BoltPack v1.5

BoltPack Release Notes

v1.5.0 — August 2026

Version: 1.5
Status: Stable

License and dependency change

• Relicensed from GPLv2 to the BSD 2-Clause "Simplified" License. BoltPack
  code is now BSD-2-Clause; bundled third-party components retain their own
  license notices.
• miniLZO 2.10 (GPLv2) removed and replaced by fastlz 0.5.0 (MIT).
  fastlz is vendored in lib/fastlz/ (C89-ported) with its MIT license notice
  preserved.
• Method ID 2 now means fastlz. Archives created by pre-1.5.0 builds using
  method 2 (LZO1X) are not compatible and will not decode. There are no
  external users yet, so no backward-compatibility shim is provided. The on-disk
  archive format version is unchanged (BP_FORMAT_VERSION stays 3).

What's new

• fastlz replaces LZO1X as the default fast general-purpose codec (the
  -2 / --fastlz flag; the long flag --minilzo is renamed --fastlz).
• fastlz level selector: -l 1 forces fastlz level 1 (8 KB window),
  -l 2 forces level 2 (64 KB window), and omitting -l lets fastlz
  auto-select level 1 below 64 KB and level 2 at or above it. Levels 3–9
  clamp to level 2.
• 16-bit behavior: fastlz decompression is supported on 16-bit builds via
  the clean-room src/core/mini/fastlz_decomp.c decoder; fastlz compression
  is not (its 8192-entry stack hash table is too large for 8086-class stacks),
  the same treatment LZO1X had on 16-bit.
• creator_ver in new archives: 0x01, 0x05.
• Mini build (bpmini) bumped to 1.3.

---

v1.4 — July 2026

Version: 1.4
Status: Stable

Archive format

Format version bumped to 3. v3 archives are not readable by BoltPack 1.3
or earlier. v3 readers cannot read v2 archives (strict version check). The
creator_ver bytes in archives written by BoltPack 1.4 are 0x01, 0x04.

What's new

Archive format v3

• Per-block CRC-32 — every compressed block now carries a 4-byte CRC-32
  field. The block header grows from 8 to 12 bytes (comp_size + orig_size + block_crc). Readers verify the CRC before decompressing; a mismatch is
  reported as BP_ERR_CHECKSUM. This makes corruption detectable at the
  earliest possible point in the read path rather than only at the whole-entry
  checksum.
• total_orig in file-table header — the 8-byte table header grows to 16
  bytes by appending the sum of all original_size values. Listing and info
  commands read total uncompressed size directly from the table header without
  scanning every entry record.
• Unix permission bits in entry flags — the entry flags field (previously
  reserved) now carries bit 15 (BP_ENTRY_FLAG_MODE_VALID) and bits 0–11
  (BP_ENTRY_FLAG_MODE_MASK) for the 12-bit Unix permission field
  (st_mode & 0x0FFF). On the Linux frontend, permissions are stored at create
  time and restored with chmod at extract time. Unknown flag bits are accepted
  silently for forward compatibility. New bp_archive_add_entry_ex and
  bp_archive_pack_entry_ex API variants let frontends set flags without
  modifying existing call sites.
• archive_size is now normative for v3 — a v3 reader must verify that the
  stored archive_size matches the actual file size; mismatch → BP_ERR_TRUNCATED.
  Writers must store the correct total file size. (v2: informational only.)

CRC-32 as the only checksum

Adler-32 (checksum_type = 0) is fully retired. Writers have not emitted it
since v1.2, and v3 now makes checksum_type = 1 (CRC-32) mandatory. Readers
encountering checksum_type != 1 on a v3 archive return BP_ERR_CORRUPT.
The BP_ENABLE_ADLER32 build flag is retained for unit-testing the function
itself.

zstd multi-threaded compression

The Linux CLI and Linux/Windows FLTK GUI frontends now run zstd compression
with multiple threads when -j N is given alongside -Z. The sequential
path is unchanged. No archive-format impact.

Mini build (bpmini 1.2)

• Lazy allocation of the LZSS work buffer (16-bit path, 29 200 bytes) and
  LZO work buffer (32-bit path, 64 KB): memory is malloc'd on the first
  create call and cached for process lifetime. Extract, list, test, and info
  operations no longer pay for compression scratch at startup.
• Per-entry extract buffers hoisted to once-per-run: two malloc/free pairs per
  run instead of two per entry, eliminating far-heap churn on DOS.
• DOS-16 and Win16 frontends: full list, info, test, extract, create, append,
  and delete command set aligned with the full build's CLI conventions.
• Watcom builds: -zm flag added for function-level segments so option eliminate can strip dead functions. linuxmini binary stripped of unwind
  tables, symbol tables, and build-id.

