VaptVupt v2.65.11

This release improves small-input encoding and makes entropy-table ownership
explicit. The wire layout and existing public entry points remain compatible.
It is a userspace codec release, not a Linux kernel port or a claim of
universal superiority over LZ4/Zstd.

• Fast one-shot inputs up to 4 KiB initialize only reachable full-width hash
  buckets and allocate a circular chain sized to the input. A 4 KiB input
  avoids 240 KiB of chain allocation at the default window; the 1 MiB primary
  map allocation remains. Streaming and larger-input setup are unchanged.
  Seven paired in-process runs measured about 2.7x faster encoding for 1 KiB
  text and +10.7% throughput for 4 KiB text, with identical compressed bytes.
  These allocation-sensitive measurements are separate from CLI/page-API
  comparisons; large-input controls were approximately unchanged.
• Fix explicit format_v2 with fast mode. Plain compressed blocks always
  decode matches with a four-byte minimum, but this combination previously
  emitted a three-byte bias and could produce undecodable data. Fast mode
  now uses ordinary v1 tokens; balanced/extreme retain the requested v2
  entropy format. Creation, chunk compression and reset apply the same
  rule, including mode changes while the requested format remains enabled.
• Add checked caller-owned workspace entry points for single/four-stream
  Huffman and ANS literal decoding, with size/alignment queries. Existing
  allocating wrappers remain available. SEQ/S/T decoding reuses its existing
  48 KiB sequence-table region during the earlier literal phase, removing
  one nested allocation and up to 17,412 bytes of peak table storage. Whole
  frame decoding still allocates, and legacy context tables are unchanged.
  Single/four-stream ANS literal decoding also uses the existing direct-table
  builder, removing its separate 4 KiB spread array from the stack. This
  reduces those individual frames, not the whole codec's worst-case stack.
• Add VV_DISABLE_SIMD=1 and a clean make SIMD=0 build mode. Scalar copy
  calls bypass runtime dispatch and its mutable state. make scalar-test
  separately builds the integer core with general-purpose registers only
  and runs eleven userspace regression suites. The normal x86-64 decoder
  still uses inline AVX2; it is not a runtime-portable binary for older CPUs.
• Add a caller-owned FAST context for independent inputs up to 64 KiB. It
  separates size/alignment/init from compression, performs no hot-path heap
  allocation, resets history on every call and preserves one-shot output
  bytes. Compact 16-bit matcher positions reduce queried workspace to 537,800
  bytes for a 4 KiB limit and 722,361 bytes for 64 KiB. Roots clear sparsely
  below 4 KiB and densely at and above 4 KiB. Even after this reduction the
  context is too large for a credible per-CPU zram proposal without more work.
• Check frame-footer capacity before writing, accept a null zero-length XXH64
  input without pointer arithmetic, and validate checksum tails and decoder
  spans by remaining length before advancing input pointers. Both AVX2
  prefetch phases validate literal capacity and match history before forming a
  lookahead pointer. New regressions exercise exact/truncated endpoints,
  oversized frame/block lengths, multiframe boundaries, streaming-capacity
  retry and both prefetch phases. These are invariant hardening changes, not a
  claim that an observed crash was repaired; valid encoded bytes are unchanged.
• Add workspace ownership/capacity/reuse regressions. On Linux, the normal
  test target injects allocation failures to require zero allocations in
  workspace literal calls and exactly one allocation in tested S/T decode
  paths. Exact-buffer, sanitizer and MemorySanitizer checks cover the new
  small-input initialization and format-selection paths.
• Add a reproducible page-sized in-process comparison harness with explicit
  one-shot API, framing, checksum and allocation caveats. Refresh English
  and Portuguese documentation while retaining historical evidence under
  its original version. Document the remaining licensing, stack, allocator,
  architecture and human-review requirements for a possible kernel port.
  No Linux patch is submitted and no new formal proof is claimed.
• Final scalar page-profile measurements cover 216 profiles across 4/16/64 KiB
  and preserve 2,304 frames byte-for-byte. On 4 KiB synthetic text, LZ4 remains
  substantially faster and Zstd level 1 remains smaller and faster to encode;
  VaptVupt has the faster decode of the two measured Zstd settings but retains
  much more context memory. Six paired builds found strong 4 KiB context-encode
  gains on random, records and repeating inputs, alongside a 2.36% 64 KiB
  records decode-batch loss and a 12.24% 4 KiB text decode-p95 loss. The release
  does not claim to supersede LZ4 or Zstd.

Source archive SHA-256: dbe268feaf120f295066fed85f9ef2c14f157bb96773aa5a46ece6c0198b7563