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https://github.com/mhx/dwarfs.git
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67 lines
1.8 KiB
Python
Executable File
67 lines
1.8 KiB
Python
Executable File
#!/bin/env python3
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"""
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A very rudimentary DwarFS image parser
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This currently doesn't do very much apart from extracting the block data
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(*without* headers) and writing the blocks to individual files.
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Note that this *cannot* currently handle DwarFS image offsets.
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The main idea behind this script is to allow experimenting with different
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compression algorithms without having to have full-fledged integration
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into DwarFS. Essentially, this allows you to individually compress the
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blocks externally and see which algorithms/configurations work best.
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"""
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import sys
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from struct import unpack
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if len(sys.argv) != 3:
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print(f"USAGE: {__file__} <image> <basename>")
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raise SystemExit(1)
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sectypes = {
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0: "block",
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7: "schema",
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8: "metadata",
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9: "index",
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}
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compalgs = {
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0: "none",
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1: "lzma",
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2: "zstd",
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3: "lz4",
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4: "lz4hc",
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}
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_, image, basename = sys.argv
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with open(image, "rb") as image:
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while True:
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header = image.read(0x40)
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if len(header) < 0x40:
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break
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ident, major, minor, sha512, xxh3, secno, sectype, compalg, blocklen = unpack(
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"<6sBB32s8sLHHQ", header
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)
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if ident != b"DWARFS":
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print(f"error: expected dwarfs header")
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raise SystemExit(1)
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if sectype not in sectypes:
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print(f"error: unexpected section type ({sectype})")
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raise SystemExit(1)
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if compalg not in compalgs:
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print(f"error: unexpected compression algorithm ({compalg})")
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raise SystemExit(1)
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print(
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f"{ident.decode('ascii')} v{major}.{minor} [{secno}] {sectypes[sectype]} ({compalgs[compalg]}) {blocklen} bytes"
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)
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block = image.read(blocklen)
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with open(f"{basename}{sectypes[sectype]}{secno}", "wb") as out:
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out.write(block)
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