Correctness and internal quality

• Append bug fix — an off-by-one in bp_archive_open_append caused the
  last byte of the old file table to be included in the first new data block,
  corrupting archives created via append on v2 archives with certain table
  alignments.
• Codec reentrancy — Fluff, zstd, and miniLZO compression contexts are now
  fully allocated per-call; no static state remains in the codec layer, making
  the core safe for process-level concurrent use (one archive per thread).
• Security fixes — path traversal checks tightened; symlink target
  validation added (bp_symlink_target_is_safe); integer overflow guards added
  to block-size arithmetic in the decompression path.
• Layering cleanup — archiver internal helpers moved out of archiver.h
  into a private header; public surface area of bp_archive_t reduced.
• zstd error strings moved out of the vendored lib/zstd/zstd.c into the
  wrapper (zstd_wrap.c) so the vendored file tracks upstream cleanly.
• stderr fallback removed from core — the archiver core no longer writes to
  stderr directly; all diagnostics go through the bp_log_fn callback.
  Frontends that do not set a log callback silently discard diagnostic messages.

Codec table

Method	Name	Intended use
0	Stored	Incompressible data or raw fallback
1	LZSS	Small-memory and 16-bit compatible compression
2	fastlz	Fast general-purpose compression; current default
3	Fluff	High compression ratio; all full-build targets
4	zstd	Best compression ratio; modern 32/64-bit targets only

---

v1.3 — July 2026

Version: 1.3
Status: Stable

What's new

• LAN send/receive — transfer archives directly between machines on the
  local network without a shared filesystem or external service.
  • boltpack listen starts a receiver; boltpack scan lists active receivers.
  • --send HOST streams a newly created archive to a named or IP-addressed
    receiver immediately after the create step.
  • Discovery uses UDP broadcast so receivers are found by friendly name; no
    manual IP entry required on typical home/office networks.
  • Broadcast is sent on every network interface, fixing discovery when a
    multi-homed host or VPN adapter is present.
• Receiver options:
  • --name NAME — advertise a friendly name (listen) or identify the sender
    (send); defaults to the system hostname.
  • --auto / --prompt — accept all incoming transfers silently, or prompt
    before each one (default: prompt).
  • --autoextract — unpack the received archive into files immediately rather
    than saving the .bolt file.
  • --autoverify — re-read and verify the saved .bolt from disk after
    download completes.
  • --timeout N — scan wait time in seconds (default: 2).
  • -o PATH — save received archives (or extracted files) to a specific
    directory; the directory is created automatically if it does not exist.
• GUI integration (FLTK frontends, Linux and Windows):
  • Create dialog gains a Send over network action alongside the existing
    Save action; choosing it opens a receiver picker populated by a live
    LAN scan.
  • The receiver picker shows each host's friendly name, IP address, and
    accept mode.
• Platform coverage — LAN networking is enabled on all 32-bit and 64-bit
  targets that have a POSIX socket layer or WinSock2: Linux (x86-64, ARM,
  ARM64, RISC-V), musl static, macOS, Haiku, FreeBSD, NetBSD, illumos, GNU
  Hurd, Windows (CLI and FLTK GUI), and all tier-3/tier-4 cross targets.
  16-bit and bare-metal targets are not affected.
• Bug fix — boltpack listen -o DIR in save mode (no --autoextract) now
  creates the output directory if it does not already exist, rather than
  failing silently and discarding the received archive.

Archive format

Format version remains 2 (no archive-format changes in this release). The
creator_ver bytes in archives written by BoltPack 1.3 are 0x01, 0x03.

Codec table

Method	Name	Intended use
0	Stored	Incompressible data or raw fallback
1	LZSS	Small-memory and 16-bit compatible compression
2	miniLZO	Fast general-purpose compression; current default
3	Fluff	High compression ratio; all full-build targets
4	zstd	Best compression ratio; modern 32/64-bit targets only

---

v1.2 — June 2026

Version: 1.2
Status: Stable

Changes

• Archive format version 2 — BP_FORMAT_VERSION bumped from 1 to 2. All
  version checks are now strict equality: archives from v1.0 and v1.1 are
  rejected with BP_ERR_VERSION, and v1.2 archives are rejected by older
  readers. No backward-compatibility layer.
• Improved LZSS codec (method 1):
  • Sliding window expanded from 2 048 to 4 096 bytes, improving compression
    ratio on...

