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// Copyright 2019 the u-root 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 uio
import (
"bytes"
"io"
)
// LineWriter processes one line of log output at a time.
type LineWriter interface {
// OneLine is always called with exactly one line of output.
OneLine(b []byte)
}
// FullLineWriter returns an io.Writer that waits for a full line of prints
// before calling w.Write on one line each.
func FullLineWriter(w LineWriter) io.WriteCloser {
return &fullLineWriter{w: w}
}
type fullLineWriter struct {
w LineWriter
buffer []byte
}
func (fsw *fullLineWriter) printBuf() {
bufs := bytes.Split(fsw.buffer, []byte{'\n'})
for _, buf := range bufs {
if len(buf) != 0 {
fsw.w.OneLine(buf)
}
}
fsw.buffer = nil
}
// Write implements io.Writer and buffers p until at least one full line is
// received.
func (fsw *fullLineWriter) Write(p []byte) (int, error) {
i := bytes.LastIndexByte(p, '\n')
if i == -1 {
fsw.buffer = append(fsw.buffer, p...)
} else {
fsw.buffer = append(fsw.buffer, p[:i]...)
fsw.printBuf()
fsw.buffer = append([]byte{}, p[i:]...)
}
return len(p), nil
}
// Close implements io.Closer and flushes the buffer.
func (fsw *fullLineWriter) Close() error {
fsw.printBuf()
return nil
}
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