Struct q_compress::standalone::Compressor

pub struct Compressor<T: NumberLike>(_);

Converts vectors of numbers into compressed bytes in .qco format.

Most compressor methods leave its state unchanged if they return an error. You can configure behavior like compression level by instantiating with .from_config()

You can use the standalone compressor at a file or chunk level.

use q_compress::standalone::Compressor;

let my_nums = vec![1, 2, 3];

// FILE LEVEL
let mut compressor = Compressor::<i32>::default();
let bytes = compressor.simple_compress(&my_nums);

// CHUNK LEVEL
let mut compressor = Compressor::<i32>::default();
compressor.header().expect("header");
compressor.chunk(&my_nums).expect("chunk");
compressor.footer().expect("footer");
let bytes = compressor.drain_bytes();

Note that in practice we would need larger chunks than this to achieve good compression, preferably containing 2k-10M numbers.

Implementations

impl<T: NumberLike> Compressor<T>

pub fn from_config(config: CompressorConfig) -> Self

Creates a new compressor, given a CompressorConfig. Internally, the compressor builds Flags as well as an internal configuration that doesn’t show up in the output file. You can inspect the flags it chooses with .flags().

pub fn flags(&self) -> &Flags

Returns a reference to the compressor’s flags.

pub fn header(&mut self) -> QCompressResult<()>

Writes out a header using the compressor’s data type and flags. Will return an error if the compressor has already written the header.

Each .qco file must start with such a header, which contains:

• a 4-byte magic header for “qco!” in ascii,
• a byte for the data type (e.g. i64 has byte 1 and f64 has byte 5), and
• bytes for the flags used to compress.

pub fn chunk(&mut self, nums: &[T]) -> QCompressResult<ChunkMetadata<T>>

Writes out a chunk of data representing the provided numbers. Will return an error if the compressor has not yet written the header or already written the footer.

Each chunk contains a ChunkMetadata section followed by the chunk body. The chunk body encodes the numbers passed in here.

pub fn footer(&mut self) -> QCompressResult<()>

Writes out a single footer byte indicating that the .qco file has ended. Will return an error if the compressor has not yet written the header or already written the footer.

pub fn simple_compress(&mut self, nums: &[T]) -> Vec<u8>

Takes in a slice of numbers and returns compressed bytes.

Unlike most methods, this does not guarantee atomicity of the compressor’s state.

pub fn drain_bytes(&mut self) -> Vec<u8>

Returns all bytes produced by the compressor so far that have not yet been read.

pub fn byte_size(&mut self) -> usize

Returns the number of bytes produced by the compressor so far that have not yet been read.

Trait Implementations

impl<T: Clone + NumberLike> Clone for Compressor<T>

fn clone(&self) -> Compressor<T>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T: Debug + NumberLike> Debug for Compressor<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: NumberLike> Default for Compressor<T>

fn default() -> Self

Returns the “default value” for a type.