retcomm-rbengine

The offline rollback core for recomp engines: the pieces of rollback that work with netplay compiled out. No dependencies.

Module	Role
snap_ring	Tick-keyed opaque snapshot ring (+ optional serialize vtable)
mono_ms	QPC / CLOCK_MONOTONIC milliseconds

Rewind and run-ahead can link this library on its own. Before the split an engine that wanted the snapshot ring without netplay had to compile rbe_snap_ring.c as a bare source file, because the library linked recomp-net and refused to configure without it.

What moved to recomp-net

Everything that compares against a peer. These now live in recomp-net beside the session and the episode FSM they serve:

Was (rbengine)	Now (recomp-net)
retcomm_rbengine/sched.h, rbe_sched_*, RbeSchedBridge, RbeSchedGates	recomp_net/sched.h, rnet_sched_*, RNetSchedBridge, RNetSchedGates
retcomm_rbengine/hash_confirm.h, rbe_hc_*, RbeHashConfirm, RBE_HC_RING	recomp_net/hash_confirm.h, rnet_hc_*, RNetHashConfirm, RNET_HC_RING
retcomm_rbengine/input_hist.h, rbe_ih_*, RbeInputHist, RBE_INPUT_HIST_*	recomp_net/input_hist.h, rnet_ih_*, RNetInputHist, RNET_INPUT_HIST_*
retcomm_rbengine/rb_post.h, rbe_rb_peer_post_tip_ok	recomp_net/rb_post.h, rnet_rb_peer_post_tip_ok

The scheduler's RBE_RB_* environment knobs kept their names.

Build

cmake -S . -B build
cmake --build build -j
ctest --test-dir build --output-on-failure

add_subdirectory(path/to/retcomm-rbengine)
target_link_libraries(your_host PRIVATE retcomm_rbengine)

Snapshot ring sketch

#include "retcomm_rbengine/retcomm_rbengine.h"

RbeSnapRing *ring = rbe_snap_ring_create(RBE_SNAP_RING_DEFAULT_DEPTH);
RbeSnapVTable vt = {
    .ctx = host,
    .serialize = host_save_blob,   /* mallocs *out */
    .deserialize = host_load_blob,
};
rbe_snap_ring_save(ring, tick, &vt);
rbe_snap_ring_load(ring, load_tick, &vt);

Game-specific savestate serialize stays in the engine.

MotK provenance

Lifted from psxrecomp/runtime (netplay_snap_ring) with PSX types removed. The modules that moved to recomp-net came from psx_netplay_sched, netplay_hash_confirm, netplay_input_hist and netplay_rb_post.

License

MIT — see LICENSE.