// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package term
import (
"bytes"
"io"
"runtime"
"strconv"
"sync"
"unicode/utf8"
)
// EscapeCodes contains escape sequences that can be written to the terminal in
// order to achieve different styles of text.
type EscapeCodes struct {
// Foreground colors
Black, Red, Green, Yellow, Blue, Magenta, Cyan, White []byte
// Reset all attributes
Reset []byte
}
var vt100EscapeCodes = EscapeCodes{
Black: []byte{keyEscape, '[', '3', '0', 'm'},
Red: []byte{keyEscape, '[', '3', '1', 'm'},
Green: []byte{keyEscape, '[', '3', '2', 'm'},
Yellow: []byte{keyEscape, '[', '3', '3', 'm'},
Blue: []byte{keyEscape, '[', '3', '4', 'm'},
Magenta: []byte{keyEscape, '[', '3', '5', 'm'},
Cyan: []byte{keyEscape, '[', '3', '6', 'm'},
White: []byte{keyEscape, '[', '3', '7', 'm'},
Reset: []byte{keyEscape, '[', '0', 'm'},
}
// Terminal contains the state for running a VT100 terminal that is capable of
// reading lines of input.
type Terminal struct {
// AutoCompleteCallback, if non-null, is called for each keypress with
// the full input line and the current position of the cursor (in
// bytes, as an index into |line|). If it returns ok=false, the key
// press is processed normally. Otherwise it returns a replacement line
// and the new cursor position.
AutoCompleteCallback func(line string, pos int, key rune) (newLine string, newPos int, ok bool)
// Escape contains a pointer to the escape codes for this terminal.
// It's always a valid pointer, although the escape codes themselves
// may be empty if the terminal doesn't support them.
Escape *EscapeCodes
// lock protects the terminal and the state in this object from
// concurrent processing of a key press and a Write() call.
lock sync.Mutex
c io.ReadWriter
prompt []rune
// line is the current line being entered.
line []rune
// pos is the logical position of the cursor in line
pos int
// echo is true if local echo is enabled
echo bool
// pasteActive is true iff there is a bracketed paste operation in
// progress.
pasteActive bool
// cursorX contains the current X value of the cursor where the left
// edge is 0. cursorY contains the row number where the first row of
// the current line is 0.
cursorX, cursorY int
// maxLine is the greatest value of cursorY so far.
maxLine int
termWidth, termHeight int
// outBuf contains the terminal data to be sent.
outBuf []byte
// remainder contains the remainder of any partial key sequences after
// a read. It aliases into inBuf.
remainder []byte
inBuf [256]byte
// history contains previously entered commands so that they can be
// accessed with the up and down keys.
history stRingBuffer
// historyIndex stores the currently accessed history entry, where zero
// means the immediately previous entry.
historyIndex int
// When navigating up and down the history it's possible to return to
// the incomplete, initial line. That value is stored in
// historyPending.
historyPending string
}
// NewTerminal runs a VT100 terminal on the given ReadWriter. If the ReadWriter is
// a local terminal, that terminal must first have been put into raw mode.
// prompt is a string that is written at the start of each input line (i.e.
// "> ").
func NewTerminal(c io.ReadWriter, prompt string) *Terminal {
return &Terminal{
Escape: &vt100EscapeCodes,
c: c,
prompt: []rune(prompt),
termWidth: 80,
termHeight: 24,
echo: true,
historyIndex: -1,
}
}
const (
keyCtrlC = 3
keyCtrlD = 4
keyCtrlU = 21
keyEnter = '\r'
keyEscape = 27
keyBackspace = 127
keyUnknown = 0xd800 /* UTF-16 surrogate area */ + iota
keyUp
keyDown
keyLeft
keyRight
keyAltLeft
keyAltRight
keyHome
keyEnd
keyDeleteWord
keyDeleteLine
keyClearScreen
keyPasteStart
keyPasteEnd
)
var (
crlf = []byte{'\r', '\n'}
pasteStart = []byte{keyEscape, '[', '2', '0', '0', '~'}
pasteEnd = []byte{keyEscape, '[', '2', '0', '1', '~'}
)
// bytesToKey tries to parse a key sequence from b. If successful, it returns
// the key and the remainder of the input. Otherwise it returns utf8.RuneError.
