Haiku API relies on pervasive
87	multithreading messaging is an essential topic for any application. Have a
88	look at the \link app_messaging Introduction to Messaging \endlink for more
89	information.
90
91	The following messaging classes which allow you to easily and securely
92	communicate between threads.
93		- BHandler
94		- BInvoker
95		- BLooper
96		- BMessage
97		- BMessageFilter
98		- BMessageQueue
99		- BMessageRunner
100		- BMessenger
101
102	The second group is the system interaction classes. These classes
103	provide hooks for your application to interact with the rest of the system.
104	The most important class in this group is BApplication. Below is a list of
105	all system interaction classes:
106		- BApplication
107		- BClipboard
108		- BCursor
109		- BLaunchRoster
110		- BNotification
111		- BPropertyInfo
112		- BRoster
113
114	A third special category is the \link app_keystore Password and Key storage
115	API:\endlink
116		- BKey
117		- BKeyStore
118
119
120	\defgroup game Game Kit
121	\brief The Game Kit provides classes for producing game sounds and
122		working with full screen apps.
123
124
125	\defgroup interface Interface Kit
126	\brief API for displaying a graphical user interface.
127
128	The Interface Kit holds all the classes you'll need to develop a GUI.
129	Building on the messaging facilities provided by the Application Kit,
130	the Interface Kit can be used to create a responsive and attractive
131	graphical user interface.
132
133 	The most important class in the Interface Kit is the BView class, which
134	handles drawing and user interaction. Pointer and keyboard events are
135	processed in this class.
136
137	Another important class is the BWindow class, which holds BViews and makes
138	them visible to the user. The BWindow class also handles BView focusing
139	and BMessage dispatching, among other things.
140
141	A new addition Haiku has added over the BeOS API is the Layout API, which
142	is based around the BLayoutItem and BLayout classes. These classes will
143	take care of making sure all your GUI widgets end up where you want them,
144	with enough space to be useful. You can start learning the Layout API
145	by reading the \link layout_intro introduction \endlink.
146
147
148	\defgroup locale Locale Kit
149	\brief Collection of classes for localizing applications.
150
151	\defgroup mail Mail Kit
152	\brief API for working with e-mail messages and protocols.
153
154	\defgroup media Media Kit
155	\brief Collection of classes that deal with audio and video.
156
157	\defgroup midi1 The old MIDI Kit (libmidi.so)
158	\brief The old MIDI kit.
159
160
161	\defgroup midi2 MIDI 2 Kit
162	\brief The Midi Kit is the API that implements support for generating,
163		processing, and playing music in MIDI format.
164
165	<A HREF="https://www.midi.org/">MIDI</A>, which  stands for 'Musical
166	Instrument Digital Interface', is a well-established  standard for
167	representing and communicating musical data. This document serves as
168	an overview. If you would like to see all the components, please look
169	at \link midi2 the list with classes \endlink.
170
171	\section book_midi2twokits A Tale of Two MIDI Kits
172
173	BeOS comes with two different, but compatible Midi Kits. This
174	documentation focuses on the "new" Midi Kit, or midi2 as we like to
175	call it, that was  introduced with BeOS R5. The old kit, which we'll
176	refer to as midi1, is more complete than the new kit, but less powerful.
177
178	Both kits let you create so-called MIDI endpoints, but the endpoints
179	from midi1 cannot be shared between different applications. The midi2
180	kit solves that  problem, but unlike midi1 it does not include a General
181	MIDI softsynth, nor does it have a facility for reading and playing
182	Standard MIDI Files. Don't worry: both kits are compatible and you can
183	mix-and-match them in your applications.
184
185	The main differences between the two kits:
186		- Instead of one BMidi object that both produces and consumes events,
187			we have BMidiProducer and BMidiConsumer.
188		- Applications are capable of sharing MIDI producers and consumers
189			with other applications via the centralized Midi Roster.
190		- Physical MIDI ports are now sharable without apps "stealing" events
191			from each other.
192		- Applications can now send/receive raw MIDI byte streams (useful if
193			an application has its own MIDI parser/engine).
