python-bindings: Add pickle support for G1Element

This is needed for plots caching in `chia-blockchain`.

python-bindings/pythonbindings.cpp

@@ -373,6 +373,16 @@ PYBIND11_MODULE(blspy, m)
                 // PythonGIL release_lock;
                 return G1Element::FromBytes(Bytes(data_ptr, G1Element::SIZE));
             })
+        .def(py::pickle(
+        [](const G1Element &dp) { // __getstate__
+            return py::make_tuple(dp.Serialize());
+            },
+            [](py::tuple t) { // __setstate__
+            if (t.size() != 1)
+                throw std::runtime_error("Invalid state!");
+            auto vecBytes = t[0].cast<std::vector<uint8_t>>();
+            return G1Element::FromByteVector(vecBytes);
+        }))
         .def("generator", &G1Element::Generator)
         .def("from_message", py::overload_cast<const std::vector<uint8_t>&, const uint8_t*, int>(&G1Element::FromMessage))
         .def("pair", &G1Element::Pair)

python-bindings/test.py

@@ -1,5 +1,6 @@
 # flake8: noqa: E501
 import binascii
+import pickle
 from copy import deepcopy
 
 from blspy import (
@@ -335,11 +336,29 @@ def test_aggregate_verify_zero_items():
     assert AugSchemeMPL.aggregate_verify([], [], G2Element())
 
 
+def test_pickle_support():
+    seed = bytes([
+        0, 50, 6, 244, 24, 199, 1, 25, 52, 88, 192, 19, 18, 12, 89, 6,
+        220, 18, 102, 58, 209, 82, 12, 62, 89, 110, 182, 9, 44, 20, 254, 22
+    ])
+    key: PrivateKey = AugSchemeMPL.key_gen(seed)
+    g1: G1Element = key.get_g1()
+    g1_data = pickle.dumps(g1)
+    g1_expected_data = bytes.fromhex("80049581000000000000008c05626c737079948c094731456c656d656e749493942981945d94284b"
+                                     "864b244b324b904bbb4bcb4bfd4b9a4be74b5b4bde4bce4b794b814b964b534b504b204b8e4bb54b"
+                                     "e94b9b4b044bd54bcd4b244be94b554bad4ba94b614bf84bc04ba14b624bde4be74b404bbe4b7b4b"
+                                     "dc4b6c4b3c4b064b134bba4b2e4bb1658594622e")
+    assert g1_data == g1_expected_data
+    g1_restored = pickle.loads(g1_data)
+    assert g1 == g1_restored
+
+
 test_schemes()
 test_vectors_invalid()
 test_vectors_valid()
 test_readme()
 test_aggregate_verify_zero_items()
+test_pickle_support()
 
 print("\nAll tests passed.")