From bcdad5767006ca03728324c656b03888507f75a1 Mon Sep 17 00:00:00 2001
From: Idan Horowitz <idan.horowitz@gmail.com>
Date: Mon, 6 Sep 2021 21:20:20 +0300
Subject: [PATCH] LibCrypto: Add naive implementation of
 {Un,}SignedBigInteger::to_double

---
 Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp  | 8 ++++++++
 Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h    | 1 +
 .../Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp     | 6 ++++++
 Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h  | 1 +
 4 files changed, 16 insertions(+)

diff --git a/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp b/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp
index 3d6bdffa55b..1ff34050a6f 100644
--- a/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp
+++ b/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp
@@ -63,6 +63,14 @@ u64 SignedBigInteger::to_u64() const
     return ~(unsigned_value - 1); // equivalent to `-unsigned_value`, but doesnt trigger UBSAN
 }
 
+double SignedBigInteger::to_double() const
+{
+    double unsigned_value = m_unsigned_data.to_double();
+    if (!m_sign)
+        return unsigned_value;
+    return -unsigned_value;
+}
+
 FLATTEN SignedBigInteger SignedBigInteger::plus(const SignedBigInteger& other) const
 {
     // If both are of the same sign, just add the unsigned data and return.
diff --git a/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h b/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h
index 099348bfd7b..4440dd9f004 100644
--- a/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h
+++ b/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h
@@ -66,6 +66,7 @@ public:
     String to_base(u16 N) const;
 
     u64 to_u64() const;
+    double to_double() const;
 
     const UnsignedBigInteger& unsigned_value() const { return m_unsigned_data; }
     const Vector<u32, STARTING_WORD_SIZE> words() const { return m_unsigned_data.words(); }
diff --git a/Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp b/Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp
index 1f036af432b..a2c8d77ef7a 100644
--- a/Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp
+++ b/Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp
@@ -112,6 +112,12 @@ u64 UnsignedBigInteger::to_u64() const
     return value;
 }
 
+double UnsignedBigInteger::to_double() const
+{
+    // FIXME: I am naive
+    return static_cast<double>(to_u64());
+}
+
 void UnsignedBigInteger::set_to_0()
 {
     m_words.clear_with_capacity();
diff --git a/Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h b/Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h
index 9b9e1912472..2d899f96eac 100644
--- a/Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h
+++ b/Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h
@@ -57,6 +57,7 @@ public:
     String to_base(u16 N) const;
 
     u64 to_u64() const;
+    double to_double() const;
 
     const Vector<Word, STARTING_WORD_SIZE>& words() const { return m_words; }