sntable.go

package sntable

import (
	"errors"

	"github.com/klauspost/compress/zstd"
)

// magic terminates a v1 footer (16 bytes: indexOffset uint64 + magic).
var magic = []byte{71, 39, 134, 190, 31, 122, 101, 219}

// magicBloom terminates a v2 footer (24 bytes: indexOffset uint64 +
// bloomOffset uint64 + magicBloom). A v2 footer is only written when a bloom
// filter is present, so files without a filter stay byte-identical to v1 and
// older readers keep working.
var magicBloom = []byte{71, 39, 134, 190, 31, 122, 101, 220}

const (
	blockNoCompression     = 0
	blockSnappyCompression = 1
	blockZstdCompression   = 2
)

// Shared, concurrency-safe zstd codec instances for the block EncodeAll/DecodeAll APIs.
var (
	zstdEnc, _ = zstd.NewWriter(nil, zstd.WithEncoderLevel(zstd.SpeedDefault))
	zstdDec, _ = zstd.NewReader(nil)
)

// ErrNotFound is returned by the reader when a key cannot be found.
var ErrNotFound = errors.New("sntable: not found")

var (
	errClosed         = errors.New("sntable: is closed")
	errBadMagic       = errors.New("sntable: bad magic byte sequence")
	errBadCompression = errors.New("sntable: bad compression codec")
	errReleased       = errors.New("sntable: iterator was released")
)

type blockInfo struct {
	MaxKey uint64 // maximum key in the block
	Offset int64  // block offset position
}

// --------------------------------------------------------------------

// Compression is the compression codec
type Compression byte

func (c Compression) isValid() bool {
	return c >= SnappyCompression && c < unknownCompression
}

// Supported compression codecs
const (
	SnappyCompression Compression = iota
	NoCompression
	ZstdCompression
	unknownCompression
)