97 lines
2.9 KiB
Markdown
97 lines
2.9 KiB
Markdown
# Test Case: LZMA Compressed File Read
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**Test ID**: TC004-lzma-compressed-read
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**G5 fixture contract**: Use [G5-MANUAL-SETUP.md](G5-MANUAL-SETUP.md).
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Its generated paths, source comparisons, structured corruption offsets, and
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cleanup rules supersede placeholder examples in this file.
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**Category**: Compression
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**Priority**: High
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**Regression**: None
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## Objective
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Verify correct decompression and reading of LZMA/MicroLZMA-compressed files (newly implemented in repo18 iteration 1).
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## Preconditions
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- EROFS image with LZMA-compressed files: `test-lzma.erofs`
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- Known reference file: `original-large.txt` (uncompressed source)
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- Compressed file in image: `/compressed/large.txt`
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- Mount point: `/mnt/test`
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## Test Steps
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1. Mount the LZMA test image:
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```sh
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unit=$(mdconfig -a -t vnode -f test-lzma.erofs)
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mount -t erofs -o ro /dev/${unit} /mnt/test
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```
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2. Verify file exists and check size:
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```
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ls -lh /mnt/test/compressed/large.txt
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stat -f "Size: %z bytes" /mnt/test/compressed/large.txt
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```
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3. Read entire compressed file:
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```
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cat /mnt/test/compressed/large.txt > /tmp/lzma-decompressed.txt
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```
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4. Verify decompression correctness:
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```
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sha256 /tmp/lzma-decompressed.txt
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sha256 original-large.txt
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```
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5. Compare byte-for-byte:
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```
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cmp /tmp/lzma-decompressed.txt original-large.txt
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echo $?
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```
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6. Test random access read:
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```
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dd if=/mnt/test/compressed/large.txt of=/tmp/lzma-middle.txt bs=1k skip=100 count=10
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dd if=original-large.txt of=/tmp/orig-middle.txt bs=1k skip=100 count=10
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cmp /tmp/lzma-middle.txt /tmp/orig-middle.txt
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```
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7. Test end-of-file read:
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```
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tail -c 1000 /mnt/test/compressed/large.txt > /tmp/lzma-tail.txt
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tail -c 1000 original-large.txt > /tmp/orig-tail.txt
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cmp /tmp/lzma-tail.txt /tmp/orig-tail.txt
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```
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## Expected Results
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- Step 1: Mount succeeds
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- Step 2: File size matches original uncompressed size exactly
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- Step 4: SHA256 checksums are identical
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- Step 5: Exit code 0 (files identical)
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- Step 6: Middle section matches (random access works)
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- Step 7: Tail matches (EOF handling correct)
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## Verification Method
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- Complete data integrity check via SHA256
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- Partial read correctness (random access)
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- No memory corruption or crashes during decompression
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- Verify LZMA decoder internal state:
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- 1846 probability models initialized
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- Range decoder normalization correct
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- Dictionary buffer within bounds
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## Cleanup
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```
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umount /mnt/test
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mdconfig -d -u "${unit}"
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rm /tmp/lzma-*.txt /tmp/orig-*.txt
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```
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## Notes
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- **NEW in repo18**: This is the first iteration with LZMA support
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- LZMA provides maximum compression ratio (~30-50% smaller than LZ4)
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- MicroLZMA is a variant without header, commonly used in EROFS
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- Self-contained implementation in `src/decompressor_lzma.c`
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- Reference implementation: XZ Embedded minimal decoder
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- Critical test for repo18 iteration 1 validation
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- Regression marker: First LZMA implementation, high priority for validation
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