Documentation
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Index ¶
Constants ¶
const DiskRecordHeaderSizeBytes = 20
CRC (4) + Timestamp (8) + KeySize (4) + ValueSize (4)
const HintRecordHeaderSizeBytes = 24
KeySize (4) + FileNameSize (4) + Offset (4) + ValueSize (4) + Timestamp (8)
Variables ¶
This section is empty.
Functions ¶
func CalculateCRC ¶
CalculateCRC computes the CRC32 checksum of the key-value pair using IEEE polynomial.
func EncodeHintRecordToBytes ¶
func EncodeHintRecordToBytes(hintRecord *HintRecord) ([]byte, error)
EncodeHintRecordToBytes serializes a HintRecord into its on-disk binary form.
Hint records are written sequentially into hint files and are used only during startup for faster KeyDir reconstruction.
func EncodeRecordToBytes ¶
func EncodeRecordToBytes(record *DiskRecord) ([]byte, error)
EncodeRecordToBytes serializes a DiskRecord into its on-disk binary form.
The returned byte slice is suitable for direct append-only writing to a Bitcask datafile.
func ValidateCRC ¶
ValidateCRC returns true if the provided checksum matches the computed CRC32 of the key-value pair
Types ¶
type DiskRecord ¶
type DiskRecord struct {
CRC uint32 // CRC checksum of Key and Value
Timestamp int64 // Unix timestamp in nanoseconds
KeySize uint32 // Length of Key in bytes
ValueSize uint32 // Length of Value in bytes (0 indicates tombstone)
Key []byte // Raw key bytes
Value []byte // Raw value bytes
}
DiskRecord represents a single append-only record stored in a Bitcask datafile.
DiskRecords are written sequentially and never modified in place. Newer versions of a key supersede older ones based on the Timestamp.
Layout on disk (little-endian):
CRC (4 bytes) Timestamp (8 bytes) KeySize (4 bytes) ValueSize (4 bytes) Key (KeySize bytes) Value (ValueSize bytes)
A record with ValueSize == 0 represents a tombstone (logical delete).
func CreateRecord ¶
func CreateRecord(key, value string) DiskRecord
CreateRecord constructs a new DiskRecord for the given key and value.
It computes the CRC over the key and value and assigns the current time as the record timestamp.
func CreateTombstoneRecord ¶
func CreateTombstoneRecord(key string) DiskRecord
CreateTombstoneRecord constructs a DiskRecord representing a logical delete (tombstone) for the given key.
Tombstone records have ValueSize == 0 and are used to invalidate older versions of the key during reads and compaction.
func DecodeRecordFromBytes ¶
func DecodeRecordFromBytes(data []byte) (*DiskRecord, error)
DecodeRecordFromBytes deserializes a DiskRecord from its binary form.
The input byte slice must contain a complete record, including the header, key, and value. Tombstone records (ValueSize == 0) are rejected.
type HintRecord ¶
type HintRecord struct {
KeySize uint32 // Length of Key in bytes
FileNameSize uint32 // Length of FileName in bytes
Offset uint32 // Byte offset of the record in the datafile
ValueSize uint32 // Length of Value in bytes
Timestamp int64 // Timestamp of the record
Key []byte // Raw key bytes
FileName []byte // Datafile name containing the record
}
HintRecord represents a compact index entry stored in a hint file.
Hint files are advisory structures used to reconstruct the in-memory KeyDir quickly on startup without scanning full datafiles.
Layout on disk (little-endian):
KeySize (4 bytes) FileNameSize (4 bytes) Offset (4 bytes) ValueSize (4 bytes) Timestamp (8 bytes) Key (KeySize bytes) FileName (FileNameSize bytes)
func DecodeHintRecordFromBytes ¶
func DecodeHintRecordFromBytes(data []byte) (*HintRecord, error)
DecodeHintRecordFromBytes deserializes a HintRecord from its binary form.
The input byte slice must contain a complete hint record, including the header, key, and file name.
Source Files