Everywhere: Hoist the Libraries folder to the top-level

Author: https://github.com/trflynn89
Commit: https://github.com/LadybirdBrowser/ladybird/commit/93712b24bf2
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2256
Reviewed-by: https://github.com/sideshowbarker

Libraries/LibCrypto/BigInt/Algorithms/Multiplication.cpp

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * Copyright (c) 2020-2021, Dex♪ <dexes.ttp@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "UnsignedBigIntegerAlgorithms.h"
+
+namespace Crypto {
+
+/**
+ * Complexity: O(N^2) where N is the number of words in the larger number
+ * Multiplication method:
+ * An integer is equal to the sum of the powers of two
+ * according to the indices of its 'on' bits.
+ * So to multiple x*y, we go over each '1' bit in x (say the i'th bit),
+ * and add y<<i to the result.
+ */
+FLATTEN void UnsignedBigIntegerAlgorithms::multiply_without_allocation(
+    UnsignedBigInteger const& left,
+    UnsignedBigInteger const& right,
+    UnsignedBigInteger& temp_shift_result,
+    UnsignedBigInteger& temp_shift_plus,
+    UnsignedBigInteger& temp_shift,
+    UnsignedBigInteger& output)
+{
+    output.set_to_0();
+
+    // iterate all bits
+    for (size_t word_index = 0; word_index < left.length(); ++word_index) {
+        for (size_t bit_index = 0; bit_index < UnsignedBigInteger::BITS_IN_WORD; ++bit_index) {
+            // If the bit is off - skip over it
+            if (!(left.m_words[word_index] & (1 << bit_index)))
+                continue;
+
+            size_t shift_amount = word_index * UnsignedBigInteger::BITS_IN_WORD + bit_index;
+
+            // output += (right << shift_amount);
+            shift_left_without_allocation(right, shift_amount, temp_shift_result, temp_shift_plus, temp_shift);
+            add_into_accumulator_without_allocation(output, temp_shift);
+        }
+    }
+}
+
+}