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
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159

use crate::{CompressSettings, DecompressSettings, Error, Result};
use flate2::Compression;
use flate2::write::{ZlibEncoder, ZlibDecoder};
use std::io::Write;

fn check_zlib_stream(inp: &[u8]) -> Result<(), Error> {
    if inp.len() < 2 {
        return Err(Error::new(53));
    }
    /*read information from zlib header*/
    if (u32::from(inp[0]) * 256 + u32::from(inp[1])) % 31 != 0 {
        /*error: 256 * in[0] + in[1] must be a multiple of 31, the FCHECK value is supposed to be made that way*/
        return Err(Error::new(24));
    }
    let cm = u32::from(inp[0]) & 15;
    let cinfo = (u32::from(inp[0]) >> 4) & 15;
    let fdict = (u32::from(inp[1]) >> 5) & 1;
    if cm != 8 || cinfo > 7 {
        /*error: only compression method 8: inflate with sliding window of 32k is supported by the PNG spec*/
        return Err(Error::new(25));
    }
    if fdict != 0 {
        /*error: the specification of PNG says about the zlib stream:
          "The additional flags shall not specify a preset dictionary."*/
        return Err(Error::new(26));
    }

    Ok(())
}

pub(crate) enum Decoder<'settings> {
    Flate(ZlibDecoder<Vec<u8>>),
    Custom(&'settings DecompressSettings, Vec<u8>, Vec<u8>),
}

impl Decoder<'_> {
    pub fn push(&mut self, chunk: &[u8]) -> Result<(), Error> {
        match self {
            Self::Flate(dec) => {
                dec.write_all(chunk).map_err(|_| Error::new(23))?;
            },
            Self::Custom(_, buf, _) => {
                buf.extend_from_slice(chunk);
            },
        }
        Ok(())
    }

    pub fn finish(self) -> Result<Vec<u8>, Error> {
        match self {
            Self::Flate(dec) => {
                Ok(dec.finish().map_err(|_| Error::new(23))?)
            },
            Self::Custom(settings, buf, mut out) => {
                check_zlib_stream(&buf)?;

                out.try_reserve((buf.len() * 3 / 2).max(16*1024))?;
                let cb = settings.custom_zlib.ok_or(Error::new(87))?; // can't fail
                (cb)(&buf, &mut out, settings)?;
                Ok(out)
            }
        }
    }
}

pub(crate) fn new_decompressor(out: Vec<u8>, zlib_data_size: usize, settings: &DecompressSettings) -> Decoder<'_> {
    if settings.custom_zlib.is_some() {
        let mut buf = Vec::new();
        let _ = buf.try_reserve_exact(zlib_data_size);
        Decoder::Custom(settings, buf, out)
    } else {
        Decoder::Flate(ZlibDecoder::new(out))
    }
}

#[inline(never)]
pub(crate) fn decompress_into_vec(inp: &[u8]) -> Result<Vec<u8>, Error> {
    check_zlib_stream(inp)?;
    let mut out = Vec::new();
    out.try_reserve((inp.len() * 3 / 2).max(16*1024))?;
    let mut dec = ZlibDecoder::new(out);
    dec.write_all(inp).map_err(|_| Error::new(23))?;
    dec.finish().map_err(|_| Error::new(23))
}

pub(crate) fn decompress(inp: &[u8], settings: &DecompressSettings) -> Result<Vec<u8>, Error> {
    if let Some(cb) = settings.custom_zlib {
        let mut out = Vec::new(); out.try_reserve(inp.len() * 3 / 2)?;
        (cb)(inp, &mut out, settings)?;
        Ok(out)
    } else {
        decompress_into_vec(inp)
    }
}

pub(crate) fn new_compressor<W: Write>(outv: W, settings: &CompressSettings) -> ZlibEncoder<W> {
    let level = settings.level();
    let level = if level == 0 {
        Compression::none()
    } else {
        Compression::new(level.min(9).into())
    };
    ZlibEncoder::new(outv, level)
}

#[inline(never)]
pub(crate) fn compress_into(out: &mut dyn Write, inp: &[u8], settings: &CompressSettings) -> Result<(), Error> {

    #[allow(deprecated)]
    if let Some(cb) = settings.custom_zlib {
        (cb)(inp, out, settings)?;
    } else {
        let mut z = new_compressor(out, settings);
        z.write_all(inp)?;
    }
    Ok(())
}

pub struct Estimator {
    gz: flate2::Compress,
    tmp: Vec<u8>,
}

impl Estimator {
    pub fn new(len: usize) -> Self {
        #[cfg(not(any(feature = "cfzlib", feature = "ngzlib")))]
        let gz = flate2::Compress::new(Compression::fast(), false);
        #[cfg(any(feature = "cfzlib", feature = "ngzlib"))]
        let gz = flate2::Compress::new_with_window_bits(Compression::fast(), false,
                (len+270).max(1<<9).min(1<<14).next_power_of_two().trailing_zeros() as u8);
        Self {
            gz,
            tmp: vec![0; len+270],
        }
    }

    pub(crate) fn estimate_compressed_size(&mut self, mut source: &[u8], _dict: &[u8]) -> usize {
        self.gz.reset();
        #[cfg(any(feature = "cfzlib", feature = "ngzlib"))]
        if !_dict.is_empty() {
            let _ = self.gz.set_dictionary(&_dict[_dict.len().saturating_sub(1<<14)..]);
        }

        let init_total_out = self.gz.total_out();
        loop {
            let last_total_in = self.gz.total_in();
            let last_total_out = self.gz.total_out();
            let _ = self.gz.compress(source, &mut self.tmp, flate2::FlushCompress::Sync);
            let consumed = (self.gz.total_in() - last_total_in) as usize;
            let written = (self.gz.total_out() - last_total_out) as usize;
            if (consumed == 0 && written == 0) || consumed >= source.len() {
                break;
            }
            source = &source[consumed..];
        }
        (self.gz.total_out() - init_total_out) as _
    }
}