hs-zstd-0.1.1.1: Haskell bindings to the Zstandard compression algorithm

Copyright(c) 2016-present Facebook Inc. All rights reserved.
LicenseBSD3
Maintainerbryano@fb.com
Stabilityexperimental
PortabilityGHC
Safe HaskellNone
LanguageHaskell2010

Codec.Compression.Zstd

Contents

Description

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

Synopsis

Basic pure API

compress Source #

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 Source #

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.

decompressedSize :: ByteString -> Maybe Int Source #

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 Source #

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 Source #

The maximum compression level supported by the library.

Dictionary-based compression

data Dict Source #

Compression dictionary.

Instances
Eq Dict Source # 
Instance details

Defined in Codec.Compression.Zstd.Types

Methods

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

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

Ord Dict Source # 
Instance details

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 Source # 
Instance details

Defined in Codec.Compression.Zstd.Types

Show Dict Source # 
Instance details

Defined in Codec.Compression.Zstd.Types

Methods

showsPrec :: Int -> Dict -> ShowS #

show :: Dict -> String #

showList :: [Dict] -> ShowS #

NFData Dict Source # 
Instance details

Defined in Codec.Compression.Zstd.Types

Methods

rnf :: Dict -> () #

mkDict :: ByteString -> Dict Source #

Smart constructor.

trainFromSamples Source #

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 Source #

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

Basic pure API

compressUsingDict Source #

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 Source #

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.