Merge bitcoin/bitcoin#29401: test: Remove struct.pack from almost all places

fa52e13ee8 test: Remove struct.pack from almost all places (MarcoFalke)
fa826db477 scripted-diff: test: Use int.to_bytes over struct packing (MarcoFalke)
faf2a975ad test: Use int.to_bytes over struct packing (MarcoFalke)
faf3cd659a test: Normalize struct.pack format (MarcoFalke)

Pull request description:

  `struct.pack` has many issues:

  * The format string consists of characters that may be confusing and may need to be looked up in the documentation, as opposed to using easy to understand self-documenting code.

  This lead to many test bugs, which weren't hit, which is fine, but still confusing. Ref: https://github.com/bitcoin/bitcoin/pull/29400, https://github.com/bitcoin/bitcoin/pull/29399, https://github.com/bitcoin/bitcoin/pull/29363, fa3886b7c6, ...

  Fix all issues by using the built-in `int` helpers `to_bytes` via a scripted diff.

  Review notes:

  * For `struct.pack` and `int.to_bytes` the error behavior is the same, although the error messages are not identical.
  * Two `struct.pack` remain. One for float serialization in a C++ code comment, and one for native serialization.

ACKs for top commit:
  achow101:
    ACK fa52e13ee8
  rkrux:
    tACK [fa52e13](fa52e13ee8)
  theStack:
    Code-review ACK fa52e13ee8

Tree-SHA512: ee80d935b68ae43d1654b047e84ceb80abbd20306df35cca848b3f7874634b518560ddcbc7e714e2e7a19241e153dee64556dc4701287ae811e26e4f8c57fe3e

contrib/seeds/generate-seeds.py

@@ -29,7 +29,6 @@ These should be pasted into `src/chainparamsseeds.h`.
 
 from base64 import b32decode
 from enum import Enum
-import struct
 import sys
 import os
 import re
@@ -115,13 +114,13 @@ def parse_spec(s):
 def ser_compact_size(l):
     r = b""
     if l < 253:
-        r = struct.pack("B", l)
+        r = l.to_bytes(1, "little")
     elif l < 0x10000:
-        r = struct.pack("<BH", 253, l)
+        r = (253).to_bytes(1, "little") + l.to_bytes(2, "little")
     elif l < 0x100000000:
-        r = struct.pack("<BI", 254, l)
+        r = (254).to_bytes(1, "little") + l.to_bytes(4, "little")
     else:
-        r = struct.pack("<BQ", 255, l)
+        r = (255).to_bytes(1, "little") + l.to_bytes(8, "little")
     return r
 
 def bip155_serialize(spec):
@@ -129,10 +128,10 @@ def bip155_serialize(spec):
     Serialize (networkID, addr, port) tuple to BIP155 binary format.
     '''
     r = b""
-    r += struct.pack('B', spec[0].value)
+    r += spec[0].value.to_bytes(1, "little")
     r += ser_compact_size(len(spec[1]))
     r += spec[1]
-    r += struct.pack('>H', spec[2])
+    r += spec[2].to_bytes(2, "big")
     return r
 
 def process_nodes(g, f, structname):

contrib/signet/miner

@@ -52,10 +52,10 @@ def signet_txs(block, challenge):
     mroot = block.get_merkle_root(hashes)
 
     sd = b""
-    sd += struct.pack("<i", block.nVersion)
+    sd += block.nVersion.to_bytes(4, "little", signed=True)
     sd += ser_uint256(block.hashPrevBlock)
     sd += ser_uint256(mroot)
-    sd += struct.pack("<I", block.nTime)
+    sd += block.nTime.to_bytes(4, "little")
 
     to_spend = CTransaction()
     to_spend.nVersion = 0