1 | use core::borrow::BorrowMut; |
2 | |
3 | use crate::frame_decoder::{BlockDecodingStrategy, FrameDecoder, FrameDecoderError}; |
4 | use crate::io::{Error, ErrorKind, Read}; |
5 | |
6 | /// High level decoder that implements a io::Read that can be used with |
7 | /// io::Read::read_to_end / io::Read::read_exact or passing this to another library / module as a source for the decoded content |
8 | /// |
9 | /// The lower level FrameDecoder by comparison allows for finer grained control but need sto have it's decode_blocks method called continously |
10 | /// to decode the zstd-frame. |
11 | pub struct StreamingDecoder<READ: Read, DEC: BorrowMut<FrameDecoder>> { |
12 | pub decoder: DEC, |
13 | source: READ, |
14 | } |
15 | |
16 | impl<READ: Read, DEC: BorrowMut<FrameDecoder>> StreamingDecoder<READ, DEC> { |
17 | pub fn new_with_decoder( |
18 | mut source: READ, |
19 | mut decoder: DEC, |
20 | ) -> Result<StreamingDecoder<READ, DEC>, FrameDecoderError> { |
21 | decoder.borrow_mut().init(&mut source)?; |
22 | Ok(StreamingDecoder { decoder, source }) |
23 | } |
24 | } |
25 | |
26 | impl<READ: Read> StreamingDecoder<READ, FrameDecoder> { |
27 | pub fn new( |
28 | mut source: READ, |
29 | ) -> Result<StreamingDecoder<READ, FrameDecoder>, FrameDecoderError> { |
30 | let mut decoder: FrameDecoder = FrameDecoder::new(); |
31 | decoder.init(&mut source)?; |
32 | Ok(StreamingDecoder { decoder, source }) |
33 | } |
34 | |
35 | pub fn inner(self) -> FrameDecoder { |
36 | self.decoder |
37 | } |
38 | } |
39 | |
40 | impl<READ: Read, DEC: BorrowMut<FrameDecoder>> Read for StreamingDecoder<READ, DEC> { |
41 | fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error> { |
42 | let decoder = self.decoder.borrow_mut(); |
43 | if decoder.is_finished() && decoder.can_collect() == 0 { |
44 | //No more bytes can ever be decoded |
45 | return Ok(0); |
46 | } |
47 | |
48 | // need to loop. The UpToBytes strategy doesn't take any effort to actually reach that limit. |
49 | // The first few calls can result in just filling the decode buffer but these bytes can not be collected. |
50 | // So we need to call this until we can actually collect enough bytes |
51 | |
52 | // TODO add BlockDecodingStrategy::UntilCollectable(usize) that pushes this logic into the decode_blocks function |
53 | while decoder.can_collect() < buf.len() && !decoder.is_finished() { |
54 | //More bytes can be decoded |
55 | let additional_bytes_needed = buf.len() - decoder.can_collect(); |
56 | match decoder.decode_blocks( |
57 | &mut self.source, |
58 | BlockDecodingStrategy::UptoBytes(additional_bytes_needed), |
59 | ) { |
60 | Ok(_) => { /*Nothing to do*/ } |
61 | Err(e) => { |
62 | let err; |
63 | #[cfg (feature = "std" )] |
64 | { |
65 | err = Error::new(ErrorKind::Other, e); |
66 | } |
67 | #[cfg (not(feature = "std" ))] |
68 | { |
69 | err = Error::new(ErrorKind::Other, alloc::boxed::Box::new(e)); |
70 | } |
71 | return Err(err); |
72 | } |
73 | } |
74 | } |
75 | |
76 | decoder.read(buf) |
77 | } |
78 | } |
79 | |