func bytesToKey(b []byte, pasteActive bool) (rune, []byte) {
if len(b) == 0 {
return utf8.RuneError, nil
}
if !pasteActive {
switch b[0] {
case 1: // ^A
return keyHome, b[1:]
case 2: // ^B
return keyLeft, b[1:]
case 5: // ^E
return keyEnd, b[1:]
case 6: // ^F
return keyRight, b[1:]
case 8: // ^H
return keyBackspace, b[1:]
case 11: // ^K
return keyDeleteLine, b[1:]
case 12: // ^L
return keyClearScreen, b[1:]
case 23: // ^W
return keyDeleteWord, b[1:]
case 14: // ^N
return keyDown, b[1:]
case 16: // ^P
return keyUp, b[1:]
}
}
if b[0] != keyEscape {
if !utf8.FullRune(b) {
return utf8.RuneError, b
}
r, l := utf8.DecodeRune(b)
return r, b[l:]
}
if !pasteActive && len(b) >= 3 && b[0] == keyEscape && b[1] == '[' {
switch b[2] {
case 'A':
return keyUp, b[3:]
case 'B':
return keyDown, b[3:]
case 'C':
return keyRight, b[3:]
case 'D':
return keyLeft, b[3:]
case 'H':
return keyHome, b[3:]
case 'F':
return keyEnd, b[3:]
}
}
if !pasteActive && len(b) >= 6 && b[0] == keyEscape && b[1] == '[' && b[2] == '1' && b[3] == ';' && b[4] == '3' {
switch b[5] {
case 'C':
return keyAltRight, b[6:]
case 'D':
return keyAltLeft, b[6:]
}
}
if !pasteActive && len(b) >= 6 && bytes.Equal(b[:6], pasteStart) {
return keyPasteStart, b[6:]
}
if pasteActive && len(b) >= 6 && bytes.Equal(b[:6], pasteEnd) {
return keyPasteEnd, b[6:]
}
// If we get here then we have a key that we don't recognise, or a
// partial sequence. It's not clear how one should find the end of a
// sequence without knowing them all, but it seems that [a-zA-Z~] only
// appears at the end of a sequence.
for i, c := range b[0:] {
if c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c == '~' {
return keyUnknown, b[i+1:]
}
}
return utf8.RuneError, b
}
// queue appends data to the end of t.outBuf
func (t *Terminal) queue(data []rune) {
t.outBuf = append(t.outBuf, []byte(string(data))...)
}
var space = []rune{' '}
func isPrintable(key rune) bool {
isInSurrogateArea := key >= 0xd800 && key <= 0xdbff
return key >= 32 && !isInSurrogateArea
}
// moveCursorToPos appends data to t.outBuf which will move the cursor to the
// given, logical position in the text.
func (t *Terminal) moveCursorToPos(pos int) {
if !t.echo {
return
}
x := visualLength(t.prompt) + pos
y := x / t.termWidth
x = x % t.termWidth
up := 0
if y < t.cursorY {
up = t.cursorY - y
}
down := 0
if y > t.cursorY {
down = y - t.cursorY
}
left := 0
if x < t.cursorX {
left = t.cursorX - x
}
right := 0
if x > t.cursorX {
right = x - t.cursorX
}
t.cursorX = x
t.cursorY = y
t.move(up, down, left, right)
}
func (t *Terminal) move(up, down, left, right int) {
m := []rune{}
// 1 unit up can be expressed as ^[[A or ^[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')
}
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() {
op := []rune{keyEscape, '[', 'K'}
t.queue(op)
}
const maxLineLength = 4096
func (t *Terminal) setLine(newLine []rune, newPos int) {
if t.echo {
t.moveCursorToPos(0)
t.writeLine(newLine)
for i := len(newLine); i < len(t.line); i++ {
t.writeLine(space)
}
t.moveCursorToPos(newPos)
}
t.line = newLine
t.pos = newPos
}
func (t *Terminal) advanceCursor(places int) {
t.cursorX += places
t.cursorY += t.cursorX / t.termWidth
if t.cursorY > t.maxLine {
t.maxLine = t.cursorY
}
t.cursorX = t.cursorX % t.termWidth
if places > 0 && t.cursorX == 0 {
// Normally terminals will advance the current position
// when writing a character. But that doesn't happen
// for the last character in a line. However, when
// writing a character (except a new line) that causes
// a line wrap, the position will be advanced two
// places.
