Write Windows line breaks on Windows; tee to stdout

internal/osutil/replacingwriter.go

@@ -0,0 +1,57 @@
+// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
+//
+// This program is free software: you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+//
+// This program is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+// more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program. If not, see <http://www.gnu.org/licenses/>.
+
+package osutil
+
+import (
+	"bytes"
+	"io"
+)
+
+type ReplacingWriter struct {
+	Writer io.Writer
+	From   byte
+	To     []byte
+}
+
+func (w ReplacingWriter) Write(bs []byte) (int, error) {
+	var n, written int
+	var err error
+
+	newlineIdx := bytes.IndexByte(bs, w.From)
+	for newlineIdx >= 0 {
+		n, err = w.Writer.Write(bs[:newlineIdx])
+		written += n
+		if err != nil {
+			break
+		}
+		if len(w.To) > 0 {
+			n, err := w.Writer.Write(w.To)
+			if n == len(w.To) {
+				written++
+			}
+			if err != nil {
+				break
+			}
+		}
+		bs = bs[newlineIdx+1:]
+		newlineIdx = bytes.IndexByte(bs, w.From)
+	}
+
+	n, err = w.Writer.Write(bs)
+	written += n
+
+	return written, err
+}