X-Git-Url: https://ruderich.org/simon/gitweb/?a=blobdiff_plain;f=rpc%2Fconn.go;fp=rpc%2Fconn.go;h=c59bbd323272b50b150fa5d6671d61bdf022b800;hb=f2f2bc47e8729548f3c10117f7f008b547c4afc5;hp=0000000000000000000000000000000000000000;hpb=dc0d431a778a50e6732b9eb91384a07a207b772d;p=safcm%2Fsafcm.git

diff --git a/rpc/conn.go b/rpc/conn.go
new file mode 100644
index 0000000..c59bbd3
--- /dev/null
+++ b/rpc/conn.go
@@ -0,0 +1,164 @@
+// Simple RPC-like protocol: implementation of connection and basic actions
+
+// Copyright (C) 2021  Simon Ruderich
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package rpc
+
+import (
+	"bufio"
+	"fmt"
+	"os/exec"
+	"strings"
+	"sync"
+
+	"ruderich.org/simon/safcm"
+)
+
+type Conn struct {
+	Events   <-chan ConnEvent
+	events   chan<- ConnEvent // same as Events, to publish events
+	eventsWg sync.WaitGroup
+
+	debug  bool
+	remote string
+
+	cmd  *exec.Cmd
+	conn *safcm.GobConn
+}
+
+type ConnEventType int
+
+const (
+	_ ConnEventType = iota
+	ConnEventStderr
+	ConnEventDebug
+	ConnEventUpload
+)
+
+type ConnEvent struct {
+	Type ConnEventType
+	Data string
+}
+
+// NewConn creates a new connection. Events in the returned struct must be
+// regularly read or the connection will stall. This must be done before
+// DialSSH is called to open a connection.
+func NewConn(debug bool) *Conn {
+	ch := make(chan ConnEvent)
+	return &Conn{
+		Events: ch,
+		events: ch,
+		debug:  debug,
+	}
+}
+
+func (c *Conn) debugf(format string, a ...interface{}) {
+	if !c.debug {
+		return
+	}
+	c.events <- ConnEvent{
+		Type: ConnEventDebug,
+		Data: fmt.Sprintf(format, a...),
+	}
+}
+
+// Wrap safcm.GobConn's Send() and Recv() to provide debug output.
+
+// Send sends a single message to the remote.
+func (c *Conn) Send(m safcm.Msg) error {
+	// No checks for invalid Conn, a stacktrace is more helpful
+
+	c.debugf("Send: sending %#v", m)
+	return c.conn.Send(m)
+}
+
+// Recv waits for a single message from the remote.
+func (c *Conn) Recv() (safcm.Msg, error) {
+	// No checks for invalid Conn, a stacktrace is more helpful
+
+	c.debugf("Recv: waiting for message")
+	m, err := c.conn.Recv()
+	c.debugf("Recv: received msg=%#v err=%#v", m, err)
+	return m, err
+}
+
+// Wait waits for the connection to terminate. It's safe to call Wait (and
+// Kill) multiple times.
+func (c *Conn) Wait() error {
+	// But check here because Wait() can be called multiple times
+	if c.cmd == nil {
+		return fmt.Errorf("Dial*() not called or already terminated")
+	}
+
+	c.debugf("Wait: waiting for connection to terminate")
+	return c.wait()
+}
+func (c *Conn) wait() error {
+	err := c.cmd.Wait()
+	c.cmd = nil
+
+	// Wait until we've received all events from the program's stderr.
+	c.eventsWg.Wait()
+	// Notify consumers that no more events will occur.
+	close(c.events)
+	// We cannot reuse this channel.
+	c.events = nil
+	// Don't set c.Events to nil because this creates a data race when
+	// another thread is still waiting.
+
+	return err
+}
+
+// Kill forcefully terminates the connection. It's safe to call Kill (and
+// Wait) multiple times.
+func (c *Conn) Kill() error {
+	if c.cmd == nil {
+		return fmt.Errorf("Dial*() not called or already terminated")
+	}
+
+	c.debugf("Kill: killing connection")
+
+	c.cmd.Process.Kill()
+	return c.wait()
+}
+
+func (c *Conn) handleStderrAsEvents(cmd *exec.Cmd) error {
+	// cmd may differ from c.cmd here!
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		return err
+	}
+
+	c.eventsWg.Add(1)
+	go func() {
+		r := bufio.NewReader(stderr)
+		for {
+			x, err := r.ReadString('\n')
+			if err != nil {
+				break
+			}
+			x = strings.TrimRight(x, "\n")
+
+			c.events <- ConnEvent{
+				Type: ConnEventStderr,
+				Data: x,
+			}
+		}
+		c.eventsWg.Done()
+	}()
+
+	return nil
+}