Igor Kovalenko authored Oct 24, 2023 and PulseAudio Marge Bot committed Oct 25, 2023

If pa_memblockq_push needs to write into the middle of a chunk, target chunk
is split into head and tail sharing the same memblock. Size of head and
tail chunks is adjusted correctly, head chunk pointer into memblock remains
unchanged from target chunk.

The problem is with tail chunk offset into memblock which should be advanced
past write region of memblock, but currently it is left as 0.

This is causing an issue where seeking a few frames back into the middle of
memblock and writing a frame there ends up with tail chunk referencing frames
from very beginning of memblock causing corrupted output from memblockq.

Fix this by adjusting tail chunk offset into memblock past write region and
add a test case.

Fixes #3789

Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/798>