ppmd_rust/
encoder_8.rs

1use std::io::Write;
2
3use crate::{
4    internal::ppmd8::{Ppmd8, RangeEncoder},
5    Error, RestoreMethod, PPMD8_MAX_MEM_SIZE, PPMD8_MAX_ORDER, PPMD8_MIN_MEM_SIZE, PPMD8_MIN_ORDER,
6    SYM_END,
7};
8
9/// A encoder to compress data using PPMd8 (PPMdI rev.1).
10pub struct Ppmd8Encoder<W: Write> {
11    ppmd: Ppmd8<RangeEncoder<W>>,
12}
13
14impl<W: Write> Ppmd8Encoder<W> {
15    /// Creates a new [`Ppmd8Encoder`] which provides a writer over the compressed data.
16    ///
17    /// The given `order` must be between [`PPMD8_MIN_ORDER`] and [`PPMD8_MAX_ORDER`] (inclusive).
18    /// The given `mem_size` must be between [`PPMD8_MIN_MEM_SIZE`] and [`PPMD8_MAX_MEM_SIZE`] (inclusive).
19    pub fn new(
20        writer: W,
21        order: u32,
22        mem_size: u32,
23        restore_method: RestoreMethod,
24    ) -> crate::Result<Self> {
25        if !(PPMD8_MIN_ORDER..=PPMD8_MAX_ORDER).contains(&order)
26            || !(PPMD8_MIN_MEM_SIZE..=PPMD8_MAX_MEM_SIZE).contains(&mem_size)
27        {
28            return Err(Error::InvalidParameter);
29        }
30
31        let ppmd = Ppmd8::new_encoder(writer, mem_size, order, restore_method)?;
32
33        Ok(Self { ppmd })
34    }
35
36    /// Returns the inner writer.
37    pub fn into_inner(self) -> W {
38        self.ppmd.into_inner()
39    }
40
41    /// Finishes the encoding process.
42    ///
43    /// Adds an end marker to the data if `with_end_marker` is set to `true`.
44    pub fn finish(mut self, with_end_marker: bool) -> Result<W, std::io::Error> {
45        if with_end_marker {
46            self.ppmd.encode_symbol(SYM_END)?;
47        }
48        self.flush()?;
49        Ok(self.into_inner())
50    }
51
52    fn inner_flush(&mut self) -> Result<(), std::io::Error> {
53        self.ppmd.flush_range_encoder()?;
54        Ok(())
55    }
56}
57
58impl<W: Write> Write for Ppmd8Encoder<W> {
59    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
60        if buf.is_empty() {
61            return Ok(0);
62        }
63
64        for &byte in buf {
65            self.ppmd.encode_symbol(byte as i32)?;
66        }
67
68        Ok(buf.len())
69    }
70
71    fn flush(&mut self) -> std::io::Result<()> {
72        self.inner_flush()
73    }
74}
75
76#[cfg(test)]
77mod test {
78    use std::io::{Read, Write};
79
80    use super::Ppmd8Encoder;
81    use crate::{Ppmd8Decoder, RestoreMethod};
82
83    const ORDER: u32 = 8;
84    const MEM_SIZE: u32 = 262144;
85    const RESTORE_METHOD: RestoreMethod = RestoreMethod::Restart;
86
87    #[test]
88    fn ppmd8encoder_without_end_marker() {
89        let test_data = include_str!("../tests/fixtures/apache2.txt");
90
91        let mut writer = Vec::new();
92        {
93            let mut encoder =
94                Ppmd8Encoder::new(&mut writer, ORDER, MEM_SIZE, RESTORE_METHOD).unwrap();
95            encoder.write_all(test_data.as_bytes()).unwrap();
96            encoder.finish(false).unwrap();
97        }
98
99        let mut decoder =
100            Ppmd8Decoder::new(writer.as_slice(), ORDER, MEM_SIZE, RESTORE_METHOD).unwrap();
101
102        let mut decoded = vec![0; test_data.len()];
103        decoder.read_exact(&mut decoded).unwrap();
104
105        let decoded_data = String::from_utf8(decoded).unwrap();
106        assert_eq!(decoded_data, test_data);
107    }
108
109    #[test]
110    fn ppmd8encoder_with_end_marker() {
111        let test_data = include_str!("../tests/fixtures/apache2.txt");
112
113        let mut writer = Vec::new();
114        {
115            let mut encoder =
116                Ppmd8Encoder::new(&mut writer, ORDER, MEM_SIZE, RESTORE_METHOD).unwrap();
117            encoder.write_all(test_data.as_bytes()).unwrap();
118            encoder.finish(true).unwrap();
119        }
120
121        let mut decoder =
122            Ppmd8Decoder::new(writer.as_slice(), ORDER, MEM_SIZE, RESTORE_METHOD).unwrap();
123
124        let mut decoded = Vec::new();
125        decoder.read_to_end(&mut decoded).unwrap();
126
127        let decoded_data = String::from_utf8(decoded).unwrap();
128        assert_eq!(decoded_data, test_data);
129    }
130}
ppmd_rust/encoder_8.rs

ppmd_rust/
encoder_8.rs