BoltPack v1.4

BoltPack Release Notes

v1.4 — July 2026

Version: 1.4
Status: Stable

Archive format

Format version bumped to 3. v3 archives are not readable by BoltPack 1.3
or earlier. v3 readers cannot read v2 archives (strict version check). The
creator_ver bytes in archives written by BoltPack 1.4 are 0x01, 0x04.

What's new

Archive format v3

• Per-block CRC-32 — every compressed block now carries a 4-byte CRC-32
  field. The block header grows from 8 to 12 bytes (comp_size + orig_size + block_crc). Readers verify the CRC before decompressing; a mismatch is
  reported as BP_ERR_CHECKSUM. This makes corruption detectable at the
  earliest possible point in the read path rather than only at the whole-entry
  checksum.
• total_orig in file-table header — the 8-byte table header grows to 16
  bytes by appending the sum of all original_size values. Listing and info
  commands read total uncompressed size directly from the table header without
  scanning every entry record.
• Unix permission bits in entry flags — the entry flags field (previously
  reserved) now carries bit 15 (BP_ENTRY_FLAG_MODE_VALID) and bits 0–11
  (BP_ENTRY_FLAG_MODE_MASK) for the 12-bit Unix permission field
  (st_mode & 0x0FFF). On the Linux frontend, permissions are stored at create
  time and restored with chmod at extract time. Unknown flag bits are accepted
  silently for forward compatibility. New bp_archive_add_entry_ex and
  bp_archive_pack_entry_ex API variants let frontends set flags without
  modifying existing call sites.
• archive_size is now normative for v3 — a v3 reader must verify that the
  stored archive_size matches the actual file size; mismatch → BP_ERR_TRUNCATED.
  Writers must store the correct total file size. (v2: informational only.)

CRC-32 as the only checksum

Adler-32 (checksum_type = 0) is fully retired. Writers have not emitted it
since v1.2, and v3 now makes checksum_type = 1 (CRC-32) mandatory. Readers
encountering checksum_type != 1 on a v3 archive return BP_ERR_CORRUPT.
The BP_ENABLE_ADLER32 build flag is retained for unit-testing the function
itself.

zstd multi-threaded compression

The Linux CLI and Linux/Windows FLTK GUI frontends now run zstd compression
with multiple threads when -j N is given alongside -Z. The sequential
path is unchanged. No archive-format impact.

Mini build (bpmini 1.2)

• Lazy allocation of the LZSS work buffer (16-bit path, 29 200 bytes) and
  LZO work buffer (32-bit path, 64 KB): memory is malloc'd on the first
  create call and cached for process lifetime. Extract, list, test, and info
  operations no longer pay for compression scratch at startup.
• Per-entry extract buffers hoisted to once-per-run: two malloc/free pairs per
  run instead of two per entry, eliminating far-heap churn on DOS.
• DOS-16 and Win16 frontends: full list, info, test, extract, create, append,
  and delete command set aligned with the full build's CLI conventions.
• Watcom builds: -zm flag added for function-level segments so option eliminate can strip dead functions. linuxmini binary stripped of unwind
  tables, symbol tables, and build-id.

Correctness and internal quality

• Append bug fix — an off-by-one in bp_archive_open_append caused the
  last byte of the old file table to be included in the first new data block,
  corrupting archives created via append on v2 archives with certain table
  alignments.
• Codec reentrancy — Fluff, zstd, and miniLZO compression contexts are now
  fully allocated per-call; no static state remains in the codec layer, making
  the core safe for process-level concurrent use (one archive per thread).
• Security fixes — path traversal checks tightened; symlink target
  validation added (bp_symlink_target_is_safe); integer overflow guards added
  to block-size arithmetic in the decompression path.
• Layering cleanup — archiver internal helpers moved out of archiver.h
  into a private header; public surface area of bp_archive_t reduced.
• zstd error strings moved out of the vendored lib/zstd/zstd.c into the
  wrapper (zstd_wrap.c) so the vendored file tracks upstream cleanly.
• stderr fallback removed from core — the archiver core no longer writes to
  stderr directly; all diagnostics go through the bp_log_fn callback.
  Frontends that do not set a log callback silently discard diagnostic messages.

