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
|
//! Utilities for converting files into blocks.
use std::convert::TryInto;
use std::fs;
use std::fs::File;
use std::io::Write;
use std::io::{BufRead, BufReader, ErrorKind};
use std::io::{Seek, SeekFrom};
use std::path::Path;
use std::path::PathBuf;
use bstr::io::BufReadExt;
use memchr;
const BUFFER_SIZE: usize = 16 * 1024;
#[derive(Debug)]
pub struct FileChunk {
path: PathBuf,
start: usize,
stop: usize,
}
impl FileChunk {
/// Iterates over just those lines the file chunk refers to.
pub fn dump<W: Write>(&self, mut w: W) {
let mut file = File::open(&self.path).expect("file available");
file.seek(SeekFrom::Start(self.start.try_into().unwrap()))
.expect("seek");
let reader = BufReader::with_capacity(BUFFER_SIZE.min(self.stop - self.start), file);
let mut current_byte = self.start;
let stop_byte = self.stop;
reader
.for_byte_line_with_terminator(|line| {
if current_byte >= stop_byte {
return Ok(false);
}
assert!(
current_byte < stop_byte + 1,
"can only overshoot if non-newline split or eof with no newline"
);
current_byte += line.len();
w.write(line).expect("write");
Ok(true)
})
.expect("read");
}
}
/// Uses up to `max_chunks + paths.len()` chunks to chunkify multiple files.
pub fn chunkify_multiple(paths: &[PathBuf], max_chunks: usize, min_size: usize) -> Vec<FileChunk> {
assert!(max_chunks > 0);
let sizes: Vec<usize> = paths
.iter()
.map(|path| {
fs::metadata(path)
.expect("metadata")
.len()
.try_into()
.unwrap()
})
.collect();
let avg_size = (sizes.iter().copied().sum::<usize>() / paths.len()).max(1);
paths
.iter()
.zip(sizes.into_iter())
.flat_map(|(path, sz)| {
let desired_chunks: usize = (sz / avg_size).max(1);
chunkify(&path, desired_chunks, min_size).into_iter()
})
.collect()
}
/// Returns a list of up to `max_chunks` file chunks splitting up the given
/// file, roughly of the same size, which should be rougly at least
/// `min_size`, newline aligned.
///
/// Of course, the file is assumed to not be modified between the start
/// of this method and the usage of the corresponding file chunks,
/// else someone will panic.
pub fn chunkify(path: &Path, max_chunks: usize, min_size: usize) -> Vec<FileChunk> {
assert!(max_chunks > 0);
let metadata = fs::metadata(path).unwrap();
let size: usize = metadata.len().try_into().unwrap();
let max_chunks = max_chunks.min(size / min_size).max(1);
let mut file = File::open(path).unwrap();
let mut chunks = Vec::with_capacity(max_chunks);
let mut current_byte = 0;
for i in 0..max_chunks {
let stop = size * (i + 1) / max_chunks;
// in the rare case when a line takes up a whole block, skip it
if current_byte >= stop {
continue;
}
file.seek(SeekFrom::Start(stop.try_into().unwrap()))
.expect("seek");
let mut reader = BufReader::new(&mut file);
let stop = stop + read_until(b'\n', &mut reader);
chunks.push(FileChunk {
path: path.to_owned(),
start: current_byte,
stop,
});
current_byte = stop;
if stop == size {
break;
}
}
chunks
}
fn read_until<R: BufRead + ?Sized>(delim: u8, r: &mut R) -> usize {
// from stdlib
let mut read = 0;
loop {
let (done, used) = {
let available = match r.fill_buf() {
Ok(n) => n,
Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
x => x.unwrap(),
};
match memchr::memchr(delim, available) {
Some(i) => (true, i + 1),
None => (false, available.len()),
}
};
r.consume(used);
read += used;
if done || used == 0 {
return read;
}
}
}
|
