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feat: change region mmap read segment impl. #72

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Merged
auula merged 1 commit into from
Nov 21, 2025
Merged

feat: change region mmap read segment impl. #72

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78 changes: 3 additions & 75 deletions vfs/lfs.go
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Original file line number Diff line number Diff line change
Expand Up @@ -248,7 +248,7 @@ func (lfs *LogStructuredFS) FetchSegment(key string) (uint64, *Segment, error) {
return atomic.LoadUint64(&inode.mvcc), segment, nil
}

_, segment, err := readSegmentMmap(region.ReaderAt, atomic.LoadInt64(&inode.Position), _SEGMENT_PADDING)
_, segment, err := readSegment(region.ReaderAt, atomic.LoadInt64(&inode.Position), _SEGMENT_PADDING)
if err != nil {
return 0, nil, fmt.Errorf("failed to read segment from mmap: %w", err)
}
Expand Down Expand Up @@ -1092,80 +1092,8 @@ func checkFileSystem(path string, fsPerm fs.FileMode) error {
return nil
}

func readSegment(fd *os.File, offset, bufsize int64) (uint64, *Segment, error) {
buf := make([]byte, bufsize)

_, err := fd.ReadAt(buf, offset)
if err != nil {
return 0, nil, err
}

var seg Segment
readOffset := 0

seg.Tombstone = int8(buf[readOffset])
readOffset++

seg.Type = kind(buf[readOffset])
readOffset++

seg.ExpiredAt = int64(binary.LittleEndian.Uint64(buf[readOffset : readOffset+8]))
readOffset += 8

seg.CreatedAt = int64(binary.LittleEndian.Uint64(buf[readOffset : readOffset+8]))
readOffset += 8

seg.KeySize = int32(binary.LittleEndian.Uint32(buf[readOffset : readOffset+4]))
readOffset += 4

seg.ValueSize = int32(binary.LittleEndian.Uint32(buf[readOffset : readOffset+4]))
readOffset += 4

if seg.KeySize < 0 || seg.ValueSize < 0 {
return 0, nil, fmt.Errorf("invalid segment size: keySize=%d, valueSize=%d", seg.KeySize, seg.ValueSize)
}

keybuf := make([]byte, seg.KeySize)
_, err = fd.ReadAt(keybuf, int64(offset)+int64(readOffset))
if err != nil {
return 0, nil, fmt.Errorf("failed to parse key in segment: %w", err)
}
readOffset += int(seg.KeySize)

valuebuf := make([]byte, seg.ValueSize)
_, err = fd.ReadAt(valuebuf, int64(offset)+int64(readOffset))
if err != nil {
return 0, nil, fmt.Errorf("failed to parse value in segment: %w", err)
}
readOffset += int(seg.ValueSize)

checksumBuf := make([]byte, 4)
_, err = fd.ReadAt(checksumBuf, int64(offset)+int64(readOffset))
if err != nil {
return 0, nil, fmt.Errorf("failed to read checksum in segment: %w", err)
}

checksum := binary.LittleEndian.Uint32(checksumBuf)
buf = append(buf, keybuf...)
buf = append(buf, valuebuf...)

if checksum != crc32.ChecksumIEEE(buf) {
return 0, nil, fmt.Errorf("crc32 checksum mismatch: %d", checksum)
}

decodedData, err := transformer.Decode(valuebuf)
if err != nil {
return 0, nil, fmt.Errorf("failed to transformer decode value in segment: %w", err)
}

seg.Key = keybuf
seg.Value = decodedData

return inodeNum(string(keybuf)), &seg, nil
}

// | DEL 1 | KIND 1 | EAT 8 | CAT 8 | KLEN 4 | VLEN 4 | KEY ? | VALUE ? | CRC32 4 |
func readSegmentMmap(reader *mmap.ReaderAt, offset, bufsize int64) (uint64, *Segment, error) {
func readSegment(reader io.ReaderAt, offset, bufsize int64) (uint64, *Segment, error) {
buf := make([]byte, bufsize)

_, err := reader.ReadAt(buf, offset)
Expand Down Expand Up @@ -1462,7 +1390,7 @@ func (lfs *LogStructuredFS) cleanupDirtyRegions() error {
readOffset := int64(len(dataFileMetadata))

for readOffset < finfo.Size() {
inum, segment, err := readSegmentMmap(reg.ReaderAt, readOffset, _SEGMENT_PADDING)
inum, segment, err := readSegment(reg.ReaderAt, readOffset, _SEGMENT_PADDING)
if err != nil {
return err
}
Expand Down