From 4b559bbe66eef6f9e9f2dce54d3e27a503b9db8a Mon Sep 17 00:00:00 2001
From: Peter Surda <surda@economicsofbitcoin.com>
Date: Wed, 8 Jun 2016 09:30:41 +0200
Subject: [PATCH] Add bencode library

- will be used for new message encoding
---
 bencode/BTL.py      |   2 +
 bencode/__init__.py | 142 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 144 insertions(+)
 create mode 100644 bencode/BTL.py
 create mode 100644 bencode/__init__.py

diff --git a/bencode/BTL.py b/bencode/BTL.py
new file mode 100644
index 00000000..58b0d6d2
--- /dev/null
+++ b/bencode/BTL.py
@@ -0,0 +1,2 @@
+class BTFailure(Exception):
+    pass
diff --git a/bencode/__init__.py b/bencode/__init__.py
new file mode 100644
index 00000000..ae5f6e9a
--- /dev/null
+++ b/bencode/__init__.py
@@ -0,0 +1,142 @@
+# coding: utf-8
+# The contents of this file are subject to the BitTorrent Open Source License
+# Version 1.1 (the License).  You may not copy or use this file, in either
+# source code or executable form, except in compliance with the License.  You
+# may obtain a copy of the License at http://www.bittorrent.com/license/.
+#
+# Software distributed under the License is distributed on an AS IS basis,
+# WITHOUT WARRANTY OF ANY KIND, either express or implied.  See the License
+# for the specific language governing rights and limitations under the
+# License.
+
+# Written by Petru Paler
+# Modifed by Peter Šurda
+
+from BTL import BTFailure
+
+
+def decode_int(x, f):
+    f += 1
+    newf = x.index('e', f)
+    n = int(x[f:newf])
+    if x[f] == '-':
+        if x[f + 1] == '0':
+            raise ValueError
+    elif x[f] == '0' and newf != f+1:
+        raise ValueError
+    return (n, newf+1)
+
+def decode_string(x, f):
+    colon = x.index(':', f)
+    n = int(x[f:colon])
+    if x[f] == '0' and colon != f+1:
+        raise ValueError
+    colon += 1
+    return (x[colon:colon+n], colon+n)
+
+def decode_list(x, f):
+    r, f = [], f+1
+    while x[f] != 'e':
+        v, f = decode_func[x[f]](x, f)
+        r.append(v)
+    return (r, f + 1)
+
+def decode_dict(x, f):
+    r, f = {}, f+1
+    while x[f] != 'e':
+        k, f = decode_string(x, f)
+        r[k], f = decode_func[x[f]](x, f)
+    return (r, f + 1)
+
+decode_func = {}
+decode_func['l'] = decode_list
+decode_func['d'] = decode_dict
+decode_func['i'] = decode_int
+decode_func['0'] = decode_string
+decode_func['1'] = decode_string
+decode_func['2'] = decode_string
+decode_func['3'] = decode_string
+decode_func['4'] = decode_string
+decode_func['5'] = decode_string
+decode_func['6'] = decode_string
+decode_func['7'] = decode_string
+decode_func['8'] = decode_string
+decode_func['9'] = decode_string
+
+def bdecode(x):
+    try:
+        r, l = decode_func[x[0]](x, 0)
+    except (IndexError, KeyError, ValueError):
+        raise BTFailure("not a valid bencoded string")
+    if l != len(x):
+        raise BTFailure("invalid bencoded value (data after valid prefix)")
+    return r
+
+from types import StringType, IntType, LongType, DictType, ListType, TupleType, UnicodeType, NoneType
+
+
+class Bencached(object):
+
+    __slots__ = ['bencoded']
+
+    def __init__(self, s):
+        self.bencoded = s
+
+def encode_bencached(x,r):
+    r.append(x.bencoded)
+
+def encode_int(x, r):
+    r.extend(('i', str(x), 'e'))
+
+def encode_bool(x, r):
+    if x:
+        encode_int(1, r)
+    else:
+        encode_int(0, r)
+        
+def encode_string(x, r):
+    r.extend((str(len(x)), ':', x))
+
+def encode_unicode(x, r):
+    raw = x.encode('utf8')
+    r.extend((str(len(raw)), ':', raw))
+
+def encode_none(x, r):
+    r.extend('0:')
+
+def encode_list(x, r):
+    r.append('l')
+    for i in x:
+        encode_func[type(i)](i, r)
+    r.append('e')
+
+def encode_dict(x,r):
+    r.append('d')
+    ilist = x.items()
+    ilist.sort()
+    for k, v in ilist:
+        r.extend((str(len(k)), ':', k))
+        encode_func[type(v)](v, r)
+    r.append('e')
+
+encode_func = {}
+encode_func[Bencached] = encode_bencached
+encode_func[IntType] = encode_int
+encode_func[LongType] = encode_int
+encode_func[StringType] = encode_string
+encode_func[ListType] = encode_list
+encode_func[TupleType] = encode_list
+encode_func[DictType] = encode_dict
+encode_func[UnicodeType] = encode_unicode
+encode_func[NoneType] = encode_none
+
+try:
+    from types import BooleanType
+    encode_func[BooleanType] = encode_bool
+except ImportError:
+    pass
+
+def bencode(x):
+    r = []
+    encode_func[type(x)](x, r)
+    return ''.join(r)