feat(scripts): implement ScriptContext

Author: glevco

hathor/transaction/scripts/execute.py

@@ -16,7 +16,7 @@
 from typing import NamedTuple, Optional, Union
 
 from hathor.transaction import BaseTransaction, Transaction, TxInput
-from hathor.transaction.exceptions import DataIndexError, FinalStackInvalid, InvalidScriptError, OutOfData, ScriptError
+from hathor.transaction.exceptions import DataIndexError, FinalStackInvalid, InvalidScriptError, OutOfData
 
 
 class ScriptExtras(NamedTuple):
@@ -54,21 +54,19 @@ def execute_eval(data: bytes, log: list[str], extras: ScriptExtras) -> None:
         :raises ScriptError: case opcode is not found
         :raises FinalStackInvalid: case the evaluation fails
     """
-    from hathor.transaction.scripts.opcode import MAP_OPCODE_TO_FN, Opcode
+    from hathor.transaction.scripts.opcode import Opcode, execute_op_code
+    from hathor.transaction.scripts.script_context import ScriptContext
+    context = ScriptContext()
     stack: Stack = []
     data_len = len(data)
     pos = 0
     while pos < data_len:
         opcode, pos = get_script_op(pos, data, stack)
         if Opcode.is_pushdata(opcode):
             continue
-        # this is an opcode manipulating the stack
-        fn = MAP_OPCODE_TO_FN.get(opcode, None)
-        if fn is None:
-            # throw error
-            raise ScriptError('unknown opcode')
 
-        fn(stack, log, extras)
+        # this is an opcode manipulating the stack
+        execute_op_code(Opcode(opcode), stack, log, extras, context)
 
     evaluate_final_stack(stack, log)
 

hathor/transaction/scripts/opcode.py

@@ -15,7 +15,6 @@
 import datetime
 import struct
 from enum import IntEnum
-from typing import Callable
 
 from cryptography.exceptions import InvalidSignature
 from cryptography.hazmat.primitives import hashes
@@ -46,6 +45,7 @@
     get_data_value,
     get_script_op,
 )
+from hathor.transaction.scripts.script_context import ScriptContext
 
 
 class Opcode(IntEnum):
@@ -157,7 +157,7 @@ def op_pushdata1(position: int, full_data: bytes, stack: Stack) -> int:
     return new_pos
 
 
-def op_dup(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
+def op_dup(stack: Stack) -> None:
     """Duplicates item on top of stack
 
     :param stack: the stack used when evaluating the script
@@ -170,7 +170,7 @@ def op_dup(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
     stack.append(stack[-1])
 
 
-def op_greaterthan_timestamp(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
+def op_greaterthan_timestamp(stack: Stack, extras: ScriptExtras) -> None:
     """Check whether transaction's timestamp is greater than the top of stack
 
     The top of stack must be a big-endian u32int.
@@ -190,7 +190,7 @@ def op_greaterthan_timestamp(stack: Stack, log: list[str], extras: ScriptExtras)
             datetime.datetime.fromtimestamp(timelock).strftime("%m/%d/%Y %I:%M:%S %p")))
 
 
-def op_equalverify(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
+def op_equalverify(stack: Stack, log: list[str]) -> None:
     """Verifies top 2 elements from stack are equal
 
     :param stack: the stack used when evaluating the script
@@ -201,13 +201,13 @@ def op_equalverify(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
     """
     if len(stack) < 2:
         raise MissingStackItems('OP_EQUALVERIFY: need 2 elements on stack, currently {}'.format(len(stack)))
-    op_equal(stack, log, extras)
+    op_equal(stack, log)
     is_equal = stack.pop()
     if not is_equal:
         raise EqualVerifyFailed('Failed to verify if elements are equal')
 
 
-def op_equal(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
+def op_equal(stack: Stack, log: list[str]) -> None:
     """Verifies top 2 elements from stack are equal
 
     In case they are the same, we push 1 to the stack and push 0 if they are different
@@ -265,7 +265,7 @@ def op_checksig(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
         log.append('OP_CHECKSIG: failed')
 
 
-def op_hash160(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
+def op_hash160(stack: Stack) -> None:
     """Top stack item is hashed twice: first with SHA-256 and then with RIPEMD-160.
     Result is pushed back to stack.
 
@@ -282,7 +282,7 @@ def op_hash160(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
     stack.append(new_elem)
 
 
-def op_checkdatasig(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
+def op_checkdatasig(stack: Stack) -> None:
     """Verifies public key, signature and data match. Expects public key to be on top of stack, followed
     by signature and data. If they match, put data on stack; otherwise, fail.
 
@@ -316,7 +316,7 @@ def op_checkdatasig(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
         raise OracleChecksigFailed from e
 
 
-def op_data_strequal(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
+def op_data_strequal(stack: Stack) -> None:
     """Equivalent to an OP_GET_DATA_STR followed by an OP_EQUALVERIFY.
 
