From e99dabc729f998d04fcd759528c8799df6fff4d4 Mon Sep 17 00:00:00 2001
From: Oleg Sikorskiy <olegsik@gmail.com>
Date: Mon, 22 Mar 2021 21:25:06 +0300
Subject: [PATCH] AK: Implement bit_cast

---
 AK/BitCast.h             | 43 ++++++++++++++++++++++++++++++++++++++
 AK/Tests/CMakeLists.txt  |  1 +
 AK/Tests/TestBitCast.cpp | 45 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 89 insertions(+)
 create mode 100644 AK/BitCast.h
 create mode 100644 AK/Tests/TestBitCast.cpp

diff --git a/AK/BitCast.h b/AK/BitCast.h
new file mode 100644
index 00000000000..475d5ac57e8
--- /dev/null
+++ b/AK/BitCast.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+namespace AK {
+
+template<typename T, typename U>
+inline T bit_cast(const U& a)
+{
+    static_assert(sizeof(T) == sizeof(U));
+
+    T result;
+    __builtin_memcpy(&result, &a, sizeof(T));
+    return result;
+}
+
+}
+
+using AK::bit_cast;
diff --git a/AK/Tests/CMakeLists.txt b/AK/Tests/CMakeLists.txt
index 3d5bc360a25..391bfbd0e06 100644
--- a/AK/Tests/CMakeLists.txt
+++ b/AK/Tests/CMakeLists.txt
@@ -9,6 +9,7 @@ set(AK_TEST_SOURCES
     TestBase64.cpp
     TestBinaryHeap.cpp
     TestBinarySearch.cpp
+    TestBitCast.cpp
     TestBitmap.cpp
     TestByteBuffer.cpp
     TestChecked.cpp
diff --git a/AK/Tests/TestBitCast.cpp b/AK/Tests/TestBitCast.cpp
new file mode 100644
index 00000000000..b251dbe9a11
--- /dev/null
+++ b/AK/Tests/TestBitCast.cpp
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/TestSuite.h>
+
+#include <AK/BitCast.h>
+
+template<typename A, typename B>
+void check_cast_both_ways(const A& a, const B& b)
+{
+    EXPECT_EQ((bit_cast<A, B>(b)), a);
+    EXPECT_EQ((bit_cast<B, A>(a)), b);
+}
+
+TEST_CASE(double_int_conversion)
+{
+    check_cast_both_ways(static_cast<u64>(0), 0.0);
+    check_cast_both_ways(static_cast<u64>(1) << 63, -0.0);
+    check_cast_both_ways(static_cast<u64>(0x4172f58bc0000000), 19880124.0);
+}
+
+TEST_MAIN(BitCast)