194		- Channels are numbered 0&ndash;15, not 1&ndash;16
195		- Timing is now specified in microseconds rather than milliseconds.
196
197	\section book_midi2concepts Midi Kit Concepts
198
199	A brief overview of the elements that comprise the Midi Kit:
200		- \b Endpoints. This is what the Midi Kit is all about: sending MIDI
201			messages between endpoints. An endpoint is like a MIDI In or MIDI
202			Out socket on your equipment; it either receives information or it
203			sends information. Endpoints that send MIDI events are called
204			\b producers; the endpoints that receive those events are called
205			\b consumers. An endpoint that is created by your own application
206			is called \b local; endpoints from other applications are
207			\b remote. You can access remote endpoints using \b proxies.
208		- \b Filters. A filter is an object that has a consumer and a producer
209			endpoint. It reads incoming events from its consumer, performs some
210			operation, and tells its producer to send out the results. In its
211			current form, the Midi  Kit doesn't provide any special facilities
212			for writing filters.
213		- \b Midi \b Roster. The roster is the list of all published producers
214			and consumers. By publishing an endpoint, you allow other
215			applications to talk to it. You are not required to publish your
216			endpoints, in which case only your own application can use them.
217		- \b Midi \b Server. The Midi Server does the behind-the-scenes work.
218			It manages the roster, it connects endpoints, it makes sure that
219			endpoints can communicate, and so on. The Midi Server is started
220			automatically when BeOS boots, and you never have to deal with it
221			directly. Just remember that it runs the show.
222		- \b libmidi. The BMidi* classes live inside two shared libraries:
223			libmidi.so and libmidi2.so. If you write an application that uses
224			old Midi Kit, you must link it to libmidi.so. Applications that use
225			the new Midi Kit must link to libmidi2.so. If you want to
226			mix-and-match both kits, you should also link to both libraries.
227
228	Here is a pretty picture:
229
230	\image html midi2concepts.png
231
232	\section book_midi2mediakit Midi Kit != Media Kit
233
234	Be chose not to integrate the Midi Kit into the Media Kit as another media
235	type, mainly because MIDI doesn't require any of the format negotiation that
236	other media types need. Although the two kits look similar -- both have a
237	"roster" for finding or registering "consumers" and "producers" -- there are
238	some very important differences.
239
240	The first and most important point to note is that BMidiConsumer and
241	BMidiProducer in the Midi Kit are \b NOT directly analogous to
242	BBufferConsumer and  BBufferProducer in the Media Kit! In the Media Kit,
243	consumers and producers are the data consuming and producing properties
244	of a media node. A filter in the Media Kit, therefore, inherits from both
245	BBufferConsumer and BBufferProducer, and implements their virtual member
246	functions to do its work.
247
248	In the Midi Kit, consumers and producers act as endpoints of MIDI data
249	connections, much as media_source and media_destination do in the Media Kit.
250	Thus, a MIDI filter does not derive from BMidiConsumer and BMidiProducer;
251	instead, it contains BMidiConsumer and BMidiProducer objects for each of its
252	distinct endpoints that connect to other MIDI objects. The Midi Kit does not
253	allow the use of multiple virtual inheritance, so you can't create an object
254	that's both a BMidiConsumer and a BMidiProducer.
255
256	This also contrasts with the old Midi Kit's conception of a BMidi object,
257	which stood for an object that both received and sent MIDI data. In the new
258	Midi Kit, the endpoints of MIDI connections are all that matters. What lies
259	between the endpoints, i.e. how a MIDI filter is actually structured, is
260	entirely at your discretion.
261
262	Also, rather than use token structs like media_node to make connections
263	via the MediaRoster, the new kit makes the connections directly via the
264	BMidiProducer object.
265
266	\section book_midi2remotelocal Remote vs. Local Objects
267
268	The Midi Kit makes a distinction between remote and local MIDI objects.
269	You can  only create local MIDI endpoints, which derive from either
270	BMidiLocalConsumer or BMidiLocalProducer. Remote endpoints are endpoints
271	that live in other applications, and you access them through BMidiRoster.
