| commit | 2726c17ebb854a1f134b82b63b03f307b5e0b3d8 | [log] [tgz] |
|---|---|---|
| author | William A. Kennington III <wak@google.com> | Fri Jun 22 19:39:04 2018 -0700 |
| committer | Brad Bishop <bradleyb@fuzziesquirrel.com> | Mon Jul 09 18:20:42 2018 +0000 |
| tree | 079d51a79c8ebb13f65f682773adfd8e97951e27 | |
| parent | 68cb1701d36a86d13979c4d9a33048e569f2ec0b [diff] |
SdBusError: Fix initialization checks
sd_bus_error_set_errno() is semantically useful in C for returning the
errno and constructing the error in a single call. However, since
successful population of the error can not be distinguished due to the
collapsed return value, we need another way to ensure the error was
built correctly. Don't check for the return of sd_bus_error_set_errno()
and instead use sd_bus_error_is_set().
Tested:
Builds still work and tests still pass.
Change-Id: Ib7546d7bb19eb2ebbaf6e2cab79a8ecd8960f280
Signed-off-by: William A. Kennington III <wak@google.com>
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_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.