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| author | Hans-Christoph Steiner <eighthave@users.sourceforge.net> | 2005-11-28 01:07:25 +0000 |
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| committer | Hans-Christoph Steiner <eighthave@users.sourceforge.net> | 2005-11-28 01:07:25 +0000 |
| commit | c50ce0e0217ea07e2d450add2ab29cecea66fa96 (patch) | |
| tree | 0700e1e5fd14ff99e5a4c6d4b4937268a1d9804f /doc/misc/devdoc.html | |
| parent | d7f71f87b112317d8303f25b4a536b943ea59d97 (diff) | |
This commit was generated by cvs2svn to compensate for changes in r4059,
which included commits to RCS files with non-trunk default branches.
svn path=/trunk/externals/pdp/; revision=4060
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diff --git a/doc/misc/devdoc.html b/doc/misc/devdoc.html new file mode 100644 index 0000000..5ce1f83 --- /dev/null +++ b/doc/misc/devdoc.html @@ -0,0 +1,167 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> +<html> + <head> + <title>PDP Developer Documentation</title> + </head> + + <body> + <h1>PDP Developer Documentation</h1> + + <h2>Introduction</h2> + + <p>There is not yet much developer information, partly because pdp is not that big and since the goals are + not completely clear yet, a lot will probably change on the inside in the future. I believe it is + not too hard to figure out how it works, once you get started somewhere. This document is a minimalistic + attempt to provide that starting point. For full prototypes see the header files. I suggest you have a look at the pdp_base base class, and some simple + modules: pdp_add, pdp_noise and pdp_gain for examples. + + <h2> PDP architecture </h2> + <p> Architecture is a big word, but pdp is organized as modules. A packet pool module (a reuse pool memory manager), + a packet class, a processing queue module, a high level type conversion module, an image packet class, and some + low level modules for image type conversion, image resampling and all sorts of other image processing. Besides that + there are 2 extension libraries: pdp_scaf, a cellular automata extension and pdp_opengl, a 3d rendering extension. + These are separate because of portability issues. The different pdp_* externs in the main pdp library use the + core modules' functionality to minimize code duplication. I'm relatively happy with how it fits together, + but some things need to change for future plans. Most objects are written in the object oriented c style of pd. + To prevent namespace conflicts, (almost) all routines start with the pdp_ prefix. The second name is the name of the + object or module they belong to. The first argument is always a pointer to an object or an integer (for packets). + + + <h2> PD ties </h2> + <p> PDP is written as an extension for PD. One of the goals of pdp is to evolve to a separate library that can + be reused in other software. The architecture will be split into two parts. A pd-independent part (the packet classes, + the packet pool, the type conversion system and the forth system) and a part with pd specific stuff (the process queue and interfaces to the + pd system like the base classes and the pd communication protocol). In order to do this the packet class will probably + evolve to a proper object model, supporting run time attribute binding (inspired by the python object model). + + <p>There are some things that put a stamp on the current pdp design. Most importantly pd's processor object model and + communication protocol. (i.e. the fact that pd only supports unidirectional messaging creates the awkward concept + of a "passing packet" to eliminate excessive data copying.) + + <p> In pd, the pdp messaging protocol is implemented as pd messages. The protocol is however 3 phase. + With a read only register phase, a read/write register phase and a process phase. This functionality + is part of the base class or the forth processor object. The dpd protocol is entirely different, + and is used in the opengl library. It is + not based on parallel dataflow but serial context passing. + + <h2> Packets </h2> + <p> PDP introduces a new atom: the data packet. This can contain all kinds of data. Images (16bit/8bit), cellular + automata (1bit), matrices (real/complex float/double), opengl textures and 3d rendering contexts. Packets + are stored in a pool to ensure fast reuse, and to enable sharing. The paradigm is centered around a + combination of an object oriented approach and a dataflow approach. + <p>The methods operating on packets + (pdp_packet_*) are mainly for administrative purposes: memory management (construction, registering, copying) + and getting or setting info. + <p>All processing is done in the pd modules. Processors can be defined using + the forth scripting language, but this is still experimental. The forth system can be accessed + from the guile library. + <p> There is a central mechanism for packet type conversion. This is to facilitate the combination of different + media