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use crate::serialization::{Addr, SerializationSink};
use memmap::MmapMut;
use std::error::Error;
use std::fs::File;
use std::io::{BufWriter, Write};
use std::path::{Path, PathBuf};
use std::sync::atomic::{AtomicUsize, Ordering};
pub struct MmapSerializationSink {
mapped_file: MmapMut,
current_pos: AtomicUsize,
path: PathBuf,
}
impl SerializationSink for MmapSerializationSink {
fn from_path(path: &Path) -> Result<Self, Box<dyn Error>> {
let file_size = 1 << 30;
let mapped_file = MmapMut::map_anon(file_size)?;
Ok(MmapSerializationSink {
mapped_file,
current_pos: AtomicUsize::new(0),
path: path.to_path_buf(),
})
}
#[inline]
fn write_atomic<W>(&self, num_bytes: usize, write: W) -> Addr
where
W: FnOnce(&mut [u8]),
{
let pos = self.current_pos.fetch_add(num_bytes, Ordering::SeqCst);
assert!(pos.checked_add(num_bytes).unwrap() <= self.mapped_file.len());
let bytes: &mut [u8] = unsafe {
let start: *mut u8 = self.mapped_file.as_ptr().offset(pos as isize) as *mut u8;
std::slice::from_raw_parts_mut(start, num_bytes)
};
write(bytes);
Addr(pos as u32)
}
}
impl Drop for MmapSerializationSink {
fn drop(&mut self) {
let actual_size = *self.current_pos.get_mut();
let file = match File::create(&self.path) {
Ok(file) => file,
Err(e) => {
eprintln!("Error opening file for writing: {:?}", e);
return;
}
};
let mut file = BufWriter::new(file);
if let Err(e) = file.write_all(&self.mapped_file[0..actual_size]) {
eprintln!("Error writing file: {:?}", e);
}
}
}