[executorch][core] NamedDataMap interface

Pull Request resolved: #7763

Add NamedDataMap interface to runtime.
ghstack-source-id: 262787385
@exported-using-ghexport

Differential Revision: [D66834552](https://our.internmc.facebook.com/intern/diff/D66834552/)

Author: lucylq

runtime/core/named_data_map.h

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <executorch/runtime/core/exec_aten/exec_aten.h>
+#include <executorch/runtime/core/freeable_buffer.h>
+#include <executorch/runtime/core/result.h>
+#include <executorch/runtime/core/span.h>
+#include <executorch/runtime/core/tensor_layout.h>
+#include <executorch/runtime/platform/compiler.h>
+
+namespace executorch {
+namespace runtime {
+
+/**
+ * Interface to access and retrieve data via name.
+ * See executorch/extension/flat_tensor/ for an example.
+ */
+class ET_EXPERIMENTAL NamedDataMap {
+ public:
+  virtual ~NamedDataMap() = default;
+  /**
+   * Get tensor metadata by fully qualified name (FQN).
+   *
+   * @param fqn Fully qualified name of the tensor.
+   * @return Result containing TensorLayout with tensor metadata.
+   */
+  ET_NODISCARD virtual Result<const executorch::runtime::TensorLayout>
+  get_metadata(const char* fqn) const = 0;
+  /**
+   * Get tensor data by fully qualified name (FQN).
+   *
+   * @param fqn Fully qualified name of the tensor.
+   * @return Result containing a FreeableBuffer with the tensor data.
+   */
+  ET_NODISCARD virtual Result<FreeableBuffer> get_data(
+      const char* fqn) const = 0;
+
+  /**
+   * Loads data corresponding to the fqn into the provided buffer.
+   *
+   * @param fqn Fully qualified name of the tensor.
+   * @param size The number of bytes to load.
+   * @param buffer The buffer to load the data into. Must point to at least
+   * `size` bytes of memory.
+   * @return An error code on if the load was successful.
+   */
+  ET_NODISCARD virtual Error
+  load_data_into(const char* fqn, size_t size, void* buffer);
+
+  /**
+   * Get the number of keys in the NamedDataMap.
+   *
+   * @return Result containing the number of keys.
+   */
+  ET_NODISCARD virtual Result<int> get_num_keys() const = 0;
+
+  /**
+   * Get the key at the given index.
+   *
+   * @param index The index of the key to retrieve.
+   * @return Result containing the key at the given index.
+   */
+  ET_NODISCARD virtual Result<const char*> get_key(int index) const = 0;
+};
+
+} // namespace runtime
+} // namespace executorch

runtime/core/targets.bzl

@@ -41,6 +41,7 @@ def define_common_targets():
             "defines.h",
             "error.h",
             "freeable_buffer.h",
+            "named_data_map.h",
             "result.h",
             "span.h",
             "tensor_layout.h",