From 42e61d3a6e069d1768fe356aa4689691c34dbbda Mon Sep 17 00:00:00 2001
From: Eugene Kozlov <nekoeuge@gmail.com>
Date: Sun, 20 Oct 2024 18:55:54 +0400
Subject: [PATCH] Restore Android SDK 21 support.

---
 BuildTools/Android/tests/build.gradle    |  2 +-
 Common/src/DefaultRawMemoryAllocator.cpp | 33 ++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/BuildTools/Android/tests/build.gradle b/BuildTools/Android/tests/build.gradle
index 7e47ed99e..6d6ae069a 100644
--- a/BuildTools/Android/tests/build.gradle
+++ b/BuildTools/Android/tests/build.gradle
@@ -9,7 +9,7 @@ android {
     defaultConfig {
         applicationId 		'DE.Android.Tests'
         targetSdkVersion 	32
-        minSdkVersion 		28
+        minSdkVersion 		21
 
         ndk {
             abiFilters = []
diff --git a/Common/src/DefaultRawMemoryAllocator.cpp b/Common/src/DefaultRawMemoryAllocator.cpp
index 84b62ac46..2cd9a125c 100644
--- a/Common/src/DefaultRawMemoryAllocator.cpp
+++ b/Common/src/DefaultRawMemoryAllocator.cpp
@@ -39,6 +39,35 @@
 namespace Diligent
 {
 
+namespace
+{
+
+void* AllocateAlignedFallback(size_t Size, size_t Alignment)
+{
+    constexpr size_t PointerSize       = sizeof(void*);
+    const size_t     AdjustedAlignment = (std::max)(Alignment, PointerSize);
+
+    void* Pointer        = malloc(Size + AdjustedAlignment + PointerSize);
+    void* AlignedPointer = AlignUp(reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(Pointer) + PointerSize), AdjustedAlignment);
+
+    void** StoredPointer = reinterpret_cast<void**>(AlignedPointer) - 1;
+    VERIFY_EXPR(StoredPointer >= Pointer);
+    *StoredPointer = Pointer;
+
+    return AlignedPointer;
+}
+
+void FreeAlignedFallback(void* Ptr)
+{
+    if (Ptr != nullptr)
+    {
+        void* OriginalPointer = *(reinterpret_cast<void**>(Ptr) - 1);
+        free(OriginalPointer);
+    }
+}
+
+} // namespace
+
 DefaultRawMemoryAllocator::DefaultRawMemoryAllocator()
 {
 }
@@ -66,6 +95,8 @@ void* DefaultRawMemoryAllocator::AllocateAligned(size_t Size, size_t Alignment,
     return _aligned_malloc_dbg(Size, Alignment, dbgFileName, dbgLineNumber);
 #elif defined(_MSC_VER) || defined(__MINGW64__) || defined(__MINGW32__)
     return _aligned_malloc(Size, Alignment);
+#elif PLATFORM_ANDROID && __ANDROID_API__ < 28
+    return AllocateAlignedFallback(Size, Alignment);
 #else
     return aligned_alloc(Alignment, Size);
 #endif
@@ -75,6 +106,8 @@ void DefaultRawMemoryAllocator::FreeAligned(void* Ptr)
 {
 #if defined(_MSC_VER) || defined(__MINGW64__) || defined(__MINGW32__)
     _aligned_free(Ptr);
+#elif PLATFORM_ANDROID && __ANDROID_API__ < 28
+    FreeAlignedFallback(Ptr);
 #else
     free(Ptr);
 #endif