From f70c36eff006526f66f61a4c0ff53f9f5369028b Mon Sep 17 00:00:00 2001
From: Yinuo Deng <i@dyn.im>
Date: Fri, 14 Apr 2023 23:32:45 +0800
Subject: [PATCH] Automatically use no_chunking if user specifies stream size

---
 actix-web/src/response/builder.rs | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/actix-web/src/response/builder.rs b/actix-web/src/response/builder.rs
index c454ee6da..bcbb01000 100644
--- a/actix-web/src/response/builder.rs
+++ b/actix-web/src/response/builder.rs
@@ -334,6 +334,27 @@ impl HttpResponseBuilder {
             self.insert_header((header::CONTENT_TYPE, mime::APPLICATION_OCTET_STREAM));
         }
 
+        let contains_length = if let Some(parts) = self.inner() {
+            parts.headers.contains_key(header::CONTENT_LENGTH)
+        } else {
+            false
+        };
+
+        if contains_length {
+            // Since contains_length is true, these two lines will not panic
+            let parts = self.inner().unwrap();
+            let length = parts.headers.get(header::CONTENT_LENGTH).unwrap().to_str();
+
+            if let Ok(length) = length { // length is now of type &str
+                if let Ok(length) = length.parse::<u64>() { //length is now of type u64
+                    // Set no_chunking
+                    // Since no_chuking() uses insert_header(),
+                    // this will not lead to duplicated header even if it exists
+                    self.no_chunking(length);
+                }
+            }
+        }
+
         self.body(BodyStream::new(stream))
     }