From 20330548cf5f44cec057c0ed099b64c81afb124d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?L=C5=91rinc?= <pap.lorinc@gmail.com>
Date: Sat, 1 Feb 2025 19:16:17 +0100
Subject: [PATCH] refactor: extract `SipHash` C0-C3 constants to class scope

Moves the `SipHash` initialization constants (C0-C3) from magic numbers to named static constexpr members of `CSipHasher`.
---
 src/crypto/siphash.cpp | 26 ++++++++++++++------------
 src/crypto/siphash.h   |  5 +++++
 2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/src/crypto/siphash.cpp b/src/crypto/siphash.cpp
index 1a9eb771a82..37ed918908f 100644
--- a/src/crypto/siphash.cpp
+++ b/src/crypto/siphash.cpp
@@ -21,10 +21,10 @@
 
 CSipHasher::CSipHasher(uint64_t k0, uint64_t k1)
 {
-    v[0] = 0x736f6d6570736575ULL ^ k0;
-    v[1] = 0x646f72616e646f6dULL ^ k1;
-    v[2] = 0x6c7967656e657261ULL ^ k0;
-    v[3] = 0x7465646279746573ULL ^ k1;
+    v[0] = C0 ^ k0;
+    v[1] = C1 ^ k1;
+    v[2] = C2 ^ k0;
+    v[3] = C3 ^ k1;
     count = 0;
     tmp = 0;
 }
@@ -101,10 +101,11 @@ uint64_t SipHashUint256(uint64_t k0, uint64_t k1, const uint256& val)
     /* Specialized implementation for efficiency */
     uint64_t d = val.GetUint64(0);
 
-    uint64_t v0 = 0x736f6d6570736575ULL ^ k0;
-    uint64_t v1 = 0x646f72616e646f6dULL ^ k1;
-    uint64_t v2 = 0x6c7967656e657261ULL ^ k0;
-    uint64_t v3 = 0x7465646279746573ULL ^ k1 ^ d;
+    // TODO moved in followup commit
+    uint64_t v0 = CSipHasher::C0 ^ k0;
+    uint64_t v1 = CSipHasher::C1 ^ k1;
+    uint64_t v2 = CSipHasher::C2 ^ k0;
+    uint64_t v3 = CSipHasher::C3 ^ k1 ^ d;
 
     SIPROUND;
     SIPROUND;
@@ -141,10 +142,11 @@ uint64_t SipHashUint256Extra(uint64_t k0, uint64_t k1, const uint256& val, uint3
     /* Specialized implementation for efficiency */
     uint64_t d = val.GetUint64(0);
 
-    uint64_t v0 = 0x736f6d6570736575ULL ^ k0;
-    uint64_t v1 = 0x646f72616e646f6dULL ^ k1;
-    uint64_t v2 = 0x6c7967656e657261ULL ^ k0;
-    uint64_t v3 = 0x7465646279746573ULL ^ k1 ^ d;
+    // TODO moved in followup commit
+    uint64_t v0 = CSipHasher::C0 ^ k0;
+    uint64_t v1 = CSipHasher::C1 ^ k1;
+    uint64_t v2 = CSipHasher::C2 ^ k0;
+    uint64_t v3 = CSipHasher::C3 ^ k1 ^ d;
 
     SIPROUND;
     SIPROUND;
diff --git a/src/crypto/siphash.h b/src/crypto/siphash.h
index 8d41a083ac8..4293fdf93b4 100644
--- a/src/crypto/siphash.h
+++ b/src/crypto/siphash.h
@@ -19,6 +19,11 @@ private:
     uint8_t count; // Only the low 8 bits of the input size matter.
 
 public:
+    static constexpr uint64_t C0{0x736f6d6570736575ULL};
+    static constexpr uint64_t C1{0x646f72616e646f6dULL};
+    static constexpr uint64_t C2{0x6c7967656e657261ULL};
+    static constexpr uint64_t C3{0x7465646279746573ULL};
+
     /** Construct a SipHash calculator initialized with 128-bit key (k0, k1) */
     CSipHasher(uint64_t k0, uint64_t k1);
     /** Hash a 64-bit integer worth of data