[SDK] Add unaligned.h header for safely accessing unaligned variables

This supersedes RtlStoreUshort/RtlRetrieveUshort etc, which have a horrible interface and are inherently unsafe.

sdk/include/reactos/unaligned.h

@@ -0,0 +1,147 @@
+/*
+ * PROJECT:     ReactOS SDK
+ * LICENSE:     MIT (https://spdx.org/licenses/MIT)
+ * PURPOSE:     Unaligened access helper functions
+ * COPYRIGHT:   Copyright 2024 Timo Kreuzer <timo.kreuzer@reactos.org>
+ */
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if defined(_M_IX86) || defined(_M_AMD64)
+#define _UNALIGNED_ACCESS_ALLOWED 1
+#else // defined(_M_IX86) || defined(_M_AMD64)
+#define _UNALIGNED_ACCESS_ALLOWED 0
+#endif // defined(_M_IX86) || defined(_M_AMD64)
+
+#if _UNALIGNED_ACCESS_ALLOWED
+
+__forceinline
+unsigned short
+ReadUnalignedU16(const unsigned short* p)
+{
+    return *p;
+}
+
+__forceinline
+unsigned long
+ReadUnalignedU32(const unsigned long* p)
+{
+    return *p;
+}
+
+__forceinline
+unsigned long long
+ReadUnalignedU64(const unsigned long long* p)
+{
+    return *p;
+}
+
+__forceinline
+void
+WriteUnalignedU16(unsigned short* p, unsigned short val)
+{
+    *p = val;
+}
+
+__forceinline
+void
+WriteUnalignedU32(unsigned long* p, unsigned long val)
+{
+    *p = val;
+}
+
+__forceinline
+void
+WriteUnalignedU64(unsigned long long* p, unsigned long long val)
+{
+    *p = val;
+}
+
+#else // !UNALIGNED_ACCESS_ALLOWED
+
+__forceinline
+unsigned short
+ReadUnalignedU16(const unsigned short* p)
+{
+    unsigned char* p1 = (unsigned char*)p;
+    return (unsigned short)(p1[0] | (p1[1] << 8));
+}
+
+__forceinline
+unsigned long
+ReadUnalignedU32(const unsigned long* p)
+{
+    unsigned char* p1 = (unsigned char*)p;
+    return (((unsigned long)p1[0] << 0) |
+            ((unsigned long)p1[1] << 8) |
+            ((unsigned long)p1[2] << 16) |
+            ((unsigned long)p1[3] << 24));
+}
+
+__forceinline
+unsigned long long
+ReadUnalignedU64(const unsigned long long* p)
+{
+    unsigned char* p1 = (unsigned char*)p;
+    return (((unsigned long long)p1[0] << 0)  |
+            ((unsigned long long)p1[1] << 8)  |
+            ((unsigned long long)p1[2] << 16) |
+            ((unsigned long long)p1[3] << 24) |
+            ((unsigned long long)p1[4] << 32) |
+            ((unsigned long long)p1[5] << 40) |
+            ((unsigned long long)p1[6] << 48) |
+         ((unsigned long long)p1[7] << 56));
+}
+
+__forceinline
+void
+WriteUnalignedU16(unsigned short* p, unsigned short val)
+{
+    unsigned char* p1 = (unsigned char*)p;
+    p1[0] = (unsigned char)(val >> 0);
+    p1[1] = (unsigned char)(val >> 8);
+}
+
+__forceinline
+void
+WriteUnalignedU32(unsigned long* p, unsigned long val)
+{
+    unsigned char* p1 = (unsigned char*)p;
+    p1[0] = (unsigned char)(val >> 0);
+    p1[1] = (unsigned char)(val >> 8);
+    p1[2] = (unsigned char)(val >> 16);
+    p1[3] = (unsigned char)(val >> 24);
+}
+
+__forceinline
+void
+WriteUnalignedU64(unsigned long long* p, unsigned long long val)
+{
+    unsigned char* p1 = (unsigned char*)p;
+    p1[0] = (unsigned char)(val >> 0);
+    p1[1] = (unsigned char)(val >> 8);
+    p1[2] = (unsigned char)(val >> 16);
+    p1[3] = (unsigned char)(val >> 24);
+    p1[4] = (unsigned char)(val >> 32);
+    p1[5] = (unsigned char)(val >> 40);
+    p1[6] = (unsigned char)(val >> 48);
+    p1[7] = (unsigned char)(val >> 56);
+}
+
+#endif // !UNALIGNED_ACCESS_ALLOWED
+
+#ifdef _WIN64
+#define ReadUnalignedUlongPtr ReadUnalignedU64
+#define WriteUnalignedUlongPtr WriteUnalignedU64
+#else // _WIN64
+#define ReadUnalignedUlongPtr ReadUnalignedU32
+#define WriteUnalignedUlongPtr WriteUnalignedU32
+#endif // _WIN64
+
+#ifdef __cplusplus
+} // extern "C"
+#endif