Struct Dictionary 

pub struct Dictionary {
    pub id: u32,
    pub fse: FSEScratch,
    pub huf: HuffmanScratch,
    pub dict_content: Vec<u8>,
    pub offset_hist: [u32; 3],
}

Zstandard includes support for “raw content” dictionaries, that store bytes optionally used during sequence execution.

https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#dictionary-format

Fields

id: u32

A 4 byte value used by decoders to check if they can use the correct dictionary. This value must not be zero.

fse: FSEScratch

A dictionary can contain an entropy table, either FSE or Huffman.

huf: HuffmanScratch

A dictionary can contain an entropy table, either FSE or Huffman.

dict_content: Vec<u8>

The content of a dictionary acts as a “past” in front of data to compress or decompress, so it can be referenced in sequence commands. As long as the amount of data decoded from this frame is less than or equal to Window_Size, sequence commands may specify offsets longer than the total length of decoded output so far to reference back to the dictionary, even parts of the dictionary with offsets larger than Window_Size. After the total output has surpassed Window_Size however, this is no longer allowed and the dictionary is no longer accessible

offset_hist: [u32; 3]

The 3 most recent offsets are stored so that they can be used during sequence execution, see https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#repeat-offsets for more.

Implementations

impl Dictionary

pub fn heap_bytes(&self) -> usize

Heap bytes owned by this dictionary: the content plus the parsed entropy tables’ heap (the fixed-size FSE decode arrays are inline, counted by size_of::<Dictionary>()).

pub fn from_raw_content( id: u32, dict_content: Vec<u8>, ) -> Result<Dictionary, DictionaryDecodeError>

Build a dictionary from raw content bytes (without entropy table sections).

This is primarily intended for dictionaries produced by the dict_builder module, which currently emits raw-content dictionaries.

pub fn decode_dict(raw: &[u8]) -> Result<Dictionary, DictionaryDecodeError>

Parses the dictionary from raw, initializes its tables, and returns a fully constructed Dictionary whose id can be checked against the frame’s dict_id.

pub fn into_handle(self) -> DictionaryHandle

Convert this parsed dictionary into a reusable shared handle.

Trait Implementations

impl AsRef<Dictionary> for DictionaryHandle

fn as_ref(&self) -> &Dictionary

Converts this type into a shared reference of the (usually inferred) input type.

impl Clone for Dictionary

fn clone(&self) -> Dictionary

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl From<Dictionary> for DictionaryHandle

fn from(dict: Dictionary) -> Self

Converts to this type from the input type.