//
// So, if we are stopping at the end of a line, we
// need to write a newline so that our cursor can be
// advanced to the next line.
t.outBuf = append(t.outBuf, '\r', '\n')
}
}
func (t *Terminal) eraseNPreviousChars(n int) {
if n == 0 {
return
}
if t.pos < n {
n = t.pos
}
t.pos -= n
t.moveCursorToPos(t.pos)
copy(t.line[t.pos:], t.line[n+t.pos:])
t.line = t.line[:len(t.line)-n]
if t.echo {
t.writeLine(t.line[t.pos:])
for i := 0; i < n; i++ {
t.queue(space)
}
t.advanceCursor(n)
t.moveCursorToPos(t.pos)
}
}
// countToLeftWord returns then number of characters from the cursor to the
// start of the previous word.
func (t *Terminal) countToLeftWord() int {
if t.pos == 0 {
return 0
}
pos := t.pos - 1
for pos > 0 {
if t.line[pos] != ' ' {
break
}
pos--
}
for pos > 0 {
if t.line[pos] == ' ' {
pos++
break
}
pos--
}
return t.pos - pos
}
// countToRightWord returns then number of characters from the cursor to the
// start of the next word.
func (t *Terminal) countToRightWord() int {
pos := t.pos
for pos < len(t.line) {
if t.line[pos] == ' ' {
break
}
pos++
}
for pos < len(t.line) {
if t.line[pos] != ' ' {
break
}
pos++
}
return pos - t.pos
}
// visualLength returns the number of visible glyphs in s.
func visualLength(runes []rune) int {
inEscapeSeq := false
length := 0
for _, r := range runes {
switch {
case inEscapeSeq:
if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') {
inEscapeSeq = false
}
case r == '\x1b':
inEscapeSeq = true
default:
length++
}
}
return length
}
// handleKey processes the given key and, optionally, returns a line of text
// that the user has entered.
func (t *Terminal) handleKey(key rune) (line string, ok bool) {
if t.pasteActive && key != keyEnter {
t.addKeyToLine(key)
return
}
switch key {
case keyBackspace:
if t.pos == 0 {
return
}
t.eraseNPreviousChars(1)
case keyAltLeft:
// move left by a word.
t.pos -= t.countToLeftWord()
t.moveCursorToPos(t.pos)
case keyAltRight:
// move right by a word.
t.pos += t.countToRightWord()
t.moveCursorToPos(t.pos)
case keyLeft:
if t.pos == 0 {
return
}
t.pos--
t.moveCursorToPos(t.pos)
case keyRight:
if t.pos == len(t.line) {
return
}
t.pos++
t.moveCursorToPos(t.pos)
case keyHome:
if t.pos == 0 {
return
}
t.pos = 0
t.moveCursorToPos(t.pos)
case keyEnd:
if t.pos == len(t.line) {
return
}
t.pos = len(t.line)
t.moveCursorToPos(t.pos)
case keyUp:
entry, ok := t.history.NthPreviousEntry(t.historyIndex + 1)
if !ok {
return "", false
}
if t.historyIndex == -1 {
t.historyPending = string(t.line)
}
t.historyIndex++
runes := []rune(entry)
t.setLine(runes, len(runes))
case keyDown:
switch t.historyIndex {
case -1:
return
case 0:
runes := []rune(t.historyPending)
t.setLine(runes, len(runes))
t.historyIndex--
default:
entry, ok := t.history.NthPreviousEntry(t.historyIndex - 1)
if ok {
t.historyIndex--
runes := []rune(entry)
t.setLine(runes, len(runes))
}
}
case keyEnter:
t.moveCursorToPos(len(t.line))
t.queue([]rune("\r\n"))
line = string(t.line)
ok = true
t.line = t.line[:0]
t.pos = 0
t.cursorX = 0
t.cursorY = 0
t.maxLine = 0
case keyDeleteWord:
// Delete zero or more spaces and then one or more characters.
