Class Zstandard

Namespace

Egami.Compression

Assembly

Egami.dll

Zstandard (RFC 8878) compression in managed code: the codec TIFF's ZSTD compression uses, for format plugins and apps that need it too, such as KTX 2's supercompressed mip levels. Both directions work on spans the caller sizes, and each thread keeps its tables, so a warm call allocates nothing.

public static class Zstandard

Inheritance

object

Zstandard

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Examples

// Compress into a buffer sized for the worst case, then keep the bytes written.
byte[] packed = new byte[Zstandard.MaxCompressedLength(data.Length)];
int written = Zstandard.Compress(data, packed, level: 9);

// Decompress into a buffer of the size you know (KTX 2 stores each level's): it returns the bytes written.
byte[] unpacked = new byte[data.Length];
int length = Zstandard.Decompress(packed.AsSpan(0, written), unpacked);

Fields

DefaultLevel

The level Compress(ReadOnlySpan<byte>, Span<byte>, int) uses when none is given, as the zstd tool's default.

public const int DefaultLevel = 3

Field Value

int

MaxLevel

The highest compression level, the smallest output.

public const int MaxLevel = 22

Field Value

int

MinLevel

The lowest compression level, the fastest.

public const int MinLevel = 1

Field Value

int

Methods

Compress(ReadOnlySpan<byte>, Span<byte>, int)

Compresses source into one Zstandard frame that records its content size and has no checksum.

public static int Compress(ReadOnlySpan<byte> source, Span<byte> destination, int level = 3)

Parameters

source ReadOnlySpan<byte>

The bytes to compress.

destination Span<byte>

Where the frame goes; it needs room for MaxCompressedLength(int) bytes.

level int

The level, from MinLevel to MaxLevel.

Returns

int

The bytes written.

Exceptions

ArgumentOutOfRangeException

level is out of range.

ArgumentException

destination is shorter than MaxCompressedLength(int).

Decompress(ReadOnlySpan<byte>, Span<byte>)

Decompresses the Zstandard frames of source, one after another, into destination. Skippable frames are skipped and a frame's checksum is checked when it has one.

public static int Decompress(ReadOnlySpan<byte> source, Span<byte> destination)

Parameters

source ReadOnlySpan<byte>

The compressed frames.

destination Span<byte>

Where the bytes go; the data must fit in it.

Returns

int

The bytes written. Bytes after that count may have been written to.

Exceptions

CorruptDataException

The data breaks the format, or needs more room than destination has.

UnsupportedFormatException

A frame needs a dictionary.

MaxCompressedLength(int)

Gets the most bytes Compress(ReadOnlySpan<byte>, Span<byte>, int) can write for length bytes of input.

public static int MaxCompressedLength(int length)

Parameters

length int

The number of bytes to compress.

Returns

int

The room the output needs.

Exceptions

ArgumentOutOfRangeException

length is negative, or the result does not fit an int.