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

use crate::utils::copy_rolling;
use crate::{DeflateOutput, OutStreamResult};
use mt_debug_counters::counter::{AtomicCounter, SumMode};
use crc32fast::Hasher;
use nightly_quirks::utils::NightlyUtils;
use std::cmp::min;
use std::mem::size_of;
use std::slice::from_raw_parts_mut;

pub struct DeflateChunkedBufferOutput<'a> {
    buffer: Box<[u8]>,
    lookback_pos: usize,
    position: usize,
    crc32: Hasher,
    written: usize,
    func: Box<dyn FnMut(&[u8]) -> Result<(), ()> + 'a>,
}

static COUNTER_THREADS_BUSY_READING: AtomicCounter<SumMode> =
    declare_counter_i64!("libdeflate_reading_threads", SumMode, false);

static COUNTER_THREADS_PROCESSING_READS: AtomicCounter<SumMode> =
    declare_counter_i64!("libdeflate_processing_threads", SumMode, false);

impl<'a> DeflateChunkedBufferOutput<'a> {
    pub fn new<F: FnMut(&[u8]) -> Result<(), ()> + 'a>(write_func: F, buf_size: usize) -> Self {
        COUNTER_THREADS_BUSY_READING.inc();
        Self {
            buffer: unsafe { NightlyUtils::box_new_uninit_slice_assume_init(buf_size) },
            lookback_pos: 0,
            position: 0,
            crc32: Hasher::new(),
            written: 0,
            func: Box::new(write_func),
        }
    }

    fn flush_buffer(&mut self, ensure_size: usize) -> bool {
        self.crc32
            .update(&self.buffer[self.lookback_pos..self.position]);
        COUNTER_THREADS_BUSY_READING.sub(1);
        COUNTER_THREADS_PROCESSING_READS.inc();
        if (self.func)(&self.buffer[self.lookback_pos..self.position]).is_err() {
            COUNTER_THREADS_BUSY_READING.inc();
            COUNTER_THREADS_PROCESSING_READS.sub(1);
            return false;
        }
        COUNTER_THREADS_BUSY_READING.inc();
        COUNTER_THREADS_PROCESSING_READS.sub(1);
        self.written += self.position - self.lookback_pos;

        let keep_buf_len = min(self.position, Self::MAX_LOOK_BACK);
        unsafe {
            std::ptr::copy(
                self.buffer.as_ptr().add(self.position - keep_buf_len),
                self.buffer.as_mut_ptr(),
                keep_buf_len,
            );
        }
        self.lookback_pos = keep_buf_len;
        self.position = keep_buf_len;

        self.buffer.len() - self.position > ensure_size
    }
}

impl<'a> DeflateOutput for DeflateChunkedBufferOutput<'a> {
    #[inline(always)]
    fn copy_forward(&mut self, prev_offset: usize, length: usize) -> bool {
        if self.buffer.len() - self.position <= length {
            if !self.flush_buffer(length) {
                return false;
            }
        }

        if prev_offset > self.position {
            return false;
        }

        unsafe {
            let dest = self.buffer.as_mut_ptr().add(self.position);
            copy_rolling(
                dest,
                dest.add(length),
                prev_offset,
                self.get_available_buffer().len() >= (length + 3 * size_of::<usize>()),
            );
        }
        self.position += length;

        true
    }

    #[inline(always)]
    fn write(&mut self, data: &[u8]) -> bool {
        if self.buffer.len() - self.position <= data.len() {
            if !self.flush_buffer(data.len()) {
                return false;
            }
        }
        self.buffer[self.position..self.position + data.len()].copy_from_slice(data);
        self.position += data.len();
        true
    }

    #[inline(always)]
    fn get_available_buffer(&mut self) -> &mut [u8] {
        unsafe {
            from_raw_parts_mut(
                self.buffer.as_mut_ptr().add(self.position),
                self.buffer.len() - self.position,
            )
        }
    }

    #[inline(always)]
    unsafe fn advance_available_buffer_position(&mut self, offset: usize) {
        self.position += offset;
        if self.buffer.len() == self.position {
            self.flush_buffer(1);
        }
    }

    #[inline(always)]
    fn final_flush(&mut self) -> Result<OutStreamResult, ()> {
        self.flush_buffer(0);
        self.position = 0;
        self.lookback_pos = 0;

        let result = OutStreamResult {
            written: self.written,
            crc32: self.crc32.clone().finalize(),
        };

        self.crc32 = Hasher::new();
        self.written = 0;
        Ok(result)
    }
}

impl Drop for DeflateChunkedBufferOutput<'_> {
    fn drop(&mut self) {
        COUNTER_THREADS_BUSY_READING.sub(1);
    }
}