tree 089336ae82e671cf48c00cec2ac1f13c89d7cd91
parent df0ef1f333304c37e638f9f46076cf7dfec403ce
author birenroy <birenroy@google.com> 1789507318 -0700
committer Copybara-Service <copybara-worker@google.com> 1789507356 -0700

Modernizes HTTP/2 frame representations in spdy_protocol.h

This is a roll-forward of the original change, with a one-line fix to build properly on 32-bit platforms.

Introduces value-semantic, standard-layout POD structs, C++20 type
traits, concepts, compile-time size calculation and serialization,
and a 64-byte single-cache-line SpdyFrame variant based on the analysis in
go/http2-frame-representations.

This change introduces the types, but does not use them anywhere, yet.

Key changes:
- Defined standard-layout POD structs for all 14 HTTP/2 frame types
  (DataFrame, HeadersFrame, PriorityFrame, RstStreamFrame, SettingsFrame,
  PushPromiseFrame, PingFrame, GoAwayFrame, WindowUpdateFrame,
  ContinuationFrame, AltSvcFrame, PriorityUpdateFrame, AcceptChFrame,
  UnknownFrame).
- Added C++20 FrameTraits<T> and Http2Frame concept.
- Added compile-time FrameSize<T> and SerializeFrame<T> in SpdyFrameBuilder.
- Added SpdyFrame variant fitting in 64 bytes (1 cache line) and dispatch
  helpers.
- Maintained backward compatibility for all existing SpdyFrameIR
  classes and SpdyFrameVisitor without changing callers.

PiperOrigin-RevId: 982039230