| use core::borrow::BorrowMut; |
| |
| use crate::frame_decoder::{BlockDecodingStrategy, FrameDecoder, FrameDecoderError}; |
| use crate::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 continously |
| /// to decode the zstd-frame. |
| 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 }) |
| } |
| |
| pub fn inner(self) -> FrameDecoder { |
| 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, alloc::boxed::Box::new(e)); |
| } |
| return Err(err); |
| } |
| } |
| } |
| |
| decoder.read(buf) |
| } |
| } |