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use crate::error::Result;
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
#[repr(u8)]
pub enum CompressionType {
NoCompression = 0,
Lz4 = 1,
Snappy = 2,
}
pub struct Compress {
inner: Compressor,
pub threshold: u32,
}
impl Compress {
pub fn new(kind: CompressionType, threshold: u32) -> Self {
Compress { inner: kind.into(), threshold }
}
}
pub const NO_COMPRESSION: Compress =
Compress { inner: Compressor::NoCompression(NoCompression), threshold: u32::MAX };
enum Compressor {
NoCompression(NoCompression),
Lz4(lz4::Lz4),
Snappy(snappy::Snappy),
}
impl From<u8> for CompressionType {
fn from(comp_type: u8) -> Self {
match comp_type {
a if a == CompressionType::NoCompression as u8 => CompressionType::NoCompression,
a if a == CompressionType::Lz4 as u8 => CompressionType::Lz4,
a if a == CompressionType::Snappy as u8 => CompressionType::Snappy,
_ => panic!("Unknown compression."),
}
}
}
impl From<CompressionType> for Compressor {
fn from(comp_type: CompressionType) -> Self {
match comp_type {
CompressionType::NoCompression => Compressor::NoCompression(NoCompression),
CompressionType::Lz4 => Compressor::Lz4(lz4::Lz4::new()),
CompressionType::Snappy => Compressor::Snappy(snappy::Snappy::new()),
#[allow(unreachable_patterns)]
_ => unimplemented!("Missing compression implementation."),
}
}
}
impl From<&Compress> for CompressionType {
fn from(compression: &Compress) -> Self {
match compression.inner {
Compressor::NoCompression(_) => CompressionType::NoCompression,
Compressor::Lz4(_) => CompressionType::Lz4,
Compressor::Snappy(_) => CompressionType::Snappy,
#[allow(unreachable_patterns)]
_ => unimplemented!("Missing compression implementation."),
}
}
}
impl Compress {
pub fn compress(&self, buf: &[u8]) -> Vec<u8> {
match &self.inner {
Compressor::NoCompression(inner) => inner.compress(buf),
Compressor::Lz4(inner) => inner.compress(buf),
Compressor::Snappy(inner) => inner.compress(buf),
#[allow(unreachable_patterns)]
_ => unimplemented!("Missing compression implementation."),
}
}
pub fn decompress(&self, buf: &[u8]) -> Result<Vec<u8>> {
Ok(match &self.inner {
Compressor::NoCompression(inner) => inner.decompress(buf)?,
Compressor::Lz4(inner) => inner.decompress(buf)?,
Compressor::Snappy(inner) => inner.decompress(buf)?,
#[allow(unreachable_patterns)]
_ => unimplemented!("Missing compression implementation."),
})
}
}
struct NoCompression;
impl NoCompression {
fn compress(&self, buf: &[u8]) -> Vec<u8> {
buf.to_vec()
}
fn decompress(&self, buf: &[u8]) -> Result<Vec<u8>> {
Ok(buf.to_vec())
}
}
mod lz4 {
use crate::error::{Error, Result};
pub(super) struct Lz4;
impl Lz4 {
pub(super) fn new() -> Self {
Lz4
}
pub(super) fn compress(&self, buf: &[u8]) -> Vec<u8> {
lz4::block::compress(buf, Some(lz4::block::CompressionMode::DEFAULT), true).unwrap()
}
pub(super) fn decompress(&self, buf: &[u8]) -> Result<Vec<u8>> {
lz4::block::decompress(buf, None).map_err(|_| Error::Compression)
}
}
}
mod snappy {
use crate::error::{Error, Result};
use std::io::{Read, Write};
pub(super) struct Snappy;
impl Snappy {
pub(super) fn new() -> Self {
Snappy
}
pub(super) fn compress(&self, value: &[u8]) -> Vec<u8> {
let mut buf = Vec::with_capacity(value.len() << 3);
{
let mut encoder = snap::write::FrameEncoder::new(&mut buf);
encoder.write_all(value).expect("Expect in memory write to succeed.");
}
buf
}
pub(super) fn decompress(&self, value: &[u8]) -> Result<Vec<u8>> {
let mut buf = Vec::with_capacity(value.len());
let mut decoder = snap::read::FrameDecoder::new(value);
decoder.read_to_end(&mut buf).map_err(|_| Error::Compression)?;
Ok(buf)
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_compression_interfaces() {
let original = vec![42; 100];
let types =
vec![CompressionType::NoCompression, CompressionType::Snappy, CompressionType::Lz4];
for compression_type in types {
let compress = Compress::new(compression_type, 0);
let v = compress.compress(&original[..]);
assert!(v.len() <= 100);
let round_tripped = compress.decompress(&v[..]).unwrap();
assert_eq!(original, round_tripped);
}
}
}