wpiutil: Add unique_function (#1761)

This is a move-only variant of std::function to support move-only captures.

Imported from LLVM with some small tweaks (changed to 4 pointer internal storage, warnings fixes).

wpiutil/src/main/native/include/wpi/Compiler.h

@@ -15,6 +15,9 @@
 #ifndef WPIUTIL_WPI_COMPILER_H
 #define WPIUTIL_WPI_COMPILER_H
 
+#include <new>
+#include <stddef.h>
+
 #if defined(_MSC_VER)
 #include <sal.h>
 #endif
@@ -468,4 +471,46 @@
 #endif
 #endif
 
+namespace wpi {
+
+/// Allocate a buffer of memory with the given size and alignment.
+///
+/// When the compiler supports aligned operator new, this will use it to to
+/// handle even over-aligned allocations.
+///
+/// However, this doesn't make any attempt to leverage the fancier techniques
+/// like posix_memalign due to portability. It is mostly intended to allow
+/// compatibility with platforms that, after aligned allocation was added, use
+/// reduced default alignment.
+inline void *allocate_buffer(size_t Size, size_t Alignment) {
+  return ::operator new(Size
+#ifdef __cpp_aligned_new
+                        ,
+                        std::align_val_t(Alignment)
+#endif
+  );
+}
+
+/// Deallocate a buffer of memory with the given size and alignment.
+///
+/// If supported, this will used the sized delete operator. Also if supported,
+/// this will pass the alignment to the delete operator.
+///
+/// The pointer must have been allocated with the corresponding new operator,
+/// most likely using the above helper.
+inline void deallocate_buffer(void *Ptr, size_t Size, size_t Alignment) {
+  ::operator delete(Ptr
+#ifdef __cpp_sized_deallocation
+                    ,
+                    Size
+#endif
+#ifdef __cpp_aligned_new
+                    ,
+                    std::align_val_t(Alignment)
+#endif
+  );
+}
+
+} // End namespace wpi
+
 #endif