bencode is back, for marshalling before going into the database - pickle module has...

diff --git a/bencode.py b/bencode.py
new file mode 100644 (file)
index 0000000..93af407
--- /dev/null
+++ b/bencode.py
@@ -0,0 +1,254 @@
+# Written by Petru Paler
+# see LICENSE.txt for license information
+
+from types import IntType, LongType, StringType, ListType, TupleType, DictType
+import re
+from cStringIO import StringIO
+
+int_filter = re.compile('(0|-?[1-9][0-9]*)e')
+
+def decode_int(x, f):
+    m = int_filter.match(x, f)
+    if m is None:
+        raise ValueError
+    return (long(m.group(1)), m.end())
+
+string_filter = re.compile('(0|[1-9][0-9]*):')
+
+def decode_string(x, f):
+    m = string_filter.match(x, f)
+    if m is None:
+        raise ValueError
+    l = int(m.group(1))
+    s = m.end()
+    return (x[s:s+l], s + l)
+
+def decode_list(x, f):
+    r = []
+    while x[f] != 'e':
+        v, f = bdecode_rec(x, f)
+        r.append(v)
+    return (r, f + 1)
+
+def decode_dict(x, f):
+    r = {}
+    lastkey = None
+    while x[f] != 'e':
+        k, f = decode_string(x, f)
+        if lastkey is not None and lastkey >= k:
+            raise ValueError
+        lastkey = k
+        v, f = bdecode_rec(x, f)
+        r[k] = v
+    return (r, f + 1)
+
+def bdecode_rec(x, f):
+    t = x[f]
+    if t == 'i':
+        return decode_int(x, f + 1)
+    elif t == 'l':
+        return decode_list(x, f + 1)
+    elif t == 'd':
+        return decode_dict(x, f + 1)
+    else:
+        return decode_string(x, f)
+
+def bdecode(x):
+    try:
+        r, l = bdecode_rec(x, 0)
+    except IndexError:
+        raise ValueError
+    if l != len(x):
+        raise ValueError
+    return r
+
+def test_bdecode():
+    try:
+        bdecode('0:0:')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('ie')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('i341foo382e')
+        assert 0
+    except ValueError:
+        pass
+    assert bdecode('i4e') == 4L
+    assert bdecode('i0e') == 0L
+    assert bdecode('i123456789e') == 123456789L
+    assert bdecode('i-10e') == -10L
+    try:
+        bdecode('i-0e')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('i123')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('i6easd')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('35208734823ljdahflajhdf')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('2:abfdjslhfld')
+        assert 0
+    except ValueError:
+        pass
+    assert bdecode('0:') == ''
+    assert bdecode('3:abc') == 'abc'
+    assert bdecode('10:1234567890') == '1234567890'
+    try:
+        bdecode('02:xy')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('l')
+        assert 0
+    except ValueError:
+        pass
+    assert bdecode('le') == []
+    try:
+        bdecode('leanfdldjfh')
+        assert 0
+    except ValueError:
+        pass
+    assert bdecode('l0:0:0:e') == ['', '', '']
+    try:
+        bdecode('relwjhrlewjh')
+        assert 0
+    except ValueError:
+        pass
+    assert bdecode('li1ei2ei3ee') == [1, 2, 3]
+    assert bdecode('l3:asd2:xye') == ['asd', 'xy']
+    assert bdecode('ll5:Alice3:Bobeli2ei3eee') == [['Alice', 'Bob'], [2, 3]]
+    try:
+        bdecode('d')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('defoobar')
+        assert 0
+    except ValueError:
+        pass
+    assert bdecode('de') == {}
+    assert bdecode('d3:agei25e4:eyes4:bluee') == {'age': 25, 'eyes': 'blue'}
+    assert bdecode('d8:spam.mp3d6:author5:Alice6:lengthi100000eee') == {'spam.mp3': {'author': 'Alice', 'length': 100000}}
+    try:
+        bdecode('d3:fooe')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('di1e0:e')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('d1:b0:1:a0:e')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('d1:a0:1:a0:e')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('i03e')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('l01:ae')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('9999:x')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('l0:')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('d0:0:')
+        assert 0
+    except ValueError:
+        pass
+    try:
+        bdecode('d0:')
+        assert 0
+    except ValueError:
+        pass
+
+def bencode_rec(x, b):
+    t = type(x)
+    if t in (IntType, LongType):
+        b.write('i%de' % x)
+    elif t is StringType:
+        b.write('%d:%s' % (len(x), x))
+    elif t in (ListType, TupleType):
+        b.write('l')
+        for e in x:
+            bencode_rec(e, b)
+        b.write('e')
+    elif t is DictType:
+        b.write('d')
+        keylist = x.keys()
+        keylist.sort()
+        for k in keylist:
+            assert type(k) is StringType
+            bencode_rec(k, b)
+            bencode_rec(x[k], b)
+        b.write('e')
+    else:
+        assert 0
+
+def bencode(x):
+    b = StringIO()
+    bencode_rec(x, b)
+    return b.getvalue()
+
+def test_bencode():
+    assert bencode(4) == 'i4e'
+    assert bencode(0) == 'i0e'
+    assert bencode(-10) == 'i-10e'
+    assert bencode(12345678901234567890L) == 'i12345678901234567890e'
+    assert bencode('') == '0:'
+    assert bencode('abc') == '3:abc'
+    assert bencode('1234567890') == '10:1234567890'
+    assert bencode([]) == 'le'
+    assert bencode([1, 2, 3]) == 'li1ei2ei3ee'
+    assert bencode([['Alice', 'Bob'], [2, 3]]) == 'll5:Alice3:Bobeli2ei3eee'
+    assert bencode({}) == 'de'
+    assert bencode({'age': 25, 'eyes': 'blue'}) == 'd3:agei25e4:eyes4:bluee'
+    assert bencode({'spam.mp3': {'author': 'Alice', 'length': 100000}}) == 'd8:spam.mp3d6:author5:Alice6:lengthi100000eee'
+    try:
+        bencode({1: 'foo'})
+        assert 0
+    except AssertionError:
+        pass
+