lzss

Documentation

Index

• Constants
• func AugmentDict(dict []byte) []byte
• func Decompress(data, dict []byte) (d []byte, err error)
• type BackrefType
  • func InitBackRefTypes(dictLen int, level Level) (short, long, dict BackrefType)
• type CompressionPhrase
• type CompressionPhrases
  • func CompressedStreamInfo(c, dict []byte) (CompressionPhrases, error)
  • func (c CompressionPhrases) ToCSV() []byte
• type Compressor
  • func NewCompressor(dict []byte, level Level) (*Compressor, error)
  • func (compressor *Compressor) Bytes() []byte
  • func (compressor *Compressor) Compress(d []byte) (c []byte, err error)
  • func (compressor *Compressor) CompressedSize256k(d []byte) (size int, err error)
  • func (compressor *Compressor) ConsiderBypassing() (bypassed bool)
  • func (compressor *Compressor) Len() int
  • func (compressor *Compressor) Reset()
  • func (compressor *Compressor) Revert() error
  • func (compressor *Compressor) Stream() compress.Stream
  • func (compressor *Compressor) Write(d []byte) (n int, err error)
  • func (compressor *Compressor) Written() int
  • func (compressor *Compressor) WrittenBytes() []byte
• type Header
  • func (s *Header) ReadFrom(r io.Reader) (int64, error)
  • func (s *Header) WriteTo(w io.Writer) (int64, error)
• type Level

Constants

const (
	MaxInputSize = 1 << 21 // 2Mb
	MaxDictSize  = 1 << 22 // 4Mb
)

const (
	SymbolDict  byte = 0xFF
	SymbolShort byte = 0xFE
	SymbolLong  byte = 0xFD
)

const (
	// Version is the current release version of the compressor.
	Version    = 0
	HeaderSize = 3
)

Functions

func AugmentDict

func AugmentDict(dict []byte) []byte

AugmentDict ensures the dictionary contains the special symbols

func Decompress

func Decompress(data, dict []byte) (d []byte, err error)

Decompress decompresses the given data using the given dictionary the dictionary must be the same as the one used to compress the data Note that this is not a fail-safe decompressor, it will fail ungracefully if the data has a different format than the one expected

Types

type BackrefType

type BackrefType struct {
	Delimiter     byte
	NbBitsAddress uint8
	NbBitsLength  uint8
	NbBitsBackRef uint8
	// contains filtered or unexported fields
}

func InitBackRefTypes

func InitBackRefTypes(dictLen int, level Level) (short, long, dict BackrefType)

type CompressionPhrase

type CompressionPhrase struct {
	Type              byte
	Length            int
	ReferenceAddress  int
	StartDecompressed int
	StartCompressed   int
	Content           []byte
}

type CompressionPhrases

type CompressionPhrases []CompressionPhrase

func CompressedStreamInfo

func CompressedStreamInfo(c, dict []byte) (CompressionPhrases, error)

func (CompressionPhrases) ToCSV

func (c CompressionPhrases) ToCSV() []byte

type Compressor

type Compressor struct {
	// contains filtered or unexported fields
}

func NewCompressor

func NewCompressor(dict []byte, level Level) (*Compressor, error)

NewCompressor returns a new compressor with the given dictionary The dictionary is an unstructured sequence of substrings that are expected to occur frequently in the data. It is not included in the compressed data and should thus be a-priori known to both the compressor and the decompressor. The level determines the bit alignment of the compressed data. The "higher" the level, the better the compression ratio but the more constraints on the decompressor.

func (*Compressor) Bytes

func (compressor *Compressor) Bytes() []byte

Bytes returns the compressed data

func (*Compressor) Compress

func (compressor *Compressor) Compress(d []byte) (c []byte, err error)

Compress compresses the given data and returns the compressed data

func (*Compressor) CompressedSize256k

func (compressor *Compressor) CompressedSize256k(d []byte) (size int, err error)

CompressedSize256k returns the size of the compressed data This is state less and thread-safe (but other methods are not) Max size of d is 256kB

func (*Compressor) ConsiderBypassing

func (compressor *Compressor) ConsiderBypassing() (bypassed bool)

ConsiderBypassing switches to NoCompression if we get significant expansion instead of compression

func (*Compressor) Len

func (compressor *Compressor) Len() int

Len returns the number of bytes compressed so far (includes the header)

func (*Compressor) Reset

func (compressor *Compressor) Reset()

func (*Compressor) Revert

func (compressor *Compressor) Revert() error

Revert undoes the last call to Write between any two calls to Revert, a call to Reset or Write should be made

func (*Compressor) Stream

func (compressor *Compressor) Stream() compress.Stream

Stream returns a stream of the compressed data

func (*Compressor) Write

func (compressor *Compressor) Write(d []byte) (n int, err error)

The compressor cannot recover from a Write error. It must be Reset before writing again

func (*Compressor) Written

func (compressor *Compressor) Written() int

Written returns the number of bytes written to the compressor

func (*Compressor) WrittenBytes

func (compressor *Compressor) WrittenBytes() []byte

WrittenBytes returns the bytes written to the compressor This returns a pointer to the internal buffer, so it should not be modified

type Header

type Header struct {
	Version uint16 // compressor release version
	Level   Level  // compression level

}

Header is the header of a compressed data. It contains the compressor release version and the compression level.

func (*Header) ReadFrom

func (s *Header) ReadFrom(r io.Reader) (int64, error)

func (*Header) WriteTo

func (s *Header) WriteTo(w io.Writer) (int64, error)

type Level

type Level uint8

const (
	NoCompression Level = 0
	// BestCompression allows the compressor to produce a stream of bit-level granularity,
	// giving the compressor this freedom helps it achieve better compression ratios but
	// will impose a high number of constraints on the SNARK decompressor
	BestCompression Level = 1

	GoodCompression        Level = 2
	GoodSnarkDecompression Level = 4

	// BestSnarkDecompression forces the compressor to produce byte-aligned output.
	// It is convenient and efficient for the SNARK decompressor but can hurt the compression ratio significantly
	BestSnarkDecompression Level = 8
)