sshd/terminal: Use N-moves in Terminal.move when possible

sshd/terminal/terminal.go

@@ -7,6 +7,7 @@ package terminal
 import (
 	"bytes"
 	"io"
+	"strconv"
 	"sync"
 	"unicode/utf8"
 )
@@ -276,34 +277,44 @@ func (t *Terminal) moveCursorToPos(pos int) {
 }
 
 func (t *Terminal) move(up, down, left, right int) {
-	movement := make([]rune, 3*(up+down+left+right))
-	m := movement
-	for i := 0; i < up; i++ {
-		m[0] = keyEscape
-		m[1] = '['
-		m[2] = 'A'
-		m = m[3:]
-	}
-	for i := 0; i < down; i++ {
-		m[0] = keyEscape
-		m[1] = '['
-		m[2] = 'B'
-		m = m[3:]
-	}
-	for i := 0; i < left; i++ {
-		m[0] = keyEscape
-		m[1] = '['
-		m[2] = 'D'
-		m = m[3:]
-	}
-	for i := 0; i < right; i++ {
-		m[0] = keyEscape
-		m[1] = '['
-		m[2] = 'C'
-		m = m[3:]
+	m := []rune{}
+
+	// 1 unit up can be expressed as ^[A
+	// 5 units up can be expressed as ^[[5A
+
+	if up == 1 {
+		m = append(m, keyEscape, '[', 'A')
+	} else if up > 1 {
+		m = append(m, keyEscape, '[')
+		m = append(m, []rune(strconv.Itoa(up))...)
+		m = append(m, 'A')
 	}
 
-	t.queue(movement)
+	if down == 1 {
+		m = append(m, keyEscape, '[', 'B')
+	} else if down > 1 {
+		m = append(m, keyEscape, '[')
+		m = append(m, []rune(strconv.Itoa(down))...)
+		m = append(m, 'B')
+	}
+
+	if right == 1 {
+		m = append(m, keyEscape, '[', 'C')
+	} else if right > 1 {
+		m = append(m, keyEscape, '[')
+		m = append(m, []rune(strconv.Itoa(right))...)
+		m = append(m, 'C')
+	}
+
+	if left == 1 {
+		m = append(m, keyEscape, '[', 'D')
+	} else if left > 1 {
+		m = append(m, keyEscape, '[')
+		m = append(m, []rune(strconv.Itoa(left))...)
+		m = append(m, 'D')
+	}
+
+	t.queue(m)
 }
 
 func (t *Terminal) clearLineToRight() {