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diff --git a/swh/core/bencode.py b/swh/core/bencode.py
new file mode 100644
--- /dev/null
+++ b/swh/core/bencode.py
@@ -0,0 +1,60 @@
+# Copyright (C) 2019 The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+"""Provides a bencode encoder.
+
+This allows encoding a nested bytes/int/list/dict structure
+into its bencode representation."""
+
+from typing import Dict, Callable, Any, Generator
+
+
+def _encode_bytes(obj: bytes) -> Generator[bytes, None, None]:
+ yield b'%d:' % len(obj)
+ yield obj
+
+
+def _encode_int(obj: int) -> Generator[bytes, None, None]:
+ yield b'i%de' % obj
+
+
+def _encode_list(obj: list) -> Generator[bytes, None, None]:
+ yield b'l'
+ for item in obj:
+ yield from _encode(item)
+ yield b'e'
+
+
+def _encode_dict(obj: dict) -> Generator[bytes, None, None]:
+ yield b'd'
+ for (key, value) in sorted(obj.items()):
+ if type(key) != bytes:
+ raise TypeError('bencode dictionary keys must be bytes, not {}.'
+ .format(type(key)))
+ yield from _encode_bytes(key)
+ yield from _encode(value)
+ yield b'e'
+
+
+_ENCODERS = {
+ bytes: _encode_bytes,
+ int: _encode_int,
+ list: _encode_list,
+ dict: _encode_dict,
+} # type: Dict[type, Callable[[Any], Generator[bytes, None, None]]]
+
+
+def _encode(obj: Any) -> Generator[bytes, None, None]:
+ encoder = _ENCODERS.get(type(obj), None)
+ if not encoder:
+ raise TypeError('Unsupported type for bencoding: {}'.format(type(obj)))
+ yield from encoder(obj)
+
+
+def encode(obj) -> bytes:
+ """Encodes a nested bytes/int/list/dict structure into its bencode
+ representation.
+ """
+ return b''.join(_encode(obj))
diff --git a/swh/core/tests/test_bencode.py b/swh/core/tests/test_bencode.py
new file mode 100644
--- /dev/null
+++ b/swh/core/tests/test_bencode.py
@@ -0,0 +1,61 @@
+# Copyright (C) 2019 The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+"""The examples are from the specification:
+https://wiki.theory.org/index.php/BitTorrentSpecification#Bencoding"""
+
+
+import pytest
+
+from swh.core.bencode import encode
+
+
+def test_bencode_bytes():
+ assert b'4:spam' == encode(b'spam')
+
+ assert b'0:' == encode(b'')
+
+
+def test_encode_int():
+ assert b'i3e' == encode(3)
+
+ assert b'i-3e' == encode(-3)
+
+ assert b'i0e' == encode(0)
+
+
+def test_encode_list():
+ assert b'l4:spam4:eggse' == encode([b'spam', b'eggs'])
+
+ assert b'le' == encode([])
+
+
+def test_encode_dict():
+ assert \
+ b'd3:cow3:moo4:spam4:eggse' == \
+ encode({b'cow': b'moo', b'spam': b'eggs'})
+
+ assert \
+ b'd4:spaml1:a1:bee' == \
+ encode({b'spam': [b'a', b'b']})
+
+ assert \
+ (b'd9:publisher3:bob17:publisher-webpage15:www.example.com'
+ b'18:publisher.location4:homee') == \
+ encode({b'publisher': b'bob',
+ b'publisher-webpage': b'www.example.com',
+ b'publisher.location': b'home'})
+
+ assert b'de' == encode({})
+
+
+def test_invalid_root_type():
+ with pytest.raises(TypeError):
+ encode('string')
+
+
+def test_invalid_dict_key_type():
+ with pytest.raises(TypeError):
+ encode({'string': b'bytes'})

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