tree 20dd2ee03eccd3e753b59129791a5c7d2a517c17
parent 95874d930f0bcc8390cd47ab3bb1e5e46db45278
author Ed Tanous <edtanous@google.com> 1617236097 -0700
committer Ed Tanous <edtanous@google.com> 1617307933 -0700

Implement path encoding and decoding

sdbus has methods for encoding and decoding paths in a lossless way.
This commit adds those methods to object_path in such a way that those
functions are called implicitly when building strings, the hope being
that any API choosing to use object_path need not write its own escaping
functions, and said escaping will happen implicitly.

The explicit changes to make this happen are.
1. filename() now calls into sd_bus_path_decode, rather than writing its
own method.  This means that the strings returned from the method now no
longer need decoding explicitly, and can largely be used as-is.  For
paths that did not require escaping, the behavior should be identical.
For paths that did require escaping, this method will now return the raw
version of the path.  Existing usages should remain the same, and impact
is unlikely, given that most sdbusplus users don't explicitly escape
strings, and filename() is relatively new.

2. a operator/ method is added to the object_path object.  Similar to
operator/ on std::filesystem::path, this allows generating a new
object_path from an existing one, by adding a new leaf node to the path.
Functionally this allows nearly any value to be escaped into a dbus
path.  An example of a common usage of this might be

object_path myPath = "/";
object_path myNewPath = myPath / "Foo-bar";

The above line will implicitly escape the - in the name.  Overloads for
both const std::string& and const char* have been added.

One motivating example where the above would be useful is to remove the
escapePathForDbus method in bmcweb.
https://github.com/openbmc/bmcweb/blob/88b3dd12851cd7bdd4b5c065ba99f40feafb775e/include/dbus_utility.hpp#L47

and the similarly named method in dbus-sensors
https://github.com/openbmc/dbus-sensors/blob/6cb732a31b7664089124b00e806311768bc24a87/src/SensorPaths.cpp#L49
both written by the same author (not me), and centralize them in
sdbusplus where they belong.

Functionally this commit also includes a new utility/memory.hpp, that
allows for C-style RAII using freep, mfree and the _cleanup_free_
attributes.  These were largely copied as-is from alloc-util.h in
systemd on latest patchset recommendations.

Tested:
Unit tests have been updated to include all new code paths, and some
common items that might need escaped.  Unit tests pass.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: If77b8bc5f75709b59353570a9c14383cac44dcd4