Add QPACK (RFC 9204) + standalone Huffman / range-coder / MTF / BWT codecs

CHANGELOG.md

@@ -7,6 +7,26 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- **HTTP/3 QPACK header compression** (RFC 9204) behind the new `qpack`
+  feature. `compcol::qpack::{QpackEncoder, QpackDecoder}` — full decoder
+  (static table, dynamic table built from the encoder-stream instructions, and
+  all field-line representations) validated byte-for-byte against the RFC 9204
+  Appendix B examples; the encoder uses the static table + literals (Required
+  Insert Count = 0). Reuses the HPACK string Huffman code and `HeaderField`.
+- **Standalone primitives / transforms**, each a first-class codec reachable
+  through the factory:
+  - `huffman` — a self-delimiting canonical (length-limited, order-0) Huffman
+    codec, `compcol::huffman_codec::Huffman` (name `"huffman"`).
+  - `rangecoder` — an adaptive order-0 binary range coder,
+    `compcol::rangecoder::RangeCoder` (name `"range"`).
+  - `mtf` — the Move-To-Front reversible transform, `compcol::mtf::Mtf`
+    (name `"mtf"`), a streaming length-preserving filter.
+  - `bwt` — a standalone block Burrows-Wheeler Transform, `compcol::bwt::Bwt`
+    (name `"bwt"`), with a per-block primary index. Pairs with `mtf` + an
+    entropy coder to build a bzip2-style pipeline from parts.
+
 ## [0.6.2](https://github.com/KarpelesLab/compcol/compare/v0.6.1...v0.6.2) - 2026-06-12
 
 ### Other

Cargo.toml

@@ -50,7 +50,8 @@ all = [
     "lha",
     "bcj", "bcj2", "delta",
     "arc_crunch", "arc_squeeze", "arc_squash",
-    "hpack",
+    "hpack", "qpack",
+    "huffman", "rangecoder", "mtf", "bwt",
 ]
 # Enables `alloc`-backed conveniences (e.g. the `factory` module, the
 # `compcol::vec` one-shot helpers). Pulled in automatically by features
@@ -246,6 +247,25 @@ arc_squash = ["alloc"]
 # (name `"h2-huffman"`). The full header codec lives behind its own
 # `compcol::hpack` API (it is stateful over header lists, not a byte stream).
 hpack   = ["alloc"]
+# HTTP/3 QPACK header compression (RFC 9204): static table (Appendix A),
+# dynamic table built from the encoder-stream instructions, and all field-line
+# representations. Reuses the HPACK string Huffman code, so it pulls `hpack`.
+# Lives behind its own `compcol::qpack` API (stateful header codec, not a byte
+# stream). Decoder is full; the encoder uses the static table + literals.
+qpack   = ["alloc", "hpack"]
+# Standalone canonical (length-limited) Huffman codec — `compcol::huffman_codec`
+# (name `"huffman"`). Self-delimiting order-0 Huffman over bytes.
+huffman = ["alloc"]
+# Standalone adaptive order-0 binary range coder — `compcol::rangecoder`
+# (name `"range"`). A self-contained entropy codec.
+rangecoder = ["alloc"]
+# Move-To-Front reversible transform — `compcol::mtf` (name `"mtf"`). A
+# length-preserving, streaming byte filter (as used inside bzip2).
+mtf     = ["alloc"]
+# Standalone block Burrows-Wheeler Transform — `compcol::bwt` (name `"bwt"`).
+# Reversible block transform with a per-block primary index; pairs with `mtf`
+# and an entropy coder.
+bwt     = ["alloc"]
 # `compcol::tokio_io` — async mirrors of compcol::io for the tokio
 # runtime. Pulls the tokio dependency for its AsyncRead/AsyncWrite
 # trait definitions; the rest of the crate stays dep-free.

README.md

@@ -77,12 +77,20 @@ flag, and a `compcol` binary turns the library into a Unix-style filter.
 | RAR 3.x | `rar3` | `.rar` | `Unsupported` (license) | full LZ77+Huffman + E8 filter; PPMd & VM filters refused | libarchive RAR3 fixtures |
 | RAR 5.x | `rar5` | `.rar` | `Unsupported` (license) | full LZ77+Huffman + x86 filter; Delta/ARM refused | RARLAB-CLI fixtures |
 | HTTP/2 HPACK (RFC 7541) | `hpack` | — | full (header codec + `h2-huffman` string codec) | full (static+dynamic tables, integer/string coding) | RFC 7541 Appendix C vectors |
-
-HPACK is HTTP/2's header-compression codec, not a byte-stream codec: it
-operates on `(name, value)` header lists with per-connection dynamic-table
-state, so it lives behind its own `compcol::hpack` API (`HpackEncoder` /
-`HpackDecoder`). The §5.2 string Huffman primitive is also exposed as the
-`Http2Huffman` codec (name `h2-huffman`) through the uniform trait surface.
+| HTTP/3 QPACK (RFC 9204) | `qpack` | — | static-table + literal encoder; full decoder | full (static+dynamic tables via encoder stream, all field representations) | RFC 9204 Appendix B vectors |
+| Canonical Huffman (standalone) | `huffman` | `.huff` | full (length-limited, self-delimiting) | full | own round-trip |
+| Range coder (adaptive order-0) | `rangecoder` | `.range` | full | full | own round-trip |
+| Move-To-Front transform | `mtf` | `mtf` | full (reversible filter) | full | round-trip identity |
+| Burrows-Wheeler Transform (standalone) | `bwt` | `bwt` | full (block BWT + primary index) | full | round-trip identity |
+
+HPACK and QPACK are HTTP header-compression codecs, not byte-stream codecs:
+they operate on `(name, value)` header lists with per-connection dynamic-table
+state, so they live behind their own `compcol::hpack` / `compcol::qpack` APIs.
+The §5.2 string Huffman primitive is also exposed as the `Http2Huffman` codec
+(name `h2-huffman`) through the uniform trait surface; QPACK reuses it. The
+`huffman` / `rangecoder` / `mtf` / `bwt` features expose standalone
+building-block codecs (entropy coding and reversible transforms) that can be
+composed into a custom pipeline.
 
 The RAR encoders are permanently `Unsupported` per RARLAB's unRAR
 license terms (every clean-room RAR reader — libarchive, The