31dfc4aa12
This adds support for the integrating libdbus into the lws event loop. Unlike the other roles, lws doesn't completely adopt the fd and libdbus insists to retain control over the fd lifecycle. However libdbus provides apis for foreign code (lws) to provide event loop services to libdbus for the fd. Accordingly, unlike the other roles rx and writeable are not subsumed into lws callback messages and the events remain the property of libdbus. A context struct wrapper is provided that is available in the libdbus callbacks to bridge between the lws and dbus worlds, along with a minimal example dbus client and server.
2.8 KiB
DBUS Role Support
DBUS-related distro packages
Fedora: dbus-devel Debian / Ubuntu: libdbus-1-dev
Enabling for build at cmake
Fedora example:
$ cmake .. -DLWS_ROLE_DBUS=1 -DLWS_DBUS_INCLUDE2="/usr/lib64/dbus-1.0/include"
Ubuntu example:
$ cmake .. -DLWS_ROLE_DBUS=1 -DLWS_DBUS_INCLUDE2="/usr/lib/x86_64-linux-gnu/dbus-1.0/include"
Dbus requires two include paths, which you can force by setting LWS_DBUS_INCLUDE1
and LWS_DBUS_INCLUDE2. Although INCLUDE1 is usually guessable, both can be
forced to allow cross-build.
If these are not forced, then lws cmake will try to check some popular places,
for LWS_DBUS_INCLUDE1, on both Fedora and Debian / Ubuntu, this is
/usr/include/dbus-1.0... if the directory exists, it is used.
For LWS_DBUS_INCLUDE2, it is the arch-specific dbus header which may be
packaged separately than the main dbus headers. On Fedora, this is in
/usr/lib[64]/dbus-1.0/include... if not given externally, lws cmake will
try /usr/lib64/dbus-1.0/include. On Debian / Ubuntu, the package installs
it in an arch-specific dir like /usr/lib/x86_64-linux-gnu/dbus-1.0/include,
you should force the path.
The library path is usually [lib] "dbus-1", but this can also be forced if
you want to build cross or use a special build, via LWS_DBUS_LIB.
Building against local dbus build
If you built your own local dbus and installed it in /usr/local, then this is the incantation to direct lws to use the local version of dbus:
cmake .. -DLWS_ROLE_DBUS=1 -DLWS_DBUS_INCLUDE1="/usr/local/include/dbus-1.0" -DLWS_DBUS_INCLUDE2="/usr/local/lib/dbus-1.0/include" -DLWS_DBUS_LIB="/usr/local/lib/libdbus-1.so"
You'll also need to give the loader a helping hand to do what you want if
there's a perfectly good dbus lib already in /usr/lib[64] using LD_PRELOAD
like this
LD_PRELOAD=/usr/local/lib/libdbus-1.so.3.24.0 myapp
Lws dbus api exports
Because of the irregular situation with libdbus includes, if lws exports the
dbus helpers, which use dbus types, as usual from #include <libwebsockets.h>
then if lws was compiled with dbus role support it forces all users to take
care about the dbus include path mess whether they use dbus themselves or not.
For that reason, if you need access to the lws dbus apis, you must explicitly include them by
#include <libwebsockets/lws-dbus.h>
This includes <dbus/dbus.h> and so requires the include paths set up. But
otherwise non-dbus users that don't include libwebsockets/lws-dbus.h don't
have to care about it.
DBUS and valgrind
https://cgit.freedesktop.org/dbus/dbus/tree/README.valgrind
- One-time 6KiB "Still reachable" caused by abstract unix domain socket + libc
getgrouplist()via nss... bug since 2004(!)