272
273	BMidiRoster only gives you access to BMidiEndpoints, BMidiConsumers, and
274	BMidiProducers. When you want to talk to remote MIDI objects, you do so
275	through the proxy objects that BMidiRoster provides. Unlike
276	BMidiLocalConsumer and BMidiLocalProducer, these classes do not provide a
277	lot of functions. That is intentional. In order to hide the details of
278	communication with MIDI endpoints in other applications, the Midi Kit must
279	hide the details of how a particular endpoint is implemented.
280
281	So what can you do with remote objects? Only what BMidiConsumer,
282	BMidiProducer, and BMidiEndpoint will let you do. You can connect
283	objects, get the properties of these objects -- and that's about it.
284
285	\section book_midi2lifespan Creating and Destroying Objects
286
287	The constructors and destructors of most midi2 classes are private,
288	which means that you cannot directly create them using the C++
289	<CODE>new</CODE> operator, on the  stack, or as globals. Nor can you
290	<CODE>delete</CODE> them. Instead, these objects are obtained through
291	BMidiRoster. The only two exceptions to this rule are BMidiLocalConsumer
292	and BMidiLocalProducer. These two objects may be directly created and
293	subclassed by developers.
294
295	\section book_midi2refcount Reference Counting
296
297	Each MIDI endpoint has a reference count associated with it, so that
298	the Midi Roster can do proper bookkeeping. When you construct a
299	BMidiLocalProducer or  BMidiLocalConsumer endpoint, it starts with a
300	reference count of 1. In addition, BMidiRoster increments the reference
301	count of any object it hands to you as a result of
302	\link BMidiRoster::NextEndpoint() NextEndpoint() \endlink or
303	\link BMidiRoster::FindEndpoint() FindEndpoint() \endlink.
304	Once the count hits  0, the endpoint will be deleted.
305
306	This means that, to delete an endpoint, you don't call the
307	<CODE>delete</CODE>  operator directly; instead, you call
308	\link BMidiEndpoint::Release() Release() \endlink.
309	To balance this call, there's also an
310	\link BMidiEndpoint::Acquire() Acquire() \endlink, in case you have two
311	disparate parts of your application working with the endpoint, and you
312	don't want to have to keep track of who needs to Release() the endpoint.
313
314	When you're done with any endpoint object, you must Release() it.
315	This is true  for both local and remote objects. Repeat after me:
316	Release() when you're done.
317
318	\section book_midi2events MIDI Events
319
320	To make some actual music, you need to
321	\link BMidiProducer::Connect() Connect() \endlink your consumers to
322	your producers. Then you tell the producer to "spray" MIDI events to all
323	the connected consumers. The consumers are notified of these incoming
324	events through a set of hook functions.
325
326	The Midi Kit already provides a set of commonly used spray functions,
327	such as  \link BMidiLocalProducer::SprayNoteOn() SprayNoteOn() \endlink,
328	\link BMidiLocalProducer::SprayControlChange() SprayControlChange()
329	\endlink, and so on. These correspond one-to-one with the message types
330	from the MIDI spec. You don't need to be a MIDI expert to use the kit, but
331	of course some knowledge of the protocol helps. If you are really hardcore,
332	you can also use the
333	\link BMidiLocalProducer::SprayData() SprayData() \endlink to send raw MIDI
334	events to the consumers.
335
336	At the consumer side, a dedicated thread invokes a hook function for every
337	incoming MIDI event. For every spray function, there is a corresponding hook
338	function, e.g. \link BMidiLocalConsumer::NoteOn() NoteOn() \endlink and
339	\link  BMidiLocalConsumer::ControlChange() ControlChange() \endlink.
340	The hardcore MIDI fanatics among you will be pleased to know that you can
341	also tap into the \link BMidiLocalConsumer::Data() Data() \endlink hook and
342	get your hands dirty with the raw MIDI data.
343
344	\section book_midi2time Time
345
346	The spray and hook functions accept a bigtime_t parameter named "time". This
347	indicates when the MIDI event should be performed. The time is given in
348	microseconds since the computer booted. To get the current tick measurement,
349	you call the system_time() function from the Kernel Kit.
