3a4d0f4684
NOTE: This changes the error handling API of `glnx_loop_write()` to be "old school POSIX" instead of "systemd". In ostree in a few places we use `g_output_stream_splice()`. I thought this would use `splice()`, but actually it doesn't today. They also, if a cancellable is provided, end up dropping into `poll()` for every read and write. (In addition to copying data to/from userspace). My opinion on this is - for *local files* that's dumb. In the big picture, you really only need cancellation when copying gigabytes. Down the line, we could perhaps add a `glnx_copy_bytes_cancellable()` that only did that check e.g. every gigabyte of copied data. And when we do that we should use `g_cancellable_set_error_if_cancelled()` rather than a `poll()` with the regular file FD, since regular files are *always* readable and writable. For my use case with rpm-ostree though, we don't have gigabyte sized files, and seeing all of the `poll()` calls in strace is annoying. So let's have the non-cancellable file copying API that's modern and uses both reflink and `sendfile()` if available, in that order. My plan at some point once this is tested more is to migrate this code into GLib. Note that in order to keep our APIs consistent, I switched the systemd-imported code to "old school POSIX" error conventions. Otherwise we'd have *3* (POSIX, systemd, and GError) and particularly given the first two are easily confused, it'd be a recipe for bugs.
libglnx is the successor to libgsystem: https://git.gnome.org/browse/libgsystem
It is for modules which depend on both GLib and Linux, intended to be used as a git submodule.
Features:
- File APIs which use
openat()like APIs, but also take aGCancellableto support dynamic cancellation - APIs also have a
GErrorparameter - High level "shutil", somewhat inspired by Python's
- A "console" API for tty output
- A backport of the GLib cleanup macros for projects which can't yet take a dependency on 2.40.
Why?
There are multiple projects which have a hard dependency on Linux and GLib, such as NetworkManager, ostree, xdg-app, etc. It makes sense for them to be able to share Linux-specific APIs.
This module also contains some code taken from systemd, which has very high quality LGPLv2+ shared library code, but most of the internal shared library is private, and not namespaced.
One could also compare this project to gnulib; the salient differences there are that at least some of this module is eventually destined for inclusion in GLib.
Porting from libgsystem
For all of the filesystem access code, libglnx exposes only
fd-relative API, not GFile*. It does use GCancellable where
applicable.
For local allocation macros, you should start using the g_auto
macros from GLib. A backport is included in libglnx. There are a few
APIs not defined in GLib yet, such as glnx_fd_close.
gs_transfer_out_value is replaced by g_steal_pointer.
Contributing
Currently there is not a Bugzilla product - one may be created in the future. You can submit PRs against the Github mirror:
https://github.com/GNOME/libglnx/pulls
Or alternatively, email one of the maintainers directly.