types. Whenever a packet class is constructed (i.e. in an extension library), a number of conversion + routines should be defined to convert the added type to one or some of the main pdp types. + + + + + + + <h2>PDP API Overview</h2> + + The pdp public api contains only a single class: the packet. (The internal api has more classes, that can be used + too if necessary, but i won't document them.) A packet is a class in pdp. The table below lists the supported methods. + The first argument of a call is a packet id. + + <TABLE border = "1"> + <TR><TH colspan = "2">pdp_packet_* + <TR><TD>new <TD>construct a raw packet (depreciated) + <TR><TD>new_* <TD>construct packet of specific type/subtype/... + <TR><TD>mark_unused <TD>release + <TR><TD>mark_passing <TD>conditional release (release on first copy ro/rw) + <TR><TD>copy_ro <TD>readonly (shared) copy + <TR><TD>copy_rw <TD>private copy + <TR><TD>clone_rw <TD>private copy (copies only meta data, not the content) + <TR><TD>header <TD>get the raw header (t_pdp *) + <TR><TD>data <TD>get the raw data (void *) + <TR><TD>pass_if_valid <TD>send a packet to pd outlet, if it is valid, and mark unused + <TR><TD>replace_if_valid <TD>delete packet and replace with new one, if new is valid + <TR><TD>copy_ro_or_drop <TD>copy readonly, or don't copy if dest slot is full + send drop notify + <TR><TD>copy_rw_or_drop <TD>same, but private copy + <TR><TD>get_description <TD>retrieve type info + <TR><TD>convert_ro <TD>same as copy_ro, but with an automatic conversion matching a type template + <TR><TD>convert_rw <TD>same as convert_ro, but producing a private copy + </TABLE> + + + <p>The pool object methods. All the packets are stored in a central packet pool. + + <TABLE border = "1"> + <TR><TH colspan = "2">pdp_pool_* + <TR><TD>collect_garbage <TD>manually free all unused resources in packet pool + </TABLE> + + <p>The process queue object methods. PDP supports a separate processing thread. + + <TABLE border = "1"> + <TR><TH colspan = "2"> pdp_queue_* + <TR><TD>add <TD>add a process method + callback + <TR><TD>finish <TD>wait until a specific task is done + <TR><TD>wait <TD>wait until processing queue is done + </TABLE> + + <p>The control methods. General pdp control messages. + + <TABLE border = "1"> + <TR><TH colspan = "2"> pdp_control_* + <TR><TD>notify_drop <TD>notify that a packet has been dropped + </TABLE> + + <p> The type mediator methods. + <TABLE border = "1"> + <TR><TH colspan = "2"> pdp_type_* + <TR><TD>description_match <TD>check if two type templates match + <TR><TD>register_conversion <TD>register a type conversion program + + +</TABLE> + + + <p>NOTE: it is advised to derive your module from the pdp base class defined in pdp_base.h + instead of communicating directly with the pdp core + + + + <h2>pdp_base class</h2> + If you want to write a pdp extern, you can derive it from the pdp_base class, instead of t_object. + This class abstracts a lot of the hassle of writing ordinary (inplace) packet processors. The base + allows you to register process callbacks. There are 3 kinds of callbacks: preproc, process and postproc. + The preproc method is called inside the pd thread. This can be used to setup some things that can only + be done inside the pd thread. The process method should do most of the work, and is called from the + pdp processing thread if it is enabled, after the preproc method is finished. You can't use most + of pd's calls in this method. The postproc method is called + from the pd thread after the process method is finished, and can be used to send data to pd outlets. Simple + packet processors only need the process method (packet input/output is handled by the pdp_base class). + + <h2>pdp_imageproc_* modules</h2> + Most of the image processing code is organized as planar 16 bit signed processors. + This is crude and oversimplified, but it helps to keep the code size small and fast + at the same time (platform dependent assembly code is reduced to a bare minimum). These + routines can be used to build higher level image processing objects that are more (cache) + efficient than an abstraction using separate pdp modules. If you plan to write your own image + processing routines, you can use the pdp_imageproc_dispatch_ routine to support all 16bit image + types at once (greyscale, subsampled YCrCb, multichannel planar). This requires you write the + image processing routine as a planar (greyscale) processor using the pdp_imageproc_ + interface. (see pdp_imageproc.h) + + <h2>pdp_llconv call</h2> + Low level image conversion routines. (operating on raw data buffers). You probably won't need this, + since the high level type conversion (pdp_packet_convert_ro/rw) covers most of its functionality. + + + + <hr> + <address><a href="mailto:pdp@zzz.kotnet.org">Tom Schouten</a></address> +<!-- Created: Mon Apr 28 15:35:12 CEST 2003 --> +<!-- hhmts start --> +Last modified: Fri Sep 19 04:52:12 CEST 2003 +<!-- hhmts end --> + </body> +</html> |