refactor(core): move empty_bytearray to trezor.utils

core/src/apps/bitcoin/ownership.py

@@ -3,12 +3,7 @@ from trezor.crypto import bip32, hashlib, hmac
 
 from apps.common.keychain import Keychain
 from apps.common.readers import read_bitcoin_varint
-from apps.common.writers import (
-    empty_bytearray,
-    write_bitcoin_varint,
-    write_bytes_fixed,
-    write_uint8,
-)
+from apps.common.writers import write_bitcoin_varint, write_bytes_fixed, write_uint8
 
 from . import common
 from .scripts import read_bip322_signature_proof, write_bip322_signature_proof
@@ -43,7 +38,7 @@ def generate_proof(
     if user_confirmed:
         flags |= _FLAG_USER_CONFIRMED
 
-    proof = empty_bytearray(4 + 1 + 1 + len(ownership_ids) * _OWNERSHIP_ID_LEN)
+    proof = utils.empty_bytearray(4 + 1 + 1 + len(ownership_ids) * _OWNERSHIP_ID_LEN)
 
     write_bytes_fixed(proof, _VERSION_MAGIC, 4)
     write_uint8(proof, flags)

core/src/apps/bitcoin/scripts.py

@@ -5,7 +5,7 @@ from trezor.messages import InputScriptType
 
 from apps.common import address_type
 from apps.common.readers import read_bitcoin_varint
-from apps.common.writers import empty_bytearray, write_bitcoin_varint
+from apps.common.writers import write_bitcoin_varint
 
 from . import common
 from .multisig import (
@@ -141,7 +141,7 @@ def bip143_derive_script_code(
 def input_script_p2pkh_or_p2sh(
     pubkey: bytes, signature: bytes, hash_type: int
 ) -> bytearray:
-    w = empty_bytearray(5 + len(signature) + 1 + 5 + len(pubkey))
+    w = utils.empty_bytearray(5 + len(signature) + 1 + 5 + len(pubkey))
     append_signature(w, signature, hash_type)
     append_pubkey(w, pubkey)
     return w
@@ -211,7 +211,7 @@ def output_script_native_p2wpkh_or_p2wsh(witprog: bytes) -> bytearray:
     length = len(witprog)
     utils.ensure(length == 20 or length == 32)
 
-    w = empty_bytearray(3 + length)
+    w = utils.empty_bytearray(3 + length)
     w.append(0x00)  # witness version byte
     w.append(length)  # pub key hash length is 20 (P2WPKH) or 32 (P2WSH) bytes
     write_bytes_fixed(w, witprog, length)  # pub key hash
@@ -231,7 +231,7 @@ def input_script_p2wpkh_in_p2sh(pubkeyhash: bytes) -> bytearray:
     # Signature is moved to the witness.
     utils.ensure(len(pubkeyhash) == 20)
 
-    w = empty_bytearray(3 + len(pubkeyhash))
+    w = utils.empty_bytearray(3 + len(pubkeyhash))
     w.append(0x16)  # length of the data
     w.append(0x00)  # witness version byte
     w.append(0x14)  # P2WPKH witness program (pub key hash length)
@@ -254,7 +254,7 @@ def input_script_p2wsh_in_p2sh(script_hash: bytes) -> bytearray:
     if len(script_hash) != 32:
         raise wire.DataError("Redeem script hash should be 32 bytes long")
 
-    w = empty_bytearray(3 + len(script_hash))
+    w = utils.empty_bytearray(3 + len(script_hash))
     w.append(0x22)  # length of the data
     w.append(0x00)  # witness version byte
     w.append(0x20)  # P2WSH witness program (redeem script hash length)
@@ -267,7 +267,7 @@ def input_script_p2wsh_in_p2sh(script_hash: bytes) -> bytearray:
 
 
 def witness_p2wpkh(signature: bytes, pubkey: bytes, hash_type: int) -> bytearray:
-    w = empty_bytearray(1 + 5 + len(signature) + 1 + 5 + len(pubkey))
+    w = utils.empty_bytearray(1 + 5 + len(signature) + 1 + 5 + len(pubkey))
     write_bitcoin_varint(w, 0x02)  # num of segwit items, in P2WPKH it's always 2
     write_signature_prefixed(w, signature, hash_type)
     write_bytes_prefixed(w, pubkey)
@@ -326,7 +326,7 @@ def witness_multisig(
         total_length += 1 + len(s) + 1  # length, signature, hash_type
     total_length += 1 + redeem_script_length  # length, script
 
-    w = empty_bytearray(total_length)
+    w = utils.empty_bytearray(total_length)
 
     write_bitcoin_varint(w, num_of_witness_items)
     # Starts with OP_FALSE because of an old OP_CHECKMULTISIG bug, which
@@ -399,7 +399,7 @@ def input_script_multisig(
         total_length += 1 + len(s) + 1  # length, signature, hash_type
     total_length += 1 + redeem_script_length  # length, script
 
-    w = empty_bytearray(total_length)
+    w = utils.empty_bytearray(total_length)
 
     # Starts with OP_FALSE because of an old OP_CHECKMULTISIG bug, which
     # consumes one additional item on the stack:
@@ -445,7 +445,7 @@ def parse_input_script_multisig(
 
 
 def output_script_multisig(pubkeys: list[bytes], m: int) -> bytearray:
-    w = empty_bytearray(output_script_multisig_length(pubkeys, m))
+    w = utils.empty_bytearray(output_script_multisig_length(pubkeys, m))
     write_output_script_multisig(w, pubkeys, m)
     return w
 
