add send_chunked_file to helpers file , in declare it in __init__.py

src/flask/__init__.py

@@ -25,6 +25,7 @@ from .helpers import get_template_attribute as get_template_attribute
 from .helpers import make_response as make_response
 from .helpers import safe_join as safe_join
 from .helpers import send_file as send_file
+from .helpers import send_chunked_file as send_chunked_file
 from .helpers import send_from_directory as send_from_directory
 from .helpers import stream_with_context as stream_with_context
 from .helpers import url_for as url_for

src/flask/helpers.py

@@ -626,6 +626,35 @@ def send_file(
         )
     )
 
+def send_chunked_file(filepath:str , chunk_size: int = 8192):
+    """ If you serve binary files, you should not iterate through lines since
+    it basically contains only one line, which means you still load the
+    whole file all at once into the RAM. The only proper
+    way to read largit checkout files is via chunks with this function: read_file_chunks(path, chunk_size)
+    send every chunks with stream_with_context function
+    :param filepath: file exists there . If not
+        provided, error occured.
+    :param chunk_size: defult size is 8192
+    """
+    name_splited = filepath.split('/')
+    filename = name_splited[len(name_splited) - 1]
+    def read_file_chunks(path, chunk_size):
+        with open(path, 'rb') as fd:
+            while 1:
+                buf = fd.read(chunk_size)
+                if buf:
+                    yield buf
+                else:
+                    break
+    if os.path.isfile(filepath):
+        return current_app.response_class(
+            stream_with_context(read_file_chunks(filepath, chunk_size)),
+            headers={
+                'Content-Disposition': f'attachment; filename={filename}'
+            }
+        )
+    else:
+        raise NotFound()
 
 def safe_join(directory: str, *pathnames: str) -> str:
     """Safely join zero or more untrusted path components to a base