From a952d000be09749de212d5807bd99e67415f3777 Mon Sep 17 00:00:00 2001
From: devgianlu <altomanigianluca@gmail.com>
Date: Sat, 26 Apr 2025 11:01:48 +0200
Subject: [PATCH] LibCrypto: Move `GCD` to method of `UnsignedBigInteger`

Having it as a method instead of a free function is necessary for the
next commits and generally allows for optimizations that require deeper
access into the `UnsignedBigInteger`.
---
 .../LibCrypto/BigFraction/BigFraction.cpp     |  2 +-
 .../LibCrypto/BigInt/UnsignedBigInteger.cpp   | 13 +++++++++
 .../LibCrypto/BigInt/UnsignedBigInteger.h     |  1 +
 Libraries/LibCrypto/CMakeLists.txt            |  1 -
 .../NumberTheory/ModularFunctions.cpp         | 28 -------------------
 .../LibCrypto/NumberTheory/ModularFunctions.h |  2 --
 .../Userland/Libraries/LibCrypto/BUILD.gn     |  1 -
 7 files changed, 15 insertions(+), 33 deletions(-)
 delete mode 100644 Libraries/LibCrypto/NumberTheory/ModularFunctions.cpp

diff --git a/Libraries/LibCrypto/BigFraction/BigFraction.cpp b/Libraries/LibCrypto/BigFraction/BigFraction.cpp
index 0bf8025faf9..81b091d972a 100644
--- a/Libraries/LibCrypto/BigFraction/BigFraction.cpp
+++ b/Libraries/LibCrypto/BigFraction/BigFraction.cpp
@@ -221,7 +221,7 @@ BigFraction BigFraction::rounded(unsigned rounding_threshold) const
 
 void BigFraction::reduce()
 {
-    auto const gcd = NumberTheory::GCD(m_numerator.unsigned_value(), m_denominator);
+    auto const gcd = m_numerator.unsigned_value().gcd(m_denominator);
 
     if (gcd == 1)
         return;
diff --git a/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp b/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp
index 641ab4bc3c4..aed8850487e 100644
--- a/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp
+++ b/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp
@@ -547,6 +547,19 @@ FLATTEN UnsignedDivisionResult UnsignedBigInteger::divided_by(UnsignedBigInteger
     return UnsignedDivisionResult { quotient, remainder };
 }
 
+FLATTEN UnsignedBigInteger UnsignedBigInteger::gcd(UnsignedBigInteger const& other) const
+{
+    UnsignedBigInteger temp_a { *this };
+    UnsignedBigInteger temp_b { other };
+    UnsignedBigInteger temp_quotient;
+    UnsignedBigInteger temp_remainder;
+    UnsignedBigInteger output;
+
+    UnsignedBigIntegerAlgorithms::destructive_GCD_without_allocation(temp_a, temp_b, temp_quotient, temp_remainder, output);
+
+    return output;
+}
+
 u32 UnsignedBigInteger::hash() const
 {
     if (m_cached_hash != 0)
diff --git a/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h b/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h
index 82b61107d68..f626fc93efc 100644
--- a/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h
+++ b/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h
@@ -109,6 +109,7 @@ public:
     [[nodiscard]] UnsignedBigInteger as_n_bits(size_t n) const;
     [[nodiscard]] UnsignedBigInteger multiplied_by(UnsignedBigInteger const& other) const;
     [[nodiscard]] UnsignedDivisionResult divided_by(UnsignedBigInteger const& divisor) const;
+    [[nodiscard]] UnsignedBigInteger gcd(UnsignedBigInteger const& other) const;
 
     [[nodiscard]] ErrorOr<UnsignedBigInteger> try_bitwise_not_fill_to_one_based_index(size_t) const;
     [[nodiscard]] ErrorOr<UnsignedBigInteger> try_shift_left(size_t num_bits) const;
diff --git a/Libraries/LibCrypto/CMakeLists.txt b/Libraries/LibCrypto/CMakeLists.txt
index eef134df949..9370208bcd3 100644
--- a/Libraries/LibCrypto/CMakeLists.txt
+++ b/Libraries/LibCrypto/CMakeLists.txt
@@ -26,7 +26,6 @@ set(SOURCES
     Hash/PBKDF2.cpp
     Hash/SHA1.cpp
     Hash/SHA2.cpp
-    NumberTheory/ModularFunctions.cpp
     PK/RSA.cpp
     PK/EC.cpp
     SecureRandom.cpp
diff --git a/Libraries/LibCrypto/NumberTheory/ModularFunctions.cpp b/Libraries/LibCrypto/NumberTheory/ModularFunctions.cpp
deleted file mode 100644
index 5a464d6de82..00000000000
--- a/Libraries/LibCrypto/NumberTheory/ModularFunctions.cpp
+++ /dev/null
@@ -1,28 +0,0 @@
-/*
- * Copyright (c) 2020, Ali Mohammad Pur <mpfard@serenityos.org>
- *
- * SPDX-License-Identifier: BSD-2-Clause
- */
-
-#include <AK/Debug.h>
-#include <AK/Random.h>
-#include <LibCrypto/BigInt/Algorithms/UnsignedBigIntegerAlgorithms.h>
-#include <LibCrypto/NumberTheory/ModularFunctions.h>
-#include <LibCrypto/SecureRandom.h>
-
-namespace Crypto::NumberTheory {
-
-UnsignedBigInteger GCD(UnsignedBigInteger const& a, UnsignedBigInteger const& b)
-{
-    UnsignedBigInteger temp_a { a };
-    UnsignedBigInteger temp_b { b };
-    UnsignedBigInteger temp_quotient;
-    UnsignedBigInteger temp_remainder;
-    UnsignedBigInteger output;
-
-    UnsignedBigIntegerAlgorithms::destructive_GCD_without_allocation(temp_a, temp_b, temp_quotient, temp_remainder, output);
-
-    return output;
-}
-
-}
diff --git a/Libraries/LibCrypto/NumberTheory/ModularFunctions.h b/Libraries/LibCrypto/NumberTheory/ModularFunctions.h
index b63dcc252e6..7a2e0924fc7 100644
--- a/Libraries/LibCrypto/NumberTheory/ModularFunctions.h
+++ b/Libraries/LibCrypto/NumberTheory/ModularFunctions.h
@@ -34,6 +34,4 @@ static IntegerType Power(IntegerType const& b, IntegerType const& e)
     return exp;
 }
 
-UnsignedBigInteger GCD(UnsignedBigInteger const& a, UnsignedBigInteger const& b);
-
 }
diff --git a/Meta/gn/secondary/Userland/Libraries/LibCrypto/BUILD.gn b/Meta/gn/secondary/Userland/Libraries/LibCrypto/BUILD.gn
index 06173b61fbb..dfaa6577daf 100644
--- a/Meta/gn/secondary/Userland/Libraries/LibCrypto/BUILD.gn
+++ b/Meta/gn/secondary/Userland/Libraries/LibCrypto/BUILD.gn
@@ -36,7 +36,6 @@ shared_library("LibCrypto") {
     "Hash/MD5.cpp",
     "Hash/SHA1.cpp",
     "Hash/SHA2.cpp",
-    "NumberTheory/ModularFunctions.cpp",
     "PK/RSA.cpp",
     "SecureRandom.cpp",
   ]