Force large c++ arrays into PSRAM

This is mostly targetted at leveldb_ which is rude and does not support
custom allocators

src/util/CMakeLists.txt

@@ -3,5 +3,6 @@
 # SPDX-License-Identifier: GPL-3.0-only
 
 idf_component_register(
+  SRCS "allocator.cpp"
   INCLUDE_DIRS "include"
   REQUIRES "database")

src/util/allocator.cpp

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <cstdint>
+
+#include "esp_heap_caps.h"
+
+void* operator new[](std::size_t sz) {
+  if (sz == 0) {
+    ++sz;  // avoid std::malloc(0) which may return nullptr on success
+  }
+
+  if (sz > 256) {
+    return heap_caps_malloc(sz, MALLOC_CAP_SPIRAM);
+  }
+
+  return heap_caps_malloc(sz, MALLOC_CAP_DEFAULT);
+}
+
+void operator delete[](void* ptr) noexcept {
+  heap_caps_free(ptr);
+}
+
+void operator delete[](void* ptr, std::size_t size) noexcept {
+  heap_caps_free(ptr);
+}