From baf8e080125614326ba9c96ca8f2404fd12b050e Mon Sep 17 00:00:00 2001
From: jvoisin
Date: Tue, 16 Aug 2011 15:31:30 +0200
Subject: Organise lib as modules (tarfile and bencode)

---
 lib/bencode/bencode.py | 142 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 lib/bencode/bencode.py

(limited to 'lib/bencode/bencode.py')

diff --git a/lib/bencode/bencode.py b/lib/bencode/bencode.py
new file mode 100644
index 0000000..4acf788
--- /dev/null
+++ b/lib/bencode/bencode.py
@@ -0,0 +1,142 @@
+# 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
+# Modified by Julien (jvoisin) Voisin
+
+'''
+    A quick (and also nice) lib to bencode/bdecode torrent files
+'''
+
+
+import types
+
+
+class BTFailure(Exception):
+    '''Custom Exception'''
+    pass
+
+
+class Bencached(object):
+    '''Custom type : cached string'''
+    __slots__ = ['bencoded']
+
+    def __init__(self, string):
+        self.bencoded = string
+
+
+def decode_int(x, f):
+    '''decode an int'''
+    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):
+    '''decode a string'''
+    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):
+    '''decode a list'''
+    result = []
+    f += 1
+    while x[f] != 'e':
+        v, f = DECODE_FUNC[x[f]](x, f)
+        result.append(v)
+    return (result, f + 1)
+
+
+def decode_dict(x, f):
+    '''decode a dict'''
+    result = {}
+    f += 1
+    while x[f] != 'e':
+        k, f = decode_string(x, f)
+        result[k], f = DECODE_FUNC[x[f]](x, f)
+    return (result, f + 1)
+
+
+def encode_bool(x, r):
+    '''bencode a boolean'''
+    if x:
+        encode_int(1, r)
+    else:
+        encode_int(0, r)
+
+
+def encode_int(x, r):
+    '''bencode an integer/float'''
+    r.extend(('i', str(x), 'e'))
+
+
+def encode_list(x, r):
+    '''bencode a list/tuple'''
+    r.append('l')
+    [ENCODE_FUNC[type(item)](item, r) for item in x]
+    r.append('e')
+
+
+def encode_dict(x, result):
+    '''bencode a dict'''
+    result.append('d')
+    ilist = x.items()
+    ilist.sort()
+    for k, v in ilist:
+        result.extend((str(len(k)), ':', k))
+        ENCODE_FUNC[type(v)](v, result)
+    result.append('e')
+
+
+DECODE_FUNC = {}
+DECODE_FUNC.update(dict([(str(x), decode_string) for x in xrange(9)]))
+DECODE_FUNC['l'] = decode_list
+DECODE_FUNC['d'] = decode_dict
+DECODE_FUNC['i'] = decode_int
+
+
+ENCODE_FUNC = {}
+ENCODE_FUNC[Bencached] = lambda x, r: r.append(x.bencoded)
+ENCODE_FUNC[types.IntType] = encode_int
+ENCODE_FUNC[types.LongType] = encode_int
+ENCODE_FUNC[types.StringType] = lambda x, r: r.extend((str(len(x)), ':', x))
+ENCODE_FUNC[types.ListType] = encode_list
+ENCODE_FUNC[types.TupleType] = encode_list
+ENCODE_FUNC[types.DictType] = encode_dict
+ENCODE_FUNC[types.BooleanType] = encode_bool
+
+
+def bencode(string):
+    '''bencode $string'''
+    table = []
+    ENCODE_FUNC[type(string)](string, table)
+    return ''.join(table)
+
+
+def bdecode(string):
+    '''decode $string'''
+    try:
+        result, lenght = DECODE_FUNC[string[0]](string, 0)
+    except (IndexError, KeyError, ValueError):
+        raise BTFailure('Not a valid bencoded string')
+    if lenght != len(string):
+        raise BTFailure('Invalid bencoded value (data after valid prefix)')
+    return result
-- 
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