t.eraseNPreviousChars(t.countToLeftWord())
case keyDeleteLine:
// Delete everything from the current cursor position to the
// end of line.
for i := t.pos; i < len(t.line); i++ {
t.queue(space)
t.advanceCursor(1)
}
t.line = t.line[:t.pos]
t.moveCursorToPos(t.pos)
case keyCtrlD:
// Erase the character under the current position.
// The EOF case when the line is empty is handled in
// readLine().
if t.pos < len(t.line) {
t.pos++
t.eraseNPreviousChars(1)
}
case keyCtrlU:
t.eraseNPreviousChars(t.pos)
case keyClearScreen:
// Erases the screen and moves the cursor to the home position.
t.queue([]rune("\x1b[2J\x1b[H"))
t.queue(t.prompt)
t.cursorX, t.cursorY = 0, 0
t.advanceCursor(visualLength(t.prompt))
t.setLine(t.line, t.pos)
default:
if t.AutoCompleteCallback != nil {
prefix := string(t.line[:t.pos])
suffix := string(t.line[t.pos:])
t.lock.Unlock()
newLine, newPos, completeOk := t.AutoCompleteCallback(prefix+suffix, len(prefix), key)
t.lock.Lock()
if completeOk {
t.setLine([]rune(newLine), utf8.RuneCount([]byte(newLine)[:newPos]))
return
}
}
if !isPrintable(key) {
return
}
if len(t.line) == maxLineLength {
return
}
t.addKeyToLine(key)
}
return
}
// addKeyToLine inserts the given key at the current position in the current
// line.
func (t *Terminal) addKeyToLine(key rune) {
if len(t.line) == cap(t.line) {
newLine := make([]rune, len(t.line), 2*(1+len(t.line)))
copy(newLine, t.line)
t.line = newLine
}
t.line = t.line[:len(t.line)+1]
copy(t.line[t.pos+1:], t.line[t.pos:])
t.line[t.pos] = key
if t.echo {
t.writeLine(t.line[t.pos:])
}
t.pos++
t.moveCursorToPos(t.pos)
}
func (t *Terminal) writeLine(line []rune) {
for len(line) != 0 {
remainingOnLine := t.termWidth - t.cursorX
todo := len(line)
if todo > remainingOnLine {
todo = remainingOnLine
}
t.queue(line[:todo])
t.advanceCursor(visualLength(line[:todo]))
line = line[todo:]
}
}
// writeWithCRLF writes buf to w but replaces all occurrences of \n with \r\n.
func writeWithCRLF(w io.Writer, buf []byte) (n int, err error) {
for len(buf) > 0 {
i := bytes.IndexByte(buf, '\n')
todo := len(buf)
if i >= 0 {
todo = i
}
var nn int
nn, err = w.Write(buf[:todo])
n += nn
if err != nil {
return n, err
}
buf = buf[todo:]
if i >= 0 {
if _, err = w.Write(crlf); err != nil {
return n, err
}
n++
buf = buf[1:]
}
}
return n, nil
}
func (t *Terminal) Write(buf []byte) (n int, err error) {
t.lock.Lock()
defer t.lock.Unlock()
if t.cursorX == 0 && t.cursorY == 0 {
// This is the easy case: there's nothing on the screen that we
// have to move out of the way.
return writeWithCRLF(t.c, buf)
}
// We have a prompt and possibly user input on the screen. We
// have to clear it first.
t.move(0 /* up */, 0 /* down */, t.cursorX /* left */, 0 /* right */)
t.cursorX = 0
t.clearLineToRight()
for t.cursorY > 0 {
t.move(1 /* up */, 0, 0, 0)
t.cursorY--
t.clearLineToRight()
}
if _, err = t.c.Write(t.outBuf); err != nil {
return
}
t.outBuf = t.outBuf[:0]
if n, err = writeWithCRLF(t.c, buf); err != nil {
return
}
t.writeLine(t.prompt)
if t.echo {
t.writeLine(t.line)
}
t.moveCursorToPos(t.pos)
if _, err = t.c.Write(t.outBuf); err != nil {
return
}
t.outBuf = t.outBuf[:0]
return
}
// ReadPassword temporarily changes the prompt and reads a password, without
// echo, from the terminal.
