2 files changed, 79 insertions, 1 deletions
diff --git a/src/memory/CMakeLists.txt b/src/memory/CMakeLists.txt
index 67e64267..69afc454 100644
--- a/src/memory/CMakeLists.txt
+++ b/src/memory/CMakeLists.txt
@@ -1,2 +1,2 @@
-idf_component_register(SRCS "arena.cpp" INCLUDE_DIRS "include" REQUIRES "span")
+idf_component_register(SRCS "arena.cpp" INCLUDE_DIRS "include" REQUIRES "span" "esp_psram")
 target_compile_options(${COMPONENT_LIB} PRIVATE ${EXTRA_WARNINGS})
diff --git a/src/memory/include/himem.hpp b/src/memory/include/himem.hpp
new file mode 100644
index 00000000..c65091d7
--- /dev/null
+++ b/src/memory/include/himem.hpp
@@ -0,0 +1,78 @@
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+
+#include "esp32/himem.h"
+#include "span.hpp"
+
+/*
+ * Wrapper around an ESP-IDF himem allocation, which uses RAII to clean up after
+ * itself.
+ */
+template <std::size_t size>
+class HimemAlloc {
+ public:
+  esp_himem_handle_t handle;
+  const bool is_valid;
+
+  HimemAlloc() : is_valid(esp_himem_alloc(size, &handle) == ESP_OK) {}
+
+  ~HimemAlloc() {
+    if (is_valid) {
+      esp_himem_free(handle);
+    }
+  }
+
+  // Not copyable or movable.
+  HimemAlloc(const HimemAlloc&) = delete;
+  HimemAlloc& operator=(const HimemAlloc&) = delete;
+};
+
+/*
+ * Wrapper around an ESP-IDF himem allocation, which maps a HimemAlloc into the
+ * usable address space. Instances always contain the last memory region that
+ * was mapped within them.
+ */
+template <std::size_t size>
+class MappableRegion {
+ private:
+  std::byte* bytes_;
+
+ public:
+  esp_himem_rangehandle_t range_handle;
+  const bool is_valid;
+
+  MappableRegion()
+      : bytes_(nullptr),
+        is_valid(esp_himem_alloc_map_range(size, &range_handle) == ESP_OK) {}
+
+  ~MappableRegion() {
+    if (bytes_ != nullptr) {
+      esp_himem_unmap(range_handle, bytes_, size);
+    }
+    if (is_valid) {
+      esp_himem_free_map_range(range_handle);
+    }
+  }
+
+  auto Get() -> cpp::span<std::byte> {
+    if (bytes_ != nullptr) {
+      return {};
+    }
+    return {bytes_, size};
+  }
+
+  auto Map(const HimemAlloc<size> &alloc) -> cpp::span<std::byte> {
+    if (bytes_ != nullptr) {
+      ESP_ERROR_CHECK(esp_himem_unmap(range_handle, bytes_, size));
+    }
+    ESP_ERROR_CHECK(esp_himem_map(alloc.handle, range_handle, 0, 0, size, 0,
+                                  reinterpret_cast<void**>(&bytes_)));
+    return Get();
+  }
+
+  // Not copyable or movable.
+  MappableRegion(const MappableRegion&) = delete;
+  MappableRegion& operator=(const MappableRegion&) = delete;
+};