Streamly.Internal.LZ4.Config

Frame and block configuration settings for LZ4.

LZ4 Frame Format

Configuration for a frame consisting of a series of blocks.

newtype FrameConfig

Defines the LZ4 frame format.

Constructors

FrameConfig

Fields

• hasEndMark :: Bool

setFrameContentSize :: Bool -> FrameConfig -> FrameConfig

Whether the frame header has a content size field.

Unimplemented

setFrameContentChecksum :: Bool -> FrameConfig -> FrameConfig

Whether the frame footer has a content checksum after the end mark. If it is True then it implicitly indicates that setEndMark is set to True.

Unimplemented

setFrameDictionaryId :: Bool -> FrameConfig -> FrameConfig

Whether the frame header has a dictionary ID field.

Unimplemented

setFrameBlockIndependence :: Bool -> FrameConfig -> FrameConfig

When False, future blocks in the frame may depend on the past blocks. Block dependency improves compression ratio, especially for small blocks. On the other hand, it makes random access or multi-threaded decoding impossible.

Unimplemented

setFrameBlockChecksum :: Bool -> FrameConfig -> FrameConfig

Indicate whether blocks in the frame are followed by a 4-byte checksum field.

Unimplemented

setFrameEndMark :: Bool -> FrameConfig -> FrameConfig

Whether the frame footer has an end mark.

defaultFrameConfig :: FrameConfig

The default settings are:

• setFrameContentSize False
• setFrameDictionaryId False
• setFrameBlockIndependence False
• setFrameBlockChecksum False
• setFrameEndMark False

LZ4 Block Format

Configuration for a single compressed block.

newtype BlockConfig

Defines the LZ4 compressed block format. Please note that the Uncompressed length field is optional and not in the LZ4 specification.

 ----------------------------------------------------------------------
| Compressed length | Uncompressed length | Data | Checksum            |
|       (4 byte)    | (4 byte) (optional) |      | (4 byte) (optional) |
 ----------------------------------------------------------------------

Compressed length is the length of the Data field only. Uncompressed length is present only when the setBlockMaxSize is set to BlockHasSize. Checksum is present when setBlockChecksum is set to True. The 4-byte fields are stored in machine byte order.

Constructors

BlockConfig

Fields

• blockSize :: BlockSize

data BlockSize

Maximum uncompressed size of a data block.

Constructors

BlockHasSize

Block header has uncompressed size after the compressed size field. Please note that this option is not in the LZ4 specification.

BlockMax64KB

BlockMax256KB

BlockMax1MB

BlockMax4MB

setBlockMaxSize :: BlockSize -> BlockConfig -> BlockConfig

Set the maximum uncompressed size of the data block.

setBlockIndependence :: Bool -> BlockConfig -> BlockConfig

When False, the block may depend on the past blocks.

Unimplemented

setBlockChecksum :: Bool -> BlockConfig -> BlockConfig

Indicate whether the block is followed by a 4-byte checksum field.

Unimplemented

defaultBlockConfig :: BlockConfig

The default settings are:

• setBlockMaxSize BlockHasSize
• setBlockIndependence False
• setBlockChecksum False