commit | 7eb0d25fbc202d9933f9429824b553c06fd49646 | [log] [tgz] |
---|---|---|
author | Patrick Williams <patrick@stwcx.xyz> | Fri Mar 13 14:33:34 2020 -0500 |
committer | Patrick Williams <patrick@stwcx.xyz> | Fri Mar 13 16:22:17 2020 -0500 |
tree | 686d02c0b4ac39652a14b5786cf8320f281e160b | |
parent | 1dfce5a2947e1fcd56fe46a93dfb31f67a98fcc8 [diff] |
sdbus++: refactor enum handling for container-types Previously an attempt was made to support container types holding an enumeration, like 'struct[int, enum[self.Foo]]', but this code was not fully functional. There are some generated functions that occur outside of the class that defines the enum, so the fully qualified namespace is required. Previously, only the enum name was given, resulting in compile errors. Refactor the enumeration type handling by inserting C++-like placeholders into the early-parsed type name and then replace those placeholders, as appropriate, when it is determined if we need a fully-qualified or locally-qualified type. Signed-off-by: Patrick Williams <patrick@stwcx.xyz> Change-Id: Iddfcf99299a1ad4770f614431474d388cb6d9088
sdbusplus contains two parts:
The sdbusplus library requires sd-bus, which is contained in libsystemd.
The sdbus++ application requires python and the python libraries mako and py-inflection.
The sdbusplus library builds on top of the sd-bus library to create a modern C++ API for D-Bus. The library attempts to be as lightweight as possible, usually compiling to exactly the sd-bus API calls that would have been necessary, while also providing compile-time type-safety and memory leak protection afforded by modern C++ practices.
Consider the following code:
auto b = bus::new_default_system(); auto m = b.new_method_call("org.freedesktop.login1", "/org/freedesktop/login1", "org.freedesktop.login1.Manager", "ListUsers"); auto reply = b.call(m); std::vector<std::tuple<uint32_t, std::string, message::object_path>> users; reply.read(users);
In a few, relatively succinct, C++ lines this snippet will create a D-Bus connection to the system bus, and call the systemd login manager to get a list of active users. The message and bus objects are automatically freed when they leave scope and the message format strings are generated at compile time based on the types being read. Compare this to the corresponding server code within logind.
In general, the library attempts to mimic the naming conventions of the sd-bus library: ex. sd_bus_call
becomes sdbusplus::bus::call
, sd_bus_get_unique_name
becomes sdbusplus::bus::get_unique_name
, sd_bus_message_get_signature
becomes sdbusplus::message::get_signature
, etc. This allows a relatively straight-forward translation back to the sd-bus functions for looking up the manpage details.
sdbusplus also contains a bindings generator tool: sdbus++
. The purpose of a bindings generator is to reduce the boilerplate associated with creating D-Bus server or client applications. When creating a server application, rather than creating sd-bus vtables and writing C-style functions to handle each vtable callback, you can create a small YAML file to define your D-Bus interface and the sdbus++
tool will create a C++ class that implements your D-Bus interface. This class has a set of virtual functions for each method and property, which you can overload to create your own customized behavior for the interface.
There are currently two types of YAML files: interface and error. Interfaces are used to create server and client D-Bus interfaces. Errors are used to define C++ exceptions which can be thrown and will automatically turn into D-Bus error responses.
[[ D-Bus client bindings are not yet implemented. See openbmc/openbmc#851. ]]
The path of your file will be the interface name. For example, for an interface org.freedesktop.Example
, you would create the files org/freedesktop/Example.interface.yaml
and org/freedesktop/Example.errors.yaml]
for interfaces and errors respectively. These can then be used to generate the server and error bindings:
sdbus++ interface server-header org.freedesktop.Example > \ org/freedesktop/Example/server.hpp sdbus++ interface server-cpp org.freedesktop.Example > \ org/freedesktop/Example/server.cpp sdbus++ error exception-header org.freedesktop.Example > \ org/freedesktop/Example/error.hpp \ sdbus++ error exception-cpp org.freedesktop.Example > \ org/freedesktop/Example/error.cpp
Markdown-based documentation can also be generated from the interface and exception files:
sdbus++ interface markdown org.freedesktop.Example > \ org/freedesktop/Example.md sdbus++ error markdown org.freedesktop.Example >> \ org/freedesktop/Example.md
See the example/Makefile.am
for more details.
Installation of sdbusplus bindings on a custom distribution requires a few packages to be installed prior. Although these packages are the same for several distributions the names of these packages do differ. Below are the packages needed for Ubuntu and Fedora.
sudo apt install git autoconf libtool pkg-config g++ autoconf-archive libsystemd-dev python python-yaml python-mako python-inflection
sudo dnf install git autoconf libtool gcc-c++ pkgconfig autoconf-archive systemd-devel python python-pip python-yaml python-mako
Install the inflection package using the pip utility (on Fedora)
pip install inflection