dirty

evm/vm/forks/byzantium/__init__.py

@@ -10,6 +10,7 @@
 from ..frontier import FRONTIER_PRECOMPILES
 from ..spurious_dragon import SpuriousDragonVM
 
+from .headers import create_byzantium_header_from_parent
 from .opcodes import BYZANTIUM_OPCODES
 from .blocks import ByzantiumBlock
 
@@ -30,4 +31,6 @@
     opcodes=BYZANTIUM_OPCODES,
     # RLP
     _block_class=ByzantiumBlock,
+    # Methods
+    create_header_from_parent=staticmethod(create_byzantium_header_from_parent),
 )

evm/vm/forks/byzantium/headers.py

@@ -0,0 +1,49 @@
+from evm.validation import (
+    validate_gt,
+    validate_header_params_for_configuration,
+)
+from evm.vm.forks.homestead.headers import (
+    create_homestead_header_from_parent,
+)
+
+
+def compute_byzantium_difficulty(parent_header, num_uncles, timestamp):
+    """
+    https://github.com/ethereum/EIPs/issues/100
+    TODO: figure out how to know about uncles in this context...
+    """
+    parent_tstamp = parent_header.timestamp
+    validate_gt(timestamp, parent_tstamp, title="Header.timestamp")
+    offset = parent_header.difficulty // DIFFICULTY_ADJUSTMENT_DENOMINATOR
+
+    sign = max(
+        1 - (timestamp - parent_tstamp) // HOMESTEAD_DIFF_ADJUSTMENT_CUTOFF,
+        -99)
+    adj_factor = max(
+        (2 if len(parent.uncles) else 1) - ((timestamp - parent.timestamp) // 9),
+        -99)
+
+    difficulty = int(max(
+        parent_header.difficulty + offset * sign,
+        min(parent_header.difficulty, DIFFICULTY_MINIMUM)))
+    num_bomb_periods = (
+        (parent_header.block_number + 1) // BOMB_EXPONENTIAL_PERIOD
+    ) - BOMB_EXPONENTIAL_FREE_PERIODS
+    if num_bomb_periods >= 0:
+        return max(difficulty + 2**num_bomb_periods, DIFFICULTY_MINIMUM)
+    else:
+        return difficulty
+
+
+def create_byzantium_header_from_parent(vm, parent_header, **header_params):
+    if 'difficulty' not in header_params:
+        header_params.setdefault('timestamp', parent_header.timestamp + 1)
+
+        parent_uncles = vm.chaindb.get_block_uncles(parent_header.uncles_hash)
+        header_params['difficulty'] = compute_byzantium_difficulty(
+            parent_header=parent_header,
+            num_uncles=len(parent_uncles),
+            timestamp=header_params['timestamp'],
+        )
+    # TODO
+    pass