test code v1

2026-08-13 10:44:59 +02:00
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+# Test Case: LZMA Compressed File Read
+
+**Test ID**: TC004-lzma-compressed-read  
+
+**G5 fixture contract**: Use [G5-MANUAL-SETUP.md](G5-MANUAL-SETUP.md).
+Its generated paths, source comparisons, structured corruption offsets, and
+cleanup rules supersede placeholder examples in this file.
+**Category**: Compression  
+**Priority**: High  
+**Regression**: None
+
+## Objective
+Verify correct decompression and reading of LZMA/MicroLZMA-compressed files (newly implemented in repo18 iteration 1).
+
+## Preconditions
+- EROFS image with LZMA-compressed files: `test-lzma.erofs`
+- Known reference file: `original-large.txt` (uncompressed source)
+- Compressed file in image: `/compressed/large.txt`
+- Mount point: `/mnt/test`
+
+## Test Steps
+1. Mount the LZMA test image:
+   ```sh
+   unit=$(mdconfig -a -t vnode -f test-lzma.erofs)
+   mount -t erofs -o ro /dev/${unit} /mnt/test
+   ```
+
+2. Verify file exists and check size:
+   ```
+   ls -lh /mnt/test/compressed/large.txt
+   stat -f "Size: %z bytes" /mnt/test/compressed/large.txt
+   ```
+
+3. Read entire compressed file:
+   ```
+   cat /mnt/test/compressed/large.txt > /tmp/lzma-decompressed.txt
+   ```
+
+4. Verify decompression correctness:
+   ```
+   sha256 /tmp/lzma-decompressed.txt
+   sha256 original-large.txt
+   ```
+
+5. Compare byte-for-byte:
+   ```
+   cmp /tmp/lzma-decompressed.txt original-large.txt
+   echo $?
+   ```
+
+6. Test random access read:
+   ```
+   dd if=/mnt/test/compressed/large.txt of=/tmp/lzma-middle.txt bs=1k skip=100 count=10
+   dd if=original-large.txt of=/tmp/orig-middle.txt bs=1k skip=100 count=10
+   cmp /tmp/lzma-middle.txt /tmp/orig-middle.txt
+   ```
+
+7. Test end-of-file read:
+   ```
+   tail -c 1000 /mnt/test/compressed/large.txt > /tmp/lzma-tail.txt
+   tail -c 1000 original-large.txt > /tmp/orig-tail.txt
+   cmp /tmp/lzma-tail.txt /tmp/orig-tail.txt
+   ```
+
+## Expected Results
+- Step 1: Mount succeeds
+- Step 2: File size matches original uncompressed size exactly
+- Step 4: SHA256 checksums are identical
+- Step 5: Exit code 0 (files identical)
+- Step 6: Middle section matches (random access works)
+- Step 7: Tail matches (EOF handling correct)
+
+## Verification Method
+- Complete data integrity check via SHA256
+- Partial read correctness (random access)
+- No memory corruption or crashes during decompression
+- Verify LZMA decoder internal state:
+  - 1846 probability models initialized
+  - Range decoder normalization correct
+  - Dictionary buffer within bounds
+
+## Cleanup
+```
+umount /mnt/test
+mdconfig -d -u "${unit}"
+rm /tmp/lzma-*.txt /tmp/orig-*.txt
+```
+
+## Notes
+- **NEW in repo18**: This is the first iteration with LZMA support
+- LZMA provides maximum compression ratio (~30-50% smaller than LZ4)
+- MicroLZMA is a variant without header, commonly used in EROFS
+- Self-contained implementation in `src/decompressor_lzma.c`
+- Reference implementation: XZ Embedded minimal decoder
+- Critical test for repo18 iteration 1 validation
+- Regression marker: First LZMA implementation, high priority for validation