350
351	If you override a hook function in one of your consumer objects, it should
352	look  at the time argument, wait until the designated time, and then perform
353	its action. The preferred method is to use the Kernel Kit's
354	<CODE>snooze_until()</CODE> function, which sends the consumer thread to
355	sleep  until the requested time has come. (Or, if the time has already
356	passed, returns immediately.)
357
358	Like this:
359
360	\code
361void MyConsumer::NoteOn(
362    uchar channel, uchar note, uchar velocity, bigtime_t time)
363{
364    snooze_until(time, B_SYSTEM_TIMEBASE);
365    ...do your thing...
366}
367	\endcode
368
369	If you want your producers to run in real time, i.e. they produce MIDI data
370	that needs to be performed immediately, you should pass time 0 to the spray
371	functions (which also happens to be the default value). Since time 0 has
372	already passed, <CODE>snooze_until()</CODE> returns immediately, and the
373	consumer will process the events as soon as they are received.
374
375	To schedule MIDI events for a performance time that lies somewhere in the
376	future, the producer must take into account the consumer's latency.
377	Producers  should attempt to get notes to the consumer by or before
378	<I>(scheduled_performance_time - latency)</I>. The time argument is still
379	the scheduled performance time, so if your consumer has latency, it should
380	snooze like this before it starts to perform the events:
381
382	\code
383snooze_until(time - Latency(), B_SYSTEM_TIMEBASE);
384	\endcode
385
386	Note that a typical producer sends out its events as soon as it can;
387	unlike a consumer, it does not have to snooze.
388
389	\section book_midi2ports Other Timing Issues
390
391	Each consumer object uses a Kernel Kit port to receive MIDI events from
392	connected producers. The queue for this port is only 1 message deep.
393	This means that if the consumer thread is asleep in a
394	<CODE>snooze_until()</CODE>, it will not read its port. Consequently,
395	any producer that tries to write a new event to this port will block until
396	the consumer thread is ready to receive a new message. This is intentional,
397	because it prevents producers from generating and queueing up thousands of
398	events.
399
400	This mechanism, while simple, puts on the producer the responsibility
401	for sorting the events in time. Suppose your producer sends three Note
402	On events, the first on t + 0, the second on t + 4, and the third on t + 2.
403	This last event won't be received until after t + 4, so it will be two ticks
404	too late. If this sort of thing can happen with your producer, you should
405	somehow sort the events before you spray them. Of course, if you have two or
406	more producers connected to the same consumer, it is nearly impossible to
407	sort this all out (pardon the pun). So it is not wise to send the same kinds
408	of events from more than one producer to one consumer at the same time.
409
410	The article Introduction to MIDI, Part 2 in <A
411	HREF="https://open-beos.sourceforge.net/nsl.php?mode=display&id=36">OpenBeOS
412	Newsletter 36</A> describes this problem in more detail, and provides a
413	solution. Go read it now!
414
415	\section book_midi2filters Writing a Filter
416
417	A typical filter contains a consumer and a producer endpoint. It receives
418	events from the consumer, processes them, and sends them out again using the
419	producer. The consumer endpoint is a subclass of BMidiLocalConsumer, whereas
420	the producer is simply a BMidiLocalProducer, not a subclass. This is a
421	common  configuration, because consumers work by overriding the event hooks
422	to do work  when MIDI data arrives. Producers work by sending an event when
423	you call their  member functions. You should hardly ever need to derive from
424	BMidiLocalProducer (unless you need to know when the producer gets connected
425	or disconnected, perhaps), but you'll always have to override one or more of
426	BMidiLocalConsumer's member functions to do something useful with incoming
427	data.
428
429	Filters should ignore the time argument from the spray and hook functions,
430	and  simply pass it on unchanged. Objects that only filter data should
431	process the  event as quickly as possible and be done with it. Do not
432	<CODE>snooze_until()</CODE> in the consumer endpoint of a filter!
433
434	\section book_midi2apidiffs API Differences
435
436	As far as the end user is concerned, the Haiku Midi Kit is mostly the same
437	as the BeOS R5 kits, although there are a few small differences in the API
438	(mostly bug fixes):
439		- BMidiEndpoint::IsPersistent() always returns false.
