Jeremy Tregunna
6fc3be617d
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Go Tests / Run Tests (1.24.2) (push) Has been cancelled
Adds a complete LSM-based storage engine with these features: - Single-writer based architecture for the storage engine - WAL for durability, and hey it's configurable - MemTable with skip list implementation for fast read/writes - SSTable with block-based structure for on-disk level-based storage - Background compaction with tiered strategy - ACID transactions - Good documentation (I hope)
122 lines
3.6 KiB
Go
122 lines
3.6 KiB
Go
package footer
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import (
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"encoding/binary"
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"fmt"
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"io"
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"time"
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"github.com/cespare/xxhash/v2"
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)
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const (
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// FooterSize is the fixed size of the footer in bytes
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FooterSize = 52
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// FooterMagic is a magic number to verify we're reading a valid footer
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FooterMagic = uint64(0xFACEFEEDFACEFEED)
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// CurrentVersion is the current file format version
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CurrentVersion = uint32(1)
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)
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// Footer contains metadata for an SSTable file
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type Footer struct {
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// Magic number for integrity checking
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Magic uint64
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// Version of the file format
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Version uint32
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// Timestamp of when the file was created
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Timestamp int64
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// Offset where the index block starts
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IndexOffset uint64
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// Size of the index block in bytes
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IndexSize uint32
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// Total number of key/value pairs
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NumEntries uint32
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// Smallest key in the file
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MinKeyOffset uint32
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// Largest key in the file
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MaxKeyOffset uint32
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// Checksum of all footer fields excluding the checksum itself
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Checksum uint64
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}
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// NewFooter creates a new footer with the given parameters
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func NewFooter(indexOffset uint64, indexSize uint32, numEntries uint32,
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minKeyOffset, maxKeyOffset uint32) *Footer {
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return &Footer{
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Magic: FooterMagic,
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Version: CurrentVersion,
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Timestamp: time.Now().UnixNano(),
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IndexOffset: indexOffset,
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IndexSize: indexSize,
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NumEntries: numEntries,
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MinKeyOffset: minKeyOffset,
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MaxKeyOffset: maxKeyOffset,
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Checksum: 0, // Will be calculated during serialization
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}
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}
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// Encode serializes the footer to a byte slice
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func (f *Footer) Encode() []byte {
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result := make([]byte, FooterSize)
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// Encode all fields directly into the buffer
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binary.LittleEndian.PutUint64(result[0:8], f.Magic)
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binary.LittleEndian.PutUint32(result[8:12], f.Version)
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binary.LittleEndian.PutUint64(result[12:20], uint64(f.Timestamp))
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binary.LittleEndian.PutUint64(result[20:28], f.IndexOffset)
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binary.LittleEndian.PutUint32(result[28:32], f.IndexSize)
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binary.LittleEndian.PutUint32(result[32:36], f.NumEntries)
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binary.LittleEndian.PutUint32(result[36:40], f.MinKeyOffset)
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binary.LittleEndian.PutUint32(result[40:44], f.MaxKeyOffset)
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// Calculate checksum of all fields excluding the checksum itself
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f.Checksum = xxhash.Sum64(result[:44])
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binary.LittleEndian.PutUint64(result[44:], f.Checksum)
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return result
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}
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// WriteTo writes the footer to an io.Writer
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func (f *Footer) WriteTo(w io.Writer) (int64, error) {
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data := f.Encode()
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n, err := w.Write(data)
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return int64(n), err
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}
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// Decode parses a footer from a byte slice
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func Decode(data []byte) (*Footer, error) {
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if len(data) < FooterSize {
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return nil, fmt.Errorf("footer data too small: %d bytes, expected %d",
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len(data), FooterSize)
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}
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footer := &Footer{
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Magic: binary.LittleEndian.Uint64(data[0:8]),
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Version: binary.LittleEndian.Uint32(data[8:12]),
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Timestamp: int64(binary.LittleEndian.Uint64(data[12:20])),
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IndexOffset: binary.LittleEndian.Uint64(data[20:28]),
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IndexSize: binary.LittleEndian.Uint32(data[28:32]),
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NumEntries: binary.LittleEndian.Uint32(data[32:36]),
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MinKeyOffset: binary.LittleEndian.Uint32(data[36:40]),
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MaxKeyOffset: binary.LittleEndian.Uint32(data[40:44]),
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Checksum: binary.LittleEndian.Uint64(data[44:]),
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}
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// Verify magic number
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if footer.Magic != FooterMagic {
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return nil, fmt.Errorf("invalid footer magic: %x, expected %x",
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footer.Magic, FooterMagic)
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}
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// Verify checksum
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expectedChecksum := xxhash.Sum64(data[:44])
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if footer.Checksum != expectedChecksum {
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return nil, fmt.Errorf("footer checksum mismatch: file has %d, calculated %d",
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footer.Checksum, expectedChecksum)
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}
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return footer, nil
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}
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