Scope shift from the original "make output a real UC2 v3 archive"
issue: that requires a new entry type or compress.c refactor (UC2
archives have one master per file, not a chain). This commit ships
the closest-in-spirit upgrade -- a self-contained format that solves
v1's main UX wart, the sidecar <archive>.blocks/ directory.
Format v2:
+0 8B magic "UC2INGST"
+8 1B version (2)
+9 1B cdc_bits
+10 2B reserved
+12 4B chunk_count
+16 ... chunk_count * 16B: 8B hash, 4B length, 4B offset
... chunk pool: unique chunks back-to-back at recorded offsets
The dedup map has a small implementation note: cap must be a power
of two for the mask-based linear probe to terminate. Caught when
test_ingest hung at 25 chunks -- initial_cap=50 is not power-of-two,
so probing wrapped to a non-empty slot indefinitely. Now rounded up
in dedup_map_init.
Trade-off: cross-archive dedup is not preserved (each --ingest call
overwrites the archive). v1 archives remain restorable through the
sidecar blockstore; the writer defaults to v2.
Tests: 6 cases (was 5). test_intra_call_dedup verifies that
identical chunks within a single ingest dedup correctly
(buffer-twice produces > 0 saved bytes). test_v2_self_contained
asserts the .blocks/ directory is NOT created for v2 archives.
Closes 96ef9b8. v3 (real UC2 v3 archive output) is filed at 59bec0d.
Eremey Valetov
7825eb47b2