header

Documentation

Index

• Constants
• Variables
• func PutBasic(b []byte, ts Timestamp, txnid TxnID, flags Flags)
• func Skip(val []byte) (value []byte, err error)
• type Flags
  • func (f Flags) IsDeleted() bool
  • func (f Flags) Masked() Flags
• type Header
  • func Parse(val []byte) (header Header, value []byte, err error)
  • func (h Header) Bytes() []byte
  • func (h Header) MarshalBinary() (data []byte, err error)
• type Timestamp
  • func ParseTimestamp(val []byte) (ts Timestamp, err error)
  • func TimestampFromTime(t time.Time) Timestamp
  • func (ts Timestamp) Time() time.Time
• type TxnID

Constants

const (
	// MinHeaderSize is the minimum header size when no extra blocks are present
	MinHeaderSize = 24
	// PreAllocSize is the number of bytes pre-allocated to fit a header
	// with extensions. Larger headers will trigger an additional heap alloc.
	PreAllocSize = 64
	// BlockSize is the number of bytes per extra block
	BlockSize = 8
)

const (
	VersionOffset      = 16
	FlagsOffset        = 17
	NumExtraOffsetHigh = 22 // uint16 high byte
	NumExtraOffsetLow  = 23 // uint16 low byte

)

Variables

var (
	ErrTooShort = errors.New("value too short to contain a header")
	ErrVersion  = errors.New("unsupported header version or not a header")
)

Functions

func PutBasic

func PutBasic(b []byte, ts Timestamp, txnid TxnID, flags Flags)

PutBasic creates a basic header in the provided slice. The slice must have a length of at least MinHeaderSize.

func Skip

func Skip(val []byte) (value []byte, err error)

Skip skips over the header and returns the remaining application value.

Types

type Flags

type Flags uint8

const (
	// FlagDeleted indicates that this entry has been deleted
	FlagDeleted Flags = 1

	// NoFlags can be used when no flags are needed, for readability
	NoFlags Flags = 0

	// FlagSyncMask is the mask of flags allowed to sync to/from a snapshot,
	// others will be cleared.
	FlagSyncMask = FlagDeleted
)

func (Flags) IsDeleted

func (f Flags) IsDeleted() bool

func (Flags) Masked

func (f Flags) Masked() Flags

type Header

type Header struct {
	Timestamp Timestamp // time of last change
	TxnID     TxnID     // lmdb Go lib uses uint64 and uintptr
	Version   int       // header version (currently always 0)
	Flags     Flags     // header flags
	NumExtra  int       // extra number of 8-byte blocks (set automatically in .Bytes())
	Extra     []byte    // bytes in extra block
}

Header describes the header of a native schema value

func Parse

func Parse(val []byte) (header Header, value []byte, err error)

Parse parses a value with header and returns the remaining application value.

func (Header) Bytes

func (h Header) Bytes() []byte

func (Header) MarshalBinary

func (h Header) MarshalBinary() (data []byte, err error)

type Timestamp

type Timestamp uint64

Timestamp is the number of nanoseconds since the UNIX epoch, which is how we write it to the header.

func ParseTimestamp

func ParseTimestamp(val []byte) (ts Timestamp, err error)

ParseTimestamp parses a timestamp from the first 8 bytes of the value

func TimestampFromTime

func TimestampFromTime(t time.Time) Timestamp

TimestampFromTime creates a Timestamp from a Time

func (Timestamp) Time

func (ts Timestamp) Time() time.Time

Time converts a Timestamp into Time

type TxnID

type TxnID uint64

TxnID is the LMDB transaction ID. The Go lmdb library inconsistently uses int64 and uintptr for this in different places.