1 files changed, 95 insertions, 0 deletions
diff --git a/libgo/go/encoding/line/line.go b/libgo/go/encoding/line/line.go
new file mode 100644
index 000000000..92dddcb99
--- /dev/null
+++ b/libgo/go/encoding/line/line.go
@@ -0,0 +1,95 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This package implements a Reader which handles reading \r and \r\n
+// deliminated lines.
+package line
+
+import (
+	"io"
+	"os"
+)
+
+// Reader reads lines from an io.Reader (which may use either '\n' or
+// '\r\n').
+type Reader struct {
+	buf      []byte
+	consumed int
+	in       io.Reader
+	err      os.Error
+}
+
+func NewReader(in io.Reader, maxLineLength int) *Reader {
+	return &Reader{
+		buf:      make([]byte, 0, maxLineLength),
+		consumed: 0,
+		in:       in,
+	}
+}
+
+// ReadLine tries to return a single line, not including the end-of-line bytes.
+// If the line was found to be longer than the maximum length then isPrefix is
+// set and the beginning of the line is returned. The rest of the line will be
+// returned from future calls. isPrefix will be false when returning the last
+// fragment of the line.  The returned buffer points into the internal state of
+// the Reader and is only valid until the next call to ReadLine. ReadLine
+// either returns a non-nil line or it returns an error, never both.
+func (l *Reader) ReadLine() (line []byte, isPrefix bool, err os.Error) {
+	if l.consumed > 0 {
+		n := copy(l.buf, l.buf[l.consumed:])
+		l.buf = l.buf[:n]
+		l.consumed = 0
+	}
+
+	if len(l.buf) == 0 && l.err != nil {
+		err = l.err
+		return
+	}
+
+	scannedTo := 0
+
+	for {
+		i := scannedTo
+		for ; i < len(l.buf); i++ {
+			if l.buf[i] == '\r' && len(l.buf) > i+1 && l.buf[i+1] == '\n' {
+				line = l.buf[:i]
+				l.consumed = i + 2
+				return
+			} else if l.buf[i] == '\n' {
+				line = l.buf[:i]
+				l.consumed = i + 1
+				return
+			}
+		}
+
+		if i == cap(l.buf) {
+			line = l.buf[:i]
+			l.consumed = i
+			isPrefix = true
+			return
+		}
+
+		if l.err != nil {
+			line = l.buf
+			l.consumed = i
+			return
+		}
+
+		// We don't want to rescan the input that we just scanned.
+		// However, we need to back up one byte because the last byte
+		// could have been a '\r' and we do need to rescan that.
+		scannedTo = i
+		if scannedTo > 0 {
+			scannedTo--
+		}
+		oldLen := len(l.buf)
+		l.buf = l.buf[:cap(l.buf)]
+		n, readErr := l.in.Read(l.buf[oldLen:])
+		l.buf = l.buf[:oldLen+n]
+		if readErr != nil {
+			l.err = readErr
+		}
+	}
+	panic("unreachable")
+}