vigna / dsi-bitstream-rs / 29653800427

65%

Build Type

push

github

Committed by vigna

Commit Message

Limit peekable bits to half the buffer instead of peeking twice

Revert the two-refill peek_bits and the associated full-buffer handling in
read_bits/skip_bits/read_unary introduced on the peek_twice branch, restoring
the original single-refill hot paths verbatim. Instead, set PEEK_BITS to
exactly one word (half the two-word bit buffer) so that a peek needs at most
one refill and the bit buffer is never completely full. This keeps all the
other fixes from the branch (copy_to/copy_from, flush retry, into_inner,
counters, dispatch, std::io::Read, word adapters) while avoiding the
per-call branch that the full-buffer handling added to read_bits/peek_bits/
skip_bits on the default (u32) read word.

One word of peekable bits is sufficient for every decoding table; the
generated check_read_table asserts guarantee this at compile time. The read
table-sweep script is clamped so it never generates a table wider than the
read word's PEEK_BITS (e.g. no 9-bit gamma tables on an 8-bit read word).

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

Coverage Stats

12 of 12 new or added lines in 1 file covered. (100.0%)

179 existing lines in 7 files now uncovered.

2228 of 3822 relevant lines covered (58.29%)

2626768.34 hits per line