test: avoid unneeded hash -> uint256 -> hash roundtrips

In the functional test framework, we often treat hashes
as uint256 integers, which seems to be confusing and for no
good reason, as hashes are just sequences of bytes. This commit
gets rid of obvious internal instances of that where individual
functional tests are not affected. In the long-term, it might make
sense to store other hashes (mostly txids) as actual bytes to
avoid annoying conversions and improve code readability.

Author: theStack

test/functional/test_framework/blocktools.py

@@ -28,7 +28,6 @@
     ser_uint256,
     tx_from_hex,
     uint256_from_compact,
-    uint256_from_str,
     WITNESS_SCALE_FACTOR,
 )
 from .script import (
@@ -111,8 +110,8 @@ def create_block(hashprev=None, coinbase=None, ntime=None, *, version=None, tmpl
     return block
 
 def get_witness_script(witness_root, witness_nonce):
-    witness_commitment = uint256_from_str(hash256(ser_uint256(witness_root) + ser_uint256(witness_nonce)))
-    output_data = WITNESS_COMMITMENT_HEADER + ser_uint256(witness_commitment)
+    witness_commitment = hash256(ser_uint256(witness_root) + ser_uint256(witness_nonce))
+    output_data = WITNESS_COMMITMENT_HEADER + witness_commitment
     return CScript([OP_RETURN, output_data])
 
 def add_witness_commitment(block, nonce=0):

test/functional/test_framework/script.py

@@ -17,9 +17,7 @@
     CTxOut,
     hash256,
     ser_string,
-    ser_uint256,
     sha256,
-    uint256_from_str,
 )
 
 from .crypto.ripemd160 import ripemd160
@@ -711,41 +709,42 @@ def sign_input_segwitv0(tx, input_index, input_scriptpubkey, input_amount, privk
 # Note that this corresponds to sigversion == 1 in EvalScript, which is used
 # for version 0 witnesses.
 def SegwitV0SignatureMsg(script, txTo, inIdx, hashtype, amount):
+    ZERO_HASH = bytes([0]*32)
 
-    hashPrevouts = 0
-    hashSequence = 0
-    hashOutputs = 0
+    hashPrevouts = ZERO_HASH
+    hashSequence = ZERO_HASH
+    hashOutputs = ZERO_HASH
 
     if not (hashtype & SIGHASH_ANYONECANPAY):
         serialize_prevouts = bytes()
         for i in txTo.vin:
             serialize_prevouts += i.prevout.serialize()
-        hashPrevouts = uint256_from_str(hash256(serialize_prevouts))
+        hashPrevouts = hash256(serialize_prevouts)
 
     if (not (hashtype & SIGHASH_ANYONECANPAY) and (hashtype & 0x1f) != SIGHASH_SINGLE and (hashtype & 0x1f) != SIGHASH_NONE):
         serialize_sequence = bytes()
         for i in txTo.vin:
             serialize_sequence += i.nSequence.to_bytes(4, "little")
-        hashSequence = uint256_from_str(hash256(serialize_sequence))
+        hashSequence = hash256(serialize_sequence)
 
     if ((hashtype & 0x1f) != SIGHASH_SINGLE and (hashtype & 0x1f) != SIGHASH_NONE):
         serialize_outputs = bytes()
         for o in txTo.vout:
             serialize_outputs += o.serialize()
-        hashOutputs = uint256_from_str(hash256(serialize_outputs))
+        hashOutputs = hash256(serialize_outputs)
     elif ((hashtype & 0x1f) == SIGHASH_SINGLE and inIdx < len(txTo.vout)):
         serialize_outputs = txTo.vout[inIdx].serialize()
-        hashOutputs = uint256_from_str(hash256(serialize_outputs))
+        hashOutputs = hash256(serialize_outputs)
 
     ss = bytes()
     ss += txTo.version.to_bytes(4, "little")
-    ss += ser_uint256(hashPrevouts)
-    ss += ser_uint256(hashSequence)
+    ss += hashPrevout
+    ss += hashSequence
     ss += txTo.vin[inIdx].prevout.serialize()
     ss += ser_string(script)
     ss += amount.to_bytes(8, "little", signed=True)
     ss += txTo.vin[inIdx].nSequence.to_bytes(4, "little")
-    ss += ser_uint256(hashOutputs)
+    ss += hashOutputs
     ss += txTo.nLockTime.to_bytes(4, "little")
     ss += hashtype.to_bytes(4, "little")
     return ss