feat: zlib preset dictionary decompressor for S7CommPlus blobs#776
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gijzelaerr wants to merge 6 commits into
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feat: zlib preset dictionary decompressor for S7CommPlus blobs#776gijzelaerr wants to merge 6 commits into
gijzelaerr wants to merge 6 commits into
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) S7-1200/1500 PLCs compress XML metadata (tag definitions, interface descriptions, network comments, etc.) using zlib with Siemens-specific preset dictionaries. Python's zlib.decompress() returns Z_NEED_DICT for these blobs. This adds the 19 known dictionaries and a decompressor that auto-selects the correct one by Adler-32 checksum. The dictionaries were extracted from thomas-v2/S7CommPlusDriver (LGPL-3.0, BlobDecompressor.cs). Key dictionary for #757: IntfDescTag (0xce9b821b) — used for I/Q/M area tag definitions on V3 PLCs (S7-1200 FW V4.5+). New modules: - s7commplus/zlib_dicts.py — 19 preset dictionaries (24KB total) - s7commplus/blob_decompressor.py — decompress_blob() with auto dictionary lookup, find_and_decompress() for scanning raw payloads Replaces the partial oracle-based dictionary reconstruction in examples/browse_tags.py with complete, verified dictionaries. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The dictionaries are 100% printable XML template fragments (with the occasional German ü). Storing them as hex blobs made them unreadable. Now stored as Python string literals, encoded to bytes at import time. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Replace the 385-line Python module of string-chunked XML with 19
individual .xml files in s7commplus/zlib_dicts/. Each file is named
{adler32}_{name}.xml and can be read directly in any editor or IDE.
The __init__.py loader scans the directory at import time and builds
the same ZLIB_DICTIONARIES/ZLIB_DICT_NAMES dicts as before.
Also adds *.xml to pyproject.toml package-data so the files ship
in the wheel.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The end-of-file-fixer hook requires a trailing newline. The loader strips it with rstrip(b"\n") so the Adler-32 checksums stay correct. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The .xml dictionary files contain raw zlib preset dictionary bytes, not valid standalone XML. Mark them as binary in .gitattributes to prevent CRLF conversion on Windows (which broke Adler-32 checksums), and exclude them from the check-xml pre-commit hook. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Add explore_xml() to both sync and async clients — sends an EXPLORE request and decompresses the zlib-compressed XML metadata from the response. Also export decompress_blob and find_and_decompress from the s7commplus package for direct use with raw EXPLORE payloads. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
blob_decompressor.pywithdecompress_blob()that auto-selects the correct dictionary by Adler-32 checksumThe key dictionary for #757 is
IntfDescTag(Adler-320xce9b821b, 1178 bytes) — used for I/Q/M area tag definitions on V3 PLCs (S7-1200 FW V4.5+). With the complete dictionary, decompression produces clean XML that can be parsed with standard tools instead of regex extraction from garbled output.Addresses #757.
Test plan
find_and_decompress()scans raw payloads for zlib streams🤖 Generated with Claude Code