feat(cdr)!: reflection-driven CDR/XCDR serialization (replaces CdrWriter/CdrReader)

[finger563]

Description

Stacked on #703 (feat/reflect-cpp-component) — merge that first, then re-target this PR to main.

Replaces the manual espp::CdrWriter/espp::CdrReader component with finger563/cdr, a reflection-driven CDR/XCDR serialization library (vendored as a detail/ submodule): the compiler generates serialization code from plain struct definitions — no IDL compiler, no hand-written write/read call sequences.

struct ImuSample {
  uint64_t stamp_us;
  std::array<float, 3> accel;
  std::array<float, 3> gyro;
  float temperature;
};

auto bytes = cdr::serialize(sample);              // XCDR2, appendable (default)
auto ros2  = cdr::serialize<cdr::xcdr1>(sample);  // ROS 2 / classic-CDR peers
auto back  = cdr::deserialize<ImuSample>(*bytes); // std::expected<ImuSample, cdr::error>

What the new library adds over the old component:

• XCDR2 (plain + delimited/appendable with DHEADER — FastDDS/OpenDDS defaults) alongside XCDR1 (ROS 2 / CycloneDDS defaults), both endiannesses
• Appendable schema evolution in both directions (unknown trailing members skipped; missing members keep defaults)
• Wire format byte-verified against pycdr2 (CycloneDDS's codec) — 10/10 differential fixtures identical; the Python side of a message is a plain pycdr2 dataclass, no native bindings
• std::expected errors with code, payload offset, and failing field name; bounds-checked, fuzz-tested deserializers (ASan/UBSan-clean incl. a ~46k-case mutation stress suite in the library repo)
• cdr::bounded_string<N> / bounded_vector<T, N>, PL_CDR param_list_writer/param_list_reader for SPDP/SEDP, zero-allocation serialize_into, body-only variants

BREAKING CHANGE

espp::CdrWriter / espp::CdrReader are gone, including their Python bindings (espp.CdrWriter/espp.CdrReader). Migrations in this PR:

• rtps: discovery string/octet-sequence parameters via cdr::serialize_body/deserialize_body; PL_CDR encapsulation handled inline
• pc tests + rtps/p4 examples: uint32 payload helpers via cdr::serialize<cdr::xcdr1> / cdr::deserialize<uint32_t>
• lib: builds C++23; cdr python bindings removed (python CDR payloads use pycdr2 / struct.pack)
• python: rtps scripts use pure-python CDR helpers

Verification

• cdr and rtps examples build on ESP32-S3 (IDF 6; also expected green on CI's v5.5.1 — its default gnu++2b provides std::expected)
• Host espp_pc lib + _espp python module build (C++23)
• pc/build/rtps_pubsub end-to-end test passes: 16/16 samples through SPDP/SEDP discovery + user data on the new serializer
• Migrated pure-python helpers byte-checked in both endiannesses
• Not build-verified: the P4 board example (long display/LVGL build; its helper change is identical in shape to the rtps example's)

Notes

• Requires C++23 (std::expected) — default on IDF 5.2+ toolchains (gnu++2b/gnu++26); manifest declares idf: >=5.2
• Keep the reflect_cpp submodule pin and finger563/cdr's FetchContent tag on the same reflect-cpp version (currently v0.25.0)
• Docs: doc/en/data/cdr.rst rewritten; example README updated; vendored detail/ excluded from cppcheck

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR replaces the manual espp::CdrWriter/espp::CdrReader API (and its Python bindings) with a reflection-driven CDR/XCDR serialization approach using the vendored finger563/cdr library backed by reflect_cpp, and migrates RTPS code/examples plus host/PC support to the new API (C++23).

Changes:

• Migrate RTPS parameter-list encoding/decoding and examples/tests from espp::CdrWriter/espp::CdrReader to cdr::{serialize,deserialize,serialize_body,deserialize_body}.
• Remove CDR Python bindings and update Python RTPS scripts to use pure-struct CDR helpers.
• Update build/docs/packaging to support the new header-only CDR library and require C++23 (std::expected).

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
suppressions.txt	Excludes vendored components/cdr/detail/* from cppcheck, consistent with other vendored trees.
python/rtps_subscriber.py	Replaces espp.CdrReader usage with pure-Python struct decoding for uint32.
python/rtps_pubsub.py	Replaces espp.CdrWriter/Reader with pure-Python struct packing/unpacking for uint32.
python/rtps_publisher.py	Replaces espp.CdrWriter with pure-Python struct packing for uint32.
pc/tests/rtps_common.hpp	Migrates test helpers to cdr::serialize/deserialize for uint32 payloads.
pc/CMakeLists.txt	Bumps host PC build standard to C++23.
lib/python_bindings/module.cpp	Removes registration of CDR Python bindings; keeps RTPS bindings.
lib/python_bindings/cdr_bindings.cpp	Deletes the hand-written CDR pybind11 shim.
lib/espp.cmake	Drops old cdr source/bindings; adds include paths for vendored CDR + reflect-cpp; bumps Python module to C++23.
lib/CMakeLists.txt	Bumps library compile features to C++23.
lib/autogenerate_bindings.py	Updates note/exclusion rationale for cdr.hpp now that Python uses pycdr2 instead of bindings.
doc/en/data/cdr.rst	Rewrites component docs to describe reflection-driven XCDR1/XCDR2 + std::expected API.
components/rtps/src/rtps.cpp	Migrates PL_CDR parameter writing/reading to new CDR helpers; introduces shared padding helper.
components/rtps/example/main/rtps_example.cpp	Migrates example payload helpers to cdr::serialize/deserialize.
components/esp32-p4-function-ev-board/example/main/esp32_p4_function_ev_board_example.cpp	Migrates example payload helpers to cdr::serialize/deserialize.
components/cdr/README.md	Updates component README to new reflection-driven library and capabilities.
components/cdr/include/cdr.hpp	Adds umbrella header that forwards to the vendored cdr library headers.
components/cdr/idf_component.yml	Updates description/tags; raises minimum IDF to >=5.2; adds dependency on espp/reflect_cpp.
components/cdr/example/README.md	Updates example documentation to match new functionality and API.
components/cdr/example/main/cdr_example.cpp	Replaces old imperative reader/writer example with reflection-driven struct-based demo.
components/cdr/example/CMakeLists.txt	Adds reflect_cpp and bumps example to C++23.
components/cdr/CMakeLists.txt	Switches cdr component to header-only registration; includes vendored headers; requires reflect_cpp.

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[finger563]

Applied all review feedback (thanks — the example error-handling one was a real UB bug):

• cdr_example.cpp: the two serialize results are checked separately, each reporting its own error
• rtps.cpp: append_cdr_parameter drops parameters whose padded length exceeds the 16-bit parameterLength instead of truncating on the wire
• rtps_example.cpp / rtps_common.hpp / P4 example: guards on the std::expected results before dereferencing

The branch was also rebased as part of fixing the stack split in #703 — the cdr submodule and old-file removals now land in this PR's first commit where they belong.

Re-verified after the rewrite: cdr and rtps examples build on ESP32-S3/IDF 6, host lib + _espp build, and pc/build/rtps_pubsub still passes 16/16 end-to-end. Note the example-build matrix only triggers once this PR re-targets to main after #703 merges.

[finger563]

Superseded by #705 — after #703 merged and its branch was deleted, GitHub could not retarget or reopen this PR (the head branch had been force-pushed while it was closed). #705 is the same branch rebased onto main with all review feedback from this PR applied.