contrib: dedup deserialization routines in utxo-to-sqlite script

These routines already exist in the functional test framework
(with the advantage of having proper unit tests executed in CI), so we
can just import them from there instead of leaving duplicated code
in the repository.

contrib/utxo-tools/utxo_to_sqlite.py

@@ -16,6 +16,11 @@ import sqlite3
 import sys
 import time
 
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), '../../test/functional'))
+
+from test_framework.compressor import decompress_amount  # noqa: E402
+from test_framework.messages import deser_compact_size, deser_varint  # noqa: E402
+
 
 UTXO_DUMP_MAGIC = b'utxo\xff'
 UTXO_DUMP_VERSION = 2
@@ -28,53 +33,9 @@ NET_MAGIC_BYTES = {
 }
 
 
-def read_varint(f):
-    """Equivalent of `ReadVarInt()` (see serialization module)."""
-    n = 0
-    while True:
-        dat = f.read(1)[0]
-        n = (n << 7) | (dat & 0x7f)
-        if (dat & 0x80) > 0:
-            n += 1
-        else:
-            return n
-
-
-def read_compactsize(f):
-    """Equivalent of `ReadCompactSize()` (see serialization module)."""
-    n = f.read(1)[0]
-    if n == 253:
-        n = int.from_bytes(f.read(2), "little")
-    elif n == 254:
-        n = int.from_bytes(f.read(4), "little")
-    elif n == 255:
-        n = int.from_bytes(f.read(8), "little")
-    return n
-
-
-def decompress_amount(x):
-    """Equivalent of `DecompressAmount()` (see compressor module)."""
-    if x == 0:
-        return 0
-    x -= 1
-    e = x % 10
-    x //= 10
-    n = 0
-    if e < 9:
-        d = (x % 9) + 1
-        x //= 9
-        n = x * 10 + d
-    else:
-        n = x + 1
-    while e > 0:
-        n *= 10
-        e -= 1
-    return n
-
-
 def decompress_script(f):
     """Equivalent of `DecompressScript()` (see compressor module)."""
-    size = read_varint(f)  # sizes 0-5 encode compressed script types
+    size = deser_varint(f)  # sizes 0-5 encode compressed script types
     if size == 0:  # P2PKH
         return bytes([0x76, 0xa9, 20]) + f.read(20) + bytes([0x88, 0xac])
     elif size == 1:  # P2SH
@@ -154,13 +115,13 @@ def main():
         # read key (COutPoint)
         if coins_per_hash_left == 0:  # read next prevout hash
             prevout_hash = f.read(32)[::-1].hex()
-            coins_per_hash_left = read_compactsize(f)
+            coins_per_hash_left = deser_compact_size(f)
-        prevout_index = read_compactsize(f)
+        prevout_index = deser_compact_size(f)
         # read value (Coin)
-        code = read_varint(f)
+        code = deser_varint(f)
         height = code >> 1
         is_coinbase = code & 1
-        amount = decompress_amount(read_varint(f))
+        amount = decompress_amount(deser_varint(f))
         scriptpubkey = decompress_script(f).hex()
         write_batch.append((prevout_hash, prevout_index, amount, is_coinbase, height, scriptpubkey))
         if height > max_height: