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package cwriter
import (
"bytes"
"errors"
"io"
"os"
"strconv"
)
// NotATTY not a TeleTYpewriter error.
var NotATTY = errors.New("not a terminal")
// http://ascii-table.com/ansi-escape-sequences.php
const (
escOpen = "\x1b["
cuuAndEd = "A\x1b[J"
)
// Writer is a buffered the writer that updates the terminal. The
// contents of writer will be flushed when Flush is called.
type Writer struct {
out io.Writer
buf bytes.Buffer
lineCount int
fd int
isTerminal bool
}
// New returns a new Writer with defaults.
func New(out io.Writer) *Writer {
w := &Writer{out: out}
if f, ok := out.(*os.File); ok {
w.fd = int(f.Fd())
w.isTerminal = IsTerminal(w.fd)
}
return w
}
// Flush flushes the underlying buffer.
func (w *Writer) Flush(lineCount int) (err error) {
// some terminals interpret clear 0 lines as clear 1
if w.lineCount > 0 {
err = w.clearLines()
if err != nil {
return
}
}
w.lineCount = lineCount
_, err = w.buf.WriteTo(w.out)
return
}
// Write appends the contents of p to the underlying buffer.
func (w *Writer) Write(p []byte) (n int, err error) {
return w.buf.Write(p)
}
// WriteString writes string to the underlying buffer.
func (w *Writer) WriteString(s string) (n int, err error) {
return w.buf.WriteString(s)
}
// ReadFrom reads from the provided io.Reader and writes to the
// underlying buffer.
func (w *Writer) ReadFrom(r io.Reader) (n int64, err error) {
return w.buf.ReadFrom(r)
}
// GetWidth returns width of underlying terminal.
func (w *Writer) GetWidth() (int, error) {
if !w.isTerminal {
return -1, NotATTY
}
tw, _, err := GetSize(w.fd)
return tw, err
}
func (w *Writer) ansiCuuAndEd() (err error) {
buf := make([]byte, 8)
buf = strconv.AppendInt(buf[:copy(buf, escOpen)], int64(w.lineCount), 10)
_, err = w.out.Write(append(buf, cuuAndEd...))
return
}
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