From c87fc693702a368ab50246d08d1fd75ce31ab93c Mon Sep 17 00:00:00 2001
From: Anthony Shoumikhin <shoumikhin@meta.com>
Date: Tue, 25 Mar 2025 11:21:44 -0700
Subject: [PATCH] Utility helper to deduce scalar type from NSNumber. (#9552)

Summary:

.

Reviewed By: mergennachin

Differential Revision: D71752750
---
 .../ExecuTorch/Internal/ExecuTorchUtils.h     | 37 +++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/extension/apple/ExecuTorch/Internal/ExecuTorchUtils.h b/extension/apple/ExecuTorch/Internal/ExecuTorchUtils.h
index e53999cd355..d514a101383 100644
--- a/extension/apple/ExecuTorch/Internal/ExecuTorchUtils.h
+++ b/extension/apple/ExecuTorch/Internal/ExecuTorchUtils.h
@@ -7,3 +7,40 @@
  */
 
 #import <Foundation/Foundation.h>
+
+#ifdef __cplusplus
+
+#import <executorch/runtime/core/exec_aten/exec_aten.h>
+
+namespace executorch::extension::utils {
+using namespace aten;
+
+/**
+ * Deduces the scalar type for a given NSNumber based on its type encoding.
+ *
+ * @param number The NSNumber instance whose scalar type is to be deduced.
+ * @return The corresponding ScalarType.
+ */
+static inline ScalarType deduceScalarType(NSNumber *number) {
+  auto type = [number objCType][0];
+  type = (type >= 'A' && type <= 'Z') ? type + ('a' - 'A') : type;
+  if (type == 'c') {
+    return ScalarType::Byte;
+  } else if (type == 's') {
+    return ScalarType::Short;
+  } else if (type == 'i') {
+    return ScalarType::Int;
+  } else if (type == 'q' || type == 'l') {
+    return ScalarType::Long;
+  } else if (type == 'f') {
+    return ScalarType::Float;
+  } else if (type == 'd') {
+    return ScalarType::Double;
+  }
+  ET_CHECK_MSG(false, "Unsupported type: %c", type);
+  return ScalarType::Undefined;
+}
+
+} // namespace executorch::extension::utils
+
+#endif // __cplusplus