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
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
//! This module contains functionality for compression.

use crate::alloc::vec;
use crate::alloc::vec::Vec;

mod buffer;
pub mod core;
pub mod stream;
use self::core::*;

/// How much processing the compressor should do to compress the data.
/// `NoCompression` and `Bestspeed` have special meanings, the other levels determine the number
/// of checks for matches in the hash chains and whether to use lazy or greedy parsing.
#[repr(i32)]
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum CompressionLevel {
    /// Don't do any compression, only output uncompressed blocks.
    NoCompression = 0,
    /// Fast compression. Uses a special compression routine that is optimized for speed.
    BestSpeed = 1,
    /// Slow/high compression. Do a lot of checks to try to find good matches.
    BestCompression = 9,
    /// Even more checks, can be very slow.
    UberCompression = 10,
    /// Default compromise between speed and compression.
    DefaultLevel = 6,
    /// Use the default compression level.
    DefaultCompression = -1,
}

// Missing safe rust analogue (this and mem-to-mem are quite similar)
/*
fn tdefl_compress(
    d: Option<&mut CompressorOxide>,
    in_buf: *const c_void,
    in_size: Option<&mut usize>,
    out_buf: *mut c_void,
    out_size: Option<&mut usize>,
    flush: TDEFLFlush,
) -> TDEFLStatus {
    let res = match d {
        None => {
            in_size.map(|size| *size = 0);
            out_size.map(|size| *size = 0);
            (TDEFLStatus::BadParam, 0, 0)
        },
        Some(compressor) => {
            let callback_res = CallbackOxide::new(
                compressor.callback_func.clone(),
                in_buf,
                in_size,
                out_buf,
                out_size,
            );

            if let Ok(mut callback) = callback_res {
                let res = compress(compressor, &mut callback, flush);
                callback.update_size(Some(res.1), Some(res.2));
                res
            } else {
                (TDEFLStatus::BadParam, 0, 0)
            }
        }
    };
    res.0
}*/

// Missing safe rust analogue
/*
fn tdefl_init(
    d: Option<&mut CompressorOxide>,
    put_buf_func: PutBufFuncPtr,
    put_buf_user: *mut c_void,
    flags: c_int,
) -> TDEFLStatus {
    if let Some(d) = d {
        *d = CompressorOxide::new(
            put_buf_func.map(|func|
                CallbackFunc { put_buf_func: func, put_buf_user: put_buf_user }
            ),
            flags as u32,
        );
        TDEFLStatus::Okay
    } else {
        TDEFLStatus::BadParam
    }
}*/

// Missing safe rust analogue (though maybe best served by flate2 front-end instead)
/*
fn tdefl_compress_mem_to_output(
    buf: *const c_void,
    buf_len: usize,
    put_buf_func: PutBufFuncPtr,
    put_buf_user: *mut c_void,
    flags: c_int,
) -> bool*/

// Missing safe Rust analogue
/*
fn tdefl_compress_mem_to_mem(
    out_buf: *mut c_void,
    out_buf_len: usize,
    src_buf: *const c_void,
    src_buf_len: usize,
    flags: c_int,
) -> usize*/

/// Compress the input data to a vector, using the specified compression level (0-10).
pub fn compress_to_vec(input: &[u8], level: u8) -> Vec<u8> {
    compress_to_vec_inner(input, level, 0, 0)
}

/// Compress the input data to a vector, using the specified compression level (0-10), and with a
/// zlib wrapper.
pub fn compress_to_vec_zlib(input: &[u8], level: u8) -> Vec<u8> {
    compress_to_vec_inner(input, level, 1, 0)
}

/// Simple function to compress data to a vec.
fn compress_to_vec_inner(input: &[u8], level: u8, window_bits: i32, strategy: i32) -> Vec<u8> {
    // The comp flags function sets the zlib flag if the window_bits parameter is > 0.
    let flags = create_comp_flags_from_zip_params(level.into(), window_bits, strategy);
    let mut compressor = CompressorOxide::new(flags);
    let mut output = vec![0; ::core::cmp::max(input.len() / 2, 2)];

    let mut in_pos = 0;
    let mut out_pos = 0;
    loop {
        let (status, bytes_in, bytes_out) = compress(
            &mut compressor,
            &input[in_pos..],
            &mut output[out_pos..],
            TDEFLFlush::Finish,
        );

        out_pos += bytes_out;
        in_pos += bytes_in;

        match status {
            TDEFLStatus::Done => {
                output.truncate(out_pos);
                break;
            }
            TDEFLStatus::Okay => {
                // We need more space, so resize the vector.
                if output.len().saturating_sub(out_pos) < 30 {
                    output.resize(output.len() * 2, 0)
                }
            }
            // Not supposed to happen unless there is a bug.
            _ => panic!("Bug! Unexpectedly failed to compress!"),
        }
    }

    output
}

#[cfg(test)]
mod test {
    use super::{compress_to_vec, compress_to_vec_inner, CompressionStrategy};
    use crate::inflate::decompress_to_vec;
    use alloc::vec;

    /// Test deflate example.
    ///
    /// Check if the encoder produces the same code as the example given by Mark Adler here:
    /// https://stackoverflow.com/questions/17398931/deflate-encoding-with-static-huffman-codes/17415203
    #[test]
    fn compress_small() {
        let test_data = b"Deflate late";
        let check = [
            0x73, 0x49, 0x4d, 0xcb, 0x49, 0x2c, 0x49, 0x55, 0x00, 0x11, 0x00,
        ];

        let res = compress_to_vec(test_data, 1);
        assert_eq!(&check[..], res.as_slice());

        let res = compress_to_vec(test_data, 9);
        assert_eq!(&check[..], res.as_slice());
    }

    #[test]
    fn compress_huff_only() {
        let test_data = b"Deflate late";

        let res = compress_to_vec_inner(test_data, 1, 0, CompressionStrategy::HuffmanOnly as i32);
        let d = decompress_to_vec(res.as_slice()).expect("Failed to decompress!");
        assert_eq!(test_data, d.as_slice());
    }

    /// Test that a raw block compresses fine.
    #[test]
    fn compress_raw() {
        let text = b"Hello, zlib!";
        let encoded = {
            let len = text.len();
            let notlen = !len;
            let mut encoded = vec![
                1,
                len as u8,
                (len >> 8) as u8,
                notlen as u8,
                (notlen >> 8) as u8,
            ];
            encoded.extend_from_slice(&text[..]);
            encoded
        };

        let res = compress_to_vec(text, 0);
        assert_eq!(encoded, res.as_slice());
    }

    #[test]
    fn short() {
        let test_data = [10, 10, 10, 10, 10, 55];
        let c = compress_to_vec(&test_data, 9);

        let d = decompress_to_vec(c.as_slice()).expect("Failed to decompress!");
        assert_eq!(&test_data, d.as_slice());
        // Check that a static block is used here, rather than a raw block
        // , so the data is actually compressed.
        // (The optimal compressed length would be 5, but neither miniz nor zlib manages that either
        // as neither checks matches against the byte at index 0.)
        assert!(c.len() <= 6);
    }
}