146 lines
3 KiB
Go
146 lines
3 KiB
Go
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// Copyright 2016 Jimmy Zelinskie
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package bencode
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import (
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"bufio"
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"bytes"
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"errors"
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"io"
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"strconv"
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)
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// A Decoder reads bencoded objects from an input stream.
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type Decoder struct {
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r *bufio.Reader
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}
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// NewDecoder returns a new decoder that reads from r.
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func NewDecoder(r io.Reader) *Decoder {
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return &Decoder{r: bufio.NewReader(r)}
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}
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// Decode unmarshals the next bencoded value in the stream.
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func (dec *Decoder) Decode() (interface{}, error) {
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return unmarshal(dec.r)
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}
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// Unmarshal deserializes and returns the bencoded value in buf.
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func Unmarshal(buf []byte) (interface{}, error) {
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r := bufio.NewReader(bytes.NewBuffer(buf))
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return unmarshal(r)
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}
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// unmarshal reads bencoded values from a bufio.Reader
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func unmarshal(r *bufio.Reader) (interface{}, error) {
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tok, err := r.ReadByte()
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if err != nil {
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return nil, err
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}
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switch tok {
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case 'i':
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return readTerminatedInt(r, 'e')
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case 'l':
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list := NewList()
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for {
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ok, err := readTerminator(r, 'e')
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if err != nil {
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return nil, err
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} else if ok {
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break
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}
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v, err := unmarshal(r)
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if err != nil {
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return nil, err
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}
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list = append(list, v)
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}
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return list, nil
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case 'd':
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dict := NewDict()
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for {
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ok, err := readTerminator(r, 'e')
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if err != nil {
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return nil, err
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} else if ok {
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break
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}
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v, err := unmarshal(r)
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if err != nil {
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return nil, err
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}
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key, ok := v.(string)
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if !ok {
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return nil, errors.New("bencode: non-string map key")
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}
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dict[key], err = unmarshal(r)
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if err != nil {
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return nil, err
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}
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}
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return dict, nil
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default:
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err = r.UnreadByte()
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if err != nil {
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return nil, err
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}
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length, err := readTerminatedInt(r, ':')
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if err != nil {
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return nil, errors.New("bencode: unknown input sequence")
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}
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buf := make([]byte, length)
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n, err := r.Read(buf)
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if err != nil {
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return nil, err
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} else if int64(n) != length {
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return nil, errors.New("bencode: short read")
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}
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return string(buf), nil
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}
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}
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func readTerminator(r io.ByteScanner, term byte) (bool, error) {
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tok, err := r.ReadByte()
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if err != nil {
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return false, err
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} else if tok == term {
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return true, nil
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}
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return false, r.UnreadByte()
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}
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func readTerminatedInt(r *bufio.Reader, term byte) (int64, error) {
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buf, err := r.ReadSlice(term)
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if err != nil {
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return 0, err
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} else if len(buf) <= 1 {
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return 0, errors.New("bencode: empty integer field")
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}
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return strconv.ParseInt(string(buf[:len(buf)-1]), 10, 64)
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}
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