From 8647201ac739506cdc692439ed8eb73bc259daea Mon Sep 17 00:00:00 2001
From: Edward Chen <18449977+edgchen1@users.noreply.github.com>
Date: Thu, 14 Nov 2019 14:21:05 -0800
Subject: [PATCH] Improved documentation for
 onnxruntime::utils::SwapByteOrderCopy(), added precondition check.

---
 onnxruntime/core/framework/endian_utils.cc |  4 ++++
 onnxruntime/core/framework/endian_utils.h  | 13 ++++++++-----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/onnxruntime/core/framework/endian_utils.cc b/onnxruntime/core/framework/endian_utils.cc
index 9fee46b22c..640ba8df29 100644
--- a/onnxruntime/core/framework/endian_utils.cc
+++ b/onnxruntime/core/framework/endian_utils.cc
@@ -32,6 +32,10 @@ void SwapByteOrderCopy(
   assert(element_size_in_bytes > 0);
   assert(source_bytes.size_bytes() % element_size_in_bytes == 0);
   assert(source_bytes.size_bytes() == destination_bytes.size_bytes());
+  // check non-overlapping
+  // given begin <= end, end0 <= begin1 || end1 <= begin0
+  assert(source_bytes.data() + source_bytes.size() <= destination_bytes.data() ||
+         destination_bytes.data() + destination_bytes.size() <= source_bytes.data());
 
   for (size_t element_offset = 0, element_offset_end = source_bytes.size_bytes();
        element_offset < element_offset_end;
diff --git a/onnxruntime/core/framework/endian_utils.h b/onnxruntime/core/framework/endian_utils.h
index 25f136705a..7da16e6709 100644
--- a/onnxruntime/core/framework/endian_utils.h
+++ b/onnxruntime/core/framework/endian_utils.h
@@ -14,11 +14,14 @@ namespace onnxruntime {
 namespace utils {
 
 /**
- * Swaps the byte order of elements in a buffer.
- * This is a low-level funtion - please be sure to pass in valid arguments.
- * In particular, source_bytes and destination_bytes should have the same size,
- * which should be a multiple of element_size_in_bytes. element_size_in_bytes
- * should also be greater than zero.
+ * Copies elements and swaps their byte orders.
+ *
+ * This is a low-level function - please be sure to pass in valid arguments.
+ * In particular:
+ * - source_bytes and destination_bytes should have the same size, which should
+ *   be a multiple of element_size_in_bytes.
+ * - element_size_in_bytes should be greater than zero.
+ * - source_bytes and destination_bytes should not overlap.
  *
  * @param element_size_in_bytes The size of an individual element, in bytes.
  * @param source_bytes The source byte span.