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unleashed-firmware/documentation/file_formats/TarHeatshrinkFormat.md
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Updater: resource compression (#3716) 
* toolbox: compress: moved decompressor implementation to separate func
* toolbox: compress: callback-based api; cli: storage unpack command
* toolbox: compress: separate r/w contexts for stream api
* targets: f18: sync API
* compress: naming fixes & cleanup
* toolbox: compress: using hs buffer size for stream buffers
* toolbox: tar: heatshrink stream mode
* toolbox: compress: docs & small cleanup
* toolbox: tar: header support for .hs; updater: now uses .hs for resources; .hs.tar: now rewindable
* toolbox: compress: fixed hs stream tail handling
* updater: reworked progress for resources cleanup; rebalanced stage weights
* updater: single-pass decompression; scripts: print resources compression ratio
* updater: fixed warnings
* toolbox: tar: doxygen
* docs: update
* docs: info or tarhs format; scripts: added standalone compression/decompression tool for heatshrink-formatted streams
* scripts: tarhs: fixed parameter handling
* cli: storage extract command; toolbox: tar: guess type based on extension
* unit_tests: added test for streamed raw hs decompressor `compress_decode_streamed`
* unit_tests: compress: added extraction test for .tar.hs
* rpc: autodetect compressed archives
* scripts: minor cleanup of common parts
* scripts: update: now using in-memory intermediate tar stream
* scripts: added hs.py wrapper for heatshrink-related ops (single object and directory-as-tar compression)
* scripts: naming fixes
* Toolbox: export compress_config_heatshrink_default as const symbol
* Toolbox: fix various types naming
* Toolbox: more of types naming fixes
* Toolbox: use size_t in compress io callbacks and structures
* UnitTests: update to match new compress API
* Toolbox: proper path_extract_extension usage

Co-authored-by: あく <alleteam@gmail.com>
2024-06-30 11:38:48 +01:00

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Heatshrink-compressed Tarball Format

Flipper supports the use of Heatshrink compression library for .tar archives. This allows for smaller file sizes and faster OTA updates.

Heatshrink specification does not define a container format for storing compression parameters. This document describes the format used by Flipper to store Heatshrink-compressed data streams.

Header

Header begins with a magic value, followed by a version number and compression parameters - window size and lookahead size.

Magic value consists of 4 bytes: 0x48 0x53 0x44 0x53 (ASCII "HSDS", HeatShrink DataStream).

Version number is a single byte, currently set to 0x01.

Window size is a single byte, representing the size of the sliding window used by the compressor. It corresponds to -w parameter in Heatshrink CLI.

Lookahead size is a single byte, representing the size of the lookahead buffer used by the compressor. It corresponds to -l parameter in Heatshrink CLI.

Total header size is 7 bytes. Header is followed by compressed data.