use crate::tags::CompressionMethod;
use std::io::{self, Write};
mod deflate;
mod lzw;
mod packbits;
mod uncompressed;
pub use self::deflate::{Deflate, DeflateLevel};
pub use self::lzw::Lzw;
pub use self::packbits::Packbits;
pub use self::uncompressed::Uncompressed;
/// An algorithm used for compression
pub trait CompressionAlgorithm {
/// The algorithm writes data directly into the writer.
/// It returns the total number of bytes written.
fn write_to<W: Write>(&mut self, writer: &mut W, bytes: &[u8]) -> Result<u64, io::Error>;
}
/// An algorithm used for compression with associated enums and optional configurations.
pub trait Compression: CompressionAlgorithm {
/// The corresponding tag to the algorithm.
const COMPRESSION_METHOD: CompressionMethod;
/// Method to optain a type that can store each variant of comression algorithm.
fn get_algorithm(&self) -> Compressor;
}
/// An enum to store each compression algorithm.
pub enum Compressor {
Uncompressed(Uncompressed),
Lzw(Lzw),
Deflate(Deflate),
Packbits(Packbits),
}
impl Default for Compressor {
/// The default compression strategy does not apply any compression.
fn default() -> Self {
Compressor::Uncompressed(Uncompressed)
}
}
impl CompressionAlgorithm for Compressor {
fn write_to<W: Write>(&mut self, writer: &mut W, bytes: &[u8]) -> Result<u64, io::Error> {
match self {
Compressor::Uncompressed(algorithm) => algorithm.write_to(writer, bytes),
Compressor::Lzw(algorithm) => algorithm.write_to(writer, bytes),
Compressor::Deflate(algorithm) => algorithm.write_to(writer, bytes),
Compressor::Packbits(algorithm) => algorithm.write_to(writer, bytes),
}
}
}
#[cfg(test)]
mod tests {
pub const TEST_DATA: &[u8] = b"This is a string for checking various compression algorithms.";
}