From 04eeb4ff13563ec098401d5253565f94958730c0 Mon Sep 17 00:00:00 2001
From: Zelda Hessler <zhessler@amazon.com>
Date: Wed, 15 Jun 2022 15:18:20 -0500
Subject: [PATCH] update: simplify and fix a latent issue with bytestream's
 streaming impl (#1461)

update: print helpful panic message for users on 32bit systems that try to stream large bodies
update: CHANGELOG.next.toml
---
 CHANGELOG.next.toml                           |  9 ++++++
 .../aws-smithy-http/src/byte_stream.rs        | 31 ++++++++++---------
 2 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/CHANGELOG.next.toml b/CHANGELOG.next.toml
index 79ce9f47c1..05fa4cd30f 100644
--- a/CHANGELOG.next.toml
+++ b/CHANGELOG.next.toml
@@ -17,6 +17,15 @@ references = ["aws-sdk-rust#547", "smithy-rs#1458"]
 meta = { "breaking" = false, "tada" = false, "bug" = true }
 author = "rcoh"
 
+[[smithy-rs]]
+message = """
+Fix a potential bug with `ByteStream`'s implementation of `futures_core::stream::Stream` and add helpful error messages
+for users on 32-bit systems that try to stream HTTP bodies larger than 4.29Gb.
+"""
+references = ["smithy-rs#1460"]
+meta = { "breaking" = false, "tada" = false, "bug" = false }
+author = "Velfi"
+
 [[aws-sdk-rust]]
 message = "Add `Debug` implementation to several types in `aws-config`"
 references = ["smithy-rs#1421"]
diff --git a/rust-runtime/aws-smithy-http/src/byte_stream.rs b/rust-runtime/aws-smithy-http/src/byte_stream.rs
index a8c18d28ed..e9b3c0ccc9 100644
--- a/rust-runtime/aws-smithy-http/src/byte_stream.rs
+++ b/rust-runtime/aws-smithy-http/src/byte_stream.rs
@@ -546,31 +546,32 @@ impl Inner<SdkBody> {
     }
 }
 
+const SIZE_HINT_32_BIT_PANIC_MESSAGE: &str = r#"
+You're running a 32-bit system and this stream's length is too large to be represented with a usize.
+Please limit stream length to less than 4.294Gb or run this program on a 64-bit computer architecture.
+"#;
+
 impl<B> futures_core::stream::Stream for Inner<B>
 where
-    B: http_body::Body,
+    B: http_body::Body<Data = Bytes>,
 {
     type Item = Result<Bytes, B::Error>;
 
     fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        match self.project().body.poll_data(cx) {
-            Poll::Ready(Some(Ok(mut data))) => {
-                let len = data.chunk().len();
-                let bytes = data.copy_to_bytes(len);
-                Poll::Ready(Some(Ok(bytes)))
-            }
-            Poll::Ready(None) => Poll::Ready(None),
-            Poll::Ready(Some(Err(e))) => Poll::Ready(Some(Err(e))),
-            Poll::Pending => Poll::Pending,
-        }
+        self.project().body.poll_data(cx)
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
         let size_hint = http_body::Body::size_hint(&self.body);
-        (
-            size_hint.lower() as usize,
-            size_hint.upper().map(|u| u as usize),
-        )
+        let lower = size_hint.lower().try_into();
+        let upper = size_hint.upper().map(|u| u.try_into()).transpose();
+
+        match (lower, upper) {
+            (Ok(lower), Ok(upper)) => (lower, upper),
+            (Err(_), _) | (_, Err(_)) => {
+                panic!("{}", SIZE_HINT_32_BIT_PANIC_MESSAGE)
+            }
+        }
     }
 }