pawelw 95f41f069f Speed table: keep it sorted and keep the signal indices valid (#178) ...

* Fix the speed table index remap in TablePurger()

TablePurger() rebuilds the speed table and has to move SemNextIndex and
SemNextStopIndex along with it. Two cases came out wrong.

A trimmed point was never invalidated: the index was first overwritten with
the position the next kept point would take, and the guard that should reset
it to -1 compared the loop counter against that new value, so it only matched
when nothing had been trimmed before it. The index then pointed at an
unrelated record, and if that record happens to sit at zero velocity the
placement can no longer be updated either, because the update requires the
recorded one to be non-zero.

An index pointing at the last entry was left untouched, because the loop stops
one short of it and that entry is appended afterwards. The stale value ended
up past the end of the trimmed table, which is what the provisory check in
TableTraceRoute() catches.

The placements are now recorded separately and assigned once the new table is
complete, with the always-kept last entry handled too. The trim condition is
shared by the counting and the copying pass instead of being spelled out
twice.

TableCheck() drops entries beyond a switch that changed under the scan without
adjusting the placements either, so they are invalidated there as well. The
check in TableTraceRoute() stays as a safety net, without the TODO.

* Sort the whole speed table in TableSort()

TableSort() made a single bubble pass over the table. That only moves an entry
one place towards the front, but TableTraceRoute() adds the scanned events of a
track before the track itself, so a track carrying k scanned events lands k
places too far and needs k passes. With two or more events in one slot - a cab
signal resonator next to a signal, a signal and a W4 - the track entry stays
behind entries that are farther away, and TableUpdate() walks the table out of
distance order until enough later scans have shifted it back.

The range before the last slot is now sorted with std::stable_sort, and the
semaphor placements are moved along by looking their events up again.

---------

Co-authored-by: pwarszawski <pwarszawski@gmail.com>

2026-09-23 01:02:11 +02:00

374 KiB

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