Add dict support for frames and blocks#218
Open
paddor wants to merge 4 commits intoPSeitz:mainfrom
Open
Conversation
FrameEncoder::with_dictionary and FrameDecoder::with_dictionary wire the LZ4 frame Dict_ID feature through to the block layer. Encoder forces independent block mode and compresses each block against the external dictionary. Decoder verifies the frame's Dict_ID matches the supplied dictionary and decompresses blocks with the dict as initial history.
Adds the primitives rlz4's RLZ4::BlockCodec needs to amortise dictionary
initialisation across many compress calls:
- `CompressTable::load_dict(dict)` — clear + hash dict positions into the
table (same work `compress_into_with_table_and_dict` does today, but
extracted so callers can do it once).
- `CompressTable::copy_from(other)` — memcpy another table's entries
into this one. Reuses the existing allocation; no heap traffic.
Delegates to new `HashTable4K::copy_from` / `HashTable4KU16::copy_from`
methods.
- `compress_into_with_loaded_table_and_dict(input, output, table, dict)`
— variant of `compress_into_with_table_and_dict` that skips the clear
and the init_dict pass, trusting the caller to have populated the
table via `load_dict` and restored it via `copy_from` before each call.
The typical per-call sequence for a dict-compressing codec becomes:
scratch_table.copy_from(&pristine_table); // ~30-100 ns memcpy
compress_into_with_loaded_table_and_dict(input, output, &mut scratch_table, dict);
vs. the ~3-5 µs `init_dict` loop on every call with the original API.
No change to existing public functions.
Covers the primitives added in 0d69f8f: - `test_loaded_table_round_trip` — load_dict → copy_from → compress_into_with_loaded_table_and_dict → decompress_into_with_dict. - `test_loaded_table_matches_with_dict` — byte-for-byte equivalence with the clear+init-dict variant `compress_into_with_table_and_dict`. - `test_copy_from_variant_mismatch_panics` — Small vs Large copy_from panics as documented.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Complete dict support. Fairly efficient reuse across multiple compressions.