@@ -507,7 +507,7 @@ def parse_output_script_multisig(script: bytes) -> tuple[list[bytes], int]:
 
 
 def output_script_paytoopreturn(data: bytes) -> bytearray:
-    w = empty_bytearray(1 + 5 + len(data))
+    w = utils.empty_bytearray(1 + 5 + len(data))
     w.append(0x6A)  # OP_RETURN
     write_op_push(w, len(data))
     w.extend(data)

core/src/apps/bitcoin/scripts_decred.py

@@ -3,7 +3,7 @@ from trezor.crypto import base58
 from trezor.crypto.base58 import blake256d_32
 from trezor.messages import InputScriptType
 
-from apps.common.writers import empty_bytearray, write_bytes_fixed, write_uint64_le
+from apps.common.writers import write_bytes_fixed, write_uint64_le
 
 from . import scripts
 from .multisig import multisig_get_pubkeys, multisig_pubkey_index
@@ -65,7 +65,7 @@ def input_script_multisig(
         total_length += 1 + len(s) + 1  # length, signature, hash_type
     total_length += 1 + redeem_script_length  # length, script
 
-    w = empty_bytearray(total_length)
+    w = utils.empty_bytearray(total_length)
 
     for s in signatures:
         if len(s):
@@ -85,7 +85,7 @@ def output_script_sstxsubmissionpkh(addr: str) -> bytearray:
     except ValueError:
         raise wire.DataError("Invalid address")
 
-    w = empty_bytearray(26)
+    w = utils.empty_bytearray(26)
     w.append(0xBA)  # OP_SSTX
     w.append(0x76)  # OP_DUP
     w.append(0xA9)  # OP_HASH160
@@ -103,7 +103,7 @@ def output_script_sstxchange(addr: str) -> bytearray:
     except ValueError:
         raise wire.DataError("Invalid address")
 
-    w = empty_bytearray(26)
+    w = utils.empty_bytearray(26)
     w.append(0xBD)  # OP_SSTXCHANGE
     w.append(0x76)  # OP_DUP
     w.append(0xA9)  # OP_HASH160
@@ -144,7 +144,7 @@ def output_script_ssgen(pkh: bytes) -> bytearray:
 
 # Retrieve pkh bytes from a stake commitment OPRETURN.
 def sstxcommitment_pkh(pkh: bytes, amount: int) -> bytes:
-    w = empty_bytearray(30)
+    w = utils.empty_bytearray(30)
     write_bytes_fixed(w, pkh, 20)
     write_uint64_le(w, amount)
     write_bytes_fixed(w, b"\x00\x58", 2)  # standard fee limits

core/src/apps/bitcoin/sign_tx/bitcoin.py

@@ -6,7 +6,7 @@ from trezor.messages import InputScriptType, OutputScriptType
 from trezor.messages.TxRequest import TxRequest
 from trezor.messages.TxRequestDetailsType import TxRequestDetailsType
 from trezor.messages.TxRequestSerializedType import TxRequestSerializedType
-from trezor.utils import HashWriter, ensure
+from trezor.utils import HashWriter, empty_bytearray, ensure
 
 from apps.common.writers import write_bitcoin_varint
 
@@ -93,7 +93,7 @@ class Bitcoin:
         self.external: set[int] = set()
 
         # transaction and signature serialization
-        self.serialized_tx = writers.empty_bytearray(_MAX_SERIALIZED_CHUNK_SIZE)
+        self.serialized_tx = empty_bytearray(_MAX_SERIALIZED_CHUNK_SIZE)
         self.tx_req = TxRequest()
         self.tx_req.details = TxRequestDetailsType()
         self.tx_req.serialized = TxRequestSerializedType()

core/src/apps/bitcoin/writers.py

@@ -4,7 +4,6 @@ from trezor.crypto.hashlib import sha256
 from trezor.utils import ensure
 
 from apps.common.writers import (  # noqa: F401
-    empty_bytearray,
     write_bitcoin_varint,
     write_bytes_fixed,
     write_bytes_reversed,

core/src/apps/common/cbor.py

@@ -7,7 +7,7 @@ from micropython import const
 
 from trezor import log, utils
 
-from . import readers, writers
+from . import readers
 
 if False:
     from typing import Any, Union, Iterator, Tuple
@@ -250,7 +250,7 @@ def encode_chunked(value: Value, max_chunk_size: int) -> Iterator[bytes]:
 
     chunks = encode_streamed(value)
 
-    chunk_buffer = writers.empty_bytearray(max_chunk_size)
+    chunk_buffer = utils.empty_bytearray(max_chunk_size)
     try:
         current_chunk_view = utils.BufferReader(next(chunks))
         while True:

core/src/apps/common/writers.py

@@ -4,16 +4,6 @@ if False:
     from trezor.utils import Writer
 
 
-def empty_bytearray(preallocate: int) -> bytearray:
-    """
-    Returns bytearray that won't allocate for at least `preallocate` bytes.
-    Useful in case you want to avoid allocating too often.
-    """
-    b = bytearray(preallocate)
-    b[:] = bytes()
-    return b
-
-
 def write_uint8(w: Writer, n: int) -> int:
     ensure(0 <= n <= 0xFF)
     w.append(n)

core/src/trezor/utils.py

@@ -268,3 +268,13 @@ def is_empty_iterator(i: Iterator) -> bool:
         return True
     else:
         return False
+
+
+def empty_bytearray(preallocate: int) -> bytearray:
+    """
+    Returns bytearray that won't allocate for at least `preallocate` bytes.
+    Useful in case you want to avoid allocating too often.
+    """
+    b = bytearray(preallocate)
+    b[:] = bytes()
+    return b