mirror of
https://github.com/strongdm/comply
synced 2024-11-09 01:14:53 +00:00
139 lines
2.8 KiB
Go
139 lines
2.8 KiB
Go
package screenbuf
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import (
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"bytes"
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"fmt"
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"io"
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)
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const esc = "\033["
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var (
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clearLine = []byte(esc + "2K\r")
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moveUp = []byte(esc + "1A")
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moveDown = []byte(esc + "1B")
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)
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// ScreenBuf is a convenient way to write to terminal screens. It creates,
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// clears and, moves up or down lines as needed to write the output to the
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// terminal using ANSI escape codes.
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type ScreenBuf struct {
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w io.Writer
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buf *bytes.Buffer
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reset bool
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flush bool
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cursor int
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height int
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}
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// New creates and initializes a new ScreenBuf.
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func New(w io.Writer) *ScreenBuf {
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return &ScreenBuf{buf: &bytes.Buffer{}, w: w}
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}
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// Reset truncates the underlining buffer and marks all its previous lines to be
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// cleared during the next Write.
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func (s *ScreenBuf) Reset() {
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s.buf.Reset()
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s.reset = true
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}
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// Write writes a single line to the underlining buffer. If the ScreenBuf was
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// previously reset, all previous lines are cleared and the output starts from
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// the top. Lines with \r or \n will fail since they can interfere with the
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// terminal ability to move between lines.
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func (s *ScreenBuf) Write(b []byte) (int, error) {
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if bytes.ContainsAny(b, "\r\n") {
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return 0, fmt.Errorf("%q should not contain either \\r or \\n", b)
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}
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if s.reset {
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for i := 0; i < s.height; i++ {
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_, err := s.buf.Write(moveUp)
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if err != nil {
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return 0, err
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}
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_, err = s.buf.Write(clearLine)
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if err != nil {
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return 0, err
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}
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}
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s.cursor = 0
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s.height = 0
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s.reset = false
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}
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switch {
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case s.cursor == s.height:
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n, err := s.buf.Write(clearLine)
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if err != nil {
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return n, err
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}
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line := append(b, []byte("\n")...)
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n, err = s.buf.Write(line)
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if err != nil {
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return n, err
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}
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s.height++
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s.cursor++
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return n, nil
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case s.cursor < s.height:
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n, err := s.buf.Write(clearLine)
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if err != nil {
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return n, err
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}
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n, err = s.buf.Write(b)
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if err != nil {
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return n, err
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}
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n, err = s.buf.Write(moveDown)
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if err != nil {
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return n, err
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}
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s.cursor++
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return n, nil
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default:
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return 0, fmt.Errorf("Invalid write cursor position (%d) exceeded line height: %d", s.cursor, s.height)
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}
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}
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// Flush writes any buffered data to the underlying io.Writer.
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func (s *ScreenBuf) Flush() error {
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for i := s.cursor; i < s.height; i++ {
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if i < s.height {
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_, err := s.buf.Write(clearLine)
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if err != nil {
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return err
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}
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}
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_, err := s.buf.Write(moveDown)
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if err != nil {
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return err
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}
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}
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_, err := s.buf.WriteTo(s.w)
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if err != nil {
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return err
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}
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s.buf.Reset()
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for i := 0; i < s.height; i++ {
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_, err := s.buf.Write(moveUp)
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if err != nil {
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return err
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}
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}
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s.cursor = 0
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return nil
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}
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// WriteString is a convenient function to write a new line passing a string.
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// Check ScreenBuf.Write() for a detailed explanation of the function behaviour.
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func (s *ScreenBuf) WriteString(str string) (int, error) {
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return s.Write([]byte(str))
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}
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