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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 {
pub fn file(&self) -> File {
let mut file = File::open(&self.path).expect("file available");
file.seek(SeekFrom::Start(self.start.try_into().unwrap()))
.expect("seek");
file
}
pub fn nbytes(&self) -> usize {
self.stop - self.start
}
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");
}
}
pub fn chunkify_multiple(paths: &[PathBuf], max_chunks: usize, min_size: usize) -> Vec<FileChunk> {
assert!(max_chunks > 0);
assert!(!paths.is_empty());
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() - 1) / paths.len();
paths
.iter()
.zip(sizes.into_iter())
.flat_map(|(path, sz)| {
let desired_chunks: usize = (sz + avg_size - 1) / avg_size;
chunkify(&path, desired_chunks, min_size).into_iter()
})
.collect()
}
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;
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 {
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;
}
}
}