use zlib_rs api
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| //! Implementation for `zlib_rs` rust backend. | ||
| //! | ||
| //! Every backend must provide two types: | ||
| //! | ||
| //! - `Deflate` for compression, implements the `Backend` and `DeflateBackend` trait | ||
| //! - `Inflate` for decompression, implements the `Backend` and `InflateBackend` trait | ||
| //! | ||
| //! Additionally the backend provides a number of constants, and a `ErrorMessage` type. | ||
| //! | ||
| //! ## Allocation | ||
| //! | ||
| //! The (de)compression state is not boxed. The C implementations require that the z_stream is | ||
| //! pinned in memory (has a fixed address), because their z_stream is self-referential. The most | ||
| //! convenient way in rust to guarantee a stable address is to `Box` the data, but it does add an | ||
| //! additional allocation. | ||
| //! | ||
| //! With zlib_rs the state is not self-referential and hence no boxing is needed. The `new` methods | ||
| //! internally do allocate space for the (de)compression state. | ||
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There was a problem hiding this comment. Lovely! This gives me the background about some fundamentals of the crate that I should have obtained years ago 😅. |
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| use std::fmt; | ||
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| use ::zlib_rs::{DeflateFlush, InflateError, InflateFlush}; | ||
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| pub const MZ_NO_FLUSH: isize = DeflateFlush::NoFlush as isize; | ||
| pub const MZ_PARTIAL_FLUSH: isize = DeflateFlush::PartialFlush as isize; | ||
| pub const MZ_SYNC_FLUSH: isize = DeflateFlush::SyncFlush as isize; | ||
| pub const MZ_FULL_FLUSH: isize = DeflateFlush::FullFlush as isize; | ||
| pub const MZ_FINISH: isize = DeflateFlush::Finish as isize; | ||
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| pub const MZ_DEFAULT_WINDOW_BITS: core::ffi::c_int = 15; | ||
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| use super::*; | ||
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| impl From<::zlib_rs::Status> for crate::mem::Status { | ||
| fn from(value: ::zlib_rs::Status) -> Self { | ||
| match value { | ||
| ::zlib_rs::Status::Ok => crate::mem::Status::Ok, | ||
| ::zlib_rs::Status::BufError => crate::mem::Status::BufError, | ||
| ::zlib_rs::Status::StreamEnd => crate::mem::Status::StreamEnd, | ||
| } | ||
| } | ||
| } | ||
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| #[derive(Clone, Default)] | ||
| pub struct ErrorMessage(Option<&'static str>); | ||
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| impl ErrorMessage { | ||
| pub fn get(&self) -> Option<&str> { | ||
| self.0 | ||
| } | ||
| } | ||
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| pub struct Inflate { | ||
| pub(crate) inner: ::zlib_rs::Inflate, | ||
| } | ||
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| impl fmt::Debug for Inflate { | ||
| fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { | ||
| write!( | ||
| f, | ||
| "zlib_rs inflate internal state. total_in: {}, total_out: {}", | ||
| self.inner.total_in(), | ||
| self.inner.total_out(), | ||
| ) | ||
| } | ||
| } | ||
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| impl From<FlushDecompress> for DeflateFlush { | ||
| fn from(value: FlushDecompress) -> Self { | ||
| match value { | ||
| FlushDecompress::None => Self::NoFlush, | ||
| FlushDecompress::Sync => Self::SyncFlush, | ||
| FlushDecompress::Finish => Self::Finish, | ||
| } | ||
| } | ||
| } | ||
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| impl InflateBackend for Inflate { | ||
| fn make(zlib_header: bool, window_bits: u8) -> Self { | ||
| Inflate { | ||
| inner: ::zlib_rs::Inflate::new(zlib_header, window_bits), | ||
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| } | ||
| } | ||
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| fn decompress( | ||
| &mut self, | ||
| input: &[u8], | ||
| output: &mut [u8], | ||
| flush: FlushDecompress, | ||
| ) -> Result<Status, DecompressError> { | ||
| let flush = match flush { | ||
| FlushDecompress::None => InflateFlush::NoFlush, | ||
| FlushDecompress::Sync => InflateFlush::SyncFlush, | ||
| FlushDecompress::Finish => InflateFlush::Finish, | ||
| }; | ||
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| match self.inner.decompress(input, output, flush) { | ||
| Ok(status) => Ok(status.into()), | ||
| Err(InflateError::NeedDict { dict_id }) => crate::mem::decompress_need_dict(dict_id), | ||
| Err(e) => crate::mem::decompress_failed(ErrorMessage(Some(e.as_str()))), | ||
| } | ||
| } | ||
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| fn reset(&mut self, zlib_header: bool) { | ||
| self.inner.reset(zlib_header); | ||
| } | ||
| } | ||
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| impl Backend for Inflate { | ||
| #[inline] | ||
| fn total_in(&self) -> u64 { | ||
| self.inner.total_in() | ||
| } | ||
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| #[inline] | ||
| fn total_out(&self) -> u64 { | ||
| self.inner.total_out() | ||
| } | ||
| } | ||
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| pub struct Deflate { | ||
| pub(crate) inner: ::zlib_rs::Deflate, | ||
| } | ||
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| impl fmt::Debug for Deflate { | ||
| fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { | ||
| write!( | ||
| f, | ||
| "zlib_rs deflate internal state. total_in: {}, total_out: {}", | ||
| self.inner.total_in(), | ||
| self.inner.total_out(), | ||
| ) | ||
| } | ||
| } | ||
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| impl DeflateBackend for Deflate { | ||
| fn make(level: Compression, zlib_header: bool, window_bits: u8) -> Self { | ||
| // Check in case the integer value changes at some point. | ||
| debug_assert!(level.level() <= 9); | ||
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| Deflate { | ||
| inner: ::zlib_rs::Deflate::new(level.level() as i32, zlib_header, window_bits), | ||
| } | ||
| } | ||
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| fn compress( | ||
| &mut self, | ||
| input: &[u8], | ||
| output: &mut [u8], | ||
| flush: FlushCompress, | ||
| ) -> Result<Status, CompressError> { | ||
| let flush = match flush { | ||
| FlushCompress::None => DeflateFlush::NoFlush, | ||
| FlushCompress::Partial => DeflateFlush::PartialFlush, | ||
| FlushCompress::Sync => DeflateFlush::SyncFlush, | ||
| FlushCompress::Full => DeflateFlush::FullFlush, | ||
| FlushCompress::Finish => DeflateFlush::Finish, | ||
| }; | ||
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| match self.inner.compress(input, output, flush) { | ||
| Ok(status) => Ok(status.into()), | ||
| Err(e) => crate::mem::compress_failed(ErrorMessage(Some(e.as_str()))), | ||
| } | ||
| } | ||
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| fn reset(&mut self) { | ||
| self.inner.reset(); | ||
| } | ||
| } | ||
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| impl Backend for Deflate { | ||
| #[inline] | ||
| fn total_in(&self) -> u64 { | ||
| self.inner.total_in() | ||
| } | ||
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| #[inline] | ||
| fn total_out(&self) -> u64 { | ||
| self.inner.total_out() | ||
| } | ||
| } | ||
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What would help me here is a quick idea of why this module exports what it exports. My guess is that these types are used to integrate with
flate2, and it expects these primitives to exist and implemented by each backend.It's probably stating the obvious then 😅, and maybe there can be more in-depth information on what makes this module a little bit special even. Are there implications for allocations? Does it allocate? I guess I'd be happy to ready about everything you were thinking at the time of writing so it's conserved.
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I wrote some things but yeah generally it's just the most bare-bones thing that satisfies the assumptions that are made about a backend.