bitcoin.py/transaction.py: API changes: rm most hex usage

Instead of some functions operating with hex strings,
and others using bytes, this consolidates most things to use bytes.

This mainly focuses on bitcoin.py and transaction.py,
and then adapts the API usages in other files.

Notably,
- scripts,
- pubkeys,
- signatures
should be bytes in almost all places now.

electrum/blockchain.py

@@ -26,7 +26,7 @@ import time
 from typing import Optional, Dict, Mapping, Sequence, TYPE_CHECKING
 
 from . import util
-from .bitcoin import hash_encode, int_to_hex, rev_hex
+from .bitcoin import hash_encode
 from .crypto import sha256d
 from . import constants
 from .util import bfh, with_lock
@@ -49,13 +49,14 @@ class MissingHeader(Exception):
 class InvalidHeader(Exception):
     pass
 
-def serialize_header(header_dict: dict) -> str:
-    s = int_to_hex(header_dict['version'], 4) \
-        + rev_hex(header_dict['prev_block_hash']) \
-        + rev_hex(header_dict['merkle_root']) \
-        + int_to_hex(int(header_dict['timestamp']), 4) \
-        + int_to_hex(int(header_dict['bits']), 4) \
-        + int_to_hex(int(header_dict['nonce']), 4)
+def serialize_header(header_dict: dict) -> bytes:
+    s = (
+        int.to_bytes(header_dict['version'], length=4, byteorder="little", signed=False)
+        + bfh(header_dict['prev_block_hash'])[::-1]
+        + bfh(header_dict['merkle_root'])[::-1]
+        + int.to_bytes(int(header_dict['timestamp']), length=4, byteorder="little", signed=False)
+        + int.to_bytes(int(header_dict['bits']), length=4, byteorder="little", signed=False)
+        + int.to_bytes(int(header_dict['nonce']), length=4, byteorder="little", signed=False))
     return s
 
 def deserialize_header(s: bytes, height: int) -> dict:
@@ -63,14 +64,13 @@ def deserialize_header(s: bytes, height: int) -> dict:
         raise InvalidHeader('Invalid header: {}'.format(s))
     if len(s) != HEADER_SIZE:
         raise InvalidHeader('Invalid header length: {}'.format(len(s)))
-    hex_to_int = lambda s: int.from_bytes(s, byteorder='little')
     h = {}
-    h['version'] = hex_to_int(s[0:4])
+    h['version'] = int.from_bytes(s[0:4], byteorder='little')
     h['prev_block_hash'] = hash_encode(s[4:36])
     h['merkle_root'] = hash_encode(s[36:68])
-    h['timestamp'] = hex_to_int(s[68:72])
-    h['bits'] = hex_to_int(s[72:76])
-    h['nonce'] = hex_to_int(s[76:80])
+    h['timestamp'] = int.from_bytes(s[68:72], byteorder='little')
+    h['bits'] = int.from_bytes(s[72:76], byteorder='little')
+    h['nonce'] = int.from_bytes(s[76:80], byteorder='little')
     h['block_height'] = height
     return h
 
@@ -82,8 +82,9 @@ def hash_header(header: dict) -> str:
     return hash_raw_header(serialize_header(header))
 
 
-def hash_raw_header(header: str) -> str:
-    return hash_encode(sha256d(bfh(header)))
+def hash_raw_header(header: bytes) -> str:
+    assert isinstance(header, bytes)
+    return hash_encode(sha256d(header))
 
 
 pow_hash_header = hash_header
@@ -413,7 +414,7 @@ class Blockchain(Logger):
         # swap parameters
         self.parent, parent.parent = parent.parent, self  # type: Optional[Blockchain], Optional[Blockchain]
         self.forkpoint, parent.forkpoint = parent.forkpoint, self.forkpoint
-        self._forkpoint_hash, parent._forkpoint_hash = parent._forkpoint_hash, hash_raw_header(parent_data[:HEADER_SIZE].hex())
+        self._forkpoint_hash, parent._forkpoint_hash = parent._forkpoint_hash, hash_raw_header(parent_data[:HEADER_SIZE])
         self._prev_hash, parent._prev_hash = parent._prev_hash, self._prev_hash
         # parent's new name
         os.replace(child_old_name, parent.path())
@@ -454,7 +455,7 @@ class Blockchain(Logger):
     @with_lock
     def save_header(self, header: dict) -> None:
         delta = header.get('block_height') - self.forkpoint
-        data = bfh(serialize_header(header))
+        data = serialize_header(header)
         # headers are only _appended_ to the end:
         assert delta == self.size(), (delta, self.size())
         assert len(data) == HEADER_SIZE