compression_codecs/bzip2/
encoder.rs

1use crate::{bzip2::params::Bzip2EncoderParams, EncodeV2};
2use bzip2::{Action, Compress, Compression, Status};
3use compression_core::util::{PartialBuffer, WriteBuffer};
4use std::{fmt, io};
5
6pub struct BzEncoder {
7    compress: Compress,
8}
9
10impl fmt::Debug for BzEncoder {
11    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
12        write!(
13            f,
14            "BzEncoder {{total_in: {}, total_out: {}}}",
15            self.compress.total_in(),
16            self.compress.total_out()
17        )
18    }
19}
20
21impl BzEncoder {
22    /// Creates a new stream prepared for compression.
23    ///
24    /// The `work_factor` parameter controls how the compression phase behaves
25    /// when presented with worst case, highly repetitive, input data. If
26    /// compression runs into difficulties caused by repetitive data, the
27    /// library switches from the standard sorting algorithm to a fallback
28    /// algorithm. The fallback is slower than the standard algorithm by perhaps
29    /// a factor of three, but always behaves reasonably, no matter how bad the
30    /// input.
31    ///
32    /// Lower values of `work_factor` reduce the amount of effort the standard
33    /// algorithm will expend before resorting to the fallback. You should set
34    /// this parameter carefully; too low, and many inputs will be handled by
35    /// the fallback algorithm and so compress rather slowly, too high, and your
36    /// average-to-worst case compression times can become very large. The
37    /// default value of 30 gives reasonable behaviour over a wide range of
38    /// circumstances.
39    ///
40    /// Allowable values range from 0 to 250 inclusive. 0 is a special case,
41    /// equivalent to using the default value of 30.
42    pub fn new(params: Bzip2EncoderParams, work_factor: u32) -> Self {
43        let params = Compression::from(params);
44        Self {
45            compress: Compress::new(params, work_factor),
46        }
47    }
48
49    fn encode(
50        &mut self,
51        input: &mut PartialBuffer<&[u8]>,
52        output: &mut WriteBuffer<'_>,
53        action: Action,
54    ) -> io::Result<Status> {
55        let prior_in = self.compress.total_in();
56        let prior_out = self.compress.total_out();
57
58        let result = self
59            .compress
60            // Safety: We **trust** bzip2 to only write initialized bytes into it
61            .compress_uninit(input.unwritten(), unsafe { output.unwritten_mut() }, action)
62            .map_err(io::Error::other);
63
64        input.advance((self.compress.total_in() - prior_in) as usize);
65        // Safety: We **trust** bzip2 to properly write bytes into it
66        unsafe { output.assume_init_and_advance((self.compress.total_out() - prior_out) as usize) };
67
68        result
69    }
70}
71
72impl EncodeV2 for BzEncoder {
73    fn encode(
74        &mut self,
75        input: &mut PartialBuffer<&[u8]>,
76        output: &mut WriteBuffer<'_>,
77    ) -> io::Result<()> {
78        match self.encode(input, output, Action::Run)? {
79            // Decompression went fine, nothing much to report.
80            Status::Ok => Ok(()),
81
82            // The Flush action on a compression went ok.
83            Status::FlushOk => unreachable!(),
84
85            // The Run action on compression went ok.
86            Status::RunOk => Ok(()),
87
88            // The Finish action on compression went ok.
89            Status::FinishOk => unreachable!(),
90
91            // The stream's end has been met, meaning that no more data can be input.
92            Status::StreamEnd => unreachable!(),
93
94            // There was insufficient memory in the input or output buffer to complete
95            // the request, but otherwise everything went normally.
96            Status::MemNeeded => Err(io::ErrorKind::OutOfMemory.into()),
97        }
98    }
99
100    fn flush(&mut self, output: &mut WriteBuffer<'_>) -> io::Result<bool> {
101        match self.encode(&mut PartialBuffer::new(&[][..]), output, Action::Flush)? {
102            // Decompression went fine, nothing much to report.
103            Status::Ok => unreachable!(),
104
105            // The Flush action on a compression went ok.
106            Status::FlushOk => Ok(false),
107
108            // The Run action on compression went ok.
109            Status::RunOk => Ok(true),
110
111            // The Finish action on compression went ok.
112            Status::FinishOk => unreachable!(),
113
114            // The stream's end has been met, meaning that no more data can be input.
115            Status::StreamEnd => unreachable!(),
116
117            // There was insufficient memory in the input or output buffer to complete
118            // the request, but otherwise everything went normally.
119            Status::MemNeeded => Err(io::ErrorKind::OutOfMemory.into()),
120        }
121    }
122
123    fn finish(&mut self, output: &mut WriteBuffer<'_>) -> io::Result<bool> {
124        match self.encode(&mut PartialBuffer::new(&[][..]), output, Action::Finish)? {
125            // Decompression went fine, nothing much to report.
126            Status::Ok => Ok(false),
127
128            // The Flush action on a compression went ok.
129            Status::FlushOk => unreachable!(),
130
131            // The Run action on compression went ok.
132            Status::RunOk => unreachable!(),
133
134            // The Finish action on compression went ok.
135            Status::FinishOk => Ok(false),
136
137            // The stream's end has been met, meaning that no more data can be input.
138            Status::StreamEnd => Ok(true),
139
140            // There was insufficient memory in the input or output buffer to complete
141            // the request, but otherwise everything went normally.
142            Status::MemNeeded => Err(io::ErrorKind::OutOfMemory.into()),
143        }
144    }
145}
compression_codecs/bzip2/encoder.rs

compression_codecs/bzip2/
encoder.rs
