Fixes and improvements (#616)

TactilityKernelCpp/Include/TactilityCpp/Allocator.h

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: Apache-2.0
+#pragma once
+
+#include <tactility/memory.h>
+
+#include <cstdint>
+#include <cstdlib>
+#include <cstddef>
+
+namespace tt {
+
+/** Allocator backed by tactility/memory.h's memory_alloc_with_policy(), with Required/Desired as
+ * its required/desired MemoryCapability flags (bitwise-OR'd, e.g. MEMORY_CAPABILITY_EXTERNAL). */
+template<typename T, uint16_t Required = 0, uint16_t Desired = 0>
+struct Allocator {
+    using value_type = T;
+
+    // libstdc++'s default rebind_alloc only pattern-matches allocator templates whose parameters
+    // are all types, which Required/Desired (non-type) breaks; spelling it out here restores it.
+    template<typename U> struct rebind { using other = Allocator<U, Required, Desired>; };
+
+    Allocator() noexcept = default;
+    template<typename U> constexpr Allocator(const Allocator<U, Required, Desired>&) noexcept {}
+
+    T* allocate(std::size_t n) {
+        const MemoryPolicy policy { .required = Required, .desired = Desired, .alignment = alignof(T) };
+        void* ptr = memory_alloc_with_policy(n * sizeof(T), &policy);
+        if (ptr == nullptr) {
+            std::abort(); // Exceptions are disabled project-wide, so OOM can't be signalled via std::bad_alloc.
+        }
+        return static_cast<T*>(ptr);
+    }
+
+    void deallocate(T* ptr, std::size_t) noexcept {
+        memory_free(ptr);
+    }
+};
+
+template<typename T, typename U, uint16_t Required, uint16_t Desired>
+bool operator==(const Allocator<T, Required, Desired>&, const Allocator<U, Required, Desired>&) noexcept { return true; }
+
+/** Prefers external memory, falling back to internal RAM when unavailable. */
+template<typename T>
+using OptExternalAllocator = Allocator<T, 0, MEMORY_CAPABILITY_EXTERNAL>;
+
+} // namespace tt