.

go/xcommon/xbufio/xbufio.go

@@ -27,10 +27,10 @@ import (
 	"lab.nexedi.com/kirr/neo/go/xcommon/xio"
 )
 
-// Reader is a bufio.Reader + bell & whistles
+// Reader is a bufio.Reader that also reports current logical position in input stream.
 type Reader struct {
 	*bufio.Reader
-	cr *xio.CountReader
+	cr *xio.CountedReader
 }
 
 func NewReader(r io.Reader) *Reader {
@@ -39,17 +39,16 @@ func NewReader(r io.Reader) *Reader {
 		return r
 	}
 
-	// idempotent(xio.CountReader)
-	cr, ok := r.(*xio.CountReader)
+	// idempotent(xio.CountedReader)
+	cr, ok := r.(*xio.CountedReader)
 	if !ok {
-		cr = &xio.CountReader{r, 0}
+		cr = xio.CountReader(r)
 	}
 
 	return &Reader{bufio.NewReader(cr), cr}
 }
 
-// InputOffset returns current position in input stream
-// XXX naming + define interface for getting current position
+// InputOffset returns current logical position in input stream.
 func (r *Reader) InputOffset() int64 {
-	return r.cr.Nread - int64(r.Reader.Buffered())
+	return r.cr.InputOffset() - int64(r.Reader.Buffered())
 }

go/xcommon/xio/xio.go

-// TODO copyright / license
+// Copyright (C) 2017  Nexedi SA and Contributors.
+//                     Kirill Smelkov <kirr@nexedi.com>
+//
+// This program is free software: you can Use, Study, Modify and Redistribute
+// it under the terms of the GNU General Public License version 3, or (at your
+// option) any later version, as published by the Free Software Foundation.
+//
+// You can also Link and Combine this program with other software covered by
+// the terms of any of the Free Software licenses or any of the Open Source
+// Initiative approved licenses and Convey the resulting work. Corresponding
+// source of such a combination shall include the source code for all other
+// software used.
+//
+// This program is distributed WITHOUT ANY WARRANTY; without even the implied
+// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+//
+// See COPYING file for full licensing terms.
+// See https://www.nexedi.com/licensing for rationale and options.
 
 // Package xio provides addons to standard package io.
 package xio
@@ -11,23 +28,27 @@ import (
 	"lab.nexedi.com/kirr/neo/go/xcommon/xcontext"
 )
 
-// XXX interface for a Reader/Writer which can report position
-// -> Nread(), Nwrote() ?
-
-// CountReader is an io.Reader that count total bytes read
-type CountReader struct {
-	io.Reader
-	Nread int64
+// CountedReader is an io.Reader that count total bytes read.
+type CountedReader struct {
+	r     io.Reader
+	nread int64
 }
 
-func (r *CountReader) Read(p []byte) (int, error) {
-	n, err := r.Reader.Read(p)
-	r.Nread += int64(n)
+func (cr *CountedReader) Read(p []byte) (int, error) {
+	n, err := cr.r.Read(p)
+	cr.nread += int64(n)
 	return n, err
 }
 
-// TODO func to get position (requiring io.Seeker to just Seek(0, SeekCurrent) is too much)
-// XXX  previously used InputOffset(), but generally e.g. for io.Writer "input" is not appropriate
+// InputOffset returns the number of bytes read.
+func (cr *CountedReader) InputOffset() int64 {
+	return cr.nread
+}
+
+// CountReader wraps r with CountedReader
+func CountReader(r io.Reader) *CountedReader {
+	return &CountedReader{r, 0}
+}
 
 
 // CloseWhenDone arranges for c to be closed either when ctx is cancelled or