ppmd_rust/
encoder_7.rs

1use std::io::Write;
2
3use crate::{
4    internal::ppmd7::{Ppmd7, RangeEncoder},
5    Error, PPMD7_MAX_MEM_SIZE, PPMD7_MAX_ORDER, PPMD7_MIN_MEM_SIZE, PPMD7_MIN_ORDER,
6};
7
8/// An encoder to compress data using PPMd7 (PPMdH) with the 7z range coder.
9pub struct Ppmd7Encoder<W: Write> {
10    ppmd: Ppmd7<RangeEncoder<W>>,
11}
12
13impl<W: Write> Ppmd7Encoder<W> {
14    /// Creates a new [`Ppmd7Encoder`] which provides a writer over the compressed data.
15    ///
16    /// The given `order` must be between [`PPMD7_MIN_ORDER`] and [`PPMD7_MAX_ORDER`] (inclusive).
17    /// The given `mem_size` must be between [`PPMD7_MIN_MEM_SIZE`] and [`PPMD7_MAX_MEM_SIZE`] (inclusive).
18    pub fn new(writer: W, order: u32, mem_size: u32) -> crate::Result<Self> {
19        if !(PPMD7_MIN_ORDER..=PPMD7_MAX_ORDER).contains(&order)
20            || !(PPMD7_MIN_MEM_SIZE..=PPMD7_MAX_MEM_SIZE).contains(&mem_size)
21        {
22            return Err(Error::InvalidParameter);
23        }
24
25        let ppmd = Ppmd7::new_encoder(writer, order, mem_size)?;
26
27        Ok(Self { ppmd })
28    }
29
30    /// Returns the inner writer.
31    pub fn into_inner(self) -> W {
32        self.ppmd.into_inner()
33    }
34
35    fn inner_flush(&mut self) -> Result<(), std::io::Error> {
36        self.ppmd.flush_range_encoder()
37    }
38}
39
40impl<W: Write> Write for Ppmd7Encoder<W> {
41    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
42        if buf.is_empty() {
43            return Ok(0);
44        }
45
46        for &byte in buf.iter() {
47            self.ppmd.encode_symbol(byte)?;
48        }
49
50        Ok(buf.len())
51    }
52
53    fn flush(&mut self) -> std::io::Result<()> {
54        self.inner_flush()
55    }
56}
57
58#[cfg(test)]
59mod test {
60    use std::io::{Read, Write};
61
62    use super::Ppmd7Encoder;
63    use crate::Ppmd7Decoder;
64
65    const ORDER: u32 = 8;
66    const MEM_SIZE: u32 = 262144;
67
68    #[test]
69    fn ppmd7encoder_encode_decode() {
70        let test_data = include_str!("../tests/fixtures/apache2.txt");
71
72        let mut writer = Vec::new();
73        {
74            let mut encoder = Ppmd7Encoder::new(&mut writer, ORDER, MEM_SIZE).unwrap();
75            encoder.write_all(test_data.as_bytes()).unwrap();
76            encoder.flush().unwrap();
77        }
78
79        let mut decoder = Ppmd7Decoder::new(writer.as_slice(), ORDER, MEM_SIZE).unwrap();
80
81        let mut decoded = vec![0; test_data.len()];
82        decoder.read_exact(&mut decoded).unwrap();
83
84        assert_eq!(decoded.as_slice(), test_data.as_bytes());
85
86        let decoded_data = String::from_utf8(decoded).unwrap();
87
88        assert_eq!(decoded_data, test_data);
89    }
90}
ppmd_rust/encoder_7.rs

ppmd_rust/
encoder_7.rs
