From 7a46c07230b8d8108c0e8e80df4522d0ac116538 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:28:17 +0200 Subject: Adding upstream version 0.3.65. Signed-off-by: Daniel Baumann --- doc/spa-index.dox | 88 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 88 insertions(+) create mode 100644 doc/spa-index.dox (limited to 'doc/spa-index.dox') diff --git a/doc/spa-index.dox b/doc/spa-index.dox new file mode 100644 index 0000000..f7f5ffe --- /dev/null +++ b/doc/spa-index.dox @@ -0,0 +1,88 @@ +/** \page page_spa SPA (Simple Plugin API) + +\ref api_spa (Simple Plugin API) is an extensible API to implement all kinds of +plugins. + +It is inspired by many other plugin APIs, mostly LV2 and +GStreamer. SPA provides two parts: + +- A header-only API with no external dependencies. +- A set of support libraries ("plugins") for commonly used functionality. + +The usual approach is that PipeWire and PipeWire clients can use the +header-only functions to interact with the plugins. Those plugins are +usually loaded at runtime (through `dlopen(3)`). + + +# Motivation + +SPA was designed with the following goals in mind: + +- No dependencies, SPA is shipped as a set of header files that have no dependencies except for the standard C library. +- Very efficient both in space and in time. +- Very configurable and usable in many different environments. All aspects + of the plugin environment can be configured and changed, like logging, + poll loops, system calls, etc. +- Consistent API. +- Extensible; new API can be added with minimal effort, existing API can be updated and versioned. + +The original user of SPA is PipeWire, which uses SPA to implement the +low-level multimedia processing plugins, device detection, mainloops, CPU +detection, logging, among other things. SPA however can be used outside +of PipeWire with minimal problems. + + +# The SPA Header-Only API + +A very simple example on how SPA headers work are the \ref spa_utils, a set +of utilities commonly required by C projects. SPA functions use the `spa_` +namespace and are easy to identify. + +\code +/* cc $(pkg-config --cflags libspa-0.2) -o spa-test spa-test.c */ + +#include +#include + +int main(int argc, char **argv) { + uint32_t val; + + if (spa_atoi32(argv[1], &val, 16)) + printf("argv[1] is hex %#x\n", val); + else + printf("argv[1] is not a hex number\n"); + + return 0; +} +\endcode + + +# SPA Plugins + +SPA plugins are shared libraries (`.so` files) that can be loaded at +runtime. Each library provides one or more "factories", each of which may +implement several "interfaces". Code that uses SPA plugins then uses those +interfaces (through SPA header files) to interact with the plugin. + +For example, the PipeWire daemon can load the normal `printf`-based logger +or a systemd journal-based logger. Both of those provide the \ref spa_log +interface and once instantiated, PipeWire no longer has to differentiate +between the two logging facilities. + +Please see \ref page_spa_plugins for the details on how to use SPA plugins. + + +# Further details + +- \ref api_spa +- \subpage page_spa_design +- \subpage page_spa_plugins +- \subpage page_spa_pod +- \subpage page_spa_buffer + + +\addtogroup api_spa + +See: \ref page_spa, \ref page_spa_design + +*/ -- cgit v1.2.3