func (t *Terminal) ReadPassword(prompt string) (line string, err error) {
t.lock.Lock()
defer t.lock.Unlock()
oldPrompt := t.prompt
t.prompt = []rune(prompt)
t.echo = false
line, err = t.readLine()
t.prompt = oldPrompt
t.echo = true
return
}
// ReadLine returns a line of input from the terminal.
func (t *Terminal) ReadLine() (line string, err error) {
t.lock.Lock()
defer t.lock.Unlock()
return t.readLine()
}
func (t *Terminal) readLine() (line string, err error) {
// t.lock must be held at this point
if t.cursorX == 0 && t.cursorY == 0 {
t.writeLine(t.prompt)
t.c.Write(t.outBuf)
t.outBuf = t.outBuf[:0]
}
lineIsPasted := t.pasteActive
for {
rest := t.remainder
lineOk := false
for !lineOk {
var key rune
key, rest = bytesToKey(rest, t.pasteActive)
if key == utf8.RuneError {
break
}
if !t.pasteActive {
if key == keyCtrlD {
if len(t.line) == 0 {
return "", io.EOF
}
}
if key == keyCtrlC {
return "", io.EOF
}
if key == keyPasteStart {
t.pasteActive = true
if len(t.line) == 0 {
lineIsPasted = true
}
continue
}
} else if key == keyPasteEnd {
t.pasteActive = false
continue
}
if !t.pasteActive {
lineIsPasted = false
}
line, lineOk = t.handleKey(key)
}
if len(rest) > 0 {
n := copy(t.inBuf[:], rest)
t.remainder = t.inBuf[:n]
} else {
t.remainder = nil
}
t.c.Write(t.outBuf)
t.outBuf = t.outBuf[:0]
if lineOk {
if t.echo {
t.historyIndex = -1
t.history.Add(line)
}
if lineIsPasted {
err = ErrPasteIndicator
}
return
}
// t.remainder is a slice at the beginning of t.inBuf
// containing a partial key sequence
readBuf := t.inBuf[len(t.remainder):]
var n int
t.lock.Unlock()
n, err = t.c.Read(readBuf)
t.lock.Lock()
if err != nil {
return
}
t.remainder = t.inBuf[:n+len(t.remainder)]
}
}
// SetPrompt sets the prompt to be used when reading subsequent lines.
func (t *Terminal) SetPrompt(prompt string) {
t.lock.Lock()
defer t.lock.Unlock()
t.prompt = []rune(prompt)
}
func (t *Terminal) clearAndRepaintLinePlusNPrevious(numPrevLines int) {
// Move cursor to column zero at the start of the line.
t.move(t.cursorY, 0, t.cursorX, 0)
t.cursorX, t.cursorY = 0, 0
t.clearLineToRight()
for t.cursorY < numPrevLines {
// Move down a line
t.move(0, 1, 0, 0)
t.cursorY++
t.clearLineToRight()
}
// Move back to beginning.
t.move(t.cursorY, 0, 0, 0)
t.cursorX, t.cursorY = 0, 0
t.queue(t.prompt)
t.advanceCursor(visualLength(t.prompt))
t.writeLine(t.line)
t.moveCursorToPos(t.pos)
}
func (t *Terminal) SetSize(width, height int) error {
t.lock.Lock()
defer t.lock.Unlock()
if width == 0 {
width = 1
}
oldWidth := t.termWidth
t.termWidth, t.termHeight = width, height
switch {
case width == oldWidth:
// If the width didn't change then nothing else needs to be
// done.
return nil
case len(t.line) == 0 && t.cursorX == 0 && t.cursorY == 0:
// If there is nothing on current line and no prompt printed,
// just do nothing
return nil
case width < oldWidth:
// Some terminals (e.g. xterm) will truncate lines that were
// too long when shinking. Others, (e.g. gnome-terminal) will
// attempt to wrap them. For the former, repainting t.maxLine
// works great, but that behaviour goes badly wrong in the case
// of the latter because they have doubled every full line.
