1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
|
use crate::frame_decoder::{BlockDecodingStrategy, FrameDecoder, FrameDecoderError};
use std::io::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> {
pub decoder: FrameDecoder,
source: READ,
}
impl<READ: Read> StreamingDecoder<READ> {
pub fn new(mut source: READ) -> Result<StreamingDecoder<READ>, FrameDecoderError> {
let mut decoder = FrameDecoder::new();
decoder.init(&mut source)?;
Ok(StreamingDecoder { decoder, source })
}
pub fn new_with_decoder(
mut source: READ,
mut decoder: FrameDecoder,
) -> Result<StreamingDecoder<READ>, FrameDecoderError> {
decoder.init(&mut source)?;
Ok(StreamingDecoder { decoder, source })
}
pub fn inner(self) -> FrameDecoder {
self.decoder
}
}
impl<READ: Read> Read for StreamingDecoder<READ> {
fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
if self.decoder.is_finished() && self.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 self.decoder.can_collect() < buf.len() && !self.decoder.is_finished() {
//More bytes can be decoded
let additional_bytes_needed = buf.len() - self.decoder.can_collect();
match self.decoder.decode_blocks(
&mut self.source,
BlockDecodingStrategy::UptoBytes(additional_bytes_needed),
) {
Ok(_) => { /*Nothing to do*/ }
Err(e) => {
let err = std::io::Error::new(
std::io::ErrorKind::Other,
format!("Error in the zstd decoder: {:?}", e),
);
return Err(err);
}
}
}
self.decoder.read(buf)
}
}
|
