feat(tools): Implement While code opcode generator

Author: marioevz

src/ethereum_test_tools/__init__.py

@@ -79,6 +79,7 @@
     Conditional,
     Initcode,
     Switch,
+    While,
     Yul,
     YulCompiler,
 )
@@ -149,6 +150,7 @@
     "TransactionTest",
     "TransactionTestFiller",
     "UndefinedOpcodes",
+    "While",
     "Withdrawal",
     "WithdrawalRequest",
     "Yul",

src/ethereum_test_tools/code/__init__.py

@@ -1,16 +1,17 @@
 """Code related utilities and classes."""
 
-from .generators import CalldataCase, Case, CodeGasMeasure, Conditional, Initcode, Switch
+from .generators import CalldataCase, Case, CodeGasMeasure, Conditional, Initcode, Switch, While
 from .yul import Solc, Yul, YulCompiler
 
 __all__ = (
-    "Case",
     "CalldataCase",
+    "Case",
     "CodeGasMeasure",
     "Conditional",
     "Initcode",
     "Solc",
     "Switch",
+    "While",
     "Yul",
     "YulCompiler",
 )

src/ethereum_test_tools/code/generators.py

@@ -235,6 +235,33 @@ def __new__(
         return super().__new__(cls, bytecode)
 
 
+class While(Bytecode):
+    """Helper class used to generate while-loop bytecode."""
+
+    def __new__(
+        cls,
+        *,
+        body: Bytecode | Op,
+        condition: Bytecode | Op,
+        evm_code_type: EVMCodeType = EVMCodeType.LEGACY,
+    ):
+        """
+        Assemble the loop bytecode.
+
+        The condition nor the body can leave a stack item on the stack.
+        """
+        bytecode = Bytecode()
+        if evm_code_type == EVMCodeType.LEGACY:
+            bytecode += Op.JUMPDEST
+            bytecode += body
+            bytecode += Op.JUMPI(
+                Op.SUB(Op.PC, Op.PUSH4[len(body) + len(condition) + 6]), condition
+            )
+        elif evm_code_type == EVMCodeType.EOF_V1:
+            raise NotImplementedError("EOF while loops are not implemented")
+        return super().__new__(cls, bytecode)
+
+
 @dataclass(kw_only=True)
 class Case:
     """