// We assume that we are working on a terminal that wraps lines
// and adjust the cursor position based on every previous line
// wrapping and turning into two. This causes the prompt on
// xterms to move upwards, which isn't great, but it avoids a
// huge mess with gnome-terminal.
if t.cursorX >= t.termWidth {
t.cursorX = t.termWidth - 1
}
t.cursorY *= 2
t.clearAndRepaintLinePlusNPrevious(t.maxLine * 2)
case width > oldWidth:
// If the terminal expands then our position calculations will
// be wrong in the future because we think the cursor is
// |t.pos| chars into the string, but there will be a gap at
// the end of any wrapped line.
//
// But the position will actually be correct until we move, so
// we can move back to the beginning and repaint everything.
t.clearAndRepaintLinePlusNPrevious(t.maxLine)
}
_, err := t.c.Write(t.outBuf)
t.outBuf = t.outBuf[:0]
return err
}
type pasteIndicatorError struct{}
func (pasteIndicatorError) Error() string {
return "terminal: ErrPasteIndicator not correctly handled"
}
// ErrPasteIndicator may be returned from ReadLine as the error, in addition
// to valid line data. It indicates that bracketed paste mode is enabled and
// that the returned line consists only of pasted data. Programs may wish to
// interpret pasted data more literally than typed data.
var ErrPasteIndicator = pasteIndicatorError{}
// SetBracketedPasteMode requests that the terminal bracket paste operations
// with markers. Not all terminals support this but, if it is supported, then
// enabling this mode will stop any autocomplete callback from running due to
// pastes. Additionally, any lines that are completely pasted will be returned
// from ReadLine with the error set to ErrPasteIndicator.
func (t *Terminal) SetBracketedPasteMode(on bool) {
if on {
io.WriteString(t.c, "\x1b[?2004h")
} else {
io.WriteString(t.c, "\x1b[?2004l")
}
}
// stRingBuffer is a ring buffer of strings.
type stRingBuffer struct {
// entries contains max elements.
entries []string
max int
// head contains the index of the element most recently added to the ring.
head int
// size contains the number of elements in the ring.
size int
}
func (s *stRingBuffer) Add(a string) {
if s.entries == nil {
const defaultNumEntries = 100
s.entries = make([]string, defaultNumEntries)
s.max = defaultNumEntries
}
s.head = (s.head + 1) % s.max
s.entries[s.head] = a
if s.size < s.max {
s.size++
}
}
// NthPreviousEntry returns the value passed to the nth previous call to Add.
// If n is zero then the immediately prior value is returned, if one, then the
// next most recent, and so on. If such an element doesn't exist then ok is
// false.
func (s *stRingBuffer) NthPreviousEntry(n int) (value string, ok bool) {
if n < 0 || n >= s.size {
return "", false
}
index := s.head - n
if index < 0 {
index += s.max
}
return s.entries[index], true
}
// readPasswordLine reads from reader until it finds \n or io.EOF.
// The slice returned does not include the \n.
// readPasswordLine also ignores any \r it finds.
// Windows uses \r as end of line. So, on Windows, readPasswordLine
// reads until it finds \r and ignores any \n it finds during processing.
func readPasswordLine(reader io.Reader) ([]byte, error) {
var buf [1]byte
var ret []byte
for {
n, err := reader.Read(buf[:])
if n > 0 {
switch buf[0] {
case '\b':
if len(ret) > 0 {
ret = ret[:len(ret)-1]
}
case '\n':
if runtime.GOOS != "windows" {
return ret, nil
}
// otherwise ignore \n
case '\r':
if runtime.GOOS == "windows" {
return ret, nil
}
// otherwise ignore \r
default:
ret = append(ret, buf[0])
}
continue
}
if err != nil {
if err == io.EOF && len(ret) > 0 {
return ret, nil
}
return ret, err
}
}
}
