erofs-freebsd-out-tree/tests/TC004-lzma-compressed-read.md

Test Case: LZMA Compressed File Read

Test ID: TC004-lzma-compressed-read

G5 fixture contract: Use 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:

   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