feedc0de/sdbus-cpp
1
0
Fork 0
forked from Kistler-Group/sdbus-cpp
Code Pull Requests Activity

docs: add section on D-Bus types to C++ types mapping (#285)

Browse Source 
* Added D-Bus type C++ type table

* docs: do corrections and rewordings in the proposed chapter

Co-authored-by: Stanislav Angelovič <stanislav.angelovic@protonmail.com>
This commit is contained in:
b-s-e
2022-09-05 13:51:05 +02:00
committed by GitHub
parent 35bffd0f25
commit f336811fc7
1 changed files with 44 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

46
docs/using-sdbus-c++.md
View File

@ -19,8 +19,9 @@ Using sdbus-c++ library
14. [Asynchronous client-side methods](#asynchronous-client-side-methods)
15. [Using D-Bus properties](#using-d-bus-properties)
16. [Standard D-Bus interfaces](#standard-d-bus-interfaces)
17. [Support for match rules](#support-for-match-rules)
18. [Conclusion](#conclusion)
17. [Using D-Bus Types](#using-d-bus-types)
18. [Support for match rules](#support-for-match-rules)
19. [Conclusion](#conclusion)
Introduction
------------
@ -1280,6 +1281,47 @@ Note that signals of afore-mentioned standard D-Bus interfaces are not emitted b
Working examples of using standard D-Bus interfaces can be found in [sdbus-c++ integration tests](/tests/integrationtests/DBusStandardInterfacesTests.cpp) or the [examples](/examples) directory.
Using D-Bus Types
-----------------
For many D-Bus interactions dealing with D-Bus types is necessary. For that, sdbus-c++ provides many predefined D-Bus types. The table below shows which C++ type corresponds to which D-Bus type.
| Category | Code | Code ASCII | Conventional Name | C++ Type |
|---------------------|-------------|------------|--------------------|---------------------------------|
| reserved | 0 | NUL | INVALID | - |
| fixed, basic | 121 | y | BYTE | `uint8_t` |
| fixed, basic | 98 | b | BOOLEAN | `bool` |
| fixed, basic | 110 | n | INT16 | `int16_t` |
| fixed, basic | 113 | q | UINT16 | `uint16_t` |
| fixed, basic | 105 | i | INT32 | `int32_t` |
| fixed, basic | 117 | u | UINT32 | `uint32_t` |
| fixed, basic | 120 | x | INT64 | `int64_t` |
| fixed, basic | 116 | t | UINT64 | `uint64_t` |
| fixed, basic | 100 | d | DOUBLE | `double` |
| string-like, basic | 115 | s | STRING | `const char*`, `std::string` |
| string-like, basic | 111 | o | OBJECT_PATH | `sdbus::ObjectPath` |
| string-like, basic | 103 | g | SIGNATURE | `sdbus::Signature` |
| container | 97 | a | ARRAY | `std::vector<T>` (if used as an array followed by a single complete type T), or `std::map<T1, T2>` (if used as an array of dict entries) |
| container | 114,40,41 | r() | STRUCT | `sdbus::Struct<T1, T2, ...>` variadic class template |
| container | 118 | v | VARIANT | `sdbus::Variant` |
| container | 101,123,125 | e{} | DICT_ENTRY | - |
| fixed, basic | 104 | h | UNIX_FD | `sdbus::UnixFd` |
| reserved | 109 | m | (reserved) | - |
| reserved | 42 | * | (reserved) | - |
| reserved | 63 | ? | (reserved) | - |
| reserved | 64,38,94 | @&^ | (reserved) | - |
A few examples:
* The D-Bus signature of an output argument of method `GetManagedObjects()` on standard interface `org.freedesktop.DBus.ObjectManager` is `a{oa{sa{sv}}}`. For this the corresponding C++ method return type is: `std::map<sdbus::ObjectPath, std::map<std::string, std::map<std::string, sdbus::Variant>>>`.
* Or an input argument of method `InterfacesRemoved` on that interface has signature `as`. Ths corresponds to the C++ parameter of type `std::vector<std::string>`.
* Or a D-Bus signature `a(bdh)` corresponds to the array of D-Bus structures: `std::vector<sdbus::Struct<bool, double, sdbus::UnixFd>>`.
To see how C++ types are mapped to D-Bus types (including container types) in sdbus-c++, have a look at individual [specializations of `sdbus::signature_of` class template](https://github.com/Kistler-Group/sdbus-cpp/blob/master/include/sdbus-c%2B%2B/TypeTraits.h#L87) in TypeTraits.h header file. For more examples of type mappings, look into [TypeTraits unit tests](https://github.com/Kistler-Group/sdbus-cpp/blob/master/tests/unittests/TypeTraits_test.cpp#L62).
For more information on basic D-Bus types, D-Bus container types, and D-Bus type system in general, make sure to consult the [D-Bus specification](https://dbus.freedesktop.org/doc/dbus-specification.html#type-system).
Support for match rules
-----------------------