Add get_effective_balance and get_new_validator_registry_delta_chain_tip

Author: hwwhww

eth/beacon/helpers.py

@@ -22,6 +22,9 @@
     get_bitfield_length,
     has_voted,
 )
+from eth.utils.blake import (
+    blake,
+)
 from eth.utils.numeric import (
     clamp,
 )
@@ -412,3 +415,29 @@ def get_attestation_participants(state: 'BeaconState',
     for bitfield_index, validator_index in enumerate(shard_committee.committee):
         if has_voted(participation_bitfield, bitfield_index):
             yield validator_index
+
+
+#
+# Misc
+#
+def get_effective_balance(validator: 'ValidatorRecord', max_deposit: int) -> int:
+    """
+    Return the effective balance (also known as "balance at stake") for the ``validator``.
+    """
+    return min(validator.balance, max_deposit)
+
+
+def get_new_validator_registry_delta_chain_tip(current_validator_registry_delta_chain_tip: Hash32,
+                                               index: int,
+                                               pubkey: int,
+                                               flag: int) -> Hash32:
+    """
+    Compute the next hash in the validator registry delta hash chain.
+    """
+    return blake(
+        current_validator_registry_delta_chain_tip +
+        flag.to_bytes(1, 'big') +
+        index.to_bytes(3, 'big') +
+        # TODO: currently, we use 256-bit pubkey which is different form the spec
+        pubkey.to_bytes(32, 'big')
+    )

tests/beacon/test_helpers.py

@@ -1,5 +1,10 @@
 import pytest
 
+from eth.constants import (
+    ZERO_HASH32,
+)
+
+
 from eth.beacon.enums.validator_status_codes import (
     ValidatorStatusCode,
 )
@@ -13,13 +18,16 @@
     get_attestation_participants,
     get_beacon_proposer_index,
     get_block_hash,
+    get_effective_balance,
     get_hashes_from_latest_block_hashes,
     get_hashes_to_sign,
     get_new_shuffling,
+    get_new_validator_registry_delta_chain_tip,
     _get_shard_committees_at_slot,
     get_block_committees_info,
 )
 
+
 from tests.beacon.helpers import (
     get_pseudo_chain,
 )
@@ -256,7 +264,7 @@ def test_get_hashes_to_sign(sample_block, epoch_length):
         ),
     ],
 )
-def test_get_shard_committee_for_slot(
+def test_get_shard_committees_at_slot(
         num_validators,
         cycle_length,
         latest_state_recalculation_slot,
@@ -606,3 +614,59 @@ def mock_get_shard_committees_at_slot(state,
         )
 
         assert result == expected
+
+
+@pytest.mark.parametrize(
+    (
+        'balance,'
+        'max_deposit,'
+        'expected'
+    ),
+    [
+        (
+            1,
+            32,
+            1,
+        ),
+        (
+            33,
+            32,
+            32,
+        )
+    ]
+)
+def test_get_effective_balance(balance, max_deposit, expected, sample_validator_record_params):
+    validator = ValidatorRecord(**sample_validator_record_params).copy(
+        balance=balance,
+    )
+    result = get_effective_balance(validator, max_deposit)
+    assert result == expected
+
+
+@pytest.mark.parametrize(
+    (
+        'index,'
+        'pubkey,'
+        'flag,'
+        'expected'
+    ),
+    [
+        (
+            1,
+            2 * 256 - 1,
+            1,
+            b')\x8a4^\xc5\xb4\x06\r\xf3\x0cX\xb8\xdd\x05\x94\xcfY+qF\xbe\xf1\x04\xe3\xe8\xbd\xe5\xef\xfaGY\t'  # noqa: E501
+        ),
+    ]
+)
+def test_get_new_validator_registry_delta_chain_tip(index,
+                                                    pubkey,
+                                                    flag,
+                                                    expected):
+    result = get_new_validator_registry_delta_chain_tip(
+        current_validator_registry_delta_chain_tip=ZERO_HASH32,
+        index=index,
+        pubkey=pubkey,
+        flag=flag,
+    )
+    assert result == expected