WIP: implement Create2 opcode

Closes #1106

eth/vm/logic/system.py

@@ -2,6 +2,10 @@
     Address,
 )
 
+from eth_hash.auto import (
+    keccak
+)
+
 from eth import constants
 from eth.exceptions import (
     Halt,
@@ -13,6 +17,9 @@
     force_bytes_to_address,
     generate_contract_address,
 )
+from eth.utils.numeric import (
+    int_to_big_endian,
+)
 from eth.utils.hexadecimal import (
     encode_hex,
 )
@@ -99,45 +106,71 @@ def _selfdestruct(computation: BaseComputation, beneficiary: Address) -> None:
     computation.register_account_for_deletion(beneficiary)
     raise Halt('SELFDESTRUCT')
 
+class CreateStackFrame:
+
+    def __init__(self,
+                 endowment: int,
+                 memory_start: int,
+                 memory_length: int,
+                 salt: int = None) -> None:
+
+        self.endowment = endowment
+        self.memory_start = memory_start
+        self.memory_length = memory_length
+        self.salt = salt
 
 class Create(Opcode):
 
     def max_child_gas_modifier(self, gas: int) -> int:
         return gas
 
-    def __call__(self, computation: BaseComputation) -> None:
-        computation.consume_gas(self.gas_cost, reason=self.mnemonic)
+    def generate_contract_address(self,
+                                  stack_frame: CreateStackFrame,
+                                  call_data: bytes,
+                                  computation: BaseComputation) -> Address:
+
+        creation_nonce = computation.state.account_db.get_nonce(computation.msg.storage_address)
+        computation.state.account_db.increment_nonce(computation.msg.storage_address)
 
-        value, start_position, size = computation.stack_pop(
+        contract_address = generate_contract_address(
+            computation.msg.storage_address,
+            creation_nonce,
+        )
+
+        return contract_address
+
+    def get_stack_frame(self, computation: BaseComputation) -> CreateStackFrame:
+        endowment, memory_start, memory_length = computation.stack_pop(
             num_items=3,
             type_hint=constants.UINT256,
         )
 
-        computation.extend_memory(start_position, size)
+        return CreateStackFrame(endowment, memory_start, memory_length)
+
+    def __call__(self, computation: BaseComputation) -> None:
+        computation.consume_gas(self.gas_cost, reason=self.mnemonic)
+
+        stack_frame = self.get_stack_frame(computation)
+
+        computation.extend_memory(stack_frame.memory_start, stack_frame.memory_length)
 
         insufficient_funds = computation.state.account_db.get_balance(
             computation.msg.storage_address
-        ) < value
+        ) < stack_frame.endowment
         stack_too_deep = computation.msg.depth + 1 > constants.STACK_DEPTH_LIMIT
 
         if insufficient_funds or stack_too_deep:
             computation.stack_push(0)
             return
 
-        call_data = computation.memory_read(start_position, size)
+        call_data = computation.memory_read(stack_frame.memory_start, stack_frame.memory_length)
 
         create_msg_gas = self.max_child_gas_modifier(
             computation.get_gas_remaining()
         )
         computation.consume_gas(create_msg_gas, reason="CREATE")
 
-        creation_nonce = computation.state.account_db.get_nonce(computation.msg.storage_address)
-        computation.state.account_db.increment_nonce(computation.msg.storage_address)
-
-        contract_address = generate_contract_address(
-            computation.msg.storage_address,
-            creation_nonce,
-        )
+        contract_address = self.generate_contract_address(stack_frame, call_data, computation)
 
         is_collision = computation.state.account_db.account_has_code_or_nonce(contract_address)
 
@@ -152,7 +185,7 @@ def __call__(self, computation: BaseComputation) -> None:
         child_msg = computation.prepare_child_message(
             gas=create_msg_gas,
             to=constants.CREATE_CONTRACT_ADDRESS,
-            value=value,
+            value=stack_frame.endowment,
             data=b'',
             code=call_data,
             create_address=contract_address,
@@ -177,3 +210,29 @@ def __call__(self, computation: BaseComputation) -> None:
         if computation.msg.is_static:
             raise WriteProtection("Cannot modify state while inside of a STATICCALL context")
         return super().__call__(computation)
+
+
+class Create2(CreateByzantium):
+
+    def get_stack_frame(self, computation: BaseComputation) -> CreateStackFrame:
+
+        endowment, memory_start, memory_length, salt = computation.stack_pop(
+            num_items=4,
+            type_hint=constants.UINT256,
+        )
+
+        return CreateStackFrame(endowment, memory_start, memory_length, salt)
+
+    def generate_contract_address(self,
+                                  stack_frame: CreateStackFrame,
+                                  call_data: bytes,
+                                  computation: BaseComputation) -> Address:
+
+        return Address(
+            keccak(
+                encode_hex('0xff')
+                + computation.msg.storage_address
+                + int_to_big_endian(stack_frame.salt)
+                + keccak(call_data)
+            )[-20:]
+        )