//! This code is copied from [zstd-rs PR #62](https://github.com/KillingSpark/zstd-rs/pull/62).//! It is vendored in and slightly modified because I am too impatient to wait for it//! to be merged and published to crates.io, and nixpkgs does not enjoy git dependencies. #![allow(dead_code)] // MIT License//// Copyright (c) 2019 Moritz Borcherding//// Permission is hereby granted, free of charge, to any person obtaining a copy// of this software and associated documentation files (the "Software"), to deal// in the Software without restriction, including without limitation the rights// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell// copies of the Software, and to permit persons to whom the Software is// furnished to do so, subject to the following conditions://// The above copyright notice and this permission notice shall be included in all// copies or substantial portions of the Software.//// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE// SOFTWARE. use core::borrow::BorrowMut; use ruzstd::frame_decoder::{BlockDecodingStrategy, FrameDecoder, FrameDecoderError};use ruzstd::io::{Error, ErrorKind, Read}; /// High level decoder that implements a io::Read that can be used with/// io::Read::read_to_end / io::Read::read_exact or passing this to another library / module as a source for the decoded content////// The lower level FrameDecoder by comparison allows for finer grained control but need sto have it's decode_blocks method called continuously/// to decode the zstd-frame.////// ## Caveat/// [StreamingDecoder] expects the underlying stream to only contain a single frame./// To decode all the frames in a finite stream, the calling code needs to recreate/// the instance of the decoder/// and handle/// [crate::frame::ReadFrameHeaderError::SkipFrame]/// errors by skipping forward the `length` amount of bytes, see <https://github.com/KillingSpark/zstd-rs/issues/57>pub struct StreamingDecoder<READ: Read, DEC: BorrowMut<FrameDecoder>> {    pub decoder: DEC,    source: READ,} impl<READ: Read, DEC: BorrowMut<FrameDecoder>> StreamingDecoder<READ, DEC> {    pub fn new_with_decoder(        mut source: READ,        mut decoder: DEC,    ) -> Result<StreamingDecoder<READ, DEC>, FrameDecoderError> {        decoder.borrow_mut().init(&mut source)?;        Ok(StreamingDecoder { decoder, source })    }} impl<READ: Read> StreamingDecoder<READ, FrameDecoder> {    pub fn new(        mut source: READ,    ) -> Result<StreamingDecoder<READ, FrameDecoder>, FrameDecoderError> {        let mut decoder = FrameDecoder::new();        decoder.init(&mut source)?;        Ok(StreamingDecoder { decoder, source })    }} impl<READ: Read, DEC: BorrowMut<FrameDecoder>> StreamingDecoder<READ, DEC> {    /// Gets a reference to the underlying reader.    pub fn get_ref(&self) -> &READ {        &self.source    }     /// Gets a mutable reference to the underlying reader.    ///    /// It is inadvisable to directly read from the underlying reader.    pub fn get_mut(&mut self) -> &mut READ {        &mut self.source    }     /// Destructures this object into the inner reader.    pub fn into_inner(self) -> READ    where        READ: Sized,    {        self.source    }     /// Destructures this object into both the inner reader and [FrameDecoder].    pub fn into_parts(self) -> (READ, DEC)    where        READ: Sized,    {        (self.source, self.decoder)    }     /// Destructures this object into the inner [FrameDecoder].    pub fn into_frame_decoder(self) -> DEC {        self.decoder    }} impl<READ: Read, DEC: BorrowMut<FrameDecoder>> Read for StreamingDecoder<READ, DEC> {    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error> {        let decoder = self.decoder.borrow_mut();        if decoder.is_finished() && decoder.can_collect() == 0 {            //No more bytes can ever be decoded            return Ok(0);        }         // need to loop. The UpToBytes strategy doesn't take any effort to actually reach that limit.        // The first few calls can result in just filling the decode buffer but these bytes can not be collected.        // So we need to call this until we can actually collect enough bytes         // TODO add BlockDecodingStrategy::UntilCollectable(usize) that pushes this logic into the decode_blocks function        while decoder.can_collect() < buf.len() && !decoder.is_finished() {            //More bytes can be decoded            let additional_bytes_needed = buf.len() - decoder.can_collect();            match decoder.decode_blocks(                &mut self.source,                BlockDecodingStrategy::UptoBytes(additional_bytes_needed),            ) {                Ok(_) => { /*Nothing to do*/ }                Err(e) => {                    let err;                    #[cfg(feature = "std")]                    {                        err = Error::new(ErrorKind::Other, e);                    }                    #[cfg(not(feature = "std"))]                    {                        err = Error::new(ErrorKind::Other, Box::new(e));                    }                    return Err(err);                }            }        }         decoder.read(buf)    }}