440		- The B_MIDI_CHANGE_LATENCY notification is now properly sent. The Be
441			kit  incorrectly set be:op to B_MIDI_CHANGED_NAME, even though the
442			rest of the  message was properly structured.
443		- If creating a local endpoint fails, you can still Release() the object
444		  without crashing into the debugger.
445
446	\section book_midi2seealso See also
447
448	More about the Midi Kit:
449		- \ref Midi2Defs.h
450		- Be Newsletter Volume 3, Issue 47 - Motor Mix sample code
451		- Be Newsletter Volume 4, Issue 3 - Overview of the new kit
452		- <A HREF="https://haiku-os.org/documents/dev/introduction_to_midi_part_1">Newsletter
453		  33</A>, Introduction to MIDI, Part 1
454		- <A HREF="https://haiku-os.org/documents/dev/introduction_to_midi_part_2">Newsletter
455		  36</A>, Introduction to MIDI, Part 2
456		- Sample code and other goodies at the
457		  <A HREF="https://haiku-os.org/about/teams/midi_kit">Haiku Midi Kit team page</A>
458
459	Information about MIDI in general:
460		- <A HREF="https://www.midi.org">MIDI Manufacturers Association</A>
461		- <A HREF="https://www.borg.com/~jglatt/tutr/miditutr.htm">MIDI Tutorials</A>
462		- <A HREF="https://www.borg.com/~jglatt/tech/midispec.htm">MIDI Specification</A>
463		- <A HREF="https://www.borg.com/~jglatt/tech/midifile.htm">Standard MIDI File Format</A>
464		- <A HREF="https://www.io.com/~jimm/midi_ref.html">Jim Menard's MIDI Reference</A>
465
466
467	\defgroup network Network Kit
468	\brief Classes that deal with all network connections and communications.
469
470	The Haiku Network Kit consists of:
471	- A modular, add-ons based network stack
472	- Two shared libraries, libnetwork.so and libnetapi.so
473	- A stack driver, acting as interface between the network stack and
474	  libnetwork.so
475	- Basic network apps
476	- A modular GUI preflet
477
478	The libnet.so shared library is the way that BeOS R5 provided POSIX/BSD
479	API sockets to apps. Being binary compatible with BeOS R5 has made this
480	library implementation tedious. To counter this, the libnetapi.so shared
481	library was developed. It contains thin C++ classes wrapping the C
482	sockets POSIX/BSD API into these BNet* classes we're used under BeOS.
483
484	The stack driver is the interface between libnet.so and the real stack
485	behind it, hosted by the network stack kernel modules. Its purposes
486	include:
487	-# Providing sockets to file descriptors translation support
488	-# Providing support for select() on sockets
489	-# Loading the network stack on first access, and then keeping it for
490	   further accesses
491
492	The following diagram illustrates the network stack design on Haiku:
493
494	\image html obos_net_stack_design_1.gif
495
496	The Network Kit includes a handful of useful networking related apps
497	including ping, ifconfig, route, traceroute, and arp.
498
499	See the User Guide for more information about the
500	<a href="https://haiku-os.org/docs/userguide/en/preferences/network.html">Network preferences app</a>
501	included as part of the Network Kit.
502
503
504	\defgroup storage Storage Kit
505	\brief Collection of classes that deal with storing and retrieving
506		information from disk.
507
508
509	\defgroup support Support Kit
510	\brief Collection of utility classes that are used throughout the API.
511
512	The Support Kit provides a handy set of classes that you can use in your
513	applications. These classes provide:
514		- \b Thread \b Safety. Haiku can execute multiple threads of an
515			application in parallel, letting certain parts of an application
516			continue when one part is stalled, as well as letting an application
517			process multiple pieces of data at the same time on multicore or
518			multiprocessor systems. However, there are times when multiple
519			threads desire to work on the same piece of data at the same time,
520			potentially causing a conflict where variables or pointers are
521			changed by one thread causing another to execute incorrectly. To
522			prevent this, Haiku implements a \"locking\" mechanism, allowing one
523			thread to \"lock out\" other threads from executing code that might
524			modify the same data.
