From 6a2e600b09044d14d58fe6d220e25580cc40864c Mon Sep 17 00:00:00 2001
From: katelyn martin <kate@buoyant.io>
Date: Mon, 13 Jan 2025 00:00:00 +0000
Subject: [PATCH] chore(http/retry): vendor `http_body::Frame<T>`

this vendors a copy of the `Frame<T>` type. we can use this to
preemptively model our peek body in terms of this type, and move to the
"real" version of it when we're upgrading in #3504.

Signed-off-by: katelyn martin <kate@buoyant.io>
---
 linkerd/http/retry/src/frame.rs | 131 ++++++++++++++++++++++++++++++++
 linkerd/http/retry/src/lib.rs   |   2 +
 2 files changed, 133 insertions(+)
 create mode 100644 linkerd/http/retry/src/frame.rs

diff --git a/linkerd/http/retry/src/frame.rs b/linkerd/http/retry/src/frame.rs
new file mode 100644
index 0000000000..3e03ca0ea2
--- /dev/null
+++ b/linkerd/http/retry/src/frame.rs
@@ -0,0 +1,131 @@
+#![allow(unused, reason = "this code is vendored from `http-body v1.0.1")]
+
+//! A frame of any kind related to an HTTP stream (body).
+//!
+//! NB: This is a vendored stand-in for [`Frame<T>`][frame], and and can be replaced once
+//! we upgrade from http-body 0.4 to 1.0. This file was vendored at commit 86fdf00.
+//!
+//! See linkerd/linkerd2#8733 for more information.
+//!
+//! [frame]: https://docs.rs/http-body/1.0.1/http_body/struct.Frame.html>
+
+use http::HeaderMap;
+
+/// A frame of any kind related to an HTTP stream (body).
+#[derive(Debug)]
+pub struct Frame<T> {
+    kind: Kind<T>,
+}
+
+#[derive(Debug)]
+enum Kind<T> {
+    // The first two variants are "inlined" since they are undoubtedly
+    // the most common. This saves us from having to allocate a
+    // boxed trait object for them.
+    Data(T),
+    Trailers(HeaderMap),
+    //Unknown(Box<dyn Frameish>),
+}
+
+impl<T> Frame<T> {
+    /// Create a DATA frame with the provided `Buf`.
+    pub fn data(buf: T) -> Self {
+        Self {
+            kind: Kind::Data(buf),
+        }
+    }
+
+    /// Create a trailers frame.
+    pub fn trailers(map: HeaderMap) -> Self {
+        Self {
+            kind: Kind::Trailers(map),
+        }
+    }
+
+    /// Maps this frame's data to a different type.
+    pub fn map_data<F, D>(self, f: F) -> Frame<D>
+    where
+        F: FnOnce(T) -> D,
+    {
+        match self.kind {
+            Kind::Data(data) => Frame {
+                kind: Kind::Data(f(data)),
+            },
+            Kind::Trailers(trailers) => Frame {
+                kind: Kind::Trailers(trailers),
+            },
+        }
+    }
+
+    /// Returns whether this is a DATA frame.
+    pub fn is_data(&self) -> bool {
+        matches!(self.kind, Kind::Data(..))
+    }
+
+    /// Consumes self into the buf of the DATA frame.
+    ///
+    /// Returns an [`Err`] containing the original [`Frame`] when frame is not a DATA frame.
+    /// `Frame::is_data` can also be used to determine if the frame is a DATA frame.
+    pub fn into_data(self) -> Result<T, Self> {
+        match self.kind {
+            Kind::Data(data) => Ok(data),
+            _ => Err(self),
+        }
+    }
+
+    /// If this is a DATA frame, returns a reference to it.
+    ///
+    /// Returns `None` if not a DATA frame.
+    pub fn data_ref(&self) -> Option<&T> {
+        match self.kind {
+            Kind::Data(ref data) => Some(data),
+            _ => None,
+        }
+    }
+
+    /// If this is a DATA frame, returns a mutable reference to it.
+    ///
+    /// Returns `None` if not a DATA frame.
+    pub fn data_mut(&mut self) -> Option<&mut T> {
+        match self.kind {
+            Kind::Data(ref mut data) => Some(data),
+            _ => None,
+        }
+    }
+
+    /// Returns whether this is a trailers frame.
+    pub fn is_trailers(&self) -> bool {
+        matches!(self.kind, Kind::Trailers(..))
+    }
+
+    /// Consumes self into the buf of the trailers frame.
+    ///
+    /// Returns an [`Err`] containing the original [`Frame`] when frame is not a trailers frame.
+    /// `Frame::is_trailers` can also be used to determine if the frame is a trailers frame.
+    pub fn into_trailers(self) -> Result<HeaderMap, Self> {
+        match self.kind {
+            Kind::Trailers(trailers) => Ok(trailers),
+            _ => Err(self),
+        }
+    }
+
+    /// If this is a trailers frame, returns a reference to it.
+    ///
+    /// Returns `None` if not a trailers frame.
+    pub fn trailers_ref(&self) -> Option<&HeaderMap> {
+        match self.kind {
+            Kind::Trailers(ref trailers) => Some(trailers),
+            _ => None,
+        }
+    }
+
+    /// If this is a trailers frame, returns a mutable reference to it.
+    ///
+    /// Returns `None` if not a trailers frame.
+    pub fn trailers_mut(&mut self) -> Option<&mut HeaderMap> {
+        match self.kind {
+            Kind::Trailers(ref mut trailers) => Some(trailers),
+            _ => None,
+        }
+    }
+}
diff --git a/linkerd/http/retry/src/lib.rs b/linkerd/http/retry/src/lib.rs
index 5aedecf8bf..5359165996 100644
--- a/linkerd/http/retry/src/lib.rs
+++ b/linkerd/http/retry/src/lib.rs
@@ -4,6 +4,8 @@
 pub mod peek_trailers;
 pub mod replay;
 
+mod frame;
+
 pub use self::{peek_trailers::PeekTrailersBody, replay::ReplayBody};
 pub use tower::retry::budget::Budget;