initial middleware refactor

pkg/bencode/decoder.go

@@ -0,0 +1,135 @@
+// Copyright 2016 The Chihaya Authors. All rights reserved.
+// Use of this source code is governed by the BSD 2-Clause license,
+// which can be found in the LICENSE file.
+
+package bencode
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"io"
+	"strconv"
+)
+
+// A Decoder reads bencoded objects from an input stream.
+type Decoder struct {
+	r *bufio.Reader
+}
+
+// NewDecoder returns a new decoder that reads from r.
+func NewDecoder(r io.Reader) *Decoder {
+	return &Decoder{r: bufio.NewReader(r)}
+}
+
+// Decode unmarshals the next bencoded value in the stream.
+func (dec *Decoder) Decode() (interface{}, error) {
+	return unmarshal(dec.r)
+}
+
+// Unmarshal deserializes and returns the bencoded value in buf.
+func Unmarshal(buf []byte) (interface{}, error) {
+	r := bufio.NewReader(bytes.NewBuffer(buf))
+	return unmarshal(r)
+}
+
+// unmarshal reads bencoded values from a bufio.Reader
+func unmarshal(r *bufio.Reader) (interface{}, error) {
+	tok, err := r.ReadByte()
+	if err != nil {
+		return nil, err
+	}
+
+	switch tok {
+	case 'i':
+		return readTerminatedInt(r, 'e')
+
+	case 'l':
+		list := NewList()
+		for {
+			ok, err := readTerminator(r, 'e')
+			if err != nil {
+				return nil, err
+			} else if ok {
+				break
+			}
+
+			v, err := unmarshal(r)
+			if err != nil {
+				return nil, err
+			}
+			list = append(list, v)
+		}
+		return list, nil
+
+	case 'd':
+		dict := NewDict()
+		for {
+			ok, err := readTerminator(r, 'e')
+			if err != nil {
+				return nil, err
+			} else if ok {
+				break
+			}
+
+			v, err := unmarshal(r)
+			if err != nil {
+				return nil, err
+			}
+
+			key, ok := v.(string)
+			if !ok {
+				return nil, errors.New("bencode: non-string map key")
+			}
+
+			dict[key], err = unmarshal(r)
+			if err != nil {
+				return nil, err
+			}
+		}
+		return dict, nil
+
+	default:
+		err = r.UnreadByte()
+		if err != nil {
+			return nil, err
+		}
+
+		length, err := readTerminatedInt(r, ':')
+		if err != nil {
+			return nil, errors.New("bencode: unknown input sequence")
+		}
+
+		buf := make([]byte, length)
+		n, err := r.Read(buf)
+
+		if err != nil {
+			return nil, err
+		} else if int64(n) != length {
+			return nil, errors.New("bencode: short read")
+		}
+
+		return string(buf), nil
+	}
+}
+
+func readTerminator(r *bufio.Reader, term byte) (bool, error) {
+	tok, err := r.ReadByte()
+	if err != nil {
+		return false, err
+	} else if tok == term {
+		return true, nil
+	}
+	return false, r.UnreadByte()
+}
+
+func readTerminatedInt(r *bufio.Reader, term byte) (int64, error) {
+	buf, err := r.ReadSlice(term)
+	if err != nil {
+		return 0, err
+	} else if len(buf) <= 1 {
+		return 0, errors.New("bencode: empty integer field")
+	}
+
+	return strconv.ParseInt(string(buf[:len(buf)-1]), 10, 64)
+}