     Consumes three parameters from stack: <data> <k> <value>. Gets the kth value
@@ -347,7 +347,7 @@ def op_data_strequal(stack: Stack, log: list[str], extras: ScriptExtras) -> None
     stack.append(data)
 
 
-def op_data_greaterthan(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
+def op_data_greaterthan(stack: Stack) -> None:
     """Equivalent to an OP_GET_DATA_INT followed by an OP_GREATERTHAN.
 
     Consumes three parameters from stack: <data> <k> <n>. Gets the kth value
@@ -383,7 +383,7 @@ def op_data_greaterthan(stack: Stack, log: list[str], extras: ScriptExtras) -> N
     stack.append(data)
 
 
-def op_data_match_interval(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
+def op_data_match_interval(stack: Stack) -> None:
     """Equivalent to an OP_GET_DATA_INT followed by an OP_MATCH_INTERVAL.
 
     :param stack: the stack used when evaluating the script
@@ -435,7 +435,7 @@ def op_data_match_interval(stack: Stack, log: list[str], extras: ScriptExtras) -
     stack.append(last_pubkey)
 
 
-def op_data_match_value(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
+def op_data_match_value(stack: Stack) -> None:
     """Equivalent to an OP_GET_DATA_STR followed by an OP_MATCH_VALUE.
 
     :param stack: the stack used when evaluating the script
@@ -484,7 +484,7 @@ def op_data_match_value(stack: Stack, log: list[str], extras: ScriptExtras) -> N
     stack.append(winner_pubkey)
 
 
-def op_find_p2pkh(stack: Stack, log: list[str], extras: ScriptExtras) -> None:
+def op_find_p2pkh(stack: Stack, extras: ScriptExtras) -> None:
     """Checks whether the current transaction has an output with a P2PKH script with
     the given public key hash and the same amount as the input.
 
@@ -604,7 +604,7 @@ def op_checkmultisig(stack: Stack, log: list[str], extras: ScriptExtras) -> None
     stack.append(1)
 
 
-def op_integer(opcode: int, stack: Stack, log: list[str], extras: ScriptExtras) -> None:
+def op_integer(opcode: int, stack: Stack) -> None:
     """ Appends an integer to the stack
         We get the opcode comparing to all integers opcodes
 
@@ -624,17 +624,34 @@ def op_integer(opcode: int, stack: Stack, log: list[str], extras: ScriptExtras)
         raise ScriptError(e) from e
 
 
-MAP_OPCODE_TO_FN: dict[int, Callable[[Stack, list[str], ScriptExtras], None]] = {
-    Opcode.OP_DUP: op_dup,
-    Opcode.OP_EQUAL: op_equal,
-    Opcode.OP_EQUALVERIFY: op_equalverify,
-    Opcode.OP_CHECKSIG: op_checksig,
-    Opcode.OP_HASH160: op_hash160,
-    Opcode.OP_GREATERTHAN_TIMESTAMP: op_greaterthan_timestamp,
-    Opcode.OP_CHECKMULTISIG: op_checkmultisig,
-    Opcode.OP_DATA_STREQUAL: op_data_strequal,
-    Opcode.OP_DATA_GREATERTHAN: op_data_greaterthan,
-    Opcode.OP_DATA_MATCH_VALUE: op_data_match_value,
-    Opcode.OP_CHECKDATASIG: op_checkdatasig,
-    Opcode.OP_FIND_P2PKH: op_find_p2pkh,
-}
+def execute_op_code(
+    opcode: Opcode,
+    stack: Stack,
+    log: list[str],
+    extras: ScriptExtras,
+    context: ScriptContext,
+) -> None:
+    """
+    Execute a function opcode.
+
+    Args:
+        opcode: the opcode to be executed.
+        stack: the stack to be manipulated.
+        log: the log list to be appended.
+        extras: auxiliary opcode arguments.
+        context: the script context to be manipulated.
+    """
+    match opcode:
+        case Opcode.OP_DUP: op_dup(stack)
+        case Opcode.OP_EQUAL: op_equal(stack, log)
+        case Opcode.OP_EQUALVERIFY: op_equalverify(stack, log)
+        case Opcode.OP_CHECKSIG: op_checksig(stack, log, extras)
+        case Opcode.OP_HASH160: op_hash160(stack)
+        case Opcode.OP_GREATERTHAN_TIMESTAMP: op_greaterthan_timestamp(stack, extras)
+        case Opcode.OP_CHECKMULTISIG: op_checkmultisig(stack, log, extras)
+        case Opcode.OP_DATA_STREQUAL: op_data_strequal(stack)
+        case Opcode.OP_DATA_GREATERTHAN: op_data_greaterthan(stack)
+        case Opcode.OP_DATA_MATCH_VALUE: op_data_match_value(stack)
+        case Opcode.OP_CHECKDATASIG: op_checkdatasig(stack)
+        case Opcode.OP_FIND_P2PKH: op_find_p2pkh(stack, extras)
+        case _: raise ScriptError(f'unknown opcode: {opcode}')

hathor/transaction/scripts/script_context.py

@@ -0,0 +1,18 @@
+#  Copyright 2023 Hathor Labs
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+
+class ScriptContext:
+    """A context to be manipulated during script execution. A separate instance must be used for each script."""
+    __slots__ = ()