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Maurus Decimus
65 lines
1.9 KiB
Python
65 lines
1.9 KiB
Python
#!/usr/bin/env python3
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"""Decode a raw Stalwart blob object into its original bytes.
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Stalwart appends a one-byte compression marker to every blob it writes to the
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blob store (see BlobStore::put_blob in crates/store/src/dispatch/blob.rs):
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0x00 (NONE_MARKER) the preceding bytes are the verbatim payload
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0xa1 (LZ4_MARKER) the preceding bytes are an lz4_flex block prefixed with a
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little-endian u32 holding the uncompressed size
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other a legacy blob stored without a marker; emitted unchanged
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This mirrors the read path, which inspects the last byte, strips the marker and,
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for LZ4, decompresses the size-prepended block.
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Reads the object from a file (or stdin with "-") and writes the decoded payload
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to stdout (or to a file with -o).
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"""
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import argparse
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import sys
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NONE_MARKER = 0x00
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LZ4_MARKER = 0xA1
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def decode(data):
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if not data:
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return data
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marker = data[-1]
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if marker == LZ4_MARKER:
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import lz4.block
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return lz4.block.decompress(data[:-1])
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if marker == NONE_MARKER:
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return data[:-1]
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print(f"warning: no known compression marker (last byte 0x{marker:02x}); "
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"emitting bytes unchanged", file=sys.stderr)
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return data
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def main():
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ap = argparse.ArgumentParser(description=__doc__,
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formatter_class=argparse.RawDescriptionHelpFormatter)
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ap.add_argument("input", help='raw blob file, or "-" to read from stdin')
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ap.add_argument("-o", "--output",
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help="write the decoded payload here (default: stdout)")
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args = ap.parse_args()
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if args.input == "-":
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data = sys.stdin.buffer.read()
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else:
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with open(args.input, "rb") as fh:
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data = fh.read()
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out = decode(data)
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if args.output:
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with open(args.output, "wb") as fh:
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fh.write(out)
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else:
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sys.stdout.buffer.write(out)
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if __name__ == "__main__":
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main()
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