building_blocks_storage 0.7.1

mod compressed_bincode;

#[cfg(feature = "lz4")]
mod lz4_compression;
#[cfg(feature = "snap")]
mod snappy_compression;

pub use compressed_bincode::BincodeCompression;

#[cfg(feature = "lz4")]
pub use lz4_compression::Lz4;
#[cfg(feature = "snap")]
pub use snappy_compression::Snappy;

use serde::{Deserialize, Serialize};

/// An algorithm for:
///     1. compressing a specific type `Data` into type `Compressed`
///     2. decompressing `Compressed` back into `Data`
pub trait Compression: Sized {
    type Data;
    type CompressedData;

    fn compress(&self, data: &Self::Data) -> Compressed<Self>;
    fn decompress(compressed: &Self::CompressedData) -> Self::Data;
}

pub trait FromBytesCompression<B> {
    fn from_bytes_compression(bytes_compression: B) -> Self;
}

/// A value compressed with compression algorithm `A`.
#[derive(Clone, Deserialize, Serialize)]
pub struct Compressed<A>
where
    A: Compression,
{
    pub compressed_data: A::CompressedData,
    marker: std::marker::PhantomData<A>,
}

impl<T, A> Compressed<A>
where
    A: Compression<CompressedData = T>,
{
    pub fn new(compressed_data: A::CompressedData) -> Self {
        Self {
            compressed_data,
            marker: Default::default(),
        }
    }

    pub fn decompress(&self) -> A::Data {
        A::decompress(&self.compressed_data)
    }

    pub fn take(self) -> A::CompressedData {
        self.compressed_data
    }
}

/// A compression algorithm that acts directly on a slice of bytes.
pub trait BytesCompression {
    fn compress_bytes(&self, bytes: &[u8], compressed_bytes: impl std::io::Write);
    fn decompress_bytes(compressed_bytes: &[u8], bytes: &mut impl std::io::Write);
}

/// A value that is either compressed or decompressed.
pub enum MaybeCompressed<D, C> {
    Decompressed(D),
    Compressed(C),
}

impl<A: Compression> MaybeCompressed<A::Data, Compressed<A>> {
    pub fn into_decompressed(self) -> A::Data {
        match self {
            MaybeCompressed::Compressed(c) => c.decompress(),
            MaybeCompressed::Decompressed(d) => d,
        }
    }

    pub fn unwrap_decompressed(self) -> A::Data {
        match self {
            MaybeCompressed::Compressed(_) => panic!("Must be decompressed"),
            MaybeCompressed::Decompressed(d) => d,
        }
    }
}