add locks + file alloc in Writer::finish

lib/Cargo.toml

@@ -17,6 +17,7 @@ zip="0.6"
 bincode = "^2.0.0-rc.2"
 zstd = "^0.10"
 memmap = "0.7.0"
+fs4 = { version = "0.6.3", features = ["sync"] }
 
 [dev-dependencies]
 tempfile = "3.3"

lib/src/db.rs

@@ -8,6 +8,8 @@ use std::{
 
 use memmap::{Mmap, MmapOptions};
 
+use fs4::FileExt;
+
 type LSize = u32;
 const LEN_SIZE: usize = std::mem::size_of::<LSize>();
 const BINCODE_CFG: bincode::config::Configuration = bincode::config::standard();
@@ -63,6 +65,7 @@ where
 {
     pub fn new<P: AsRef<Path>>(path: P, opts: WriterOpts) -> Result<Self, String> {
         let out = fs::File::create(path).str_err()?;
+        out.try_lock_exclusive().str_err()?;
         let out = io::BufWriter::with_capacity(opts.out_buf_size, out);
         let data_buf: Vec<u8> = Vec::with_capacity(opts.data_buf_size);
         let data_buf = Cursor::new(data_buf);
@@ -133,6 +136,9 @@ where
         let pos: LSize = self.data_buf.position() as LSize;
         self.table.push(pos);
 
+        let output_size: u64 = (self.table.len() * LEN_SIZE) as u64 + self.data_buf.position();
+        self.out.get_ref().allocate(output_size).str_err()?;
+
         // write tab
         let tab_size = (self.table.len() * LEN_SIZE) as LSize;
         for pos in self.table {
@@ -147,6 +153,7 @@ where
         io::copy(&mut data, &mut self.out).str_err()?;
 
         self.out.flush().str_err()?;
+        self.out.get_ref().unlock().str_err()?;
         Ok(())
     }
 }
@@ -167,6 +174,7 @@ where
 {
     pub fn new<P: AsRef<Path>>(path: P, _buf_size: usize) -> Result<Self, String> {
         let file = fs::File::open(path).str_err()?;
+        file.try_lock_shared().str_err()?;
         let mmap = unsafe { MmapOptions::new().map(&file).str_err()? };
 
         // read first pos and records count