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|
//! Common code for the compression writers.
use crate::{
Error,
Result,
};
/// Compression level.
///
/// This value is used by the encoders to tune their compression
/// strategy. The level is restricted to levels commonly used by
/// compression libraries, `0` to `9`, where `0` means no compression,
/// `1` means fastest compression, `6` being a good default, and
/// meaning `9` best compression.
///
/// Note that compression is [dangerous when used naively]. To mitigate some of
/// these issues messages should [use padding].
///
/// [dangerous when used naively]: https://mailarchive.ietf.org/arch/msg/openpgp/2FQUVt6Dw8XAsaMELyo5BNlh2pM
/// [use padding]: ../serialize/stream/padding/index.html
///
/// # Examples
///
/// Write a message using the given [CompressionAlgorithm]:
///
/// [CompressionAlgorithm]: enum.CompressionAlgorithm.html
///
/// ```
/// use sequoia_openpgp as openpgp;
/// # fn main() -> openpgp::Result<()> {
/// use std::io::Write;
/// use openpgp::serialize::stream::{Message, Compressor, LiteralWriter};
/// use openpgp::serialize::stream::padding::{Padder, padme};
/// use openpgp::types::{CompressionAlgorithm, CompressionLevel};
///
/// let mut sink = Vec::new();
/// let message = Message::new(&mut sink);
/// let message = Compressor::new(message)
/// .algo(CompressionAlgorithm::Zlib)
/// # .algo(CompressionAlgorithm::Uncompressed)
/// .level(CompressionLevel::fastest())
/// .build()?;
///
/// let message = Padder::new(message, padme)?;
///
/// let mut message = LiteralWriter::new(message).build()?;
/// message.write_all(b"Hello world.")?;
/// message.finalize()?;
/// # Ok(()) }
/// ```
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct CompressionLevel(u8);
impl Default for CompressionLevel {
fn default() -> Self {
Self(6)
}
}
impl CompressionLevel {
/// Creates a new compression level.
///
/// `level` must be in range `0..10`, where `0` means no
/// compression, `1` means fastest compression, `6` being a good
/// default, and meaning `9` best compression.
pub fn new(level: u8) -> Result<CompressionLevel> {
if level < 10 {
Ok(Self(level))
} else {
Err(Error::InvalidArgument(
format!("compression level out of range: {}", level)).into())
}
}
/// No compression.
pub fn none() -> CompressionLevel {
Self(0)
}
/// Fastest compression.
pub fn fastest() -> CompressionLevel {
Self(1)
}
/// Best compression.
pub fn best() -> CompressionLevel {
Self(9)
}
}
#[cfg(feature = "compression-deflate")]
mod into_deflate_compression {
use flate2::Compression;
use super::*;
impl From<CompressionLevel> for Compression {
fn from(l: CompressionLevel) -> Self {
Compression::new(l.0 as u32)
}
}
}
#[cfg(feature = "compression-bzip2")]
mod into_bzip2_compression {
use bzip2::Compression;
use super::*;
impl From<CompressionLevel> for Compression {
fn from(l: CompressionLevel) -> Self {
if l <= CompressionLevel::fastest() {
Compression::Fastest
} else if l <= CompressionLevel::default() {
Compression::Default
} else {
Compression::Best
}
}
}
}
|