525		  - \b Archiving \b and \b IO. These classes allow a programmer to
526			convert objects into a form that can more easily be transferred to
527			other applications or stored to disk, as well as performing basic
528			input and output operations.
529		  - \b Memory \b Allocation. This class allows a programmer to hand off
530			some of the duties of memory accounting and management.
531		  - \b Common \b Datatypes. To avoid unnecessary duplication of code
532			and to make life easier for programmers, Haiku includes classes that
533			handle management of ordered lists and strings.
534
535	There are also a number of utility functions to time actions, play system
536	alert sounds, compare strings, and atomically manipulate integers. Have a
537	look at the overview, or go straight to the complete
538	\link support list of components \endlink of this kit.
539
540	\section book_overview Overview
541		- Thread Safety:
542			- BLocker provides a semaphore-like locking mechanism allowing for
543				recursive locks.
544			- BAutolock provides a simple method of automatically removing a
545				lock when a function ends.
546			- \ref TLS.h "Thread Local Storage" allows a global variable\'s
547				content to be sensitive to thread context.
548		- Archiving and IO:
549			- BArchivable provides an interface for \"archiving\" objects so
550				that they may be sent to other applications where an identical
551				copy will be recreated.
552			- BArchiver simplifies archiving of BArchivable hierarchies.
553			- BUnarchiver simplifies unarchiving hierarchies that have been
554				archived using BArchiver.
555			- BFlattenable provides an interface for \"flattening\" objects so
556				that they may be easily stored to disk.
557		- BDataIO provides an interface for generalized read/write streams.
558			- BPositionIO extends BDataIO to allow seeking within the data.
559			- BBufferIO creates a buffer and attaches it to a BPositionIO
560				stream, allowing for reduced load on the underlying stream.
561			- BMemoryIO allows operation on an already-existing buffer.
562			- BMallocIO creates and allows operation on a buffer.
563		- Memory Allocation:
564			- BBlockCache allows an application to allocate a \"pool\" of
565				memory blocks that the application can fetch and dispose of as
566				it pleases, letting the application make only a few large memory
567				allocations, instead of many small expensive allocations.
568		- Common Datatypes:
569			- BList allows simple ordered lists and provides common access,
570				modification, and comparison functions.
571			- BString allows strings and provides common access, modification,
572				and comparison functions.
573		- BStopWatch allows an application to measure the time an action takes.
574			- \ref support_globals "Global functions"
575			- \ref TypeConstants.h "Common types and constants"
576			- Error codes for all kits
577
578
579	\defgroup translation Translation Kit
580	\brief Provides a framework for converting data streams between media
581		formats.
582
583
584	\defgroup libtranslation (libtranslation.so)
585
586	\defgroup libbe (libbe.so)
587
588
589	\defgroup libroot (libroot.so)
590	\brief Implements the C and POSIX standard libraries.
591*/
592
593///// Subgroups /////
594
595/*!
596	\defgroup support_globals Global functions
597	\ingroup support
598
599	\defgroup layout Layout API
600	\brief Provides classes for automatically laying out UIs.
601	\ingroup interface
602*/
603
604
605///// Special Topics /////
606
607/*!
608	\defgroup drivers Device Drivers
609
610	\defgroup json Json Handling
611	\brief Provides for parsing and writing of data in Json encoding.
612
613	\defgroup netservices Experimental Network Services Support
614	\brief Experimental API to do higher level network requests
615
616	This API currently is marked as experimental. It is part of the
617	<code>BPrivate::Network</code> namespace, the header files are found at
618	<code>headers\\private\\netservices</code>, and you have to link your
619	application to <code>libnetservices.a</code>.
620*/
621
622
623///// Namespace Documentation /////
624
625
626//! \brief Internal or experimental API
627namespace BPrivate {
628	/*!
629		\brief Experimental Network Services API
630
631		See \ref netservices for more information.
632	*/
633	namespace Network {
634
635	}
636}
637