support suspend process (#48)

* support suspend process

* fix suspend in windows

* add comments

char.go

@@ -20,6 +20,7 @@ const (
 	CharTranspose = 20
 	CharCtrlU     = 21
 	CharCtrlW     = 23
+	CharCtrlZ     = 26
 	CharEsc       = 27
 	CharEscapeEx  = 91
 	CharBackspace = 127

operation.go

@@ -186,6 +186,10 @@ func (o *Operation) ioloop() {
 			if o.IsInCompleteMode() {
 				o.OnComplete()
 			}
+		case CharCtrlZ:
+			o.buf.Clean()
+			o.t.SleepToResume()
+			o.Refresh()
 		case MetaBackspace, CharCtrlW:
 			o.buf.BackEscapeWord()
 		case CharEnter, CharCtrlJ:

terminal.go

@@ -3,6 +3,7 @@ package readline
 import (
 	"bufio"
 	"fmt"
+	"strings"
 	"sync"
 	"sync/atomic"
 )
@@ -15,6 +16,7 @@ type Terminal struct {
 	kickChan  chan struct{}
 	wg        sync.WaitGroup
 	isReading int32
+	sleeping  int32
 }
 
 func NewTerminal(cfg *Config) (*Terminal, error) {
@@ -32,6 +34,20 @@ func NewTerminal(cfg *Config) (*Terminal, error) {
 	return t, nil
 }
 
+// SleepToResume will sleep myself, and return only if I'm resumed.
+func (t *Terminal) SleepToResume() {
+	if !atomic.CompareAndSwapInt32(&t.sleeping, 0, 1) {
+		return
+	}
+	defer atomic.StoreInt32(&t.sleeping, 0)
+
+	t.ExitRawMode()
+	ch := WaitForResume()
+	SuspendMe()
+	<-ch
+	t.EnterRawMode()
+}
+
 func (t *Terminal) EnterRawMode() (err error) {
 	return t.cfg.FuncMakeRaw()
 }
@@ -99,6 +115,10 @@ func (t *Terminal) ioloop() {
 		expectNextChar = false
 		r, _, err := buf.ReadRune()
 		if err != nil {
+			if strings.Contains(err.Error(), "interrupted system call") {
+				expectNextChar = true
+				continue
+			}
 			break
 		}
 

utils.go

@@ -4,6 +4,8 @@ import (
 	"bufio"
 	"bytes"
 	"strconv"
+	"sync"
+	"time"
 
 	"golang.org/x/crypto/ssh/terminal"
 )
@@ -12,6 +14,31 @@ var (
 	isWindows = false
 )
 
+// WaitForResume need to call before current process got suspend.
+// It will run a ticker until a long duration is occurs,
+// which means this process is resumed.
+func WaitForResume() chan struct{} {
+	ch := make(chan struct{})
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		ticker := time.NewTicker(10 * time.Millisecond)
+		t := time.Now()
+		wg.Done()
+		for {
+			now := <-ticker.C
+			if now.Sub(t) > 100*time.Millisecond {
+				break
+			}
+			t = now
+		}
+		ticker.Stop()
+		ch <- struct{}{}
+	}()
+	wg.Wait()
+	return ch
+}
+
 // IsTerminal returns true if the given file descriptor is a terminal.
 func IsTerminal(fd int) bool {
 	return terminal.IsTerminal(fd)

utils_unix.go

@@ -17,6 +17,16 @@ type winsize struct {
 	Ypixel uint16
 }
 
+// SuspendMe use to send suspend signal to myself, when we in the raw mode.
+// For OSX it need to send to parent's pid
+// For Linux it need to send to myself
+func SuspendMe() {
+	p, _ := os.FindProcess(os.Getppid())
+	p.Signal(syscall.SIGTSTP)
+	p, _ = os.FindProcess(os.Getpid())
+	p.Signal(syscall.SIGTSTP)
+}
+
 // get width of the terminal
 func getWidth(stdoutFd int) int {
 	ws := &winsize{}

utils_windows.go

@@ -4,6 +4,9 @@ package readline
 
 import "syscall"
 
+func SuspendMe() {
+}
+
 func GetStdin() int {
 	return int(syscall.Stdin)
 }