test: add SipHash implementation for generic data in Python

We will need this in the next commit to calculate ranged hashes
of scriptPubKeys as defined in BIP158.

test/functional/test_framework/siphash.py

@@ -1,15 +1,17 @@
 #!/usr/bin/env python3
-# Copyright (c) 2016-2018 The Bitcoin Core developers
+# Copyright (c) 2016-2022 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
-"""Specialized SipHash-2-4 implementations.
+"""SipHash-2-4 implementation.
 
-This implements SipHash-2-4 for 256-bit integers.
+This implements SipHash-2-4. For convenience, an interface taking 256-bit
+integers is provided in addition to the one accepting generic data.
 """
 
 def rotl64(n, b):
     return n >> (64 - b) | (n & ((1 << (64 - b)) - 1)) << b
 
+
 def siphash_round(v0, v1, v2, v3):
     v0 = (v0 + v1) & ((1 << 64) - 1)
     v1 = rotl64(v1, 13)
@@ -27,37 +29,37 @@ def siphash_round(v0, v1, v2, v3):
     v2 = rotl64(v2, 32)
     return (v0, v1, v2, v3)
 
-def siphash256(k0, k1, h):
-    n0 = h & ((1 << 64) - 1)
-    n1 = (h >> 64) & ((1 << 64) - 1)
-    n2 = (h >> 128) & ((1 << 64) - 1)
-    n3 = (h >> 192) & ((1 << 64) - 1)
+
+def siphash(k0, k1, data):
+    assert(type(data) == bytes)
     v0 = 0x736f6d6570736575 ^ k0
     v1 = 0x646f72616e646f6d ^ k1
     v2 = 0x6c7967656e657261 ^ k0
-    v3 = 0x7465646279746573 ^ k1 ^ n0
+    v3 = 0x7465646279746573 ^ k1
+    c = 0
+    t = 0
+    for d in data:
+        t |= d << (8 * (c % 8))
+        c = (c + 1) & 0xff
+        if (c & 7) == 0:
+            v3 ^= t
+            v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+            v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+            v0 ^= t
+            t = 0
+    t = t | (c << 56)
+    v3 ^= t
     v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
     v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
-    v0 ^= n0
-    v3 ^= n1
-    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
-    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
-    v0 ^= n1
-    v3 ^= n2
-    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
-    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
-    v0 ^= n2
-    v3 ^= n3
-    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
-    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
-    v0 ^= n3
-    v3 ^= 0x2000000000000000
-    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
-    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
-    v0 ^= 0x2000000000000000
-    v2 ^= 0xFF
+    v0 ^= t
+    v2 ^= 0xff
     v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
     v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
     v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
     v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
     return v0 ^ v1 ^ v2 ^ v3
+
+
+def siphash256(k0, k1, num):
+    assert(type(num) == int)
+    return siphash(k0, k1, num.to_bytes(32, 'little'))