LibJS: Add all of the DataView.prototype.set* methods

Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp

@@ -55,6 +55,14 @@ String SignedBigInteger::to_base10() const
     return builder.to_string();
 }
 
+u64 SignedBigInteger::to_u64() const
+{
+    u64 unsigned_value = m_unsigned_data.to_u64();
+    if (!m_sign)
+        return unsigned_value;
+    return ~(unsigned_value - 1); // equivalent to `-unsigned_value`, but doesnt trigger UBSAN
+}
+
 FLATTEN SignedBigInteger SignedBigInteger::plus(const SignedBigInteger& other) const
 {
     // If both are of the same sign, just add the unsigned data and return.

Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h

@@ -65,6 +65,8 @@ public:
     static SignedBigInteger from_base10(StringView str);
     String to_base10() const;
 
+    u64 to_u64() const;
+
     const UnsignedBigInteger& unsigned_value() const { return m_unsigned_data; }
     const Vector<u32, STARTING_WORD_SIZE> words() const { return m_unsigned_data.words(); }
     bool is_negative() const { return m_sign; }

Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp

@@ -102,6 +102,17 @@ String UnsignedBigInteger::to_base10() const
     return builder.to_string();
 }
 
+u64 UnsignedBigInteger::to_u64() const
+{
+    VERIFY(sizeof(Word) == 4);
+    if (!length())
+        return 0;
+    u64 value = m_words[0];
+    if (length() > 1)
+        value |= static_cast<u64>(m_words[1]) << 32;
+    return value;
+}
+
 void UnsignedBigInteger::set_to_0()
 {
     m_words.clear_with_capacity();

Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h

@@ -56,6 +56,8 @@ public:
     static UnsignedBigInteger from_base10(const String& str);
     String to_base10() const;
 
+    u64 to_u64() const;
+
     const Vector<Word, STARTING_WORD_SIZE>& words() const { return m_words; }
 
     void set_to_0();