https://gitlab.synchro.net/main/sbbs/-/commit/aaf394a0d833acd89a64d3a9
Modified Files:
docs/v322_new.md src/sbbs3/sexyz.c
Log Message:
sexyz: keep the transmit window >= 4x the block size, like lsz (#1197)

sexyz's -w set only the ZMODEM transmit window and left the block size independent (from -2/-4/-8, default 1 KB), so a window at or below the
block size was configurable -- and it stalled the transfer to roughly one window per second. lsz and Forsberg sz never allow this: when -w is
given they force the block down to a quarter of the window
(blkopt = Txwspac = Txwindow/4), guaranteeing window >= 4*block so the ack-every-quarter-window scheme always has several blocks in flight.

Do the same after argument parsing, so -8 -w8192 and -w8192 -8 both
resolve the same way: floor the window to 256, round to a multiple of 64,
and reduce max_block_size to window/4 when it exceeds it (and the start block_size with it). A one-line notice reports the reduction.

Effect: the formerly-hanging window<=block configurations now complete --
-8 -w8192 reduces the block to 2048 and transfers, -4 -w4096 to 1024,
and so on -- while windows that already left four blocks of headroom
(-w32768 and up with -8) are untouched and unchanged (4.75 and 4.88 MB/s
here, streaming still 11.3). This also makes the divide-by-zero guarded
in 04b47329aa unreachable by configuration, since window/block/4 is now
always >= 1.

This does not make sexyz's windowed throughput competitive with lsz --
at the same block and window sexyz is still many times slower, and very
small windows (which force tiny blocks) remain slow with occasional
one-second stalls. That is the separate sexyz windowed-send overhead
tracked in #1195; this change is only about not permitting the degenerate window<=block configuration that lsz forbids by construction.

sexyz.c version 3.3 -> 3.4. No zmodem.c change, so SyncTERM is
unaffected (it never sets a transmit window anyway).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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