--- /dev/null
+/*
+netstring -- netstring format serialization library
+Copyright (C) 2015-2020 Sergey Matveev <stargrave@stargrave.org>
+
+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, version 3 of the License.
+
+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 netstring
+
+import (
+ "bufio"
+ "bytes"
+ "errors"
+ "io"
+ "strconv"
+)
+
+type Reader struct {
+ r *bufio.Reader
+ left uint64
+ eof bool
+}
+
+// Create new Reader.
+// Pay attention that bufio.Reader is used to read from it.
+func NewReader(r io.Reader) *Reader {
+ return &Reader{r: bufio.NewReader(r), eof: true}
+}
+
+// Parse netstring prefix. It returns data length.
+// After this method you have to call either Read() or Discard().
+// io.EOF is returned when underlying reader has no data anymore.
+func (r *Reader) Next() (uint64, error) {
+ if !r.eof {
+ return 0, errors.New("current chunk is unread")
+ }
+ p, _ := r.r.Peek(21)
+ if len(p) == 0 {
+ return 0, io.EOF
+ }
+ idx := bytes.Index(p, []byte{':'})
+ if idx == -1 {
+ return 0, errors.New("no length separator found")
+ }
+ size, err := strconv.ParseUint(string(p[:idx]), 10, 64)
+ if err != nil {
+ return 0, err
+ }
+ if _, err = r.r.Discard(idx + 1); err != nil {
+ return 0, err
+ }
+ r.left = size
+ r.eof = false
+ return size, nil
+}
+
+func (r *Reader) checkTerminator() error {
+ b, err := r.r.ReadByte()
+ if err != nil {
+ return err
+ }
+ if b != ',' {
+ return errors.New("no terminator found")
+ }
+ return nil
+}
+
+// Read current netstring chunk.
+// This method must be called after Next().
+// Terminator check and error raising are performed only at the end.
+func (r *Reader) Read(buf []byte) (n int, err error) {
+ if r.eof {
+ return 0, io.EOF
+ }
+ if uint64(len(buf)) > r.left {
+ buf = buf[:r.left]
+ }
+ n, err = r.r.Read(buf)
+ r.left -= uint64(n)
+ if r.left == 0 {
+ err = r.checkTerminator()
+ if err == nil {
+ r.eof = true
+ }
+ }
+ return
+}
+
+// Discard remaining bytes in the chunk, possibly fully skipping it.
+// This method must be called after Next().
+func (r *Reader) Discard() (err error) {
+ _, err = r.r.Discard(int(r.left))
+ if err != nil {
+ return
+ }
+ err = r.checkTerminator()
+ if err != nil {
+ return
+ }
+ r.eof = true
+ return
+}