Codec table

Method	Name	Intended use
0	Stored	Incompressible data or raw fallback
1	LZSS	Small-memory and 16-bit compatible compression
2	miniLZO	Fast general-purpose compression; current default
3	Fluff	High compression ratio; all full-build targets
4	zstd	Best compression ratio; modern 32/64-bit targets only

---

v1.3 — July 2026

Version: 1.3
Status: Stable

What's new

• LAN send/receive — transfer archives directly between machines on the
  local network without a shared filesystem or external service.
  • boltpack listen starts a receiver; boltpack scan lists active receivers.
  • --send HOST streams a newly created archive to a named or IP-addressed
    receiver immediately after the create step.
  • Discovery uses UDP broadcast so receivers are found by friendly name; no
    manual IP entry required on typical home/office networks.
  • Broadcast is sent on every network interface, fixing discovery when a
    multi-homed host or VPN adapter is present.
• Receiver options:
  • --name NAME — advertise a friendly name (listen) or identify the sender
    (send); defaults to the system hostname.
  • --auto / --prompt — accept all incoming transfers silently, or prompt
    before each one (default: prompt).
  • --autoextract — unpack the received archive into files immediately rather
    than saving the .bolt file.
  • --autoverify — re-read and verify the saved .bolt from disk after
    download completes.
  • --timeout N — scan wait time in seconds (default: 2).
  • -o PATH — save received archives (or extracted files) to a specific
    directory; the directory is created automatically if it does not exist.
• GUI integration (FLTK frontends, Linux and Windows):
  • Create dialog gains a Send over network action alongside the existing
    Save action; choosing it opens a receiver picker populated by a live
    LAN scan.
  • The receiver picker shows each host's friendly name, IP address, and
    accept mode.
• Platform coverage — LAN networking is enabled on all 32-bit and 64-bit
  targets that have a POSIX socket layer or WinSock2: Linux (x86-64, ARM,
  ARM64, RISC-V), musl static, macOS, Haiku, FreeBSD, NetBSD, illumos, GNU
  Hurd, Windows (CLI and FLTK GUI), and all tier-3/tier-4 cross targets.
  16-bit and bare-metal targets are not affected.
• Bug fix — boltpack listen -o DIR in save mode (no --autoextract) now
  creates the output directory if it does not already exist, rather than
  failing silently and discarding the received archive.

Archive format

Format version remains 2 (no archive-format changes in this release). The
creator_ver bytes in archives written by BoltPack 1.3 are 0x01, 0x03.

Codec table

Method	Name	Intended use
0	Stored	Incompressible data or raw fallback
1	LZSS	Small-memory and 16-bit compatible compression
2	miniLZO	Fast general-purpose compression; current default
3	Fluff	High compression ratio; all full-build targets
4	zstd	Best compression ratio; modern 32/64-bit targets only

---

v1.2 — June 2026

Version: 1.2
Status: Stable

Changes

• Archive format version 2 — BP_FORMAT_VERSION bumped from 1 to 2. All
  version checks are now strict equality: archives from v1.0 and v1.1 are
  rejected with BP_ERR_VERSION, and v1.2 archives are rejected by older
  readers. No backward-compatibility layer.
• Improved LZSS codec (method 1):
  • Sliding window expanded from 2 048 to 4 096 bytes, improving compression
    ratio on most real-world files.
  • Back-distance encoding replaces the old absolute ring-buffer position.
    The decoder now reads matches directly from the output buffer; the scratch
    buffer for decompression is eliminated entirely (was 2 KB minimum).
  • Token format is now a 12+4 bit back-distance/length split (was 11+5
    absolute-position/length). Back-distance range 1–4 096, match length 3–18.
  • Lazy matching and BST-based encoder retained; encoder scratch grows from
    14 900 to 29 200 bytes (fits comfortably in the 16-bit far data segment).
• Mini build (bpmini) version bumped to 1.1. Shares the improved LZSS
  codec; decoder scratch eliminated on 16-bit targets as well.
• Archive format version is now 2; creator_ver in new archives: 0x01, 0x02.

Codec table

Method	Name	Intended use
0	Stored	Incompressible data or raw fallback
1	LZSS	Small-memory and 16-bit compatible compression
2	miniLZO	Fast general-purpose compression; current default
3	Fluff	High compression ratio; all full-build targets
4	zstd	Best compression ratio; modern 32/64-bit targets only

---

v1.1 — June 2026

Version: 1.1
Status: Stable

What's new

• Method 4: zstd (Zstandard) — best compression ratio in BoltPack, enabled
  by default on all mode...