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