Codec.Compression.Zstd

A fast lossless compression algorithm, targeting real-time compression scenarios at zlib-level and better compression ratios.

Basic pure API

compress

Arguments

:: Int

Compression level. Must be >= 1 and <= maxCLevel.

-> ByteString

Payload to compress.

-> ByteString

Compress the given data as a single zstd compressed frame.

data Decompress

The result of a decompression operation.

Constructors

Skip

Either the compressed frame was empty, or it was compressed in streaming mode and so its size is not known.

Error String

An error occurred.

Decompress ByteString

The payload was successfully decompressed.

Instances

Eq Decompress

Defined in Codec.Compression.Zstd.Types

Methods

(==) :: Decompress -> Decompress -> Bool

(/=) :: Decompress -> Decompress -> Bool

Read Decompress

Defined in Codec.Compression.Zstd.Types

Methods

readsPrec :: Int -> ReadS Decompress

readList :: ReadS [Decompress]

readPrec :: ReadPrec Decompress

readListPrec :: ReadPrec [Decompress]

Show Decompress

Defined in Codec.Compression.Zstd.Types

Methods

showsPrec :: Int -> Decompress -> ShowS

show :: Decompress -> String

showList :: [Decompress] -> ShowS

decompressedSize :: ByteString -> Maybe Int

Return the decompressed size of a compressed payload, as stored in the payload's header.

The returned value will be Nothing if it is either not known (probably because the payload was compressed using a streaming API), empty, or too large to fit in an Int.

Note: this value should not be trusted, as it can be controlled by an attacker.

decompress :: ByteString -> Decompress

Decompress a single-frame payload of known size. Typically this will be a payload that was compressed with compress.

Note: This function is not capable of decompressing a payload generated by the streaming or lazy compression APIs.

maxCLevel :: Int

The maximum compression level supported by the library.

Dictionary-based compression

data Dict

Compression dictionary.

Instances

Eq Dict

Defined in Codec.Compression.Zstd.Types

Methods

(==) :: Dict -> Dict -> Bool

(/=) :: Dict -> Dict -> Bool

Ord Dict

Defined in Codec.Compression.Zstd.Types

Methods

compare :: Dict -> Dict -> Ordering

(<) :: Dict -> Dict -> Bool

(<=) :: Dict -> Dict -> Bool

(>) :: Dict -> Dict -> Bool

(>=) :: Dict -> Dict -> Bool

max :: Dict -> Dict -> Dict

min :: Dict -> Dict -> Dict

Read Dict

Defined in Codec.Compression.Zstd.Types

Methods

readsPrec :: Int -> ReadS Dict

readList :: ReadS [Dict]

readPrec :: ReadPrec Dict

readListPrec :: ReadPrec [Dict]

Show Dict

Defined in Codec.Compression.Zstd.Types

Methods

showsPrec :: Int -> Dict -> ShowS

show :: Dict -> String

showList :: [Dict] -> ShowS

NFData Dict

Defined in Codec.Compression.Zstd.Types

Methods

rnf :: Dict -> ()

mkDict :: ByteString -> Dict

Smart constructor.

fromDict :: Dict -> ByteString

trainFromSamples

Arguments

:: Int

Maximum size of the compression dictionary to create. The actual dictionary returned may be smaller.

-> [ByteString]

Samples to train with.

-> Either String Dict

Create and train a compression dictionary from a collection of samples.

To create a well-trained dictionary, here are some useful guidelines to keep in mind:

• A reasonable dictionary size is in the region of 100 KB. (Trying to specify a dictionary size of less than a few hundred bytes will probably fail.)
• To train the dictionary well, it is best to supply a few thousand training samples.
• The combined size of all training samples should be 100 or more times larger than the size of the dictionary.

getDictID :: Dict -> Maybe Word

Return the identifier for the given dictionary, or Nothing if not a valid dictionary.

Basic pure API

compressUsingDict

Arguments

:: Dict

Compression dictionary.

-> Int

Compression level. Must be >= 1 and <= maxCLevel.

-> ByteString

Payload to compress.

-> ByteString

Compress the given data as a single zstd compressed frame, using a prebuilt dictionary.

decompressUsingDict

Arguments

:: Dict

Dictionary.

-> ByteString

Payload to decompress.

-> Decompress

Decompress a single-frame payload of known size, using a prebuilt dictionary. Typically this will be a payload that was compressed with compressUsingDict.

Note: This function is not capable of decompressing a payload generated by the streaming or lazy compression APIs.