shared: add PTY helper

This Pty API wraps the ugliness that is POSIX PTY. It takes care of:
  - edge-triggered HUP handling (avoid heavy CPU-usage on vhangup)
  - HUP vs. input-queue draining (handle HUP _after_ draining the whole
    input queue)
  - SIGCHLD vs. HUP (HUP is no reliable way to catch PTY deaths, always
    use SIGCHLD. Otherwise, vhangup() and friends will break.)
  - Output queue buffering (async EPOLLOUT handling)
  - synchronous setup (via Barrier API)

At the same time, the PTY API does not execve(). It simply fork()s and
leaves everything else to the caller. Usually, they execve() but we
support other setups, too.

This will be needed by multiple UI binaries (systemd-console, systemd-er,
...) so it's placed in src/shared/. It's not strictly related to
libsystemd-terminal, so it's not included there.

1 files changed, 77 insertions, 0 deletions

diff --git a/src/shared/pty.h b/src/shared/pty.h
new file mode 100644
index 0000000000..a87ceb58ca
--- /dev/null
+++ b/src/shared/pty.h
@@ -0,0 +1,77 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#pragma once
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 David Herrmann <dh.herrmann@gmail.com>
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "barrier.h"
+#include "macro.h"
+#include "sd-event.h"
+#include "util.h"
+
+typedef struct Pty Pty;
+
+enum {
+        PTY_CHILD,
+        PTY_HUP,
+        PTY_DATA,
+};
+
+typedef int (*pty_event_t) (Pty *pty, void *userdata, unsigned int event, const void *ptr, size_t size);
+
+int pty_new(Pty **out);
+Pty *pty_ref(Pty *pty);
+Pty *pty_unref(Pty *pty);
+
+#define _pty_unref_ _cleanup_(pty_unrefp)
+DEFINE_TRIVIAL_CLEANUP_FUNC(Pty*, pty_unref);
+
+Barrier *pty_get_barrier(Pty *pty);
+
+bool pty_is_unknown(Pty *pty);
+bool pty_is_parent(Pty *pty);
+bool pty_is_child(Pty *pty);
+bool pty_has_child(Pty *pty);
+pid_t pty_get_child(Pty *pty);
+
+bool pty_is_open(Pty *pty);
+int pty_get_fd(Pty *pty);
+
+int pty_make_child(Pty *pty);
+int pty_make_parent(Pty *pty, pid_t child);
+int pty_unlock(Pty *pty);
+int pty_setup_child(Pty *pty);
+void pty_close(Pty *pty);
+
+int pty_attach_event(Pty *pty, sd_event *event, pty_event_t event_fn, void *event_fn_userdata);
+void pty_detach_event(Pty *pty);
+
+int pty_write(Pty *pty, const void *buf, size_t size);
+int pty_signal(Pty *pty, int sig);
+int pty_resize(Pty *pty, unsigned short term_width, unsigned short term_height);
+
+pid_t pty_fork(Pty **out, sd_event *event, pty_event_t event_fn, void *event_fn_userdata, unsigned short initial_term_width, unsigned short initial_term_height);